 What's the best way to stay healthy in the face of so much conflicting nutrition information? Well, ideally you would go to the source, the gold standard, the peer-reviewed medical literature, and read through the stacks of the latest medical journals. But who's got time for that? I do! Welcome to the Nutrition Facts podcast. I'm your host, Dr. Michael Greger. Today we look at the pros and cons of coffee for the liver, mind, and brain. And we start by asking which coffee is healthier—light roast or dark roast? For those drinking non-paper-filtered coffee like boiled French press or Turkish coffee, the amount of cholesterol-raising compounds in the lightest roast coffee may be twice as high compared to using very dark-roasted beans. So it appears some of the cholesterol-raising compounds are destroyed by roasting. So in this case darker would be better, or you can just use a paper filter and eliminate 95% of the cholesterol-raising activity of coffee regardless of the roast as I've described before. But I did another video showing dark roasting may also destroy up to nearly 90% of the chlorogenic acids, which are the antioxidants and anti-inflammatory phytonutrients purported to account for many of coffee's benefits. So in that case, light roast would be better. On the other hand, dark roasting can wipe out up to 99.8% of pesticides in conventionally grown coffee and more than 90% of a fungal contaminant called ochrotoxin, which is a potent kidney toxin found in a wide range of food ingredients that can get moldy. But then what about the polycyclic aromatic hydrocarbon products of combustion that are suspected to be carcinogenic and DNA-damaging darker roasts may have up to four times more than light roasts. Thus they advocate controlling roasting conditions to cut down on these combustion compounds. Just to put things in perspective, even the darkest roast coffee might only max out at a fraction of an anagram of benzopyrin per cup, considered to be the most toxic of these compounds, whereas a single medium portion of grilled chicken could have over a thousand times more. Overall, you don't know if light versus dark roast is better until you put it to the test. This study found that dark roast coffee is more effective than light roast coffee in reducing body weight. Folks were randomized to a month of drinking two cups a day of light roast coffee or dark roast coffee, roasted from the same batch of green coffee beans. And in normal weight subjects, it didn't seem to matter, no significant weight changes either month. But in overweight study subjects, they ended up about six pounds lighter drinking dark roast coffee compared to light roast coffee, more than a pound a week lost just drinking a different type of coffee. What about light versus dark in relation to blood sugars? We've known since 2015 that even a single cup of coffee can affect the blood sugar response. What is not known is whether this increase in blood sugars is actually clinically meaningful. I mean, after all, coffee consumption does not seem to increase the risk of diabetes. And if you compare light roast coffee to dark roast coffee right before chugging down about 20 teaspoons of sugar, there didn't appear to be any difference. Perhaps the take-home message is light or dark, maybe we shouldn't be adding 20 spoonfuls of sugar. And finally, what about the effects of different roasts on heartburn and stomach upset? We know that coffee consumption is sometimes associated with symptoms of stomach discomfort. And so researchers stuck pH probes down in the people's stomachs to measure the amount of stomach acid generated by different types of coffee. The way you chart stomach acid secretion in the stomach is called a gastrogram. You basically give people some baking soda, which starts out alkaline, and measure the pH in the stomach to see how long it takes the body to restore the stomach back into an acid bath, about 15-20 minutes. But if you mix that same amount of baking soda with dark roast coffee, it takes longer, meaning the dark roast coffee is suppressing stomach acid secretion since it takes longer to normalize the pH. Give people more of a medium roast coffee, though, and we see a dramatically different effect. In acceleration of stomach acid secretion, returning the stomach to acidic conditions three times faster than drinking dark roast coffee. Hence the title, Dark Roast Coffee, is less effective at stimulating stomach acid secretion compared to a medium roast coffee. But you don't know if that translates into symptoms, clinical effects, until you put it to the test. The most commonly used coffee bean roasting process is referred to as convection or flash roasting, which just takes a few minutes. An alternative method is conduction roasting, which roasts at a lower temperature for longer time hours, and this results in so-called low acid coffee. And supposedly, there are anecdotes from coffee-sensitive individuals suggesting that this low acid coffee does not precipitate or aggravate heartburn. When you look up that citation though, they just cite data from the pure roast coffee