Cow’s Milk versus Soy Milk: How Do They Differ Nutritionally?

If you’re avoiding dairy due to a milk allergy or lactose intolerance, soy milk is one alternative you might consider. Unlike cow’s milk that comes from the mammary gland of a cow, soy milk is plant-based, derived from soy beans. To make soy milk, you first soak soybeans to soften them up and then grind and strain them. You can even make it at home using one of the many soy milk makers available online. The beverage that you get has a texture that’s somewhat similar to dairy milk although thinner. Also, the taste is a bit “beanier” than dairy milk, although it’s hard to tell the difference when you pour it on cereal in the morning.


Nutritional Differences

Both cow’s milk and soy milk are good sources of protein with cow’s milk having around 8 grams of protein per serving and soy milk about 7 grams. Cow’s milk is higher in carbohydrates, about 12 grams in a serving, while a serving of soy milk only has around 5 grams. Depending upon the brand and whether it contains added sugar, it may be slightly higher than this. If you’re trying to watch your carbs, choose a brand without added sugar. Soy milk has around half the fat of cow’s milk, 8 grams versus 4 grams.


Chalk one up for soy milk. It has much protein as cow’s milk, but fewer carbs and half the fat. Where soy milk falls short is in terms of the micronutrients it contains. We all know cow’s milk is a good source of calcium, one cup supplies almost a third of a day’s requirements. Unless soy milk is fortified, it’s a poor source of calcium and contains no natural vitamin B12, a vitamin found almost exclusively in meat and dairy foods.


Fortunately, you can buy fortified soy milk with calcium, vitamin B12, vitamin D, and other vitamins added back in. In reality, cow’s milk is NOT a good source of vitamin D and has to be fortified with this important vitamin most people don’t get enough of. If you’re using soy milk as a source of calcium and vitamin B12, read the label carefully to make sure the brand you’re using is fortified.


The Lactose Issue 

One reason people choose to drink soy milk is because they don’t consume animal products, but that’s not the only one. A significant portion of the population doesn’t have enough of the enzyme that breaks down lactose, a sugar found in cow’s milk. People suffering from lactose intolerance, as this condition is called, develop cramping, bloating and diarrhea when they consume dairy products in significant quantities. If you fall into this category, you can still drink soy milk since it’s free of lactose.


Soy Milk: A Good Source of Isoflavones

Unlike cow’s milk, soy milk contains compounds called isoflavones that have weak estrogen-like properties. Some research suggests that the isoflavones in soy may protect against breast cancer, although this is somewhat controversial and still unproven. Some experts have raised concerns that consuming soy products might actually increase your breast cancer risk. The verdict is still out. Drinking soy milk may help lower LDL-cholesterol, the type most strongly linked with heart disease. If soymilk does lower the risk of heart disease, data suggests that you need around 25 grams of soy protein daily to get the benefits, the equivalent of 2-3 cups of soy milk daily.


The Bottom Line 

Each type of milk has its advantages and disadvantages. Plus, soy milk is only one of a growing number of non-dairy milk substitutes you can buy at natural food markets. If you’ve never explored the world of “alternative milks,” maybe now’s the time to give one a try.

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