Calcium Update
Drinking a glass of skim milk with a whole-wheat sandwich can increase the body’s absorption of the bone-building mineral calcium, according to a new study by Purdue University researchers.
The researchers set out to test whether eating whole-wheat bread interfered with the body’s absorption of calcium--a finding first reported 40 years ago by British scientists. The concern has been that phytic acid, commonly found in wheat, might bind calcium and other minerals, thus preventing their use by the body.
An improvement in scientific techniques allowed the Purdue University researchers to measure more accurately the amount of calcium absorbed from food. The study was conducted using specially grown wheat that contained radio-labeled calcium. The wheat was then made into bread, cereal and cookies, and included in meals that were fed to volunteers.
Combining whole-wheat products with a glass of skim milk did not “tie up the calcium in the milk,” the study found. In addition, “calcium from bread is just as well absorbed (by the body) as calcium from dairy products,” said Connie Weaver, head of the Food and Nutrition Department at Purdue University and lead author of the study.
The only exception, Weaver said, was a very high-fiber cereal, rich in wheat bran, which cut the amount of calcium absorbed from the milk from 37% to 26%.
As calcium gains growing interest for its role in helping to prevent such wide-ranging illnesses as cancer, high blood pressure and osteoporosis, researchers are looking for ways to increase calcium intake without necessarily turning to supplements.
The reason is that not all supplemental pills release calcium properly, according to a report to the Senate published earlier this fall by the Department of Health and Human Services. “The preferred source of calcium is food,” the HHS report noted.
For most Americans, dairy products remain the leading source of calcium, accounting for 70% of calcium consumed. According to the Department of Agriculture, each glass of skim milk provides about 300 milligrams of calcium--about one-fifth the daily amount needed by a post-menopausal woman and roughly a quarter of that recommended for a teen-ager, two of the groups that need the most calcium.
About 4% of dietary calcium for Americans comes from whole-wheat bread products.
Other rich sources of calcium include kale, broccoli, bok choy and tofu, reports the USDA. Three ounces of tofu, the bean curd made from soybeans, contains 128 mg of calcium, roughly the same amount of calcium found in three ounces of skim milk.
People who consume a high-calcium diet run a lower risk of developing debilitating osteoporosis, a condition in which bones become brittle; it strikes an estimated 24 million Americans, accounts for 1.3 million bone fractures per year and costs $7 billion to $10 billion to treat annually, according to the HHS report published last fall.
One recent study cited by the HHS report found that women ages 30 to 42 who increased their calcium intake by 610 milligrams per day--about the amount found in two 8-ounce glasses of skim milk--significantly reduced their rate of bone loss when compared to a control group of women the same ages.