company, makers of low acid coffee. It should therefore come to no surprise that it was the same company that funded the study. If you go to their website, they claim that the health benefits associated with drinking pure roast low acid coffee will become almost immediately obvious to those who suffer from acid reflux, heartburn, or indigestion, with over 90% of customers surveyed receiving symptom relief, and so they decided to put their money where their mouth was. But before I get to the results, I mean it's important to realize that when they say low acid, they're not talking about stomach acid, they're talking about roasting so long that they destroy more of the chlorogenic acid within the coffee bean. You know the antioxidant polyphenol phytonutrient chlorogenic acid. You know the anti-diabetic anti-cancer, anti-inflammatory, anti-obesity antioxidant. But hey, I mean if it causes less stomach discomfort, maybe it's worth it? 30 coffee-sensitive individuals completed a randomized double-blind crossover study in which the symptoms of heartburn, regurgitation, and stomach upset were assessed following the consumption of the pure roast brand low acid coffee, versus conventionally roasted regular Starbucks coffee. And to the funder chagrin, no benefit whatsoever was found with the low acid coffee. Consumption of both coffees resulted in heartburn, regurgitation, and stomach upset in most individuals. So much for that ridiculous 9% of customers' claim. No significant differences in the frequency or severity of heartburn, regurgitation, or dyspepsia were demonstrated. Between the two coffees, either in a fasting state or after a test meal, they couldn't find any way to make the low acid coffee look better. So they had this initial thought that a difference in coffee acidity, explained that companies' claims, however, when put to the test in a randomized controlled study, they found no difference in symptoms, suggesting the whole coffee acidity thing doesn't explain the sensitivity some people have. And I think further acts as a reminder that we should never believe claims made by anyone trying to sell us something. In our next story, we discover new data that suggests even paper-filtered coffee may raise LDL cholesterol. In a video I did a decade ago, I explained that the cholesterol-raising factor in coffee does not pass through a drip coffee paper filter, give people French pressed coffee, which is filtered, but without paper. And their cholesterol swells up over time, starting within just two weeks, but switch them to paper-filtered coffee, and their cholesterol comes right back down. Same amount of coffee, but just prepared differently. The cholesterol-raising factor from coffee beans has since been identified as the fatty substances in the oil within coffee beans. One reason it took us so long to figure that out is that it didn't raise cholesterol in rats, or hamsters, or even monkeys, but it did in human beings. But it apparently gets stuck in the paper filter. This explains why filtered coffee doesn't affect cholesterol whereas boiled or French pressed or Turkish coffees do. Expresso as well, which has 20 times more the cholesterol-raising substance canfasthol than paper-filtered drip coffee, with Turkish and boiled coffee being the worst, though instant and percolator coffee are pretty low, even without the paper filter. Note if you make drip coffee with one of those metal mesh filters without the paper, it would presumably be just as bad as French pressed. So the studies in general appeared to consistently find that it was this fatty component that was then filtered out by paper. But a small number of studies suggested that filtered coffee may also increase cholesterol levels and began to cast some doubt into what appeared to be a fairly clear picture. So yeah, the cholesterol-raising effects brought about by the consumption of filtered coffee may not be as strong as that of boiled coffee. Maybe we shouldn't discard the possibility that filtered coffee may also play a small but important role in raising cholesterol. I know about this study where three cups a day filtered coffee raised total cholesterol, but the rise in LDL-bad cholesterol was not statistically significant. Same with stopping filtered coffee reduced total cholesterol, suggesting perhaps only partial removal, but no one had ever just measured the levels of the cholesterol-raising compounds in the paper filters until now. The results showed that most of the cholesterol-raising canvastol was retained by the coffee grounds rather than actually getting stuck in the filter itself. In other words, the principal function of the paper filter is not necessarily to block the compound itself, but to block any fine particles that are carrying the compound. Like when you make French pressed coffee, there's that fine mesh screen, but you still notice a little sludge at the bottom of the cup? That's the tiny particles that pass through and can carry some of the risk. But a little caffistol does get through the filter, so yeah, I mean you can cut out more than 90%, switching from French press or one