Soy milk and skim milk have a place in a healthy diet as a protein-rich beverage and source of bone-building calcium. Soy milk, however, is fortified to match milk's levels of calcium and other nutrients. The shelf life of soy milk is longer than that of skim milk, making it the economical choice if your family doesn't drink much milk.
Calories
The difference in calories between soy milk and skim milk varies by type of soy milk. An 8 oz. serving of soy milk can have anywhere from 80 to 130 calories per serving, depending on whether it is unsweetened or how much added sugar the manufacturer has put in. Skim milk has a consistent 90 calories and 12 g of sugar per serving. The calories in both skim milk and soy milk come from a mix of carbohydrates, fat and protein.
Carbohydrates
Unsweetened soy milk has about 4 g of sugar per 8 oz. cup. These 4 g of sugar consist of fructose, which is a type of sugar found naturally in soybeans. Some people may find unsweetened soy milk satisfying, but others prefer it sweeter. Manufacturers often use cane sugar to sweeten soy milk to enhance its palatability, adding up to 8 g of sugar, bringing the total to 12 g of carbohydrates. Skim milk, on the other hand, has 12 g of sugar, which is comprised mainly of lactose. People with a lactose intolerance cannot break down lactose into its two component sugars, glucose and galactose, so they experience an upset stomach and intestinal distress.
Fat and Cholesterol
In spite of being called fat-free, skim milk may actually contain trace amounts of fat. According to the U.S. Department of Agriculture, skim milk must contain no more than 0.5 g of fat per serving to be labeled skim or fat-free. This negligible amount of fat is composed mostly of saturated fat. Soy milk contains 3.5 g of fat per 8 oz. serving, which is mainly unsaturated fatty acids and 0.5 g of saturated fat. The USDA dietary guidelines recommend you obtain no more than 10 percent of your total calories from saturated fat. An 8 oz. serving of skim milk contains 5 mg of cholesterol; soy milk has no cholesterol.
Protein
Both soy milk and skim milk are protein-rich drinks. Soy milk contains 7 g of protein per cup; skim milk has 9 g of protein per cup. Milk solids called casein and whey are added to commercially-prepared skim milk to amp up its protein content and to add back nutrients. Casein and whey are what remain after the milk fat is removed and the water evaporates from milk, in the production of cheese, for example.
Calcium
An 8 oz. serving of skim milk can provide about 300 mg of calcium, or 30 percent of the recommended daily allowance for calcium if you are on a 2000-calories diet. Without calcium fortification, an 8 oz. serving of soy milk provides much less than this amount, only about 60 mg of calcium. Manufacturers use a powdered calcium supplement to increase the calcium content of soy milk to a level equivalent to dairy milk. The USDA recommends that adult men and women obtain at least 1000 mg of calcium per day.
Member Comments