From The October 2000 Issue of Nutrition Science News

Calcium Less Available from Soy Milk

Seventy percent of calcium in the American diet comes from dairy products. Increasingly, however, consumers are turning to soy milk as a dairy substitute. Since soy milk contains only 10 mg calcium per cup, it is often fortified with an extra 80­500 mg calcium per cup. But calcium supplemented in soy milk may not be as bioavailable as calcium naturally found in cow's milk.

Robert Heaney, M.D., of the Osteoporosis Research Center at Creighton University in Omaha, Neb., recently reported on calcium incorporated into soy milk. In his study, 16 men aged 22 to 51 consumed either 2 percent fat cow milk or calcium-fortified 2-percent fat soy milk with breakfast. Both milks were radioactively labeled and contained an estimated 300 mg calcium.

After five hours, the level of labeled calcium was assessed in the men's serum. Absorption of calcium from soy milk was a third less than expected; therefore, more calcium should be added to make it nutritionally equivalent to milk. For example, fortification of 500 mg per cup would yield an equivalent amount of bioavailable calcium as the 300 mg of calcium found in dairy milk.

—American Journal of Clinical Nutrition 2000 May;71(5):1166-9.