- With Mayo Clinic nutritionist
Katherine Zeratsky, R.D., L.D.read biographyclose window
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.
Nutrition basics (31)
- Phenylalanine in diet soda: Is it harmful?
- Water softeners: How much sodium do they add?
- Diet soda: Is it bad for you?
- see all in Nutrition basics
Healthy diets (11)
- Canola oil: Does it contain toxins?
- Butter vs. margarine: Which is better for my heart?
- Detox diets: Do they work?
- see all in Healthy diets
Healthy cooking (7)
- When the heat is on, which oil should you use?
- Moldy cheese: Is it OK to eat?
- Food poisoning: How long can you safely keep leftovers?
- see all in Healthy cooking
Healthy menus and shopping strategies (8)
- White whole-wheat bread: Is it nutritious?
- Sodium nitrate in meat: Heart disease risk factor?
- Brominated vegetable oil: Why is BVO in my drink?
- see all in Healthy menus and shopping strategies
Nutritional supplements (18)
- What is wheatgrass — And why is it in my drink?
- Prenatal vitamins: OK for women who aren't pregnant?
- Too much vitamin C: Harmful?
- see all in Nutritional supplements
Chocolate: Does it impair calcium absorption?
A friend told me that chocolate impairs absorption of calcium. Is this true?
from Katherine Zeratsky, R.D., L.D.
Chocolate contains oxalate — a naturally occurring compound in cocoa beans — which can inhibit the absorption of calcium. The jury is still out, however, on whether chocolate causes problems for healthy people who eat calcium-rich diets.
The concern about calcium absorption and bone health comes from a 2008 study. It found that older women who ate one or more servings of chocolate a day had lower bone density and less 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.
On the plus side, dark chocolate (or cocoa) 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 health.
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 question
Calcium supplements: Do men need them too?
- 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. July 13, 2012.
- Massey LK. Food oxalate: Factors affecting measurement, biological variation, and bioavailability. Journal of the American Dietetic Association. 2007;107:1191.