What’s the first thing you reach for when you wake up in the morning? If you’re like me, it’s probably a big, steaming mug of coffee. 85% of adults in the United States drink coffee daily — 1.5 cups on average. The effects of coffee on human health have therefore been the subject of much debate and controversy. What does the research say? Let’s take a look.
What is it?
Coffee is made from coffee beans, which are the seeds of a fruit called a coffee cherry. The two main species of coffee plants used for their beans are called Arabica (most popular, but expensive to grow because it requires very specific environmental conditions to thrive) and Robusta (more resilient and economical). Coffee beans are roasted and then ground into the fine powder that you use to make your morning cup.
What’s in it?
When most people think about coffee, they think about caffeine: the “wake up” drug. One 8-oz cup of brewed coffee has about 95 mg of caffeine. Caffeine promotes alertness by blocking the effects of a biological compound called adenosine, which accumulates in the brain throughout the day and causes drowsiness.
When you drink a cup of coffee, caffeine peaks in your blood in 15 minutes to 2 hours and can take up to 10 hours to clear. The speed at which your body metabolizes it is partly dependent on genetics but also influenced by lifestyle factors; smoking speeds up the rate, for example. Some medications slow down caffeine metabolism because they are metabolized by the same liver enzymes. These include some heart medications, antidepressants, and oral contraceptives.
Consuming more caffeine than your body can tolerate may cause unpleasant side effects such as anxiety and insomnia. If you’re a habitual caffeine drinker and stop suddenly, you may experience withdrawal symptoms such as headaches, a depressed mood, and fatigue. These symptoms usually last anywhere from 2-9 days.
While caffeine is coffee’s most famous constituent, it’s not the only one. Coffee has over 1,000 different components, including vitamins, minerals, and bioactive plant compounds called polyphenols. These substances can have a variety of beneficial effects on the body, such as bolstering the microbiome and modulating fat and sugar metabolism. They may also counteract some of the less desirable effects of caffeine and lower chronic disease risk.
What does it mean for my health?
Cardiovascular disease: Although caffeine tends to raise blood pressure on its own, studies have shown that coffee intake is not associated with long-term increased blood pressure, even in individuals with hypertension. This may be because other components in coffee counteract caffeine’s effect. Overall, research up to this point has actually shown that moderate coffee intake is associated with a reduced risk of stroke, coronary artery disease, and cardiovascular morbidity.
Type 2 diabetes: The relationship between coffee intake and blood sugar control is somewhat complicated. In the short term, drinking caffeine appears to reduce insulin sensitivity, meaning that the body is not able to take glucose up into the cells as easily. However, moderate coffee consumption in the long-term is not associated with increased insulin resistance, meaning that it is unlikely to increase your risk for diabetes. This may again be due to some of the counter effects of other compounds in coffee.
Cancer: Drinking coffee does not increase your risk of getting or dying from cancer. It may even slightly reduce your risk of getting certain cancers, such as breast cancer, skin cancer, and prostate cancer. It’s important to note here the importance of smoking status as a confounding variable. Smokers have a higher risk of getting cancer than the general population and are also more likely to be coffee drinkers, which might make it seem like coffee drinkers are more at risk for developing and/or dying from cancer. However, once you adjust for smoking status that association goes away.
Pregnancy: Some research has shown that coffee intake is associated with pregnancy loss and low birth weight, as caffeine can get through the placenta to a developing fetus. This evidence is not conclusive, but expecting mothers are advised to limit caffeine intake to 200 mg per day (the amount in approximately 2 cups of coffee).
Conclusions
The state of current evidence suggests that coffee can be part of a healthy lifestyle, with the lowest risk for chronic disease seen with the consumption of 4-5 cups/day. This doesn’t mean that you should necessarily start drinking it if you don’t already, or that this is the right amount for you. I know that for me personally, drinking that much coffee would affect my sleep and stress levels, which would obviously negatively impact my health. If you do choose to drink coffee, limit total caffeine intake to 400 mg/day for adults who are not pregnant or lactating and 200 mg/day for adults who are. Remember to practice mindfulness and pay attention to how coffee makes you feel; the amount that’s right for you will depend on your individual response.
References
Dam, Rob M. van, et al. “Coffee, Caffeine, and Health.” The New England Journal of Medicine, vol. 383, no. 4, 2020, pp. 369–78, doi:10.1056/NEJMra1816604.
Grosso, Giuseppe, et al. “Coffee, Caffeine, and Health Outcomes: An Umbrella Review.” Annual Review of Nutrition, vol. 37, no. 1, 2017, pp. 131–56, doi:10.1146/annurev-nutr-071816-064941.
Harpaz, Eynav, et al. “The Effect of Caffeine on Energy Balance.” Journal of Basic and Clinical Physiology and Pharmacology, vol. 28, no. 1, 2017, pp. 1–10, doi:10.1515/jbcpp-2016-0090.
McLellan, Tom M., et al. “A Review of Caffeine’s Effects on Cognitive, Physical and Occupational Performance.” Neuroscience & Biobehavioral Reviews, vol. 71, 2016, pp. 294–312, doi:10.1016/j.neubiorev.2016.09.001.
Nehlig, Astrid. “Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption.” Pharmacological Reviews, edited by Stephen P. H. Alexander, vol. 70, no. 2, 2018, pp. 384–411, doi:10.1124/pr.117.014407.