Caffeine might also function as a pain reliever. A study from September suggested as much when its authors stumbled across caffeinated coffee as a possible confounding variable in its study of the back, neck, and shoulder pains plaguing office drones: Those who reported drinking coffee before the experiment experienced less intense pain.
The data is even more intriguing—and more convincing—for caffeine's effects as a salve against more existential pains. While a small study this month found that concentrated amounts of caffeine can increase positivity in the moment, last September the nurses' cohort demonstrated a neat reduction in depression rates among women that became stronger with increased consumption of caffeinated coffee.
But that caffeine is only mechanism behind coffee's health effects is supported by a small study of 554 Japanese adults from October that looked at coffee and green tea drinking habits in relation to the bundle of risk factors for coronary artery disease, stroke, and type 2 diabetes known together as metabolic syndrome. Only coffee—not tea—was associated with reduced risk, mostly because of dramatic reductions observed in serum triglyceride levels.
So aside from caffeine, just what are you getting in a cup, or two, or six? Thousands of mostly understudied chemicals that contribute to flavor and aroma, including plant phenols, chlorogenic acids, and quinides, all of which function as antioxidants. Diterpenoids in unfiltered coffee may raise good cholesterol and lower bad cholesterol. And, okay, there's also ash which, to be fair, is no more healthful than you would think—though it certainly isn't bad for you.
Some of the chemicals in coffee are known carcinogens, though as far as we know that's only been seen in rodents, not in the small levels we encounter in everyday consumption. Findings, on the other hand, have been supporting that coffee can protect against some cancers. When the Harvard School of Public Health visited the Health Professionals Follow-Up cohort in May 2011, it found that coffee's protective effects extend only to some types of prostate cancer (the most aggressive types, actually). In a separate study of the same population from this past July, they also found a reduced risk of basal cell carcinoma with increased caffeine intake.
The association was strongest for those who drank six or more cups per day.
That same high dosage is also effective in fighting against colorectal cancer, according to a prospective study from June of almost 500,000 adults conducted by the American Society for Nutrition. While the association was greatest for caffeinated varieties, decaf made a small but significant showing. A meta-analysis of 16 independent studies this past January added endometrial cancer to the group of cancers whose relative risk decreases with increased "dosage" of coffee. And in 2011, a large population of post-menopausal women in Sweden saw a "modest" reduction in breast cancer risk with immoderate consumption of 5 or more daily cups.
Taking the benefits of coffee any further requires being patient-specific, but findings apply to a broad range of populations and conditions: