Calcium and Common Sense
Women, take your calcium. If that message seems contrary to headlines of just a few months back, you've gotten the wrong idea. This past February, the government-sponsored Women's Health Initiative reported that women ages 50 to 79 who took calcium and vitamin D for seven years didn't lower their risk of fractures compared with those on a placebo. But those who faithfully took their pills had 29 percent fewer broken hips. That "but" was all too often lost in translation.
Last week, an Australian study in the Archives of Internal Medicine came up with almost identical results. At first blush, there was no difference between the elderly women taking calcium and those on dummy pills. In fact, among those who took supplements at least 80 percent of the time, the extra calcium reduced hip fractures by one third.
Getting personal. Part of the reason for the communication misfire on the nuances of the studies may be that scientific research reports are just not written as health announcements. Complex reports laden with statistics can easily obscure a message about individual health. From a pure public-health standpoint, it doesn't matter if pills fail because they stay in the medicine cabinet or because they are biologically ineffective--the impact is the same. From a media perspective, a contrarian finding that questions years of milk mustache ads and established medical dogma calling for menopausal women to take 1,200 to 1,500 milligrams of calcium and up to 800 IUs of vitamin D a day will easily steal the headlines. Meantime, you and I want to know what will work for us.
Rebecca Jackson, an osteoporosis expert at Ohio State University and lead author of the WHI paper, says "biological plausibility" must come into play when one translates studies to individuals. In other words, the biological processes at work must be considered in interpreting and acting on contradictory outcomes. For example, hip fractures do not usually occur in women in their 50s or early 60s, though during that critical time around menopause they are facing a silent loss of calcium from their bones and need to shore it up. So though these women appear to get no benefit from supplements in terms of reduced fracture risk, we know for sure that they are being set up for fractures a decade or more later. For these women to throw away their calcium pills based on the insignificant number of fractures in their age group is just plain silly.
The importance of patients knowing biological context is also seen in the companion WHI study that looked at whether a low-fat diet affects cancer risk. Growing evidence has suggested that too much fat is not just bad for your heart but also sets you up for certain cancers, particularly colon cancer. Here again, on the surface, the study contradicted that suspicion, showing that a low-fat diet offered no protective value after seven years. But the lower fat intake was tied to significantly fewer precancerous polyps. Since it takes a decade or more for a benign polyp to turn into a cancer, the finding hints strongly that the low-fat link may have biological merit. The smart move is to stick to a prudent diet: low in fats, high in fruits and vegetables--and rich in calcium and vitamin D.
Health by headlines can obviously be dangerous if the message reverberating in the echo chamber misses the mark. When it comes to calcium, the mark is that American women are malnourished. That includes young girls just building their adult skeletons, who on average run 500 mg short daily. For menopausal women, the intake gap can easily be as wide as 900 mg, in part because of plummeting estrogen. Estrogen blocks bone breakdown and makes the body more efficient at taking up and holding on to calcium. The news of great biological--and motivational--importance is that correcting the calcium and vitamin D gap with consistency reduces the risk of fracture almost immediately.
Common sense says know your daily calcium intake, and add supplements if it's short. A glass of milk or a carton of yogurt offers 300 to 400 milligrams, as do calcium-fortified drinks like orange juice. And, for both bone health and cancer prevention, don't forget exercise.
This lesson is a key one for the great mass of baby boomers about to become fragile-boned, cancer-prone seniors. Like most preventive measures, be they vaccines or birth-control pills, you have to take them to get a benefit.
This story appears in the May 8, 2006 print edition of U.S. News & World Report.