The Downside of Soy Milk

Soy milk is made by grinding dry soy beans with water. The resulting liquid resembles milk and is widely consumed as a beverage or a milk substitute. Dairy-sensitive individuals, strict vegetarians and those who wish to regulate their fat and cholesterol intake may also substitute soy milk for cow's milk. It is an excellent source of protein, B-vitamins and iron but contains very little saturated fat and no cholesterol. However, there are possible side effects to drinking soymilk. For example, soy milk contains a trypsin inhibitor that interferes with protein digestion. You should not use soy milk without first consulting with your doctor or pharmacist.

Soy Allergy

The U.S. Food and Drug Administration identifies soy among the top 11 causes of food allergies. If you have soy allergies, do not consume soy milk. The most common symptoms are diarrhea, vomiting and irritability, but severe anaphylactic reactions may also develop. Soy allergy is more common in infants than adults. However, infants often outgrow their allergic responses by the age of two.

Gout

Soy milk contain moderate amounts of natural substances called purines, which are converted to uric acid in the body. If you have gout, you should exercise moderation in consuming soy milk and other soy products. High levels of uric acid can deposit in the joints as small, needle-like urate crystals, causing the involved joint to swell and become painful. It usually affects a single joint, most commonly the big toe.

Hypothyroidism

Soy milk contains phytoestrogens, plant-based estrogens, which reduce the action of thyroid peroxidase and 5'-deiodinase, the key enzymes involved in the body's production of thyroid hormone. If you are taking prescription medications for hypothyroidism, you should never take soy milk or should check with your doctor before consuming soy milk. Your body can compensate for the decreased level of thyroid hormone by secreting more thyroid stimulating hormone, according to Dr. Barbara Klein, Ph.D., of the College of Agricultural, Consumer, and Environmental Sciences. TSH, or thyroid stimulating hormone, causes the thyroid gland to enlarge. Adding iodine to the diet, however, prevents goiter.

Soy Phytoestrogens and Breast Cancer

Soy phytoestrogens resemble endogenous estrogen and exert an estrogen-like effect by binding to estrogen receptors that lie inside the cells. Breast cancer is believed to be related to long-term exposure of estrogen. Therefore, drinking soy milk may raise breast-cancer risk in women who are at high risk, due to its estrogenic property.

Mineral Deficiency

Unfermented soybeans are rich in the antinutrient phytic acid, a powerful inhibitor of mineral absorption. It binds minerals such as iron, calcium, magnesium and reduces their absorption in the body, according to Barbara P. Klein, Ph.D., of the College of Agricultural, Consumer and Environmental Sciences. Therefore, high intakes of unfermented soybeans can reduce mineral levels, especially when you consume a low-mineral diet.