Soy vs Dairy

Proponents of soy milk tout it as a natural, plant-based source of protein and point to research that shows that soy milk lowers LDL (low density lipoprotein), or “bad” cholesterol in the body, thereby cutting a person’s risk of heart diseases. Soy critics argue that soy contains phytoestrogens, which are thought to interfere with a child’s development.

How do you, as a consumer, make an informed choice? To help you, we discuss here some important questions about soy and cow’s milk, namely:

1. What is the difference between soy and cow’s milk?
2. Can I give my baby soy formula instead of cow’s milk formula?
3. Should people with gout avoid soy?
4. Is soy or dairy better for patients with cancer?

What is the difference between soy and cow’s milk?
Soy is a good source of low-fat and plant-based protein. It is cholesterol-free, has less saturated fat than cow’s milk and lowers the LDL in the body. Cow’s milk, on the other hand, has more calcium than natural soy. Calcium, as we know, helps to build bones and prevents osteoporosis. Cow’s milk also contains more vitamins, such as vitamin B12 and D.

These days, however, commercially made soy milk is often fortified to have calcium and nutrients similar to cow’s milk. At the same time, cow’s milk now comes in low-fat versions and these sometimes have lower saturated fat than commercial soy milk (see table below).

Both calcium-fortified soy milk and low-fat milk are good sources of protein and calcium. However, there is evidence that soy products, together with a diet low in saturated fat, can help to lower LDL level, and hence reduce the risk of heart disease.

Soy milk for babies?
One of the biggest concerns about soy milk is the high level of phytoestrogens, which are dietary estrogens found naturally in some foods. Soy beans and soy products contain high concentration of isoflavones, a group of phytoestrogens.

There is concern that soy milk, because of its high levels of phytoestrogens, could affect a child’s development, such as causing early puberty, breast development in males or reproductive problems. However, according to a restrospective study conducted in 1999 on a group of 811 adults aged 20 to 341, there is no significant difference in the development and reproductive outcomes between those fed on soy formula and those on cow’s milk formula in infancy. These 415 men and 396 women had been enrolled, when they were infants, in a controlled feeding study at the University of Iowa, United States. They were fed either soy formula or cow’s milk formula from nine days till they were 16 weeks’ old.

In any case, experts are unanimous about this – breast milk is still the best for babies. Doctors may recommend soy formula if the baby is lactose-intolerant or suffers from galactosemia, a rare genetic disorder where the body is not able to break down the sugar, galactose, properly. While soy milk has many benefits, it has no proven advantage over cow’s milk in preventing colic, vomiting or fussiness in babies.

Can people with gout eat soy?
Many people think that if you suffer from gout, you should not eat any soy. This is not totally true. Gout is due to excessive uric aid in the blood, which causes crystal deposits to form in the joints, leading to inflammation and pain. Uric acid is formed from purine, which is found in protein-containing foods such as soy.

If you suffer from gout, it is important to lose weight if you are overweight. Drink adequate fluids; restrict alcohol intake and refrain from eating large meals. As for food, you should avoid fatty foods and foods which are high in purine. Foods like soy, which are moderate in purine, can be consumed in moderate amounts as part of a healthy and balanced diet

Is soy or dairy better for cancer patients?
Some people think that because soy is plant-based, it is better for cancer patients. Dairy products are thought to “feed” cancer cells. There is no scientific evidence to prove this theory. Cancer patients in general need a high energy and high protein diet. Both soy and dairy products are good sources of protein and should benefit a patient undergoing cancer treatment. However, women with estrogen receptor-positive breast cancer should avoid soy supplements and not eat excessive amount of soy products.

Reference:
1 Strom BL, Schinnar R, Ziegler EE, et al. Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood. JAMA. 2001;286:807-814