What Research Into Soy Milk And Other Soy Products Tells Us

While many researchers are calling for more focused studies to back up positive or negative recommendations, it is interesting to examine what existing research into soy milk and other soy food products made from soya beans tells us.

In the latter part of the 20^th century (which is when my highly allergic first child was born) there were many claims made about the benefits of soy. These ranged from aiding weight loss, to warding off osteoporosis and preventing several types of cancer. Even though these were based on what is now termed “preliminary evidence,” in 1999 the FDA approved the common claim that diets that were low in cholesterol and saturated fat, and contained soy, might reduce heart disease risks. This, as the bloggers at the Harvard School of Public Health point out was based largely on old research that seemed to indicate soy protein had the effect of lowering levels of bad cholesterol. Further, they cite recent research studies that temper previous findings regarding the effects of soy on a variety of diseases, including coronary heart disease (CHD).

Soy Research is Increasingly Inconclusive

The attention soy protein and its component isoflavones (a plant hormone that are similar to human estrogen, also known as phytoestrogens) has had on reducing the risks for CHD and other diseases has led to numerous new studies and new assessments of old studies.

In 2006 professionals from an American Heart Association nutrition committee assessed 22 clinical trials, most of which contained isoflavones in isolated soy protein. They found there had been no significant effects on so-called “good” HDL cholesterol, blood pressure, triglycerides (a type of fat found in the bloodstream), or the lipoproteins that carry cholesterol through the blood. Further, they found that there was no evidence that soy isoflavones had been used successfully to treat breast, prostate or endometrium cancer. However, they did believe that soy products in general were healthy and beneficial to cardiovascular health because they have a low saturated fat content, high polyunsaturated fat content, as well as high fiber, vitamins and minerals.

A study out of the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment in 2008 considered exposure to isoflavones both in early and later adult life in relation to risks of breast cancer. Reporting “conflicting evidence” the researchers concluded that it wouldn’t be safe to accept indisputably that soy can be used to prevent breast cancer.

A US study published in The Journal of Nutrition in late 2010 considered the effects of soy on breast tissue to try and assess whether it is safe or increases the risks of breast cancer. The researchers, led by Leena Hilakivi-Clarke from Georgetown University in Washington, concluded that it is safe, and that women who consume soy early in life have a lower risk of breast cancer. However, they admitted that there were probably other lifestyle factors (including physical activity) that played a positive role. They also warned that soy products can promote breast cancer, so those who have been diagnosed should avoid foodstuffs with any soy content.

The FDA’s current publication on Food and Drugs Regulations discusses health claims relating to soy protein, saturated fat and cholesterol, and the risk of CHD. Updated in April 2015, it states that there is no “degree of risk reduction” of CHD for people on low saturated fat, low cholesterol diets that include soy protein. It also states that a daily intake of 25 g of soy protein is associated with a reduced risk of CHD, but that this is not the only way to reduce the risks of CHD. 

Examples of Soy Milk Specific Research

In a study undertaken in the early 2000s, A Zung and several other Israeli researchers from the Hadassah Medical School in Jerusalem evaluated the “estrogenic effect” of the phytoestrogens in soy-based infant formulas on the breast development of female infants. Their aim was to assess whether soy-based infant formulas are safe or not. Their study, published in the Journal of Pediatric Gastroenterology & Nutrition in 2008, reported that babies who had been fed soy rather than cow’s milk-based formula had more prevalent breast buds during their second year of life. However, they found that the isoflavones in soy did not actually induce breast development, but rather maintained its presence once developed. Ultimately, they supported earlier studies that recommend soy-based formula only be used for medical indications like lactose intolerance, and not to provide a vegetarian diet for infants.

Heather B Patisaul and Wendy Jefferson from the National Institute of Environmental Health Sciences in North Carolina published an article on the pros and cons of phytoestrogens in 2011. In the lengthy document, they concluded that beneficial effects are often overstated, but that potentially harmful effects were “likely underappreciated.” Their greatest concern was infants given soy formulas because this exposes them to estrogen-like compounds, and the fact that “virtually nothing” is known how these might affect their “future reproductive health.”

READ Soy Protein Vs. Whey Protein - Who Wins?

In 2012, in a letter published in the Indian Journal of Postgraduate Medicine, Professor V Wiwanitkit from Hainan Medical College in Thailand produced proof that the “excessive consumption of soybean milk” can result in hepatitis. The affected patient was a 53-year-old woman who had drunk 2.5 to 3 liters of soybean milk every day for a year.

Writing in the same publication in 2013, S Senthilkumaran from the Department of Emergency and Critical Care Medicine at Sri Gokulam Hospitals and Research Institute and several colleagues from other medical institutions in India stated that soybeans and its derivatives were one of the big eight most allergenic foods. They called on further clinical studies to be undertaken and urged those producing soy milk to warn consumers that too much soy milk can have toxic effects.

While this doesn’t prove that soy milk per se is toxic, it does warn that it can be.