Soy beverages, while wholesome and nutritious, are not the nutritional equivalent of milk. Since soy beverages are naturally low in calcium (about 10 milligrams per serving), manufacturers fortify them with calcium salts to boost the calcium content. However, the amount of calcium salts added is not regulated and may vary from 80 to 500 milligrams per serving. Some soy beverages are not fortified with calcium at all. It is critical that consumers read the food label.

Even fortified soy beverages that contain the same amount of calcium as cow's milk do not provide the same health benefit due to less absorption. Creighton University researchers calculated that the body absorbs about 25 percent less calcium from a fortified soy beverage than from cow's milk. A serving of milk (8 ounces) contains about 300 milligrams of calcium. It would take 500 milligrams of calcium in an 8-ounce serving of fortified soy beverage to equal the calcium in a glass of cow's milk.

A bigger issue is the settling problem in calcium-fortified soy drinks. Most soy beverages have appreciable sedimentation of the added calcium; in other words, it settles to the bottom of the glass. A study conducted by Heaney in 2006 found that in a shaken sample, the mean calcium level was 59 percent of the value shown on the label. Unshaken samples only contained on average 31 percent of the calcium listed on the label. Very few consumers would shake a carton of soy beverage, pour out a glass and then chug it down quickly. It you set the glass aside, even for a few minutes, the calcium settles to the bottom of the glass. Reduced bioavailability and sedimentation combine to make the calcium content in soy beverages far less than in milk.   

Milk is a nutrient-rich food that provides a large number of nutrients relative to the calories consumed. Check this page to see a listing of the major nutrients in milk.

Maureen Bligh, M.A., R.D.

Project Manager