Even coffee drinkers find it hard to believe that their favorite pick-me-up is healthful, but it seems to be true. People who drink coffee regularly are less likely to have a stroke or get diabetes or Parkinson’s disease than those who don’t drink it. There’s even some evidence that coffee can help prevent cancer, although the link between coffee and various cancers is preliminary and still being investigated.
Coffee contains hundreds of antioxidants and other bioactive compounds, including some of the same polyphenols that are found in fruits, vegetables, wine and green tea. Polyphenols are potent antioxidants that inhibit inflammation as well as cell damage.
Both caffeinated and decaffeinated coffees contain antioxidants. However, some of the health benefits occur only with regular coffee. This suggests that caffeine also plays a role.
More coffee might be better for disease prevention. For example, coffee has a dose-response relationship with diabetes. People who drink five cups a day seem to benefit more than those who drink three cups…and two or three cups a day might be better than just one cup. But not everyone is better off with more. Some people get jittery with too much coffee, and it can cause other problems, such as stomach upset and bladder irritation.
More than 20 studies have found that coffee drinkers are less likely to get diabetes than those who don’t drink coffee. When we analyzed the data from nine previous studies, which included a total of more than 193,000 people, we found that those who drank more than six or seven cups of coffee daily were 35% less likely to have type 2 diabetes (the most common form) than those who drank two cups or less. Those who consumed four to six cups daily had a 28% lower risk for diabetes.
Some of the studies were conducted in Europe, where people who drink a lot of coffee—up to 10 cups daily—are the ones least likely to have diabetes.
Both decaf and regular coffee seem to be protective against diabetes. This suggests that the antioxidants in coffee—not the caffeine—are the active agents. It’s possible that these compounds protect insulin-producing cells in the pancreas. The minerals in coffee, such as chromium and magnesium, have been shown to improve insulin sensitivity.
It’s not a coincidence that coffee is the beverage of choice at the workplace. People who drink coffee have short-term improvements in memory and other cognitive functions. Coffee also seems to improve long-term brain health. Example: Coffee drinkers are at least 30% less likely to get Parkinson’s disease than people who don’t drink coffee. Parkinson’s disease is characterized by a lack of dopamine in the brain.
Some researchers believe that coffee also can help reduce the risk for Alzheimer’s disease. One study, which followed 1,400 participants for about 20 years, found that regular coffee consumption (three to five cups daily) reduced the risk for Alzheimer’s and other forms of dementia by 65%, compared with those who drank little or no coffee.
You will get the brain benefits only if you drink regular coffee—decaf doesn’t have the same effects. It’s possible that caffeine contributes to the benefits.
Caffeinated coffee raises blood pressure temporarily, but people who drink it regularly have no increased risk for high blood pressure.
There is emerging evidence that coffee drinkers have a lower risk for stroke and other cardiovascular diseases.
Example: Data from the long-running Nurses’ Health Study found that women who drank four or more cups of coffee a day had about a 20% lower risk for stroke than those who drank little or no coffee.
Other studies indicate that coffee may reduce the risk for heart disease, possibly by reducing arterial inflammation that can lead to atherosclerosis and blood clots. However, the evidence is not conclusive.
It’s not a substitute for sunscreen, but drinking coffee could protect you from the most common type of skin cancer.
In a new report presented at the American Association of Cancer Research meeting in Boston, researchers found that coffee drinkers were less likely to develop basal-cell carcinoma than noncoffee drinkers.
In the study, researchers followed more than 112,000 people for up to 24 years. During this time, they tracked the incidence of basal-cell carcinomas and other skin cancers. Men who drank the most coffee had a 13% lower risk for basal-cell carcinomas than those who drank the least…in women, the risk was 18% lower.
Decaffeinated coffee didn’t provide the same protection, so it appears that caffeine is responsible—but the reason isn’t known.
Coffee reduced the risk for only this one type of skin cancer. Other skin cancers, such as melanoma and squamous-cell carcinoma, weren’t affected. Because this is the first large study to find this effect, it will have to be repeated—by different researchers and with different groups of people—to confirm that coffee does, in fact, protect the skin.
Caffeine may protect against other cancers as well. New finding: Women who drink four or more cups a day of caffeinated coffee reduced their risk for endometrial cancer by 30%. And drinking two or more cups of decaffeinated coffee reduced risk by about 22%.
It’s important to remember that the majority of research about coffee is observational. Researchers interview large numbers of people…ask them about their coffee consumption and other habits…look at their health status…and then make conclusions about what caused what.
Unlike double-blind, randomized clinical trials, which are considered the gold standard of scientific research, observational studies cannot prove cause and effect, but they do offer evidence.
Some caveats about coffee…
Moderation matters. Some people get the jitters or have insomnia when they drink coffee. In rare cases, the caffeine causes a dramatic rise in blood pressure. It’s fine for most people to have three, four or five cups of coffee a day—or even more. But pay attention to how you feel. If you get jittery or anxious when you drink a certain amount, cut back. Or drink decaf some of the time.
Hold the milk and sugar. Some of the coffee “beverages” at Starbucks and other coffee shops have more calories than a sweet dessert. Coffee may be good for you, but limit the add-ons.
Use a paper filter. Boiled coffee, coffee made with a French press or coffee that drips through a metal filter has high levels of oils that can significantly raise levels of LDL, the dangerous form of cholesterol. Better: A drip machine that uses a paper filter. It traps the oils and eliminates this risk.
Source: Frank B. Hu, MD, PhD, an epidemiologist, nutritional specialist and professor of medicine at Harvard Medical School and the Harvard School of Public Health, both in Boston. He is codirector of Harvard’s Program in Obesity Epidemiology and Prevention.