- With Mayo Clinic nutritionist
Katherine Zeratsky, R.D., L.D.
read biographyclose windowBiography of
Katherine Zeratsky, R.D., L.D.
Katherine Zeratsky, R.D., L.D.
As a specialty editor for the Food & Nutrition Center, 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, she 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 pediatrics at Mayo Clinic Rochester and nutrition education related to the physiology and recommended intakes for premature infants.
Other areas of interest include breast milk and formula safety, neonatal feeding, and nutrition for breast-feeding mothers.
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.
As chocolate contains relatively small amounts of oxalate, it is unclear to what extent chocolate consumption affects healthy people who eat calcium-rich diets. A 2008 study in the American Journal of Clinical Nutrition found that elderly women who consume one or more servings of chocolate on a daily basis have lower bone density and strength than those women who eat a serving of chocolate six times a week or less. 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. Chocolate also contains flavonoids, a substance that is thought to be beneficial to bone health. Further tests are needed to fully determine the role chocolate plays in calcium balance and bone strength.
It is clear, however, that consuming foods high in oxalate — and in turn their effect on calcium absorption — is a more significant concern for people with oxalate kidney stones, which occur when there is too much oxalate in the urine. These people, especially, should reduce their oxalate intake and increase their calcium intake.
In addition to chocolate, oxalate is found in varying amounts in many other foods, such as beans, nuts, spinach, sweet potatoes, okra, kale, collards, chard, berries and tea.
Calcium from food sources, such as milk and yogurt, are your best sources of calcium. If you consume 1,200 to 1,500 milligrams of calcium and 400 to 800 international units of vitamin D daily from food or calcium supplements, eating chocolate in moderation is unlikely to adversely affect your bone health.
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