 Hey everybody, Dr. O here. Welcome to chapter 5. So chapter 5 on lipids, which include your dietary fats, one of the most important chapters in the course. So hopefully I made it clear to you in the last chapter that the quality of the carbohydrates you eat is just as important really as the amount for most people. And I think the same goes with fats, right? The types of fats you eat have a massive impact on your health and they all can be part of a healthy diet, but it's all about the amounts and how many calories you're consuming and things like that. So we're going to talk about the chemistry here to begin with and then we'll get into dietary fats and their impact on your health. And we'll cover that again later. We have separate chapters where we really talk about things like cardiovascular disease. We're just kind of introducing the lipids here. Okay, so before we get in here, just what are lipids? So you hear that word lipids and you hear fats, but you see that the lipids, lipids are things that are insoluble in water. So yes, you have your triglycerides, which would be most of your dietary fats, but we also have phospholipids like the lipids that are in our cell membranes and we have sterols, which are things like cholesterol and the precursor to the steroid hormones. Things like wax would also be classified as a lipid. So lipids are just chemically they're insoluble in water, but we're primarily going to focus on your triglycerides, your dietary fats here, but that's what a lipid is compared to a fat. Okay. Icebreaker, in what way does fat affect the taste of your foods? Are any fats good for you? Why are why not? So a lot of people think that all fats are bad and that's just not true. I think almost anyone would agree that the fats you see here on this image, you've got the monounsaturated fats that come from nuts. You see the fats that come from avocado. Maybe that's some extra virgin olive oil there, I'm not sure, and you see the fats from olives. These would all be parts of some of the healthiest diets on the planet. You have diets that are high in nuts, and the Mediterranean diet is high in these healthy type of fats, so there absolutely are fats that are good for you. There are fats that are essential as well, right, that you look at like the fats that end up becoming your fish oils that we'll talk about later, the omega-3 fats. Those are essential, meaning that you have to consume them because your body can't make them. Your body can make almost every fat that it needs, but there are a couple essential fatty acids that we'll talk about. But how does fat, I mean, fat makes food taste better, right? You know, that's for lots of reasons, and I think it improves for a lot of people. It improves the mouth feel, but it makes foods more satiating, at least to some extent. So those are the kind of things we'll talk about here in this chapter. All right, by the end of this chapter, we'll recognize the chemistry of fatty acids and triglycerides. We'll talk about what does it mean to be a saturated fat? What is this omega-3 that I mentioned? Describe the chemistry of food sources and roles of phospholipids and sterols. So we will talk about those, but again, they're going to be a pretty minor part of the conversation. We'll talk about fat digestion, absorption, and transport. I promise you we'd review digestion and absorption of each of the macronutrients. Remembering that fat is kind of unique, right? Most of your nutrients are absorbed into your bloodstream, but we'll see here, we'll review here, that fat is actually carried into your lymphatic system first, and I'll explain why. Outline the major roles of fat in the body, including a discussion of the essential fatty acids and the omega fatty acids. Explain the relationship among saturated fats, trans fats, and cholesterol, and chronic diseases, noting the recommendations, and explain the relationships between monounsaturated and polyunsaturated fats in health, noting recommendations. So we'll talk about, by the end of this chapter, you'll have an understanding of why we need to eat fat, basically how much a typical person should eat, and then the breakdown of the different types of fats and which are really good for you, things like monounsaturated fats, the omega-3 fatty acids, which are really bad for you, things like the trans fats, and then what are the things that are kind of in the middle, and that's where you see really the ratio of saturated fat to polyunsaturated fat appears to be a really key player there, and I'll explain all that. All right, the chemist's view of fatty acids and triglycerides. So almost everyone has heard of fats or fatty acids, and almost everyone's heard the terms like omega-3 and this term, saturated fat and trans fat. We'll talk about the chemistry, where those names actually come from. So just a reminder, lipids are insoluble in water and your triglycerides, your dietary fats are a type of lipid. A lot of times we use the words interchangeably, and I think that's okay. But so a triglyceride, and I'll show you a picture in a little bit, but a triglyceride has three tails. That's where the term triglyceride comes from. It's built on a glycerol backbone with these three tails hanging off of it. And whether these tails are saturated or unsaturated will determine the properties of the fat. So we'll get there. So these fatty acid tails are always even numbers of carbons. They can be saturated or unsaturated, I'll show you that. But some of our fatty acids are short chain fats with maybe six carbons long. Some are medium chain fats, maybe 10 carbons long. And then we have your long chain fats. I typically think of something around 18 carbons being a typical fatty acid, 16, 18 in that area. So they're always even numbers. And that has to do with how these fats are metabolized. Fatty acids are broken down for fuel in a process called beta-oxidation, where the carbons are cut off two at a time. And then those carbons become something called acetyl-CoA, which we haven't covered yet, and that's part of your metabolism. All right, and then we have the terms omega-3 and omega-6. So where does this omega term come from? And where do we get them in our diet and can we make them? Can our body make them? That's a really important question. All right, so the first reflection here, I'll skip to the answers and I'll chat about having too much or too little fat can lead to poor health. Again, the typical person understands that a diet with too much fat can lead to poor health. But a diet with too little fat can also do that. I mean, even if you're a bodybuilder that goes on a really relatively low-fat diet, because a lot of times bodybuilders consume a moderate to high protein and a moderate to high carb diet, they know that you've got to consume 50, 60, 70 grams of fat a day because if you don't and you're not getting your essential fatty acids, then you can't make some of your hormones and leads to poor health outcomes. So too little fat can be a problem as well, especially if you're not getting the essential fatty acids. Fatty acids always have an even number of carbons. I explained why because they're metabolized in pairs. Triglycerides consist of a glycerol backbone and three fatty acid tails. So we'll focus primarily on the tails, but glycerol is important. About 6% of the energy stored in your body right now is in glycerol because when you break down fats for fuel, you burn those fatty acid tails, but then glycerol can become glucose. So they're in a process that we covered in the last chapter called gluconeogenesis. If your body isn't getting enough carbs from the diet, it can make them and it usually makes them from protein, but it can turn this glycerol backbone into glucose and burn it for fuel that way. All right, so certain fats are essential to good health. A well-balanced diet ensures an adequate amount of fat for optimal health and hopefully remember from a couple of chapters to go. An adequate amount means you're reaching that floor. You're getting the bare minimum. All right, what's the answer here? Unsaturated fats are called such because they have a double bond. And I haven't shown you that yet, but that's a saturated fat, has zero double bonds because it's saturated with hydrogens. Unsaturated fats have one or more double bonds. So a monounsaturated fat like you'd find in olive oil has a single double bond in its fatty acid tail. Polyunsaturated fats like you'd find in vegetable oil will have more than one double bond. So that's where the terms, so saturated, zero double bonds. Monounsaturated has one. Polyunsaturated has more than one. All right, so let's, we can read through this but I'll show you the picture, it'll make more sense. So the double bonds that we're talking about are nearest to the methyl end of the carbon chain. I'll show you that. So you think alpha and the omega alpha means the