The
Real Scoop on Coffee and Caffeine
JoAnn
E. Manson, MD, DrPH
Harvard Medical School
o
you worry that coffee could harm your health? Relax. Studies
suggest that, when consumed in moderation -- meaning two to
four eight-ounce servings daily -- coffee may in fact be good
for you.
It is
not clear whether the benefits come from coffee itself or its
caffeine. Even decaffeinated coffee may have some caffeine, and
there is limited research on other caffeinated beverages, such as
tea. Per cup, coffee has about 100 mg of caffeine... black tea has
about half as much. Studies show that coffee
may...
Reduce risk for some cancers. An analysis of nine
studies found that drinking two cups of coffee daily lowered liver
cancer risk by 43%. Coffee also may protect against colorectal
cancer.
Help prevent diabetes. Among 200,000 study
participants, those who drank four to six cups of regular or
decaffeinated coffee daily were 28% less likely to develop type 2
diabetes than people who drank two cups or less daily.
Possible reason: Chlorogenic acid,
an antioxidant in coffee, slows sugar’s release into the
bloodstream.
Protect memory. In a study of 7,000 seniors, women
who drank more than three cups of caffeinated coffee or six cups of
caffeinated tea daily had less memory loss than women who drank two
cups or less.
Prevent gallstones. In a study of 80,000 female
nurses, drinking two or more cups of caffeinated coffee daily cut
gallstone risk by about 20%.
Why: Caffeine may aid the digestive
fluid bile, reducing formation of cholesterol crystals that become
stones... and stimulate gallbladder contractions, flushing away
crystals.
Lower Parkinson’s disease risk. In the nurses’ study,
women who drank one to three cups of caffeinated coffee daily were
40% less likely than nondrinkers to develop Parkinson’s, a movement
disorder caused by loss of brain cells.
Improve physical performance. The amount of caffeine
in two to five cups of coffee boosts endurance... helps the body
burn fat instead of carbohydrates... and eases muscle soreness.
Reassuring: Coffee drinkers are no
more likely to have heart attacks or chronic high blood pressure
than nondrinkers. Coffee oils can raise cholesterol, but paper
filters remove these oils. Coffee doesn’t appear to increase risk
for ovarian or breast cancer. Some women say coffee worsens
premenstrual syndrome and fibrocystic breast disease (benign breast
lumps), but research does not support this.
Cautions: Both regular and decaf
coffee can cause digestive upset. Caffeine can trigger migraine or
cause insomnia. Animal studies suggest that at high doses, caffeine
may weaken bones by blocking calcium absorption. Moderate amounts
of caffeine do not impair fertility or cause birth defects, but
consuming more than 200 mg daily may double miscarriage risk -- so
limit caffeine to 100 mg per day while pregnant.