Friday, February 1, 2008
Slate.com's Medical Examiner's "Your Health This Week" column concerns whether chocolate is bad for women's bones. (Yikes - say it isn't so!) Slate reports:
Question: One of the plusses of chocolate is that it contains materials called flavonoids. These are known to enhance bone health. But does chocolate do more harm than good to the bones?
Research: Jonathan M. Hodgson and his associates looked at whether calcium supplements might prevent the loss of minerals from the bones of older women, which leads to weakness and risk of fractures. As part of their study of about 1,000 randomly selected elderly women, these scientists examined the effects of diet. One of the foods they studied was chocolate, both as a solid and as cocoa. Given chocolate's flavonoids, they expected that it would improve calcium absorption into bone, which they measured using the standard method: X-ray densitometry.
Findings: To the great surprise of the researchers, the women who ate a lot of chocolate—on average, more than one portion a day (a cup of cocoa, say, or a bar of chocolate)—had lower bone density five years after the experiment began than the women who didn't. The chocolate-eaters and -drinkers were also, unexpectedly, more energetic and leaner.
Explanation: The authors speculate that the lower bone density may be due to another natural ingredient in chocolate: oxalic acid. Oxalic acid can bind the calcium in our diet (from leafy green vegetables and dairy products) and block its absorption, so its presence in chocolate might prevent some calcium from ever reaching the bones. But, as always, we need to keep in mind that association doesn't necessarily imply causation. It may be that some other factor, having nothing to do with chocolate, controls the intake and absorption of calcium.
Speculation: Here's another thought, or really speculation: The chocolate-eaters in the study were somewhat lower in weight and body fat than the women who avoided chocolate. Especially in older women, body fat contributes to estrogen level, which, in turn, promotes increased bone calcium. Perhaps the slightly heavier post-menopausal women in the study, who ate less chocolate, had higher levels of calcium in their bones, on average, because of the additional estrogen produced by their body fat.
Conclusion: So, does this study also apply to younger women or to men? It's hard to say, since we don't know the true mechanism which leads to lower bone density in older women who like chocolate. But we do know one thing which helps maintain and increase bone density and strength: exercise. Which certainly seems preferable to giving up chocolate.
I must admit that I tend to be rather picky as to which of these scienfic studies on dietary issues I believe; i.e., Dark chocolate good for you - completely scientifically sound. A glass of wine good for you - again completely scientifically sound. Chocolate potentially not so good - I am suspicious about the scientific method used in this study . . . .