Is the magic bean a magic bullet?
On almost every list of the 10 healthiest foods, you’ll find soy. This seemingly “magic bean” has been reputed to help prevent heart disease, ease the discomforts of menopause, slow bone loss and even ward off certain cancers. So recent findings in the journal Circulation that almost all of soy’s health benefits have been vastly overrated came as a real shock.
A team of top nutrition researchers, organized by the American Heart Association, reviewed dozens of the most recent studies on soy. Consider the most prominent claim: that soy dramatically lowers LDL, the artery-clogging form of cholesterol. In 1999, the FDA gave foods that contain at least 6.25 grams of soy protein per serving the green light to boast that they lower cholesterol and help prevent heart disease. Trouble is, recent randomized trials suggest that soy may not deliver on that promise. On average, studies now show, LDL falls a mere three points—and that’s among volunteers who consume around 50 grams of soy per day or about half their total protein. “If you buy a box of cereal because a serving has 6.25 grams of soy, expecting to lower your LDL and your risk of heart disease, you’re likely to be disappointed,” says Tufts University researcher Alice Lichtenstein, a member of the review panel.
Blood pressure? Soy has no benefit, the panel concluded. Hot flashes during menopause? Only three of eight studies showed any improvement, and even that was modest and short-lived. Osteoporosis? Studies suggest that even if there is a benefit, it’s far from dramatic. The biggest disappointment, perhaps, is that soy doesn’t seem to offer much protection against hormone-related cancers, such as breast, endometrial, and prostate cancer.
“We don’t know why early studies showed such positive results and more recent ones haven’t,” admits Penn State nutrition expert Penny Kris-Etherton, another member of the AHA panel. But the recent findings are so discouraging, she believes, that the FDA should reconsider whether products containing soy should be allowed to put health claims on their labels.
Not everyone has given up on soy. Michael Adams, a professor of pathology at Wake Forest University School of Medicine in Winston-Salem, North Carolina, recently showed in animal experiments that components in soy protein can dramatically reduce the formation of atherosclerotic plaques, which clog arteries and lead to heart attacks. “Our work suggests that soy may lower cardiovascular risk through a very different mechanism than reducing LDL,” says Adams. “The fact is, no one has yet done a large prospective study to test whether soy protein reduces heart disease.” For his part, Adams suspects that it does.
Even the members of the AHA panel, despite their gloomy assessment, remain keen on the bean. “Soybeans are a great source of good protein, polyunsaturated fat, and fiber,” says Kris-Etherton. “If soy protein is used instead of fatty meat, no question it’s healthier.”