first and omega needs the last. So omega is gonna be, you count from the end of the fatty acid tail, you count in. Where's the closest double bond? So in omega three fat, the closest double bond is three carbons in and omega six fat, the closest double bond is six carbons in and then we have omega nine fats that the closest double bond is nine in. So that's actually where this term omega comes from. And then we'll look at linolytic acid and alpha linolytic acid are essential fatty acids in just a little bit. Okay, so some examples of the type of fats we're talking about and it still doesn't make enough sense. I need to show you these fatty acid tails. But here's some examples of different fats. So you see that animal fats are usually saturated fats because they have zero double bonds and steric acid is a good example there. The next one, oleic acid is what you're gonna find primarily in olive oil. That's a monounsaturated fat because it has the one double bond and then linolytic acid is a polyunsaturated fat with two double bonds and linolytic acid is a polyunsaturated fat with three double bonds. So you see that linolytic acid comes from like your soybean oils and corn oils and those type of vegetable oils and that's gonna be an omega six fat and then linolytic acid which comes from flax seeds and walnuts and those types of things that's going to be an omega three fat. I'll show you those more later. All right, here's our first actual look at a fatty acid tail. So you see that they're called fatty acids because they have an acid end, they're on the right side but the other end, the methylene is the one we're counting from. So linolytic acid, you see that first double bond right here is three carbons from the omega end from the end of the tail. So you count in three, that's where you see the first double bond and that's why linolytic acid is an omega three fat and this is the fatty acid we use to make our fish oils we call them, right? EPA and DHA. Then the bottom one, linolytic acid you have to count in six carbons to reach the first double bond. That's an omega six fat. Your body uses this one to make things like arachidonic acid and this would be our omega six fat. All right, lot more about that later. So the chemistry of fats and oils influences their characteristics. So this is the, so the first one is firmness. Let me actually find a picture here. So yeah, good. So I don't know, the PowerPoint goes a little bit out of order here, but this is why we, this is why a saturated and unsaturated fat will determine how firm a fat is at room temperature. So on the left hand side, we see a saturated fat. Notice there's no double bonds and the fatty acid tails are straight. So they can stack on top of each other like plates. So they can get real close together which is why at room temperature saturated fats are solid. Now the, like, so that's why if you have a steak sitting out, the fat doesn't melt away at room temperature. It's solid at room temperature. Now the saturated fats you find in coconut oil and things like that, they are saturated and they do stack pretty well. So they're generally solid at room temperature but when it gets a little warmer than room temperature they will start to liquefy. Like if you have a bottle of, if you have a bottle of coconut oil at home and let's say your house is in the mid-70s that may actually become a liquid. But saturated fats, as you remember, they are solid at room temperature because they have no double bonds. So these tails stack real close together. On the right side we see an unsaturated fat and notice every time there's a double bond there's a kink in the tail. And since these tails are kinked like this up and down they can't get very close together. So when these fatty acids stack on top of each other they're still far away from each other which is why they are liquid at room temperature. So your vegetable oil, your corn, your bottle of corn oil or canola oil is gonna be liquid at room temperature. Your butter is gonna be solid at room temperature. So that's why. Let me go back to what we're describing but I want you to see that. So that's why the firmness is determined by the chemistry. So you see here it says most polyunsaturated fats are liquid at room temperature. And then your monounsaturated fats are kind of in the middle. Like if you have a really good bottle of olive oil it'll be liquid at room temperature. But if you put it in the refrigerator it will become a solid whereas your vegetable oils will still probably be liquids in the refrigerator depending on how cold it is. So saturated animal fats are solid at room temperature. I explained why. Some fats like cocoa butter, palm oil and coconut oil are firmer than vegetable oils because of saturation but softer than animal fats because of shorter carbon chain. So coconut oil, about half of the fat in coconut oil is medium chain triglycerides. So you have your short chain fats you find in things like butter and your gut bacteria make them. Medium chain fats are in things like coconut oil and then long chain fats are gonna be most of your animal fats. So that's why if you have a steak and a bottle of coconut oil sitting out in a warm room the fat in the steak doesn't melt and it doesn't become a liquid but the coconut oil will. I think I remember I'd leave town for the weekend or whatever and I'd come back and so I'd have my air conditioning off and if my apartment was let's say 77, 78 degrees my coconut oil would be a liquid. All right, so that's the first. So the chemistry determines if they're solid or liquid at room temperature then we have stability. This is a very important point. It maybe gets overblown sometimes but stability, so what does this mean? Oxidation produces a variety of compounds that smell and taste rancid. So basically when a fat goes rancid it's basically going bad and the more double bonds that a fat has the more rapidly this occurs. So your saturated fats are the most stable because anywhere there's a double bond that's where this oxidation can occur. So if you've got, so I think about this when I think about how long I would keep fats around just to be safe, right? I'm kind of a better safe than sorry type but if you've got butter or coconut oil and it's around for a couple of years it shouldn't have oxidized very much it shouldn't have gone rancid but then if I have monoinsaturated fats like olive oil I will generally use a bottle, we buy smaller bottles and then we use them over a three month or six month period sorry and then if we haven't used it all in six months we toss it and then with your polyinsaturated fats I kind of have a three month rule. So if you've got like your vegetable oils or even like maybe you have fish oil pills like I take some fish oil pills occasionally I keep them in the refrigerator to slow this process down and then if I haven't used the bottle in three months I toss them. So that's just kind of my not medical advice with my personal stance on how the type of fats impacts their stability but you will notice like if you look at your vegetable oil that you have in your cupboard they add vitamin E usually. So they add antioxidants to try to slow this process down. So there, so I think that so firmness and stability are two things that are definitely influenced by the chemistry of the fats. So let's say a year with saturated fats they can sit around for a year. Monounsaturated fats six months polyunsaturated fats no more than three months. That's just, that's my general rule. Okay, so how do we build fatty acids? Hopefully you remember what condensation reactions are. Remember you remove water as you build things. So we talked about condensation reactions when we were building carbohydrates last chapter. On the flip side, if you're digesting and breaking this fatty acid down you would use hydrolysis reactions where you add water to split things apart. That's what lysis means to split or tear apart. But right now we're building them. So you take your glycerol backbone and then you have three condensation reactions to build those fatty acid tails onto them. So that's how you build a triglyceride. And remember there's that glycerol we talked about earlier that on the flip side when you digest this fat and you release that glycerol it can become glucose in that process of gluconeogenesis. All right, I'll be taking a lot of drink breaks in the morning. Knowledge check. Which fatty acids tend to be solid at room temperature? So we just explained. That'd be the saturated fats because their tails stack like kind of dinner plates because they're straight and they're straight because they have no double bonds. All right, then you see their fats spoil when exposed to oxygen. Polyunsaturated fats spoiled the most readily. So I've already mentioned that. All right, we covered all that. So back to this picture. I didn't mention one thing. So why doesn't a