Is chocolate bad for the bones?

Health and medicine explained.
Jan. 30 2008 12:12 PM

Your Health This Week

Is chocolate bad for the bones? And more.

Chocolate
Are chocolate consumption and bone density linked?

This week, Dr. Sydney Spiesel discusses whether chocolate is bad for your bones, evidence across racial groups that exercise promotes longevity, and a creepy-crawly (and possibly delusional) condition called Morgellons.

Chocolate and bone density

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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.

Question: Speaking of exercise, a substantial amount of research has shown that physically fit people are likely to live longer than others—but the evidence has only involved middle-class or wealthy whites. Does the relationship hold for other groups?

Research: Peter Kokkinos and colleagues compared the fitness level of almost 16,000 veterans with their mortality risk. The participants walked and ran on a treadmill designed to evaluate heart function until they needed to stop because they were tired, and then were assigned to one of four groups (low, medium, high, and very high fitness) based on performance. In this research population, blacks were little younger than whites but had higher blood pressures, a greater likelihood of smoking, and a higher probability of obesity. They were also more likely to have cardiovascular disease and diabetes or abnormal blood lipids. These differences between the black and white research subjects were taken into account. Most of the participants—white or black—were of the same relatively low socioeconomic level.

Findings: Once all the variables were controlled for, the results were remarkably similar across the racial groups. At a seven-and-a-half year follow-up, it was clear that as fitness level improved, mortality rate dropped. The relationship was pretty much linear and almost the same for blacks and whites

Conclusion: As usual, we have to be careful not to assume that the improved fitness was the cause of the greater life expectancy. (People could test poorly for fitness because of an underlying illness that's the real cause of lower life expectancy, though the researchers made efforts to correct for this effect.) The message: Fitness results, on average, improved life expectancy, and the effect applies whether you're black or white, rich or poor.

History: About 340 years ago, an English physician, philosopher, and collector of odd things, Sir Thomas Browne, described a strange illness he had apparently encountered years earlier in children in Languedoc, a region in the southeast corner of France. The illness began with coughs and convulsions—symptoms which resolved, Browne said, when "harsh" (coarse?) hairs appeared on the backs of the sufferers. The only other thing Browne related about this disease was its name—Morgellons.

Condition: Morgellons, or at least a condition given the same name, has now reappeared, in the form of an illness in which sufferers are tormented by the sensation that bugs are crawling under their skin. This is accompanied by itching, as well as the sense of being stung or bitten. Many sufferers find relief by scratching or picking. What binds this new condition to Browne's description is the appearance of red, blue, or black fibers or granules in the picked skin. Sometimes, when doctors examine under high magnification the sites of sensations, similar fibers are seen embedded below the skin's surface.

Effect: Morgellons disease makes people miserable. They are often intensely anxious and, understandably, strongly focused on finding a cause and effective treatment. They are sometimes reluctant to have contact with other people, including family members, for fear of passing on an infection. For the same reason, they sometimes get rid of furniture or clothing. They are often frustrated and deeply unsatisfied by their encounters with doctors. Many patients also describe being chronically exhausted and having joint or muscle pains.

Explanation: Most dermatologists consider Morgellons disease to be a variant of a well-known condition: delusional parasitosis—the sense of infestation of the skin by bugs—though they are quick to point out that no matter what the cause, patients genuinely and strongly experience the sensations they describe. Patients with this illness often have concomitant psychological problems, which would not be surprising no matter what the cause: A debilitating disease is as likely to be a cause of depression as the result of it.

Parallels: Are there are other conditions that might help clarify whether Morgellons is a collective delusion or a physical condition caused by some kind of parasitic invasion of the skin? Maybe. There are a whole collection of shared delusional illnesses—think "mass hysteria." One of the most famous is "koro" (also called "suo-yang"). It is a high-anxiety delusion, often shared simultaneously by many people, that one's genitals are shrinking inward. It is usually a male delusion, but sometimes women experience a similar sense that their nipples are inverting or that their vagina is closing. Epidemics of koro have been reported in China, India, Malaysia, Thailand, and Nigeria. Sufferers sometimes believe the shrinking organ was stolen from them, and this has led to the very real beating or lynching of the perceived perpetrator. Similarly, every year, groups (frequently of adolescents) experience collective panic, often with mass fainting and vomiting, when they imagine smelling a strange odor.

Conclusion: These examples make it easy to dismiss patients with Morgellons as victims of delusion. But I am compelled to point out that occasionally an epidemic of teenagers collectively smelling an off-odor and fainting has turned out to be the result of exposure to carbon monoxide from a defective furnace or to insecticide contamination. The CDC has now begun to look at Morgellons in a scientific way, so perhaps soon we will have a better handle on cause and treatment.

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