Now the Good
Remember, most of the health benefits I'm going to talk about refer to MODERATE consumption of coffee! We all know that drinking coffee increases alertness and wakefulness, but less well known is this: people who drink coffee in moderation are less likely to have Type 2 Diabetes, Alzheimer's Disease, Parkinson's Disease, heart arrhythmias, stroke, liver disease and certain cancers. Coffee can also help treat asthma and headaches and can help with weight management and enhance athletic performance. Caffeine wakes us up because it blocks adenosine receptors in the brain. Adenosine causes reduced arousal and sleepiness because it inhibits excitatory neurotransmitters in the brain. By blocking adenosine receptors, caffeine keeps the excitatory neurotransmitters working which increases mental alertness, decreases reaction time (we're faster), and improves information processing.
There are more than 15 published studies that establish that coffee consumption may help prevent Type 2 Diabetes—some research indicates that decaf helps just as much as caffeinated coffee. In this instance alone, increased coffee consumption showed greater protection (compared people who drink fewer than 2 "cups" of coffee per day, people who drank 4-5 cups a day had a 28% reduction in risk vs. 35% reduction in those who drank 6-7+ cups a day). Personally, I'd go with decaf if I were to add coffee-as-diabetes-prevention into my lifestyle. Coffee also is high in antioxidants and contains some magnesium and chromium—all of which help manage blood sugar and insulin.
There is a lot of research linking coffee consumption to decreased risk of Parkinson's disease. The benefit here seems to come from the caffeine content, though the mechanism isn't clear. A 2009 study from Finland and Sweden showed than, out of 1,400 people followed fro about 20 years, those who reported drinking 3-5 cups of cofee daily were 65% less likely to develop dementia and Alzheimer's disease, compared with nondrinkers or occasional coffee drinkers.
The reduced risk of heart disease and stroke observed with moderate coffee consumption comes from reduction in Type 2 Diabetes (a risk factor for heart disease) as well as a decrease in heart arrhythmias in men and women who drink 1-3 cups of coffee a day. Women who drink 2 or more cups of coffee a day are 20% less likely to have a stroke than women who drink none.
Moderate coffee consumption has very definitively been found to decrease risk of liver cancer and cirrhosis but the mechanism isn't fully understood. Some research indicates that coffee consumption decreases your risk of developing gall stones. The evidence isn't as strong for coffee's protection from other cancers, but is fairly consistently showing benefit in ovarian, endometrial, and colorectal cancer.
The health benefits in regard to asthma, headache, and exercise can be attributed to coffee's caffeine content. Caffeine is very similar to theophylline, an anti-asthma drug. Caffeine is also often included in migraine medication because it constricts blood vessels (this is helpful for people who get vasodilatory migraines but can make things worse for vasoconstrictive headaches). In relation to athletic performance, caffeine improves muscular work performance in all types of activities, though the mechanism is not fully understood. In a 2004 review of 39 previously published trials, Doherty et al. found that caffeine improved performance by 12.4%. Low amounts of caffeine (the equivalent of 1-2 "cups" of coffee) consumed pre-workout can help you to perform longer before tiring. In last week's post, I cautioned about the risks of dehydration from excess coffee consumption. Recent research shows that drinking 3-4 cups of coffee (300 milligrams of caffeine) does not have any adverse effect on hydration and in fact coffee can contribute toward your daily fluid intake.
My current relationship with coffee is as it always has been—love and hate. But now the tables have turned; I love coffee, but it doesn't love me back. A few years ago I did a food allergy test and found out that the main reason for all of my horrible digestive symptoms was an allergy to coffee. After 2 years avoiding each other, I think coffee and I are working things out. I now drink coffee once or twice a week and it doesn't give me any trouble. So for me, I'll have to miss out on most of the health benefits, but I can still enjoy my relationship with coffee. As for you, I'll tell you what I usually tell my patients when they guiltily admit to drinking coffee: if you NEED coffee in order to make it through your day or you don't handle stress well, then you may need to give up coffee for a while and focus on getting your adrenals in better shape. If you are just friendly with coffee, rather than codependent, keep your coffee consumption to no more than 16 ounces a day, preferably filtered and drink the good stuff!