saturated fat not have any double bonds? So that's where the term saturated comes with. You can't see it here in this drawing. Actually, let me see what the other one will show you. No, so they're just showing the bonds and that's fine. But what you see everywhere you see one of those carbons here in the middle there would be two hydrogens, a hydrogen on each side. So the reason a saturated fat is saturated is it's saturated with hydrogen meaning there's no room for any other hydrogens to join these fatty acid tails. So that's why they're called saturated fats. They're saturated with hydrogen. On the right, you have a double bond between these two carbons here because there aren't enough hydrogens. So it's an unsaturated fat. It doesn't have the maximum number of hydrogens around each carbon. And that's why it is an unsaturated fat and why it relies on double bonds. Okay, the fatty acid composition of our common foods. So the main thing to note here is that there really aren't foods that are one pure form of fat. When you think of butter, for example, you think of saturated fats. But look, butter has monoinsaturated fats in it and it has a little bit of polyunsaturated fats in it. Or when you look at the bottom, when you think of, let's see, fish oil, right? When you think of fish oil, you always think of the omega-3 fats which you see is that yellow bar here. But there are saturated fats, monoinsaturated fats and omega-6 fats in fish oil. So everything you eat is basically a combination of different types of fat. Like, yeah, just look at the food. So if you have like, hmm, you'd be a good example. So yeah, if you look at like beef tallow which is beef fat or lard which is pork fat, again, you would look at it and you'd assume that it's an animal fat, it's gonna have all the saturated fat in it, which it does, but remember that it has a profile of other kind of fats as well. All right, what are some other big ones there? But you do notice though, when you think saturated fats, it's animal products and then what are called tropical oils. So you see coconut oil and palm oil on the list and the rest are animal fats. So your key sources of saturated fats are animal fats and tropical oils. Then you have your key sources of monoinsaturated fats. The best example is olive oil, but canola oil and peanut oil as well. But I would stick with olive oil if you're looking for healthy monoinsaturated fats. And then you have your omega-6 polyunsaturated fats. These are gonna be the rest of your vegetable oils. So corn oil, soybean oil, cottonseed oil, these are all commonly used. And then it's harder to find the omega-3 fats. Remember, these are essential. So there's only a few places where you can find these in the diets. You have to make sure you're doing so. And you see flaxseed oil and then you have your fish oil. And we'll come back to the difference between those two because when we talk about the essential fatty acids, because I believe that you need, the essential fatty acids, meaning the ones that you need to consume are the precursors to the omega-3 fats, the fish oils, EPA and DHA. I think EPA and DHA should be considered essential. We have to find a way to get them in our diet. And you can, right? You can eat fish, you can eat fatty fish, you can take fish oil pills. If you don't consume animal products, you can get DHA from algae and then your body can turn it into EPA. It's pretty cool. So there are ways to get the preformed fish oils. We call them EPA and DHA without consuming fish. All right, next we have, so we've covered what's this saturated mean. We've talked about what's omega-3 mean. Now you've all heard the term trans fats or leasing packages that says zero trans fats or whatever. So what is trans? And the opposite of trans is cis. So we have cis versus trans fats. A cis just means that it's on there on the same side. So if you're, we're talking about these hydrogens and I'll show you in a picture in a moment. A cis fatty acid is gonna have, the hydrogens are gonna be on the same side of the double bond, so pointing in the same direction. A trans fat, the hydrogens are gonna be on the opposite sides, one pointing up, one pointing down. And then you'll see though that the benefit of trans fats and it's not for your health for sure. But let me read this. A trans fatty acid has its hydrogens on the opposite sides of the double bond. Trans molecules are more linear. So you can take a cheap vegetable oil and you can hydrogenate it is the term they use and you can generate these trans fats and that causes that oil to stiffen up. So you can replace more expensive animal fats and tropical oils in the diet in foods with these cheaper foods that now have trans fats. So that's the reason. So trans fats became really popular because they made food cheaper and they extended its shelf life. Trans fats are really stable. So all the benefits was for the food producers. They could sell you food that it cost them less to make and it would have a longer shelf life. So that's why like when you open a Twinkie, the fat doesn't pour out of the bottom of it, right? At least back when they used a ton of these fats. But the downsides are huge. I mean, anyone would agree that these artificially produced trans fats are bad for health. All right, so the transform typically occurs in partially hydrogenated foods. When hydrogen atoms, I was gonna say hydrogen, when hydrogen atoms shift around some double bonds and change the configuration from consist of trans. So that's why if you see this term hydrogenated or partially hydrogenated on ingredient list, you know there are gonna be trans fats in the food. All right, so we've already said this, cis and trans just talk about configuration. Cis fats have both hydrogen on the same side and that causes a little kink in the chain. Trans fats, they're pointing on opposite directions and that causes it to be more straight. I don't know why there's not a picture there of a cis versus a trans fat, but I went through the PowerPoint and I think this is just a mistake. I don't think the slide's supposed to be here. Fiber's awesome, but we covered it in the last chapter. There's nothing about fat here, so I don't know what happened there. So I didn't make these PowerPoints. I'm just using the ones that came with the textbook. All right, so the chemist view. So we talked about triglycerides, your dietary fats. I don't know if you can hear Ruby, but she's having a dream. All right, so the chemist view of phospholipids and sterols. So again, a minor part of this chapter, but we do have to talk about them. So phospholipids, the first thing I think about with phospholipids is the phospholipid bilayer of our cell membranes. What makes them special is we have the phosphate end of a phospholipid is hydrophilic or water-loving and the fatty acid tails, which you see two tails here, not three, are hydrophobic or water-fearing. So that's why phospholipids are soluble in both fat and water. Like if you poured a bunch of phospholipids into a glass of water, it would form a spherical membrane where the water-loving heads would stay on the outside. The water-fearing tails would tuck in on the inside. So it's actually really cool. So yeah, the main thing to think about with phospholipids is that they are a big part of your cell membranes, but from a dietary standpoint, they are used as emulsifiers. So emulsifiers basically, they can change the texture and mouthfeel of food. They can keep food from getting too moist or wet, which would affect how long it would keep. So lecithin or soy lecithin is gonna be the best known emulsifier. So these are good for processed foods, for making them taste better and have a better mouthfeel when they extend their shelf life. The downside is it does appear that lecithin and other emulsifiers can impact our gut. They can impact the mucous layer in our gut that can maybe have a negative impact on our microbiome. I mean, I've seen research that says that it does have a negative impact on our microbiome. I just don't know how big of an impact. All right, so I've mentioned the roles of phospholipids. They are the phospholipid bilayer of your cell membranes and they're used as emulsifiers in the food industry. So sterols, we talk about these a lot because cholesterol is the main sterol that's found in animal products. So we have cholesterol is in animal products and plant sterols would be in plant products. So they both have sterols, they're just different ones. So if you go down the grocery store aisle and you see corn oil and it's got a big banner that says zero cholesterol. Well, it's like, yeah, plant cells don't make cholesterol. There never was any there. They're just, you always gotta be careful with the grocery store. Like I'm not saying that's a bad thing, but they're advertising it like it's something special but plant cells just don't make the animal version