Chow Line: Calcium difficult for body to absorb (for 5/25/08)

May 16, 2008

I always have milk in the morning with my high-fiber cereal. But a friend told me that fiber prevents the body from absorbing calcium. If that's true, what should I do?

That's not completely true, but 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 percent to 40 percent of the calcium they consume.

There are a number of reasons why, and one of them is associated with certain substances that interfere with calcium absorption. One of those substances is phytate, and 100 percent wheat bran has a lot of 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 on that goal each day.

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 -- in part because 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, notably dry beans and legumes such as pinto beans, navy beans and peas. 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 protein, 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.

Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or filipic.3@cfaes.osu.edu.

Editor: May is National Osteoporosis Awareness and Prevention Month. This column was reviewed by Robert DiSilvestro, professor of human nutrition in the College of Education and Human Ecology and researcher with the Ohio Agricultural Research and Development Center.

Author(s): 
Martha Filipic
Source(s): 
Robert DiSilvestro