Myths and facts about soya bean

By Frank Marful-Sau, RD, LD, MPH | August 11, 2023

Soybean is a legume that is extensively grown globally for its versatility and valuable characteristics. Originating from East Asia, soybeans offer a range of nutritional benefits, including high protein content; high levels of essential amino acids, beneficial fats, dietary fibre, vitamins (such as folate, vitamin K, and vitamin C), and minerals (such as iron, calcium, and potassium). These make them a popular choice for those seeking plant-based protein options. Industrially, the extracted soybean oil is widely used in cooking, food processing, and biodiesel production. Soybeans are processed into various products like tofu/soy khebab, tempeh, soy milk, soy flour, and soy-based meat alternatives, catering for the preferences beyond vegetarian, vegan, and plant-based diets. With all these benefits, soybean has been subjected to both commendations and condemnations over for years. This article aims to bring to light some of these misconceptions and debunk them based on available evidence.

A common myth surrounding soy and its products is it link to an increased breast cancer risk. Theoretically, phytoestrogens contained in soy are deemed to have a similar structure to oestrogen hence the assumption they put females at risk of breast cancer when taken in excess. Despite these claims, several meta analyses have concluded that an increase intake of soy was associated with lower risk of breast cancer. Substantial research done over the past few years have shown that average intake of soy was not associated with breast cancer risk and also a higher amount might be beneficial in breast cancer prevention.

Another popular myth about soy is it infant formula being deemed harmful. This is due to the assumption that soy formula have oestrogen like effects and can cause problems later in life just as it was reported in certain animal studies. Soy products have also been noted to have high aluminium content which could impact infant development. However according to Tesla et al. (2018) and Leung et al. (2009), soy formulas showed no difference in development when compared to standard infant formulas.

Soy negatively affecting thyroid function particularly in individuals with hypothyroidism is also one of the misconceptions. Soy has been thought to interfere with the body’s ability to absorb medication in case of hypothyroidism. A systematic review by Otun et al. (2019) showed that there was a significant change in thyroid stimulating hormone (TSH) as a result of soy protein intake but there was no significant change in Free triiodothyronine (FT3) and free thyroxine (FT4) levels suggesting that while soy can affect thyroid function, it may not be clinically significant. In addition, in humans with normal thyroid and consuming adequate iodine, evidence available shows that soy foods don't cause thyroid problems and hence consumption should be encouraged.

Furthermore, another tenacious myth suggests that soy intake can lead to feminization in men. This was thought to be as a result of activities of phytoestrogens/isoflavones present in soy, lowering testosterone levels. Some clinical studies reported a reduction levels following soy intake. A small case control also concluded that consumption of soy was associated with lower sperm concentration among certain individuals. However, extensive clinical data published over the past decades concludes that, neither isoflavones nor soy intake in men (even for longer periods) affects overall testosterone, estradiol, estrone or free testosterone.

The belief that all soybean products are genetically modified is also one of the misconceptions. Genetically modified organisms according to the World Health Organization (WHO) are organisms (plants, microorganisms, animals) in which their genetic material has been altered in a way that does not occur naturally by mating. Although there are soybeans that have been genetically modified, unaltered or wild soybeans do exist especially in Ghana and this gives individuals the chance to choose what suits them. While industries have been mandated to label these products, reading these food labels is essential in making such choices.

In conclusion, Soybean and its various products have faced numerous misconceptions and myths over the years. However, extensive scientific research has consistently debunked many of these claims. By dispelling these myths, the aim is to encourage individuals to make informed decisions about consuming soy, so they can fully benefit from its nutritional advantages and versatility.


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