of cholesterol or animal version of sterols, which is cholesterol. Now cholesterol gets a bad rap and we'll talk about that. You certainly don't want high LDL cholesterol. We'll cover that later in this chapter. But for most people, dietary consumption of cholesterol is not actually what causes your cholesterol to go up. Your body's smarter than that. So if you consume more dietary cholesterol, your liver just synthesizes less of it and it doesn't really have an impact. If it does have an impact, it's transient for a couple of weeks. But so we do need cholesterol. Cholesterol is, it's in every cell membrane in our body. It keeps them from ripping open. Cholesterol is the reason that we don't need cell walls like bacteria and plant cells do. Cholesterol is also needed. Like you see, it is made in the body. Every cell in the body has the ability to make its own cholesterol. That's why you don't want a whole bunch of cholesterol in your bloodstream. You don't want high cholesterol in your bloodstream because that's just like an extra storage area where if a cell occasionally needs more cholesterol, it dips into this store. But cells already have the ability to produce their own. It is part of your cell membranes. And then cholesterol is needed to make your steroid hormones. So your hormones that are lipid-based. You see vitamin D here, which isn't really a vitamin, it is a hormone. So vitamin D3 or vitamin D comes from cholesterol. So do your steroid hormones. So your sex hormones like testosterone and estrogen, cortisol, which is called your stress hormone, aldosterone, an important hormone for maintaining fluid balance in the body. These are all examples of hormones that need cholesterol. So cholesterol, it has been demonized and in many ways for good reason. You don't want high cholesterol, you don't want excess cholesterol, but you would absolutely not want zero cholesterol either. Your body needs it for a lot of really important things. And that's one of the reasons why even if you go on a low-fat diet, you have to make sure you reach this minimum threshold where you're getting enough of these things so that your body will be good. Not hard to do though. All right, so which of the following are true of sterols and phospholipids? Let's go look at the answers. So sterols, so cholesterol is a sterol. Vitamin D is an example of a sterol or something made from cholesterol. And it's the structural component in our cell membranes. Phospholipids, the example they give is lecithin, which is found in the diet and like in soy lecithin and it's an emulsifier. Phospholipids are soluble in fat and water. I explained why the phosphate head likes water and the fatty acid tails hate water. And phospholipids form the phospholipid bilayer of our cell membranes. Okay, digestion, absorption and transport of lipids. This is gonna be a really important topic. I mean, to me, more important than when we're talking about carbs and protein because it's unique, it's different, but also the transport of lipids is where we get into the whole idea of good cholesterol, bad cholesterol, et cetera. And neither are actually cholesterol. Okay, so fat digestion, let's start there. Remember in the mouth, we do have an enzyme called lingual lipase, which does play a role in breaking down some fat. So if I ask you, right, where does fat digestion begin? It does begin in the mouth, but it's a pretty minor part of it. So as you're chewing and breaking down your food, you know, the fat in your meal, it's warming up and mixing with saliva, but the enzyme lingual lipase is active here. Then you get to the stomach. Now, I don't think this is a huge deal, but there is a little bit of an enzyme called gastric lipase that would also continue digestion of fat, but for all intents and purposes, there's not really fat digestion going on in the stomach, especially in adults. You see that the lingual lipase and gastric lipase were both especially important in children in breaking down milk fats from mother's milk. But, excuse me. But I do like to talk about the lingual lipase one, but there is some gastric lipase there just so you know. And then we get into, so the huge majority of fat digestion is going to occur in the small intestine, but notice here, so we have a hormone called cholecystokinin, or CCK, signals the gallbladder to release bile. And if you don't have a gallbladder, your liver is where bile is made. It's just stored in a gallbladder. So if you don't have a gallbladder, then your liver will produce and secrete bile. It won't be as concentrated, which is why if you've had your gallbladder removed recently, you can't eat as much fat, or at least most people can't. But, so what does bile do? It's very important to remember, bile doesn't digest fat. Bile emulsifies fat. So I like to say that bile doesn't digest fat. It makes it digestible. So emulsification takes these huge droplets of fat and turns them into thousands of tiny ones, which increases the surface area for the digestive enzymes to come in and attack it. So bile doesn't digest fat, but it makes it digestible. That's why if you've had your gallbladder removed like I did almost 10 years ago now, I couldn't eat like a thing of yogurt without having gastric issues, GI issues, because I couldn't emulsify that much fat. So a lot of it was passing through me, and that's where you get the pain and bloating and these types of things. All right, so fat is emulsified by bile, not digested. And then the digestive enzymes are gonna take over, and that's gonna be the pancreatic lipase from the pancreas is gonna do most of the work. It's gonna break your fats down, and they're not fully digested though. Like with carbs, they're broken down into monosaccharides, the simplest building block, and absorbed. Protein, same thing. But notice here, pancreatic lipase, then the lipase is in your small intestines. They turn a triglyceride into a monoglyceride. So it has the glycerol and a single fatty acid tail. Then the other two fatty acid tails are chopped off. So you don't fully break fat down into individual fatty acids like you do carbs and protein. The rest occurs in the body. And that, because remember, we're inside this hollow tube running through our body at this point. And then, so we'll talk about why it has to be transported differently because of that size as well. Then the last thing to note here, it says in the large intestine, some fat and cholesterol, which is trapped in fiber, exits in feces. So if you, this is one of the benefits of eating a diet that's high in fiber, especially soluble fiber, it will trap some fat and trap some cholesterol and take carried out of your body. So why do most people want that? Well, most people have high or relatively high cholesterol. Even normal cholesterol is on the high end of normal, would still be considered a little high by most lipidologists. So if you, the bile that's made from your liver, you need, bile salts are made by cholesterol. So basically, your liver squirts cholesterol into your gut. If you don't capture it with fiber, then it gets reabsorbed and reused. If you capture it with fiber and it exits your body in feces, then your liver says, oh, I have to make new bile. So it grabs cholesterol from the bloodstream and makes new bile with it. So if you think about it, every time you're going to the bathroom, you can be getting rid of cholesterol, which means your body has to use up what it has and that's why a high fiber diet lowers your blood cholesterol levels. It's actually, that's a very good thing unless for some reason your cholesterol was already too low. Okay, so we just covered all this, but lingual lipase breaks down fats in the mouth, in the stomach, it's basically just being churned up, but there is that gastric lipase that has a small function. We talked about olcolysis dekinin, releases bile from the gallbladder and it emulsifies fats, not digest them. Pancreatic lipase will break them down and then we just talked about how bile that's been trapped is going to be pulled out of your body and your body would have to use new cholesterol to make new bile, that's a great thing. All right, but most bile, or a lot of the bile would be reabsorbed. It really depends on how much fiber is in your diet. The soluble fiber specifically. Okay, so now it's time to absorb it. So your carbs and your proteins and your vitamins, they're all absorbed right into the bloodstream. And so are small chain fats and medium chain fats, I have to make sure I know that, but the typical long chain fatty acid that you eat is going to be, along with your fat-soluble vitamins, are going to be absorbed into the lymphatic system first and then they'll skip the liver and they'll work their way into your circulation. So the term is going to be a micelle, I'll show you this in a picture, there's really good pictures coming up. So the monoglycerides and