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.

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

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.



Slate Plus Early Read: The Self-Made Man

The story of America’s most pliable, pernicious, irrepressible myth.

Rehtaeh Parsons Was the Most Famous Victim in Canada. Now, Journalists Can’t Even Say Her Name.

Mitt Romney May Be Weighing a 2016 Run. That Would Be a Big Mistake.

Amazing Photos From Hong Kong’s Umbrella Revolution

Transparent Is the Fall’s Only Great New Show

The XX Factor

Rehtaeh Parsons Was the Most Famous Victim in Canada

Now, journalists can't even say her name.


Lena Dunham, the Book

More shtick than honesty in Not That Kind of Girl.

What a Juicy New Book About Diane Sawyer and Katie Couric Fails to Tell Us About the TV News Business

Does Your Child Have Sluggish Cognitive Tempo? Or Is That Just a Disorder Made Up to Scare You?

  News & Politics
Damned Spot
Sept. 30 2014 9:00 AM Now Stare. Don’t Stop. The perfect political wife’s loving gaze in campaign ads.
Sept. 29 2014 7:01 PM We May Never Know If Larry Ellison Flew a Fighter Jet Under the Golden Gate Bridge
Atlas Obscura
Sept. 30 2014 10:10 AM A Lovable Murderer and Heroic Villain: The Story of Australia's Most Iconic Outlaw
  Double X
Sept. 29 2014 11:43 PM Lena Dunham, the Book More shtick than honesty in Not That Kind of Girl.
  Slate Plus
Slate Fare
Sept. 29 2014 8:45 AM Slate Isn’t Too Liberal. But… What readers said about the magazine’s bias and balance.
Brow Beat
Sept. 29 2014 9:06 PM Paul Thomas Anderson’s Inherent Vice Looks Like a Comic Masterpiece
Future Tense
Sept. 30 2014 7:36 AM Almost Humane What sci-fi can teach us about our treatment of prisoners of war.
  Health & Science
Bad Astronomy
Sept. 30 2014 7:30 AM What Lurks Beneath The Methane Lakes of Titan?
Sports Nut
Sept. 28 2014 8:30 PM NFL Players Die Young. Or Maybe They Live Long Lives. Why it’s so hard to pin down the effects of football on players’ lives.