Your cup of coffee may do more than get you going in the morning. Previous research suggests that if you drink enough of it, coffee fends off type 2 diabetes, heart disease, asthma, gallstones, Parkinson's disease and liver cancer.
Coffee's latest health perk? According to a report released this week, the daily brew may protect some women from breast cancer.
The study, published online in the journal Breast Cancer Research, involved 5,929 postmenopausal Swedish women aged 50 to 74 and found heavy coffee drinkers had a significantly lower risk of developing estrogen receptor-negative (ER-negative) breast cancer.
Compared with women who drank less than one cup of coffee a day, those who consumed more than five cups were 57 per cent less likely to develop the cancer. (One cup of coffee was defined as six ounces.)
Doctors test breast-cancer cells to see if they have hormone receptors. Hormone receptor-positive tumours are fuelled by the female hormones estrogen and progesterone. Hormone receptor-negative cancer cells are not affected by estrogen or progesterone.
Heavy coffee drinkers were also less likely to be diagnosed with estrogen receptor-positive breast cancer, but this finding was not statistically significant, meaning that it could have been a chance finding.
It is thought that coffee raises blood levels of enterolactone, a phytochemical that has been associated with a lower risk of ER-negative breast cancer.
In Sweden, coffee is boiled, not drip-filtered. Similar to French press coffee, boiled coffee contains more coffee-specific fatty acids than filtered coffee. (This may explain why previous research found a weaker link between coffee and a lower breast-cancer risk among women who drank primarily filtered coffee.)
This new finding adds to mounting evidence that coffee does more good than harm. Coffee does warrant a few cautions, however.
Here's a look at the most recent research on coffee and health:
Coffee's perks
Type 2 diabetes: More than 15 published studies have revealed that drinking coffee reduces the risk of getting diabetes. According to one large report, people who drank four to six cups of coffee a day were 28 per cent less likely to develop type 2 diabetes compared with those who drank two cups or fewer. Consuming more than six cups each day reduced the risk by 35 per cent.
Coffee's benefits are attributed to antioxidants, some of which become more potent during roasting. Antioxidants in coffee - in both caffeinated and decaffeinated - are thought to dampen inflammation in the body and improve how the body uses insulin, the hormone that lowers blood sugar. Coffee also contains magnesium and chromium, minerals linked to blood-sugar regulation.
Heart disease and stroke: Despite earlier concerns that coffee might be bad for your heart, studies haven't found a connection. In fact, one study conducted among 41,836 healthy women, aged 55 to 69, found that drinking one to six cups of coffee a day - caffeinated or decaffeinated - reduced the risk of dying from heart disease. A daily intake of four to six cups was found to be the most protective.
Coffee may also shield women from stroke. A 10-year study published this year found that among almost 35,000 women, those who drank one or more cups of coffee a day - versus less than one - were significantly less likely to suffer a stroke.
Cancer: In addition to the breast-cancer risk, coffee also seems to cut the risk liver cancer. Many studies have found that daily coffee drinking helps to protect people with and without a history of cirrhosis from liver cancer. The more coffee consumed each day, the lower the risk.
(In cirrhosis, scar tissue replaces normal, healthy tissue, blocking the blood flow and preventing the liver from functioning properly. Chronic alcohol abuse and hepatitis C are the most common causes.)
Scientists speculate that antioxidants in coffee protect the liver from the effects of carcinogens. Caffeine may also play a role.
Parkinson's disease: Habitual coffee consumption has been linked with protection from Parkinson's disease. Harvard University researchers found that men who consumed the most caffeine reduced their risk for Parkinson's disease by 48 per cent. Among women, those who drank one to three cups of coffee a day had a 50-per-cent reduction in risk.
Alzheimer's disease: Interest in coffee's potential protective effect on dementia has been growing over the past decade. Most recently, Swedish and Finnish researchers followed 1,409 men and women for 21 years and found that those who drank coffee during midlife - compared with those who didn't - were less likely to develop dementia and Alzheimer's later in life. The lowest risk was found in people who drank three to five cups of coffee a day.
Coffee's downsides
Heartburn: You should curb your coffee intake if you have heartburn or reflux disease. Coffee - both regular and decaffeinated - relaxes the muscle that keeps stomach acid from rising into the esophagus and throat. Coffee also stimulates acid secretion in the stomach.
Pregnancy: Based on studies suggesting that high coffee intakes may increase the risk of miscarriage, Health Canada advises women of childbearing age to consume no more than 300 milligrams of caffeine a day (roughly two eight-ounce cups of coffee). Keep in mind that most coffee cups are larger than eight ounces.
Side effects: For most healthy adults, a daily intake of 400 milligrams of caffeine is not associated with any adverse effects such as high blood pressure, heart disease and low bone density. However, some people are sensitive to side effects such as insomnia, headaches and irritability.
Excess calories: Black coffee won't break your diet at five calories a cup. But high-fat, sugar-laden coffee drinks can. A large (14-ounce) double-double at Tim Hortons will cost you 230 calories. A grande (16-ounce) Caramel Brûlée Latte at Starbucks has 300 calories.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.
Leslie Beck