the fatty acid tails are captured and packaged in these micelles. So why are they being packaged? Remember, oil and water don't mix and your body is mainly water. So these large fats have to be carried in and around and through. So it's called a micelle and I'll show you that in a moment and then the triglycerides are going to be built back together and they're going to be transported throughout your body. Well, triglycerides and cholesterol are going to be transported primarily on LDL and HDL which are considered your bad cholesterol and your good cholesterol. So that's why this conversation is going to be so important and it does skip the liver at first, it doesn't go straight to the liver like everything else does, it travels through the lymphatic system where the triglycerides are delivered throughout the body and then what's left over basically comes back to the liver. All right, let me show you these pictures. So here we see some of your glycerol backbones and then short chain fats and medium chain fats, they actually are just absorbed directly in the bloodstream. That's why let's say you're an endurance athlete, you might try using medium chain triglycerides, they have these oils like MCT oils you can buy that medium chain triglycerides are absorbed really quickly, they don't need bile, they're absorbed in the bloodstream. So if you're an athlete and you're trying to get some extra fuel into your system then it would make more sense to consume a medium chain triglyceride than it would a typical long chain fat. Now that's why endurance athletes primarily fuel themselves with carbs but if you're looking for more energy than you can get from carbs alone then something like a medium chain triglyceride might be a good idea. The other benefit of medium chain triglycerides and short chain fats is they don't need bile. So I always recommend people and not medical advice but if you've had your gallbladder removed and you're having trouble getting the fat calories you need, you may wanna try using some medium chain triglycerides and see how that works for you. So glycerol, short chain fats and your medium chain fats they're gonna be absorbed right into the bloodstream. So we're gonna focus over here on number two, large lipids. So the monoglycerides and then those tails that are partially digested, they're gonna be packaged in what are called micelles and micelles are just a way to, I'll just read it to you here. So let's see, large lipids such as monoglycerides and long chain fatty acids combined with bile forming micelles that are sufficiently water soluble to penetrate the watery solution that bathes the absorptive cells. So meaning that without these micelles these fats would basically be trapped in your gut because they wouldn't be able to penetrate that watery barrier. There the lipid contents of the micelles diffuse into the cells. So the micelles basically just used to get it across the membrane. All right, knowledge check and then we'll talk about chylamichrons and the rest coming up. Which of the following are absorbed directly into the bloodstream? And the answer there would be glycerol, the glycerol backbones, your short chain fats and your medium chain fats. They handle completely differently than your typical long chain fats. But trust me, unless you're on a very specific diet short and medium chain fats are a very small percent of your fat calories. All right, here, this is a really important one where we look at the absorption of fat but then also it's transported around the body because maybe I'm sure you've heard of some of these things. But I like how these shows you based on size. I'm gonna do a lot of reading here because they did a phenomenal job with this image. On the left-hand side, notice how large the fat-filled chylamichron is. That's the purple thing in the background. So compared with the others and how the others get progressively smaller as the proportion of fat declines and protein increases. So we start with the chylamichron is just loaded with fat because this is gonna be, this is how we deliver fat out to the body. And then as you'll notice as the chylamichron and the VLDL, which is the very low density lipoprotein, LDL, low density lipoprotein, and HDL, high density lipoprotein, they all have less and less triglycerides. So chylamichrons are primarily what are carrying these triglycerides or fats out to the body. All right, so what are these? This is where there's lots of confusion. So you see the chylamichron, you see the LDL, VLDL, and HDL there in the picture. So what are these, what does HDL and LDL mean? When we talk about them, we call LDL the bad cholesterol. And we call HDL the good cholesterol. But neither is true, right? These are the L, in the LDL and HDL stands for lipoprotein. So a lipoprotein, this is like the best analogy you always hear is like a boat. A lipoprotein is a boat that is carrying different amounts of fat and cholesterol. So there's only one kind of cholesterol. There's not a good cholesterol and a bad cholesterol. There's cholesterol that's being carried basically out to your tissues on this LDL boat. And there's cholesterol that's being carried back to your liver for recycling on the HDL boats. So that's why, so LDL is considered the bad cholesterol because it's the one out in circulation that can get trapped in your blood vessel walls and lead to atherosclerosis. HDL is out there picking up cholesterol to bring it back. So that's why you want a lower LDL cholesterol. So you have less of it being transported where it can be trapped into your blood vessels. And you want a high HDL, meaning more of it's being cleared from your body, right? They call that reverse cholesterol transport. But there is only one cholesterol. It's there's not a good cholesterol and a bad cholesterol. We're talking about the boats, what direction the boat is moving is basically what separates HDL and LDL. All right, let me read this here then. A typical lipoprotein contains an interior of triglycerides and cholesterol, which you see in the chart there, surrounded by the phospholipids. So those phospholipids are what's keeping the fats and the cholesterol's happy on the inside because those tails are hydrophobic. And it's what allow, it's carrying itself through the water because it's heads that you see there. The purple phosphate heads are hydrophilic or water-loving. All right, proteins near the outer end of the phospholipids cover the structure. Now this protein is super important. This is called APOB or Lipoprotein B or APOB 100. The reason this is important is this, each of these, every one of these, except for HDL, has an APOB protein on it. So now you go to the doctor and you get your cholesterol levels checked. That's great. But for a large chunk of people, around 25% of people, you'd be better off, I mean, everyone could get it, but you'd be better off getting your APOB levels tested because some people, usually if you have high LDL cholesterol, you also have high APOB, meaning you have a, each one of these cholesterol are LDLs and the LDLs and color microns is gonna be carrying a single one of these proteins. So basically you can count how many of these proteins you have and that can tell you how many of these potentially dangerous LDLs you have swimming around. But that's called concordance, where the two agree. You have high cholesterol, you have high APOB, but about 25% of the time, someone will have high cholesterol, LDL cholesterol, but low APOB, meaning they don't have a lot of these LDLs, it's just the ones they do have are carrying a lot of cholesterol. And then the flip side, somebody else might have normal LDL cholesterol, but their APOB is elevated, meaning they have a whole bunch of these little LDLs flying around that can be atherogenic, that can lead to atherosclerosis. So about 25% of the time, you really can't know what someone's risk of heart disease is unless you've seen this APOB number. And that's because of this protein that wraps up these different molecules. So I would recommend, and again, not medical advice, but when you go to the doctor, I would recommend if you're worried about heart disease risk and you're getting your lipid panel or you're getting cholesterol checked, you would also want to get that APOB looked at as well. All right. So that's the protein we're talking about and I've already mentioned how the hydrophilic heads allow it to travel through water and the hydrophobic tails keep the fats happy. All right, let's look at these four down here then. And one thing you don't see, yeah. So you've got your triglycerides are going to be in these packages, but we will talk about triglycerides quite a bit now and then the chapter on heart disease as well. Chylomicrons contain so little protein and so much triglyceride that they are the lowest in density. So chylomicrons are huge because they're just stuffed full of