Magic Beans or Tragic Beans? – Debunking Soy Myths

Oh, boy! Are you confused about soy?               

Soybeans have been consumed as a staple food in many Asian countries for centuries, yet are still misunderstood. More recently, these nutritious legumes have also become a common food source in western diets and elsewhere in the world.

Thankfully, the nutrition and health benefits of soy has been thoroughly researched! Soybeans are becoming a popular component of plant-based diets due to their versatility and high protein content. They are the one of the few plant proteins considered equivalent to animal protein, providing all the essential amino acids that must be obtained from your diet [1]. Along with being a complete protein, soy is also rich in fibre and a great source of several vitamins and minerals. Furthermore, eating soy has been found to reduce “bad” LDL cholesterol and total cholesterol, while improving “good” HDL cholesterol, especially in those with already high cholesterol levels [2].

However, despite the numerous health benefits of soy, there remains a concerning number of misconceptions regarding the potential dangers of soy consumption. These claims largely arise from uninformed beliefs and are often based on little scientific evidence. So let’s take a closer look at all the confusion about soybeans and tackle these myths one by one!


Myth #1: Soy Causes Breast Cancer
Myth #2: Soy Contains Estrogen
Myth #3: Soy Causes Feminizing Effects in Men
Myth #4: Soy Interferes with Thyroid Function
The Final Verdict


    Myth #1: Soy Causes Breast Cancer

    pink breast cancer ribbon

    We’ve all heard this one before… But, there’s actually no scientific evidence that supports the notion that soy increases the risk of breast cancer development. Instead, many clinical and long-term epidemiological studies have demonstrated that moderate soy consumption is perfectly safe and may even have a protective effect on break cancer risk. Also, eating soy was associated with a lower risk of cancer recurrence among breast cancer survivors [3].  
    Bottom line: Soy may have a PROTECTIVE effect against breast cancer occurrence, or at the very least, is safe for consumption.

    Myth #2: Soy Contains Estrogen

    strip of pills

    Wrong! Soy contains isoflavones which are also known as phytoestrogens or “plant estrogens” and are NOT the same as female estrogens. Phytoestrogens are plant hormones and are much weaker than human estrogen! They can actually bind to estrogen in the human body, and ultimately give off anti-estrogenic effects in the breast tissue, while also having weak estrogen-mimicking effects in the bone tissue. This beneficial effect has been associated with a lower risk of breast cancer occurrence, as well as improved bone health in women! [3] As well, research suggests that because of their effects, phytoestrogens may potentially ease symptoms of menopause, such as hot flashes and night sweats [3].  

    Bottom line: Soy isoflavones are beneficial for bone health and have cancer-protective effects.

    Myth #3: Soy Causes Feminizing Effects in Men

    doctor explaining results to patient

    There is a misconception that soy intake is not good for men, as there are claims that suggest it may have feminizing effects or lead to infertility.

    This heavily circulated myth originates from two previously reported cases in the literature. Of the two, one prior case-report described an older man who developed enlarged breasts (or gynecomastia, the medical term for “man boobs”), whereas another case was of a man who reported feelings of sexual dysfunction as a result of excessively high levels of soy intake of about 3L per day!!!  In both these cases, the level of soy consumed per day was unusually high and continued over an extended period of time. As well, the reported symptoms from these individuals were reversed when soy intake was discontinued.

    Many well-controlled studies and meta-analyses have failed to replicate these findings, despite using study protocols with levels of soy protein that greatly surpass typical dietary intake. The results from multiple scientific studies do not show a consistent link between soy consumption and markers of male fertility, such as sperm count or changes in circulating sex hormone levels (testosterone or estrogen) [4]. As such, studies have concluded that there is no evidence to suggest that soy consumption adversely affects male reproductive hormone levels or fertility. Instead, health and nutrition research demonstrates that the consumption of soy-based foods is actually beneficial for men, as it may help REDUCE the risk of prostate cancer and the development of other diseases [4]. 

