Soy: Friend or Foe?

Soy and soy products today are seen as popular health foods, used as alternative infant formula foods, and in hormone replacement (HRT) products. Along with increased consumption among adults, about 20 to 30% of infants are now drinking soy formulas and as a breast milk and cow’s milk alternative. Soy-milk’s use as a milk alternative is particularly popular, as incidences of lactose-intolerance and lactose-intolerant adults increase in the US. Sometimes it is also used as a protein source for vegetarians and a milk alternative for vegans. All this has raised many concerns because of the one of the naturally occurring products in soy is called genistein. It belongs to the isoflavone class of flavonoids and it is classified as a phytoestrogen. This is a naturally occurring plant estrogen or phytoestrogen that can mimic effects of estrogen in the body. This has prompted the call for more research as to potential soy product risks and benefits.

The US Center for the Evaluation of Risks to Human Reproduction (CERHR) of the National Institute of Environmental Health Services (NIEHS) and National Toxicology Program conducted a major study on the effects of soy on infants and human production in March 2006. The study made some observations on how infant formula made of soy should be made. Soy infant formula isolate has about 90% protein. This is fortified with L-methionine, L-carnitine, and taurine. L-methionine improves the biological quality of the protein, L-carnitine is needed for the oxidation of long-chain fatty acids and taurine is an antioxidant that is a major conjugate of bile acids in infants. Carnitine and taurine are found in human milk.

Fats are added with vegetable oils, corn or tapioca starch and sucrose are the carbohydrate sources. This is further fortified with phosphorus, calcium, iron and zinc. These infant foods are usually fed to babies who have dairy allergies, are lactose intolerant, or have intolerance to galactose and cow’s milk protein. It was found that soy formula powders and liquid concentrates had more isaflavones. The quantity of genistein and daidzein were also definitely higher than in human or cow’s milk.

The good news is that the panel found a "negligible concern" in neonates and infants who are fed on soy formula foods. Studies on rats and humans suggest that there is no need for concern and it safe for infants who cannot be breast-fed and cannot tolerate cow’s milk.

The report however brought to the fore concerns about soy-induced thyroid toxicity. There is concern that individuals with hypothyroidism may be susceptible to thyroid problems or that it may interfere with the medications used to treat the condition. However epidemiologic studies suggested no association between phytoestrogen exposure through soy consumption and thyroid cancer risk in humans.

The study also stated that people in Japan had been consuming soy products without side effects. It also stated that incidents of lower cardiovascular disease, cancer and postmenopausal symptoms could be attributed to the lifestyle of people in the region, including high consumption of soy, as well as any genetic disposition.

Should soy be part of our diet? Should it be eaten only if it is prepared the traditional way? The debate still rages on and the health benefits are still being studied. However, there are many vegetarians and vegans who swear by it and extol its many health virtues.