triglycerides. This is how your liver spits out these chylomicrons to transport fats to your body so it can be used for fuel. Very low density lipoproteins are, these are made by the liver, are half triglycerides accounting for their very low density. So these, and then when these will deliver triglycerides, then you're going to have less, and once they've delivered a bunch of their triglycerides then they become an LDL. So LDL or low density lipoprotein are half cholesterol accounting for their implications in heart disease because you'll notice they don't have a whole lot of fat anymore. Most of it's been delivered. So you see all this cholesterol here and then HDL or high density lipoproteins are half protein accounting for their high density and these are going to be totally different. You actually want a lot of HDL and you don't want a lot of LDL. All right, another really good, another really good slide here. Let's look at, let's look at what happens with fats how they're carried throughout their body. So right here from the intestines. Intestinal cells form the chylomicrons so that you remember your liver makes your VLDLs but chylomicrons come from the triglycerides that are being brought in from your gut. So intestinal cells form chylomicrons from dietary fats or dietary lipids. The chylomicrons deliver lipids to most of your body cell. You see muscles, fat cells. As cells remove lipids from the chylomicron it becomes what's called a chylomicron remnant and then your liver has to clear it and get rid of it. Liver cells remove chylomicron remnates from the blood. That's how we get fat from our gut through our body so our cells can take the fat and use it to our liver to clear up the excess. Then the liver, well actually on the other side the liver is gonna make so the liver cells form these VLDLs, very low density lipoproteins which deliver fats to your body cells. And as they've done that and they deposit so remember these are boats. These boats are stopping and stopping and stopping and every stop they get triglycerides are getting off. At some point these VLDLs have lost so much of their triglyceride that they become an LDL cholesterol which is smaller and that's what makes them more atherogenic, more dangerous. They're not carrying very much fat anymore. They're carrying a lot of cholesterol and they're small enough to penetrate the artery wall and lead to plaque formation. So as cells remove lipids from their VLDL they become the smaller LDL. LDL delivers lipids to the body cells which you can still do or returns to the liver and then hopefully your liver will clear it and get rid of it. We all have LDLs but if your liver is doing a good job of clearing it then your cholesterol levels will be normal. If your liver can't clear the LDL fast enough that's when you have high cholesterol in your blood. And then HDL, let's follow the whole loop, liver cells also form HDL which they go out and pick up cholesterol and bring it back. So whereas LDLs carrying cholesterol out where it can get trapped in your blood vessels HDLs picking it up and bringing it back and then HDL will deliver cholesterol to the liver so you can get rid of it. You can dump it in the GI tract or do whatever. So this is why if you have a whole lot of LDLs you are at risk for heart disease. You're at risk for plaque formation in your blood vessels. This cholesterol, it's way more complicated than this but this cholesterol, this waxy cholesterol gets trapped in your blood vessels then there's an inflammatory reaction and immune reaction and this plaque forms around it and if that plaque ever is fragile and breaks free it can lodge in your heart, cause a heart attack, lodge in your brain and cause a stroke. So that's why you don't want that to happen. But if you have high HDL, HDL will go out and clear cholesterol and bring it back to the liver. So if your liver's functioning well and you have high HDL and low LDL your risk of heart disease is much lower than if you have high LDL and low HDL. So we'll cover that a little bit more here today still but we're just introducing it but we'll have a whole section on heart disease later maybe chapter 11 I can't remember. All right, so let's match these. Kylo-microns contain the highest amount of triglycerides, these are huge and that's why they're not very dense. This is how our body, this is the first boat that fat's gonna get in once it's carried across your gut in what's called the micelle. Then it's gonna jump on this huge boat and it's gonna carry fat to the body cells. Very low density lipoproteins are made by the liver and then like it says here, they shrink as they give up their triglycerides and when they shrink to a certain point they become an LDL which we call the bad cholesterol which remember LDL and HDL are carrying the same cholesterol. LDL is considered the bad cholesterol because it's carrying out to your body where it can get trapped. HDL is considered the good cholesterol because it's bringing it back to the liver so it can be recycled or spit into your gut. All right, so LDL, low density lipoproteins are higher in cholesterol, lower in triglycerides, taken up by cells after binding to receptors and that's gonna be the key. Like the entire role that your diet plays in your cholesterol levels is the receptors. How well are the LDL receptors working? All right, HDL, high density lipoproteins they carry cholesterol back and I've already said that's called reverse cholesterol transport. So we'll come back to those receptors when we talk about wire saturated fats, raising cholesterol, et cetera, et cetera. All right, so what did triglycerides do? Why do we need fat? So it's actually your, like it says here, provides the cell with energy, virtually unlimited ability to store fat. We probably don't like to hear that but there is virtually an unlimited ability to store fat energy and it's also your body's primary fuel at rest. A gram of fat is nine calories, a pound of fat is 3,500 calories of the stored energy. So fat is a phenomenal energy source. The downside, so we haven't really talked about this yet but so we talk about, so fat is your primary energy source at rest because fat is super energy dense. It doesn't burn very quickly though. So the more intense an activity is if you're just taking a nice leisurely walk your body can run on fat. Even mild to moderate activity, your body can primarily run on fat but then as the intensity goes up, the percentage of calories you're burning that comes from carbs has to go up. So think about it like a campfire, right? The fat is these logs, right? They'll burn for hours but they won't burn quickly. So if you want to get the fire started quickly, you add little kindling or newspaper or something. That's the carbs. So carbs don't provide a bunch of energy but they burn really quickly. Fat provides tons of energy but it burns pretty slowly. So that's kind of the relationship between fat and carbs when it comes to fuel. Add a post-tissue, store as body fat. That's gonna be your fat tissue. Does secrete hormones, right? We now know that fat is basically an endocrine organ and the more fat you have, especially visceral fat around the abdomen, the more inflammatory it is, the more of these chemicals that are being released but your fat cells do release hormones that kind of tell your brain about how much energy you have stored but this can be a bad thing if there's too much of it. Fat cells also release an enzyme called aromatase that turns testosterone into estrogen. All right, other uses of fat in the body. So insulation, shock absorption, like you have a fat pattern on your kidneys, behind your eyeballs, et cetera. Cell membrane material, the phospholipid bilayer of your cell membranes and cell signaling pathways. We have fat soluble hormones. We have the local hormones and then we also have other hormones that are made out of fat. We talked about them earlier. The steroid hormones like testosterone and cortisol. All right, so your essential fats. So what's the term essential mean? You have to eat these because your body can't make them or can't make enough of them so they have to be supplied from the diet. So out of all the fats, your body can make oleic acid. So your body can make olive oil. Your body can make saturated fats. What your body can't make is these two. The omega-6 fats, your body can't make arachidonic acid which is an omega-6 fat and it can't make enough EPA and DHA. Really it can't make linoleic acid that becomes arachidonic acid and it can't make the omega-3 fats that become EPA. But what we care about is the end result here. And the reason it can't make them is we don't have the enzymes to produce fats that are this long. You see that these are 20 carbons long. So that's the reason that they can't be made and have to be consumed in the diet. All right, so they're, what do you need to know about this? So the