    Bottom line: Men do not have to worry about the feminizing effects of soy. When consumed in moderation, soy does not impair male reproductive health or fertility. 


    Myth #4: Soy Interferes with Thyroid Function


    prostate throat pain woman grey shirt

    Soybean consumption has been previously linked to diet-induced goiter (enlarged thyroid), a consequence of impaired iodine deficiency and absorption. This relationship was first discovered in the early 1960s, as infants fed soy formula developed goiter, due to a lack of iodine in their diet, but at the time the exact cause of this relationship was unclear [5].

    More recently, concerns regarding the adverse effects of soy consumption on thyroid function are mainly based on test-tube and animal research. However, several human studies have reported that the influence of soy on the thyroid is not clinically significant in healthy men and women. An in-depth 2006 review of 14 clinical trials collectively found little to no evidence for any negative impact of either soy or isoflavone exposure on normal thyroid function [6]. It was further concluded that individuals with compromised thyroid function (or hypothyroidism) do not need to avoid soy foods, provided that they are consuming sufficient amounts of iodine [6].

    More recent studies published after this review have also concluded similar findings [7]. Additionally, in 2015 the European Food Safety Authority (EFSA) concluded that soy isoflavones do not affect thyroid function [8]. 

    Bottom line: Soy consumption does not compromise normal thyroid function in healthy individuals.

    The Final Verdict: Magic Beans!

    soybeans wood bowl scoop table

     As you just saw, myths regarding soy and isoflavones are rampant. However, it's important to address these misconceptions of soy with evidence-based science. While our understanding of soy-based foods continues to evolve, the overall evidence shows that soy is a healthful food that can be safely incorporated into the diets of healthy individuals, provided that they do not have a soy allergy. It’s also worth noting that soy allergies are quite rare – only 0.1% of Canadians are allergic to soy, while 1.1% of Canadians are allergic to peanuts, an eleven-fold increase [9]! Additionally, some studies suggest that foods that contain soy confer additional health benefits besides their nutritional value. So, it’s safe to say that adding these *magic* beans to your diet can provide plenty of benefits to your overall health!


    1. Singh P, Kumar R, Sabapathy SN, Bawa AS. Functional and Edible Uses of Soy Protein Products. Comprehensive Reviews in Food Science and Food Safety. 2008; 7(1):14-28. 

    2. Tokede OA, Onabanjo TA, Yansane A, Gaziano JM, Djoussé L. Soya products and serum lipids: A meta-Analysis of randomised controlled trials. British Journal of Nutrition. 2015;114(6):831-843.

    3. Messina M. Insights Gained from 20 Years of Soy Research. Journal of Nutrition. 2010;140(12):2289S-2295S.

    4. Messina M. Soybean isoflavone exposure does not have feminizing effects on men: A critical examination of the clinical evidence. Fertility and Sterility. 2010;93(7):2095-2104.

    5. Hydovitz JD. Occurrence of goiter in an infant on a soy diet. The New England Journal of Medicine. 1960;262:351–353.

    6. Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: A review of the relevant literature. Thyroid. 2006;16(3):249-258.

    7. Otun J, Sahebkar A, Östlundh L, Atkin SL, Sathyapalan T. Systematic Review and Meta-analysis on the Effect of Soy on Thyroid Function. Scientific Reports. 2019;9(1):3964.

    8. EFSA ANS Panel (EFSA Panel on Food Additives and Nutrient Sources added to Food). Risk assessment for peri- and post-menopausal women taking food supplements containing isolated isoflavones. EFSA Journal. 2015;13(10):4246.

    9. AllerGen – The Allergy, Genes and Environment Network. Canadian Food Allergy Prevalence; 2017.


    Rahbika Ashraf

    Rahbika Ashraf is a Business Development and Growth Marketing Assistant at Neophyto Foods, with a background in Human Health and Nutritional Sciences from University of Guelph. She is passionate about health and wellness research, and bridging knowledge gaps with science! When she is not typing away, you can find her meditating, hiking, playing sports and watching TV shows.

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