Coffee Science: A Clinician's Guide to a Beloved Bean

Jeanette Brooks: Welcome to Medicine With a Fork, a podcast from the educational nonprofit Gaples Institute. I'm Jeanette Brooks, the Director of E-Learning Experience, and with me today is Dr Steven Devries. He's our Executive Director, and he's also a preventive cardiologist. Welcome, Steve.

Dr Stephen Devries: Thanks, Jeanette. Great to be with you.

Brooks: Good to be with you too. So, those who have listened to our podcast before probably already know that the Gaples Institute's mission is to advance the role of nutrition and lifestyle in medicine. And for that reason, today's topic might seem a little bit surprising, because we're talking about coffee—which, maybe we don't necessarily think of coffee as relating to a healthy lifestyle. So, Steve, we certainly know that coffee is a huge part of our culture, but what do we know about coffee and health? Is this really a health topic?

Devries: For sure it is. And I have to say that many people, myself included, consider themselves to be coffee lovers. And fortunately, coffee loves us right back. And here's the data: with consumption of up to four cups of coffee, comparing to non-drinkers, there's a 29% reduced risk of all-cause mortality over a seven-year period. A 15% reduction in all cardiovascular disease. And there is a reduced risk even of developing type 2 diabetes: down 29% by the highest consumers of coffee compared to those who drink none at all. And, there's very surprising data showing very recently that coffee is associated with a reduced risk of developing both acute and chronic kidney disease.

Brooks: Okay, that is impressive. I did not know that about the kidney benefit. That is surprising. And I can see all the clinicians out there doing a fist pump with their coffee cup in their hand! So what's the secret sauce in coffee that is so helpful? Is it about the caffeine or is it something else?

Devries: For sure caffeine is thought to be one of the contributors to the health benefits. It's in the methylxanthine family, like theophylline, and it's an adenosine receptor antagonist. But beyond caffeine, coffee—and tea for that matter—have a really wide range of polyphenols. These are plant-derived chemicals that act both as anti-inflammatories and antioxidants. Perhaps the best of all studied in coffee is chlorogenic acid. It's a potent anti-inflammatory and antioxidant also found in peaches and eggplants.

Brooks: Oh, interesting. So we're putting coffee right up there with peaches and eggplant; that's starting to feel pretty healthy, right?

Devries: It's sounding better all the time!

Brooks: Yeah this is some good news! So about the caffeine though, could you tell us a little bit about how the body handles caffeine?

Devries: Well, caffeine is very rapidly absorbed after drinking. Typically in about 45 minutes. Metabolism is primarily in the liver with the Cytochrome P 450 system. And about 90% of it takes place by CYP1A2. Now, what's really interesting is that there are polymorphisms of CYP1A2 that account for the wide variation that everyone knows is present in the metabolism of caffeine by different individuals. And the reason you know that is when you go out for dinner sometimes with people, there are some people who can order caffeinated coffee in the evening and still sleep well, and others couldn't dream of doing that.

Brooks: And I'm definitely in the latter group. So while we're focusing on caffeine, just how much caffeine are we talking about in coffee?

Devries: Well, it depends on the type of coffee and how it's made. A small drip coffee, 8 ounces, has anywhere from about 90 to say 150 milligrams of caffeine. On the other end, an extra-large 16-ounce drip coffee from, say, a popular national coffee chain has up to 310 milligrams of caffeine. So, it's quite a wallop. Now what's interesting, people consider espresso to maybe have a high caffeine content, and because it's a smaller volume, actually a single shot of espresso has only 75 milligrams of caffeine – that's less than a typical 8-ounce cup of drip coffee. So if you have multiple shots of espresso they can certainly add up, but a single shot of espresso, less than a small cup of drip coffee. Beyond the coffee and tea world, a can of cola beverage has about 34 milligrams of caffeine. So, still significant.

Brooks: And I'm actually glad that you brought up the cola because it made me think about energy drinks. I know that those aren't coffee, but they're definitely high in caffeine and I know there's some concern about them, right? Especially since they seem to be especially appealing to young people.

Devries: For sure. And what they do in some of the energy drinks is put in a couple of ingredients at least that are known to rev people up. So for instance, a 12-ounce can of a popular energy drink has about 110 milligrams of caffeine—about the same as in a small cup of coffee. But in addition, there's lots of added sugar. In fact, there's about the same amount of sugar in one of these 12-ounce popular energy drinks as there is in a can of a cola beverage. So you put those two together and you've got a pretty potent force. And then there's these energy shots—these small, concentrated, say about two 2-ounce shots—and they can be loaded with over 200 milligrams of caffeine. About twice of what you'd find in a small cup of coffee.

Brooks: Wow. Just for one gulp. A little tiny gulp.

Devries: Exactly. And what's even worse is that unbelievably, some public schools are loading up their vending machines with these energy drinks. I've seen it myself and it's an especially bad idea because, not surprisingly, the combination of caffeine and added sugar is linked to increased risk-taking, especially among teenagers.

Brooks: As if families of teenagers need more risks to be concerned about, right? It's definitely something to avoid. Earlier you mentioned that the preparation method can affect the caffeine amount in coffee. Does it also affect any of its health benefits?