essential fatty acids are linoleic acid and linoleic acid but then our body uses those to make the fats that we see here at the bottom. So arachidonic acid is the key omega-6 fat that's produced. The omega-3 fats we have, EPA and DHA. So EPA is E.Cosa pentanoic acid. I'm not asking you to know that but it just tells you about its structure. And DHA is Dacosa hexanoic acid. But EPA and DHA are what we consider our fish oils. So we need both of these and I know sometimes we talk negatively about the omega-6 fats but you have to have them. But the omega-6 fats generally, let me show you here on the next slide, they do produce these chemical messengers that are like hormones. And the ratio of the two is important because the omega-6 fats produce more chemical messengers that cause inflammation that are pro-inflammatory. And the omega-3 fats produce more chemical messengers that are anti-inflammatory. So you're basically looking at a ratio of inflammatory to anti-inflammatory chemicals. And we need both, inflammation is important. We just don't need too much of it. So I'd say the typical American is consuming too many omega-6 fats and not enough omega-3 fats. So fixing that ratio is the key. You don't need to consume salmon every day and take 10 fish oil pills but you do need to slightly increase your omega-3 fat consumption and then look for ways to maybe trim out some of the excess omega-6 that are being produced. But over deficiencies are pretty rare because we don't need a ton, as you'll see, we just need them to be a small fraction of our calories. Like if you eat any processed and packaged foods, use any vegetable oils, then you're getting the omega-6 fats you need. Even people that don't ever eat salmon or deep sea fish or those kind of things, they're usually getting little tiny bits of the omega-3 fats. So they're not over deficiencies but the average American is not consuming enough omega-3 fats for sure. Oh, let's go back to... Okay, I do want to say, so this conversion, though, this is what I mentioned earlier, that this conversion from the essential fatty acid to EPA is pretty poor. So I do recommend, especially if you consume animal products, that you consume something like salmon or sardines or anchovies or maybe you take some fish oil pills. And if you don't consume animal products, you can buy fish oil pills that you can buy DHA that comes from algae. So I do recommend trying to get some of this preformed, the EPA and DHA. And that's because the conversion, the numbers every study is a little different, but the conversion from that little enic acid to EPA is maybe 5% and the conversion and probably less. The conversion of EPA to DHA is maybe under 2%. So yes, you can eat flax seeds and chia seeds to get your omega-3 fats, but that conversion is pretty poor. And in some people, it's worse than others. So I do recommend when possible if you actually can get the preformed EPA and DHA. So if you're going to the health food store and you're like, should I buy, sorry, my bag fell on me, should I buy flaxseed oil pills or fish oil pills? I'd recommend the fish oil pills. I'm just saying, this conversion is kind of tough. So it makes more sense to try to get it in the preformed status. And the DHA, the algae-based DHA works really well. If you're a vegetarian, you're a vegan, those are phenomenal options. All right, so lipid metabolism now. So we can store fat as fat, which kind of makes sense, right? We can store anything as fat. Any excess calories can be turned into fat, but when we use, so we can store fat as fat and use it for energy later, or we can use it for energy. So here's a couple of important enzymes that are needed for fat metabolism or lipid metabolism. So we have lipoprotein or lipoprotein, lipase and hormone-sensitive lipase. So lipoprotein lipase is the one that actually will tear apart triglycerides and then dump the building blocks into the cells. So lipoprotein lipase is how we get fat into our cells, into our fat cells, into our muscle cells, et cetera. Hormone-sensitive lipase is the enzyme that breaks down fats and dumps them into your bloodstream. So this one, you might, maybe you have a part of your body, a problem area where you can't get fat to go. You know, you're trying to get rid of the fat at the bottom of your abdomen or on your thighs or somewhere. So you go on a diet and you lose weight and you're like, why am I losing fat where I don't want to lose it from? But it's sticking around where I want to get rid of it. So you can't really spot-reduce fat and the reason that happens, so like, yeah, I'm losing weight and my legs are losing fat faster than my abdomen. I don't like that, but I can't change that either. And it has to do with these hormones. So there must be more hormone-sensitive lipase in the fat that's in my legs because my body can release that as energy easier than the fat that's in my abdomen. So that's why everyone has different areas where they accumulate fat and different areas where they release it when they lose weight because of these enzymes. All right, how much of the body's ongoing energy is supplied by fat during times of rest? The answer is 60% and it can be higher than that, but yeah, 60% give or take. So that's why I say that fat is your primary fuel at rest, but as exercise intensity increases, fat contributes less and carbs contribute more. So that's why the intensity of the activity that you're doing should determine the fuel mixture that you're consuming because it's gonna determine what your body's using. All right, finally to the health effects. Health effects and recommended intakes of saturated fats, trans fats and cholesterol. So the current American diet has an excess amount of solid fats or your trans fats and your saturated fats. So heart disease, so let's look here. Elevated LDL cholesterol is a risk factor. Saturated fats increase LDL cholesterol. Trans fats increase LDL cholesterol and then we'll look at other fats that decrease them. So why do they do that? Pretty much all of the effects that your diet have on your LDL cholesterol levels have to do with the LDL receptors. So the LDL receptor is where that APOB protein, I talked about earlier, where it docks and then it dumps its payload into your cells. So if an LDL receptor grabs an LDL cholesterol and uses it, then it's taken out of your bloodstream. So if you have more LDL receptors and they're more active, your LDL cholesterol in your blood will go down because your cells are taking up this cholesterol. If you have less LDL receptors or they're less active, then your cholesterol will be high. So for example, there are people that have a genetic condition or several of them called familial hypercholesterolemia. So there are some people that have high cholesterol because of their genes and they actually have, they have less receptors. So they have less LDL receptors so their blood cholesterol is higher. Let's say, so a typical person that has a familial hypercholesterolemia, they'll have half as many LDL receptors, which means their LDL cholesterol is gonna be like two and a half or three times higher than it should be. So if you want lower LDL cholesterol in your blood, then you need your receptors to work better and if your receptors aren't working while your cholesterol goes up. So what are some factors here? Saturated fat decreases LDL receptor activity, which is why saturated fat causes cholesterol to go up in your blood. Trans fats, even worse. They shut off, they shut down the LDL receptor activity so your cholesterol goes up. So saturated fats and trans fats cause LDL cholesterol to go up. Insulin resistance. So if you're becoming insulin resistant, if you're diabetic or pre-diabetic, that's gonna decrease LDL receptor activity, causing your LDL cholesterol to go up, which you don't want, right? The more of it's in your blood, it's basic diffusion. The more cholesterol there is in your blood, the more of it's gonna be driven into your blood vessels. What else can do that? Thyroid hormone. So if you don't have enough thyroid hormone, your LDL receptor activity will be decreased. In some countries, they actually treat borderline high cholesterol by giving people thyroid hormone. So insulin resistance, thyroid hormone, saturated fat and trans fats, those are a lack of thyroid hormone, sorry. Those are all things that are causing cholesterol to go up. Mono-insaturated fats, they will increase activity a little bit, so they'll cause LDL cholesterol to go down, but the polyunsaturated fats are the ones that increase LDL receptor activity the best and cause your LDL cholesterol to go down. So this is why one of the most important things they look at when they're looking at your risk of heart disease is your polyunsaturated to saturated fat intake ratio. So if you have high cholesterol right now, and let's say that 20% of your calories are coming from saturated