Sunday, June 14, 2015

The verdict is in: Coffee is good for you again!

Coffee and I go way back. Some of my earliest memories are of sitting at the kitchen table with my grandmother while she ate grapefruit for breakfast and drank a cup of coffee. I would sip my own cup of what was probably 10% coffee and 90% cream. Coffee even inspired my professional path when I learned as a hospital volunteer that premature babies are prescribed caffeine citrate to catalyze respiratory development. Even today, I spend a good portion of my time either trying to get more coffee, enjoying coffee, or making plans about when I will have coffee next. Luckily, I am not alone. This behavior is well-integrated into my family, American culture, and has been a major part of the human experience since its discovery in Ethiopia around 850 A.D. Despite its ubiquity, somewhere along the way, coffee developed a bad reputation where our physical health is concerned. But, like many trends in health advice, those opinions were based on anecdotes and not evidence, and the tides are turning.
This week, I thought I would share what we know about coffee and different health risks and even benefits. Last year, there were two great articles published on this topic. The first reviews what we know about the links between coffee and health by Elvira Gonzalez de Mejia and her colleagues from the University of Illinois Department of Food Science and Human Nutrition.

In the past decade, several studies have consistently shown that drinking coffee is associated with weight loss due to increased metabolism and lipid oxidation, a 7% reduction in risk for Type 2 Diabetes, enhances memory consolidation, and is protective against the development of prostate, colon, liver, and endometrial cancers. However, there are some diseases that may be more likely in people who drink too much coffee, mix caffeine with alcohol, or who have other risk factors. For example, drinking coffee may be related to bone loss and osteoporosis later in life. The authors suggest that this association may be offset by drinking coffee with milk as opposed to black. There are other studies showing that coffee can increase cholesterol and blood pressure, which may increase risk for heart disease. There are other studies suggesting that drinking coffee can worsen pre-existing conditions, such as heart disease or anxiety. What remains to be understood in many of these studies is whether these effects are related to caffeine or specific to coffee. Coffee, compared with other sources of caffeine, actually have a number of health benefits like reducing inflammation that are independent of caffeine, especially when you avoid adding sugar.

The overall conclusion of the article was that drinking coffee can confer more health benefits than risks, but that moderation is critical. But, what is moderation anyway? The authors recommend that adults drink fewer than 400 mg of caffeine per day. A cup of coffee can range from 95-330 mg per cup, while an espresso can range between 50-150 mg. The recommendations for pregnant women and children are a bit different. Pregnant women should limit daily caffeine intake to less than 300 mg, while children and adolescents should limit their daily caffeine intake to less than 2.5 mg/ kg of weight. This means that the average 10 year old in the US, who weighs ~70 lbs or 32 kg, should have less than 80 mg of caffeine per day. Also, it's important to keep in mind that caffeine isn't only found in coffee. There are meaningful doses of caffeine in tea, chocolate, soda, and energy drinks. Kids, unlike adults, generally get caffeine from soda, which also contains high doses of sugar that contribute to risk for Type 2 Diabetes considerably.

The second article I found was a meta-analysis conducted by Alessio Crippa and colleagues at the Institute of Environmental Medicine at the Karolinska Institute in Sweden. The purpose of this study was to aggregate all of the studies that have looked at the association between coffee consumption (measured in number of cups per day) and mortality between 1966 and 2013. This ultimately included data from 997,464 individuals, 120,915 of whom had passed away. They divided their findings up into studies that examined all-cause mortality, cardiovascular disease, and cancer. They found that drinking coffee was associated with lower all-cause mortality risk compared with individuals who drank none, but the mortality related benefits of drinking coffee stopped increasing after about 4 cups per day. With respect to cardiovascular disease, similar results were observed. Specifically, mortality risk was highest among individuals who did not drink any coffee, lowest for individuals who drink 3 cups per day, and the benefits of drinking coffee taper off and even begin to reverse after 4 cups per day. Unfortunately, the same pattern was not observed for cancer, and drinking coffee was not related to any differences in cancer-related mortality.

One limitation of everything I've just shared with you is that I am unapologetically biased. It would take an enormous amount of evidence to convince me to quit drinking coffee, however I have learned quite a lot from reading these articles. Before now, I assumed that coffee was good for my own health because I enjoy it so much, and because walking to get coffee constitutes much of my daily exercise. However, these data speak to additional health-benefits that I wasn't aware of. Now obviously the most important limitation of these studies is the lack of causal associations. The only way we would know that caffeine prevents disease or causes anything is by randomly assigning one group of humans to drink coffee daily and one group to drink something else. But then we would have to follow them for the rest of their lives, and alas we are only guaranteed one life to live. In the absence of good causal data, these are enough to reassure us coffee-drinkers that if we keep our enjoyment below 400 mg per day, with some exceptions, we not harming ourselves and can continue as T.S. Eliot and measure out our lives with coffee spoons.

Crippa, A., Discacciati, A., Larsson, S. C., Wolk, A., & Orsini, N. (2014). Coffee consumption and mortality from all causes, cardiovascular disease, and cancer: a dose-response meta-analysis. American Journal of Epidemiology, kwu194.

de Mejia, E. G., & Ramirez-Mares, M. V. (2014). Impact of caffeine and coffee on our health. Trends in Endocrinology & Metabolism, 25(10), 489-492.

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