MEDICINE / CAFFEINE : Study Links Coffee to Risk of Bone Fractures in Women
Add one more to the long list of ills associated with coffee drinking. Researchers at UC San Diego report today in the Journal of the American Medical Assn. that women who drink more than two cups of caffeinated coffee per day suffer a loss of bone density that can lead to bone fractures in later life.
Scientists have suspected such a link for several years, but the report provides the strongest evidence of its existence.
The study of 980 Anglo women in the Rancho Bernardo community had good news as well. The researchers found that the effects of the coffee were offset if the women also drank a glass of milk every day.
“Coffee is a diuretic that washes nutrients out of the body,” said Dr. Elizabeth Barrett-Connor of UC San Diego, primary author of the report. “I think the take-home message is that if you are going to drink more than two cups of coffee a day, you should be sure to consume enough calcium to restore your calcium balance.”
The UC San Diego results are compatible with what he has seen in his own study, said Dr. Walter Willett of Harvard University School of Medicine, director of the Nurses Health Study. “Coffee and caffeine do seem to be detrimental for bone density. But Barrett-Connor goes another step and suggests that this effect might be counteracted by increased calcium intake. That’s not been shown before.”
Unfortunately, Barrett-Connor added: “Almost no woman in this country gets enough calcium.”
Not surprisingly, the study also revealed that the women who drank the most coffee drank the least milk, so that those who most needed the calcium were least likely to get it.
The list of ailments associated with coffee drinking has been growing in recent years. The latest results suggest that four cups of coffee per day increase the risk of heart attack 40% or more. It also might increase blood pressure. Some studies suggest that decaffeinated coffee raises cholesterol levels in blood. Caffeinated coffee may be linked to bladder cancer. Giving up coffee can cause depression.
Studies in rodents have shown that caffeine can deplete the body’s calcium by causing it to be excreted in urine. But the eight to 10 human studies performed have yielded contradictory results, Barrett-Connor said, largely because they did not account for the women’s intake of calcium.
At least one project, the massive Framingham study, indicated that women who drank more than two cups of coffee per day had as much as a 69% increase in the risk of serious fractures. Women have been the focus of such studies because they are more likely to lose bone density after menopause.
Among the 850 women in the Rancho Bernardo study, ages 50 to 98, only 115 reported little or no consumption of coffee, and seven said they drank only decaffeinated coffee. The researchers determined the women’s lifetime consumption of coffee, milk and a variety of other potential risk factors.
They found that women who had drunk more than four cups of coffee per day for most of their lives, and little or no milk, had on average less than 90% of the bone density of women who drank fewer than two cups per day. In contrast, those who drank four cups of coffee and an average of a glass of milk per day had normal bone density for their ages.
