 When we talk about carbohydrates in the diet, we're usually talking about foods that are rich in either starch, so starchy foods, and another phrase for that is complex carbohydrate. I'll just write complex carbs for short. And these also have another name, and that name is polysaccharide and the name comes from the fact that starchy foods are made up of many sugars, so poly and saccharide, poly meaning many and saccharide is another chemical name for sugars, and those sugars are linked together by chemical bonds. Now, the other kinds of food that come to mind when we're talking about dietary carbohydrates are simple carbs or simple sugars, and the simplest simple sugars are single-unit sugars called glucose. You might have heard of this one, fructose, I'm sure you've heard of this one, and you probably know that this is the kind of sugar that is found in fruits and also galactose. So these three are called monosaccharides. Mono meaning one and saccharide meaning sugar, so these are single sugars. Now when glucose and fructose are combined or linked together, they form another kind of sugar that I'm sure you've heard of called sucrose, and that is regular table sugar. So interestingly, table sugar has gotten kind of a bad rap in recent years. It's even been called a toxin in our diets by many scientists, and the truth is that the way in which we consume sugar, much, much too much of it, in many cases, it does make this kind of sugar into a toxin. But you might be surprised to hear that most of the excess sugar in the average Western diet is from processed food. So things like sugary cereals or sodas, and these often have huge amounts of sugar added to increase their palatability, to increase their taste, or to increase the shelf life of packaged foods. But actually, if we use sugar in moderation, if we don't drink the big two liter soda every day, and we use small amounts of table sugar, it's probably okay for individuals who are healthy individuals who have no medical conditions. It's probably okay to have a small amount of sugar in our diets. Moderation is the key. Okay, back to our discussion of simple sugars. The other two-unit sugar that you may have heard of is called lactose, and it's a combination of glucose and galactose. It's the sugar found in milk, and some people have a hard time digesting it. What happens then is that the lactose passes through the part of the gut where it's supposed to be absorbed, and that part is called the small intestine, and it gets digested in the large intestine. I'll just write initials here for these parts of the gut, but it goes into the large intestine where it gets digested by gas-producing bacteria in the large intestine instead. That's why people with lactose intolerance can feel sometimes bloated and uncomfortable if they drink regular milk that's quite high in lactose. Okay, so these two, sucrose and lactose, are examples of disaccharides or two-unit sugars. Now, both of these types of carbohydrates give us energy. They give us four calories, and I'm writing calorie with a capital C because that's actually a kilo calorie, but anyway, these guys give us energy. Now, there's another type of carbohydrate, also a type of complex carbohydrate that gives us no energy because our bodies can't break it down, but it's important, and it's called dietary fiber. There are two kinds of dietary fiber. There's soluble fiber and insoluble fiber, soluble fiber. You might have guessed it from the name. It dissolves in water. It's believed to support the health of the intestinal walls or the walls of the gut, and there's also evidence that it might help regulate cholesterol levels, also a good thing for many of us. Insoluble fiber doesn't dissolve in water, but instead it absorbs water, kind of like a sponge, and because it absorbs water, it acts as a stool softener. It prevents us from getting constipated, and it also speeds up the passage of food through the intestinal tract or through our digestive system. By the way, fiber is also a polysaccharide, but our bodies can't break these bonds, so it doesn't give us any energy. Now, both types of fiber are found in fruits and veggies. When we choose things like brown rice over white rice, or when we choose whole grain bread over white bread, we're basically making a choice that increases the amount of fiber that's connected to our starchy carbohydrates. And this is better for our health, and will also prevent us from getting hungry again too quickly, so it's a good thing to do.