Nutritional differences between soy- and cow's milk

Originally Published: March 2, 2001 - Last Updated / Reviewed On: October 5, 2012
Share this
Dear Alice,

What are the nutritional differences between soymilk and regular milk? What are the benefits, and is one better than the other?

— Udderly confused

Dear Udderly confused,

The major difference between soymilk and "regular" milk (predominantly cow's milk in the United States; goat and sheep's milk are other options) is that one is derived from a plant and the other from an animal. Although ethical, hypothetical, or debatable issues frequently arise when discussing this subject, this answer is going to deal strictly with the nutritional differences between these two kinds of milk.

What's most commonly referred to as simply “milk” is cow's milk, a product of the cow’s mammary gland. As with all other animal-based foods, it's a complete protein; that is, it supplies people with all the necessary amino acids to form proteins. Cow's milk contains 8 grams of protein and 12 grams of carbohydrates per 8-ounce cup. Cow's milk is a rich source of other nutrients as well. One cup provides adults with about 30 percent of their daily calcium needs and about 50 percent of their vitamin B12 and riboflavin requirements. Often, milk is fortified with vitamin D to facilitate the absorption of calcium. Vitamin A is usually added to milk as well. Depending on the selection, cow's milk can have a significant amount of fat. (See the chart at the end of the answer for a comparison of the fat content of some varieties of milk.)

Lactose, the primary carbohydrate in cow's milk, poses a digestive problem for some people. These folks are deficient in the lactase enzyme that's needed to break down this milk sugar, causing gas, bloating, and diarrhea after consuming some forms of dairy products. The solution is to purchase products with the lactose already broken down, to take the enzyme in the form of a pill or drops, or to find a substitute for these foods. Check out Lactose intolerance for more information.

Soymilk is not technically milk, but a beverage made from soybeans. It is the liquid that remains after soybeans are soaked, finely ground, and then strained. Since it doesn't contain any lactose, soymilk is suitable for lactose intolerant folks. It's also a popular cow's milk substitute for vegans and vegetarians since it's based on a plant source (others include rice, oat, almond, coconut, and potato milk).

One cup of unfortified soymilk contains almost 7 grams of protein, 4 grams of carbohydrate, 4½ grams of fat, and no cholesterol. Although soymilk supplies some B vitamins, it's not a good source of B12, nor does it provide a significant amount of calcium. Since many people substitute soy beverages for cow's milk, manufacturers offer fortified versions. These varieties may include calcium and vitamins E, B12, and D, among other nutrients. If you do choose to use soymilk instead of cow’s milk, read labels carefully to be sure you're getting enough of these important nutrients or consider getting them from alternative food sources.

Soymilk may help some people reduce their risk for heart disease. Soy naturally contains isoflavones, plant chemicals that help lower LDL ("bad" cholesterol) if taken as part of a "heart healthy" eating plan. The recommendation is to take in about 25 grams of soy protein per day. One cup of soymilk has about 7 - 10 grams of protein, depending on the brand. Previously, researchers thought soy consumption was correlated with increased rates of breast cancer, but recent research suggests that soymilk consumption may actually reduce breast cancer rates for some populations, including post-menopausal women and Asian populations. Soy’s unique effect on Asian women is thought to be the result of larger amounts of dietary soy consumed over longer periods of time than other in women.

All in all, what you choose to drink is really a matter of personal preference and your health objectives. You may find this chart helpful in comparing the nutritional qualities between cow's milk and soymilk [per 1 cup (8 oz.) serving]:

Product Calories Fat(g) %Fat Calcium(mg)* Vit. B12(mcg)*
Cow's Milk:
         
Whole milk 150 8 48 290 .87
Reduced fat (2%) 120 5 38 297 .89
Low fat (1%) 100 3 27 300 .90
Skim 85 .4 4 302 .93
Soy:
         
Unfortified 79 4.5 51 10 0
Fortified** 130 3.5 30 585 1.2

*RDA (men and women) for: Calcium: 1,000 - 1,300 milligrams/day (depending upon age) Vitamin B12: 2.0 micrograms/day

**Silk Vanilla

May you always have a tall glass of (soy or cow's) milk with your cookies!

Alice

January 28, 2013

522619
Some people find that taking lactase pills while eating their meal helps to break down the lactose, and decrease or eradicate symptoms.
Some people find that taking lactase pills while eating their meal helps to break down the lactose, and decrease or eradicate symptoms.

January 17, 2013

521848
Very well explained. I learned a lot.
Very well explained. I learned a lot.

March 26, 2012

509141
Soy foods are not the only plant based food that contain complete proteins. Quinoa is a grain and an example of a complete protein. Amaranth and hempseed are other examples.
Soy foods are not the only plant based food that contain complete proteins. Quinoa is a grain and an example of a complete protein. Amaranth and hempseed are other examples.