A study of 980 post-menopausal women has found that a lifetime of coffee consumptionsharply increased their risk of osteoporosis, but that a glass of milk a day abolishedthis bone-loss danger.
In Rancho Bernardo, a San Diego suburb, aging women have been participating in anannual Heart and Chronic Disease Study since 1972. The project is conducted by the Familyand Preventive Medicine Department of the University of California, San Diego (UCSD).
The population of 980 white, upper middle-class women represents 80 percent of thesurviving participants, down from the original 3,000 participants 20 years ago. Thecurrent cohort ranges in age from 50 to 98 (with the average age of 72.7 years). Decreasesin their hip and lumbar bone mineral density (BMD), measured by X-ray absorption,correlated closely with their life-long intake of caffeinated coffee.
Of the 980 women, 88 percent (865) reported regular use of caffeinated coffee at sometime in their lives, but only 53 percent (523) drink it currently. Only seven women drinkonly decaffeinated coffee; they are irrelevant to the study. Statistically, the coffeelovers were also relatively big on alcohol and tobacco use.
The BMD finding implicating coffee in post-menopausal osteoporosis was statisticallyindependent of age, obesity, number of childbirths, vigorous physical activity, yearssince menopause, or use of tobacco, alcohol or medications. But daily milk consumption,presumably thanks to its calcium content, completely negated the coffee-associatedosteoporosis.
Alcohol proved protective of bone mass, too, said the project’s seniorstatistician, Sharon Edelstein, but not tobacco. “Smoking told us two interestingthings,“ she told BioWorld. “As first reported about 20 years ago, theamount of cigarette smoking by Rancho Bernardo women was predictive of decreased BMD atthe hip. Currently, we find the same exact pattern. People who quit, even at an older age,had better bone density than those who continued to smoke.“
Epidemiologist Elizabeth Barrett-Connor, who chairs the Family Health andPreventiveMedicine Department at UCSD, is the first author of the report in today’s issue ofthe Journal of the American Medical Association. She noted that “coffeesupplies over 80 percent of caffeine in the Western diet and is consumed regularly by themajority of adults in the United States.“ Hence, she cautioned, “health risks ofcaffeinated coffee would have broad public health implications.“
Despite the JAMA paper’s title, “Coffee-Associated Osteoporosis Offsetby Daily Milk Consumption,“ its authors warned that their survey could not establish“how much milk is necessary to preserve bone in the face of heavy coffeeintake.“ Its designation of at least one glass a day takes no account of varyingcontainer size and includes women who drank much more than one glass daily.
By the same token, the study scrutinized caffeinated coffee rather than caffeine perse because the amount of alkaloid per cup varies widely by brand and method ofbrewing.
A footnote to the paper advises that the project’s assistant statistician, JaeChun Chang, was supported in part by an unrestricted grant from the National CoffeeAssociation.
--David N. Leff