fat, if you drop that from 20% to 10%, and you replace that, the fat you were getting from your rib eye with nuts or something that has mono- and polyunsaturated fats, you improve that ratio and your cholesterol will go down. Other ways to get your cholesterol to go down you've already talked about is fiber. So to me, the big things is consuming less trans fats for sure, there's no healthy limit, no healthy level of trans fats. So you want your trans fats to be near zero. Saturated fats, I think they can be a part of a healthy diet, but you definitely don't want to get, when your saturated fat intake is reaching 18% of your total calories per day, that's when you start to see a real increase in heart disease risk, but the government recommends 10%. So even 10% of your calories can come from saturated fat. And then, so if you bring your saturated fat down to a normal level, not eliminating it, you get rid of trans fats because they just suck. You increase your mono- and saturated polyunsaturated fats, you increase the fiber, which traps that bile and pulls cholesterol out of your body and you stop eating added sugar and you stop having insulin resistance, all those things will promote a healthy cholesterol level. All right, so those are the big ones that I would say. So if you're looking at your blood lipid panel, those are some things I would look at. Now, if you're real worried about it, I would also get that ApoB test, that's A-P-O space, the letter B. All right, so other conditions here just about done, fat links to cancer and obesity. What's interesting is dietary fat is linked with certain cancers, but it's promotion, not initiation of cancer. So like it makes cancer that's already around worse. It's hard to really get the link here between dietary fat and cancer risk because a lot of times when people's diets are high in fat and especially saturated fat, they're eating a lot of other unhealthy foods too and it's really hard to tease apart the relationship here, but the key thing is that it does appear to promote cancer more than initiate it. Obesity is just that, you know, fat's got a lot of calories, right? There's nine calories in a gram of fat. So if you're trying to cut calories from your diet, the simplest place to do it is to cut fat, but if you're trying to cut calories, you can cut it from pretty much anywhere. I wouldn't recommend cutting them from protein though. All right, so the recommended intakes. What's the government's recommendations based on our dietary guidelines for Americans? The acceptable macronutrient distribution range, or AMDR for fat, is 20 to 35% of daily energy from your fat. Less than 10% should come from saturated fat and again, definitely staying under that 18% number. As little trans fats as possible, close to zero as possible, you avoid that. Just look for foods that say they have zero trans fats. Look for foods that don't have hydrogenated or partially hydrogenated vegetable oils. That's getting easier and easier to do because we're phasing them out. Cholesterol, so they changed the recommendations here. This is a little as possible, but honestly, in the European Union and stuff, they don't worry about it at all. I think for most people, if you consume dietary cholesterol, it'll cause maybe a temporary or transient changing cholesterol at best. Dietary cholesterol doesn't appear to be the big problem for the huge majority of people. The reason they still recommend avoiding these foods that have a lot of cholesterol is because they also have a lot of saturated fat. Usually, things like eggs and stuff, but I'm a big fan of eggs actually. But keeping within these recommendations, I'm still not getting too much saturated fat. Avoid getting too little fat. So you see here the recommendation is a teaspoon of fat with every meal. Gotta make sure you're getting enough fat to produce hormones and you've gotta make sure you're getting the essential fatty acids because by definition, they are essential. All right, health effects and recommended intakes of the monoinsaturated and polyunsaturated fats. So here we see just this is just showing how you can replace, I mentioned this already, you change that ratio, the P to S ratio, which is called by removing saturated fats, replacing them with unsaturated fats, and because of LDL receptor activity, your LDL cholesterol should go down. Now how far it goes down will depend on you, probably how much saturated fat you're eating to begin with. Like if you drop your saturated fat intake from 15% to 10% of calories, you probably won't see a huge difference, but from 20% to 10% you will. If you drop it from 10% to 5%, it'll barely move the needle, right? It just depends on kind of where you're starting. And then also genetics, right? At some point, you can pull every dietary lever that exists and your cholesterol will still be too high. That's why there's drugs and that's why there's other things. All right, so we already talked about 20 to 35% of calories coming from fat. The linoleic acid is the one that becomes the omega-6 fat. And I did, now I see there was actually a type on one of the slides earlier, it showed both linoleic acid. Linoleic acid is the precursor fat, the essential fatty acid, that we need to make the omega-6 fats. And that should be 5 to 10% of your daily energy. Linoleic acid is the essential fatty acid that we use to make our omega-3 fats like REPA and DHA. That should be 0.6 to 1.2% of daily energy. So a very, very small number, right? It's like a bit, a decent size serving of salmon two times a week would probably get you there. All right, so from guidelines to groceries, what do we do? I mean, we, you, this is something we haven't talked about yet, but you need fat. One of the reasons you need fat in every meal is to absorb the fat-civil vitamins. I generally recommend, there's no magic number, but from what I've seen, I generally recommend making sure you get eight grams of fat in every meal. That's not a huge number at all. Because without dietary fat, you won't release bile and you won't absorb fat, and if you're not absorbing fat, you can't absorb the fat-civil vitamins, A, D, E, and K. So I definitely recommend getting eight grams of fat per meal. Fat does make food taste good, right? You'll notice that you look at a lot of the reduced fat foods that are out there. They don't taste as good. And they also, when they remove fat, they add sugar, right? So sometimes your reduced fat options are the same number of calories or really close. Just be careful with that. Changing your dietary fat, obviously, you look at buying leaner cuts of meat will decrease your saturated fat intake and maybe eating some more nuts, these types of things. So there, now, I want to talk about milk and milk products, dairy products. So yes, dairy products have saturated fat, just like ribeyes do, but studies have shown that dairy fat doesn't affect cardiovascular disease risk the same way that meat fat does. So if you're really worried about cardiovascular disease, but you want to consume some animal products because of the protein and calcium, et cetera, dairy fat does appear to be better for you, especially like your fermented dairy products. There is less risk or it may be none. And in some cases, it's beneficial to be consuming dairy fats. And that's not the case for your fatty cuts of meat. Just nothing to keep in mind. All right, read food labels. We talked about that. Fat replacers, we really haven't talked about them much because they're not very big anymore. And it wasn't college like olene and olestra and those things existed, but they cause a lot of problems, right? There are still some dietary things or there are supplements that help people lose weight, that impact fat digestion. So there are supplements out there that try to block fat digestion. But just remember, if you don't digest fat, it's gonna travel through you. And if it gets to your large intestine, it's going to be partially digested by some microbes and it's gonna lead to gas and bloating and diarrhea and things like that. So keep those in mind. All right, we are done. Now the lesson is in that you should have learned to recognize the chemistry of fatty acids and triglycerides and the difference between saturated and unsaturated fats. I think you've done that. Describe the chemistry, food sources and roles of phospholipids and sterols. Cover that. Summarize fat, digestion, absorption and transport. Got all that. Now the lesson is in, outline the major roles of fat in the body, including a discussion of essential fatty acids and the omega fatty acids. Explain the relationship among saturated fats, trans fats and cholesterol and chronic disease, did that and then the last one there. So okay, very important chapter. The quality of fats you eat, super, super important. I hope this helps. We'll cover protein next. Have a wonderful day. Be blessed.