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Diet and Nutrition

Does Fiber Prevent the Body from Absorbing Calcium?

High-fiber CerealYou may know that eating a high-fiber cereal and drinking plenty of milk is beneficial to your health, but what happens when you take them together? There has been some concern that fiber may actually prevent your body from absorbing calcium. Though this is not completely true, it is something to be aware of.

First, you should know that calcium isn't easily absorbed by the body to begin with. In fact, nutritionists estimate that most people absorb only about 20 - 40% of the calcium they consume. One reason for this is that certain substances, like phytate, interfere with calcium absorption. Cereal made with 100% wheat bran has a lot of phytate in it. So, it's not really the fiber, it's the phytate that causes the problem.

If the cereal you're eating is 100 percent wheat bran, your body will likely have trouble absorbing the calcium from the milk that's also in your cereal bowl. Still, that doesn't mean you should stop eating high-fiber cereals. Women need an average of 25 grams of fiber a day, and men need as much as 38 grams. Enjoying a high-fiber cereal in the morning is a good way to start you toward that goal each day. And although phytate may inhibit calcium absoprtion from milk, some of that calcium still makes it through.

Of course, you also need to be concerned about getting enough calcium. Adults up to age 50 need 1,000 milligrams a day, and those 50 and older should get 1,200 milligrams. Keep in mind that the body's ability to absorb calcium decreases with age. Younger folks between the ages of 9 and 18 need a whopping 1,300 milligrams a day, mainly because that's when so much of the body's bones form.

You should know that other foods also contain phytate. For example, dry beans and legumes, such as pinto beans, navy beans and peas are rich in phytate. The level can be reduced if you soak the dry beans in water for several hours, discard the water, and cook them in fresh water.

Other substances that interfere with calcium absorption include oxalate -- in particular, oxalate in foods that also contain calcium. Oxalate in calcium-containing foods such as spinach, rhubarb and beet greens binds with the calcium and inhibits absorption. In addition, a diet too high in sodium or caffeine can decrease the body's ability to absorb calcium.

So, what can you do? Sure, enjoy your cereal with some milk, but be sure to drink milk or consume other high-calcium foods at other times of the day, too -- at least two hours before or after eating your 100-percent wheat bran cereal. Or, switch to another high-fiber cereal, such as oatmeal or a dry cereal made with oat bran. Check the Nutrition Facts labels for information.

This article originally appeared in Chow Line (05/16/08), a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center and was adapted for use on NetWellness with permission, 2010.

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Last Reviewed: Mar 30, 2010

Robert  DiSilvestro, PhD Robert DiSilvestro, PhD
Professor of Human Nutrition
College of Education and Human Ecology
The Ohio State University