of the metal mesh filters by using a paper filter. If you use coffee that starts out with a high level of the caffistol compound, you're still clearing out about 95% with the paper, but there may be enough left to still bump your LDL. But you don't know until you put it to the test. They started out with a high caffistol coffee. After a month of drinking two cups a day, their LDL cholesterol went up significantly, even though it was paper filter. So if you have high cholesterol, despite eating a healthy diet, you may want to try cutting out coffee and getting retested, or you can try switching to a lower caffistol coffee. There's all sorts of variables, such as roasting degree or grind size that may affect caffistol levels. One can imagine a smaller particle size would allow for greater extraction. Roasting appears to destroy some of it, so a really dark roast should have less, but there's not much difference between just like light and medium roast. And indeed, in this study, there was no significant difference between the rising cholesterol after a medium light roast versus a medium roast. They both raised bad cholesterol. Finally today, we look at the effects of tea and coffee for artery function. There are dietary guidelines for food, but what about for beverages? A beverage guidance panel was assembled to provide guidance on the relative health and nutritional benefits and risks of various beverage categories. They ranked them from one to six, and water ranked number one. Soda ranked last at number six. Whole milk was grouped with beer, with a recommendation for 0 ounces a day. In part out of concern for links between milk and prostate cancer, as well as aggressive ovarian cancer, thanks to IGF-1. Number two on the list, though, after water was tea and coffee, preferably without creamer or sweetener. Even without creamer, though, lots of unfiltered coffee can raise cholesterol levels, but the cholesterol-raising compounds are trapped by the paper filter in brewed coffee, so filtered coffee is probably better. But 10 years ago, a study was published on the effects of coffee and endothelial function, the function of our arteries. Within 30 minutes of drinking a cup of coffee, there was a significant drop in the ability of our arteries to dilate, whereas decaf did not seem to have a significant effect. This was the first study to demonstrate an acute unfavorable effect on arterial function for caffeinated coffee, but one cup of decaf didn't seem to affect performance, and two cups of decaf appeared to have a beneficial effect. So maybe it's a battle between caffeine and antioxidants, something in caffeinated coffee, appears to be hurting arterial function, whereas something in decaf appears to be helping, maybe the antioxidants. It's like the story with red wine. Dealcoholized red wine significantly improves arterial function, so there's grape components trying to help, but the presence of alcohol counteracts and erases the benefit. Drinking really high antioxidant coffee by preparing it Greek style, for example, where you actually drink some of the grounds may actually offer an advantage. That something in caffeinated coffee that appears to hurt, though, may not be the caffeine. In a randomized double blind placebo control crossover study, researchers found that caffeine alone, about two and a half cups worth, cups of coffee worth, significantly improved arterial function in both people without and with heart disease. See, coffee contains more than a thousand different components, other than caffeine, many of which are also removed by the decaffeination process. So there must be something else in the coffee bean that's causing the problem. In fact, caffeine may even enhance the repair of the fragile inner lining of our arteries by enhancing the migration of endothelial progenitor cells, the stem cells that patch up holes in our potholes in our artery walls, one could say. But how might we get the potential benefit of caffeine without the risky compounds in caffeinated coffee? Tea. Tea consumption enhances artery function. Substantial beneficial effects from both green tea and black tea. Instead of other components in tea leaves undermining caffeine's potential benefits, they appear to boost the benefit in healthy individuals, as well as heart disease patients, reversing some of their arterial dysfunction, both immediately and in the long term. Now all the measurements in this and the other studies were done on the brachial artery, the main artery in the arm, just because it's easier to get to. What we care about, though, is blood flow to the heart, and caffeine appears to impair blood flow to our heart muscle during exercise, even in healthy folks, but especially those with heart disease. Thankfully, caffeine in tea form appears to have the opposite effect, significantly improving coronary blood flow, suggesting that tea consumption has a beneficial effect on coronary circulation, though the addition of milk may undermine the protective effects. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. 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