Devries: Yes, for sure. There are differences in how coffee is prepared. And one of the key ones is whether it's prepared with a paper filter or not. So the standard drip coffee, where you use a paper filter, that is good to go. But the unfiltered coffee, such as that you might make with a French press, or Turkish-style coffee, or even espresso—although it's typically served in much smaller amounts—these unfiltered coffees are associated with a small, but still significant, increase in blood levels of LDL cholesterol. And the reason is that the filtering of coffee removes a lot of a particular chemical called cafestol. And this cafestol is a compound that's naturally found in coffee that raises blood cholesterol, but fortunately is removed largely by paper filters.

Brooks: So it sounds like if given the choice, a filtered coffee is better than say a French press coffee.

Devries: I'd say for most of your consumption, yes. That would definitely be true.

Brooks: And Steve, you mentioned also that both coffee and tea have these helpful polyphenols. How is the caffeine content in tea? It's less than coffee, right?

Devries: Yes, for sure. For instance, a small black tea, 8 ounces, has about 40 milligrams of caffeine. And green tea, even less. The same size is about 30 milligrams. And herbal teas, like ginger and chamomile, typically have no caffeine at all.

Brooks: Okay, so tea might be a good alternative for people that are a little bit sensitive. But even for people who tolerate caffeine well, we know that it's possible to have too much of a good thing, right? How much caffeine is too much?

Devries: Well, the FDA cites 400 milligrams as the daily maximum for caffeine, but of course we need to acknowledge that many people are especially sensitive to caffeine and for any given person, much lower intake than 400 milligrams may be needed to avoid some of the adverse effects, which can be nervousness and anxiety, and of course, difficulty sleeping.

Brooks: Right. And are there some patients who, even beyond just this this idea of sleep or the jitters, are there some people who really need to be medically concerned about their caffeine intake?

Devries: Yes, pregnant women should be concerned about their caffeine intake. The American College of Obstetricians and Gynecologists recommends limiting caffeine intake to less than 200 milligrams a day. And that translates to between one and two small cups of caffeinated coffee per day. But after saying that, it's also important to acknowledge that there is some more recent data that has come forward that suggests that perhaps even this amount, 200 milligrams, may be associated with an increased risk of an adverse outcome in pregnancy. So of course the very safest strategy would be to switch completely to decaf during pregnancy. But absolutely it's a topic that should be discussed with one's individual obstetrician.

Brooks: And if you do switch to decaf, obviously the caffeine mostly goes away when you drink decaf, but are the health benefits still there? Does decaf still give us some of those benefits that you spoke of earlier?

Devries: Yes, there are definite benefits even for drinking decaf, and the data is pretty clear on that. And it really supports the idea that it's not only the caffeine responsible for the health benefits, but it's this wide range of polyphenols. And fortunately, the polyphenols in decaf are present almost as concentrated as in fully caffeinated coffee. So that's the good news: decaf is still on target for good health benefits.

Brooks: Okay, good to know. And if somebody switches instead to tea to avoid or reduce their caffeine, what do we know about the health benefits of tea?

Devries: Well, tea lovers are also in good shape because there are a host of health benefits also associated with tea, including reduced risk of cardiovascular events and a reduction in cardiovascular disease mortality. The reason is thought to be the very high level of a special class of polyphenols found in tea called flavonoids, and in particular there are flavonoids called epicatechin and catechin; these are especially powerful anti-inflammatory and antioxidant agents.

Brooks: Now, before we wrap up today, I have to ask, what is your take on all of these fancy coffee-shop drinks that we see everywhere, the mochas and the pumpkin spice lattes and stuff like that?

Devries: Maybe the word is if the drink is described by more than five words, probably not a good idea, but actually a lot of these coffee-shop creations are just loaded with extra sugar. In fact, a 16-ounce drink of many of these that you were referring to can top out at over 400 calories. For sure the best plan is to stick to plain unadulterated coffee with as little as possible of anything added, but especially without a lot of added sugar.

Brooks: That sounds like really good advice, Steve, thank you so much for brewing up some coffee knowledge for us this morning. We really appreciate it.

Devries: It was really fun. Thanks Jeanette.

Brooks: And for clinicians out there who want to learn more about nutrition science and how to guide your patients toward a healthier diet, we invite you to check out NutritionForDocs.org. That's where you'll find the Gaples Institute's condensed nutrition science course specifically for health professionals. It's a self-paced course, it's four hours of CME, and AMA members do receive a discount. And we also invite you to follow the Gaples Institute on social media and stay connected with us that way. Thanks for joining us today. Steve and I are raising our coffee cups to you, and we look forward to joining you next time on Medicine With a Fork.

© Copyright 2022 - Gaples Institute

Disclosures: Dr. Devries is the salaried executive director and Jeanette Brooks is the salaried director of e-learning for the Gaples Institute, an educational nonprofit that offers accredited continuing medical education courses for sale to health professionals. Courses are developed entirely through philanthropy to the Gaples Institute, a nonprofit that does not seek or receive corporate support. Neither Dr. Devries nor Jeanette Brooks receive royalties or personal consideration of any kind from the sale of these courses. This podcast was developed with no corporate support.