I’m a coffee lover. I love its smell, taste, and the ritual of starting my day with a hot mug or icy glass of java. Even after going caffeine-free several years ago (more on this below), I’ve remained a coffee enthusiast. And as a registered dietitian, I’m often asked about coffee’s pros and cons.
The good news for my fellow coffee fanatics is that the beloved beverage—which comes in at just 2 calories per 8-ounce cup—offers several health benefits. Here are six, along with a few potential issues to be aware of, and how decaf fits in.
Coffee supports happiness
One study from a few years back confirmed what many of us intuitively believe: coffee is happy juice. Researchers found that drinking coffee is linked to positive emotions, including pleasure, kindness, affection, satisfaction, friendship, calm, and yes, happiness. The findings also noted that no negative emotions were tied to coffee consumption.
Another Harvard study of over 50,000 women found that depression risk decreased as caffeinated coffee consumption increased.
Coffee contains antioxidants
Coffee beans are actually the seeds inside a small bright red or yellow fruit. Both the seeds and fruit are rich in antioxidants. In fact, one study found coffee to be the single greatest contributor to total antioxidant intake.
This is likely because 65% of American adults say they drink coffee, while only one in 10 eat the minimum recommended five daily servings of fruits and veggies. In other words, coffee becomes the top source of antioxidants by default.
Nonetheless, the antioxidants in coffee have been linked to health protection. Chlorogenic acid, a polyphenol abundant in coffee, has been shown to reduce inflammation, and it may play a key role in protection against chronic diseases, including obesity.
And just in case you’re wondering about the coffee fruit, it can be turned into compost, or dried and brewed as tea. It’s also being used in products like energy drinks, since the fruit also contains caffeine.
Coffee may reduce the risk of type 2 diabetes
A 2018 meta-analysis of 30 previously published studies concluded that coffee consumption is inversely associated with the risk of type 2 diabetes. Researchers found that chance of developing the disease decreased by 6% for each cup per day increase in coffee consumption. Scientists say the possible reasons for the link include coffee's antioxidative and anti-inflammatory effects, ability to boost calorie burning, and impact on the content and diversity of health-protective gut microbes.
Coffee is tied to lower rates of other diseases
Studies show that coffee consumption may protect against certain cancers, including breast, colorectal, endometrial, and prostate cancers, as well as heart disease and Parkinson's disease. Lifelong coffee/caffeine consumption is also associated with prevention of cognitive decline, and a reduced stroke risk.
In terms of brain health, caffeinated coffee ups alertness and may also improve memory for up to 24 hours after consumption.
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Coffee may give your workout a boost
Several studies have shown that in moderation, caffeine enhances athletic performance. The effects include improved circulation, increases in muscular strength, endurance, and power, plus reduced pain. That may help you push just a little bit harder during workouts, resulting in better improvements in muscle strength and/or endurance.
A study published in the Journal of Applied Physiology found that muscle carbohydrate stores are replenished more rapidly when athletes consume both carbs and caffeine following exhaustive exercise. Compared to carbohydrates alone, the combo resulted in a 66% increase in muscle glycogen (the storage form of carbs) four hours after intense exercise. This surge in energy reserves ups your ability to exercise harder and/or longer the next time you’re ready to get your heart rate up.
Coffee isn’t dehydrating if you’re consistent
Caffeine has long been criticized for contributing to dehydration due to its diuretic effect, which triggers fluid loss. However, newer research indicates that after about four days of consistent caffeine intake, your body adjusts, which negates the dehydrating effect. The trick is, you have to be consistent. In other words, if you sometimes have one cup of coffee in the morning, sometimes three, or if you occasionally reach for it in the afternoon, you may feel the diuretic side effects, such as headache and low energy.
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Decaf can also offer benefits
After I gave up caffeine, I began to sleep better and the evenness of my energy improved. I also felt more tuned into my true energy level, unmasked by the stimulating effect of caffeine. And fortunately, decaf still offers health benefits, such as antioxidants, disease protection (including against type 2 diabetes), and even increased alertness. So if you enjoy coffee like I do, but caffeine doesn’t agree with you, you can still reap many of its rewards in decaffeinated form.
Potential downsides to consider
How caffeine affects your body is linked to your genes. People who are genetically slow metabolizers of caffeine actually have an increased risk of heart attack, high blood pressure, and prediabetes after increasing caffeinated coffee consumption, whereas fast metabolizers do not carry these risks. For slow metabolizers, research also shows that caffeine inhibits athletic performance, rather than enhancing it.
Testing your genes for the variants that impact caffeine metabolism isn’t something you can typically request from your doctor. But research-based testing is available through a company called Nutrigenomix.
For some people caffeine can also trigger digestive irritation, including heartburn, as well as an upset stomach, anxiety, rapid heartbeat, and rebound fatigue. Finally, coffee consumption during pregnancy is linked to low birth weight, pre-term birth, and pregnancy loss.
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Bottom line advice
If you love coffee, enjoy its benefits. But aim for consistency, and don’t overdo it—drink no more than 5 8-ounce cups a day (the amount in 5 short cups or 2.5 grande cups from Starbucks). Also, avoid doctoring it up with undesirable add-ins like artificial sweeteners or large amounts of added sugar. If you drink regular coffee, don’t combine it with other stimulants, and cut off your caffeine intake at least six hours before bed to optimize sleep (even if you think it doesn’t affect you).
As with many things nutrition-related, the best advice is to listen to your body. If you suspect that caffeine is triggering some unwanted effects or limiting your performance, try decaf. And, don’t forget good old H2O, which should always remain your primary and most consumed beverage.
Cynthia Sass, MPH, RD, is Health's contributing nutrition editor, a New York Times best-selling author, and a private practice performance nutritionist who has consulted for five professional sports teams.
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