- With Mayo Clinic nutritionist
Katherine Zeratsky, R.D., L.D.
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Katherine Zeratsky, R.D., L.D.
Katherine Zeratsky, R.D., L.D.
As a specialty editor for the nutrition and healthy eating guide, Katherine Zeratsky helps you sort through the facts and figures, the fads and the hype to learn more about nutrition and diet.
A Marinette, Wis., native, Katherine is certified in dietetics by the state of Minnesota and the American Dietetic Association. She has been with Mayo Clinic since 1999.
She is active in nutrition-related curriculum and course development in wellness nutrition at Mayo Clinic in Rochester, Minn., and nutrition education related to weight management and practical applications of nutrition-related lifestyle changes.
Other areas of interest include food and nutrition for all life stages, active lifestyles and the culinary arts.
She graduated from the University of Wisconsin-Madison, served a dietetic internship at the University of Iowa Hospitals and Clinics, and worked as a registered dietitian and health risk counselor at ThedaCare of Appleton, Wis., before joining the Mayo Clinic staff.
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Question
Chocolate: Does it impair calcium absorption?
A friend told me that chocolate impairs absorption of calcium. Is this true?
Answer
from Katherine Zeratsky, R.D., L.D.
Chocolate contains oxalate — a naturally occurring compound in cocoa beans — which can inhibit the absorption of calcium. Calcium binds to oxalate in your intestines, limiting its absorption into your bloodstream. People with oxalate kidney stones, which could occur when there is too much oxalate in the urine, should limit the amount of oxalate in their diets.
The jury is still out, however, on whether chocolate causes problems for healthy people who eat calcium-rich diets. A 2008 study suggests there might be reason for concern. The study found that elderly women who ate one or more servings of chocolate a day had lower bone density and strength than did women who ate fewer servings of chocolate. Researchers believe this may be due to oxalate inhibiting calcium absorption — but it could also be due to the chocolate's sugar content, which may increase calcium excretion. In addition, chocolate also contains flavonoids, which are thought to be beneficial to health. Further research is needed to fully determine the role chocolate plays in calcium balance and bone strength.
In the meantime, if you get the daily recommended amounts of calcium and vitamin D from food or supplements, and practice weight-bearing exercise, eating chocolate in moderation is unlikely to adversely affect your bone health.
Next questionWhat is wheatgrass — And why is it in my drink?
- Hodgson, et al. Chocolate consumption and bone density in older women. American Journal of Clinical Nutrition. 2008;87:175.
- Zeratsky KA (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 10, 2010.
- Barbara Woodward Lips Patient Education Center. Nutritional Management of Enteric Hyperoxaluria. Rochester, Minn.: Mayo Foundation for Medical Education and Research, 2007:2.
- Massey LK. Food oxalate: Factors affecting measurement, biological variation, and bioavailability. Journal of the American Dietetic Association. 2007;107:1191.
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