Should I worry about eating too much soy?

Should I worry about eating too much soy?

There is an impression that soy could be a hormone disrupter because it contains plant-based oestrogens called isoflavones.

Since soya is used in so many of the new meat substitute foods – from vege-burgers to vege-sausages to vegan ready meals – it’s a legitimate question to ask.

Especially when there is soy in foods as different as mayonnaise, peanut butter, tofu, miso, even plant milk.


This article was written by Colin Rose, a Senior Associate Member of the Royal Society of Medicine, who has been writing on health science for over 30 years. He is also the founder and Director of Research and Innovation of Uni-Vite Healthcare.

New research disputes the biggest soy myths

A new 2021 study has just been published in the journal Critical Reviews in Food Science and Nutrition.  It was reported in the Physicians' Committee for Responsible Medicine.

The study looked at 417 other reports based on human data and found that:

Isoflavones and soy foods do not have adverse effects on breast or endometrial tissue or oestrogen levels in women, or testosterone levels, sperm or semen in men. It also showed no adverse effect in children.

On the contrary, soy products are associated with a reduced risk of breast and prostate cancer, as compounds called soy isoflavones appear to act to reduce the blood supply to early-stage cancer cells – choking off nutrients needed for the cancer cells to grow.


Lower risk of breast cancer – and lower risk of recurrence

Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals
Edamame (soy) beans

A 2013 meta-analysis that analysed data from 22 studies found that Asian women who consumed the most soy isoflavones had a 32% lower risk of breast cancer than those who consumed the least. A 2014 meta-analysis reached similar conclusions.

The effect even extended to women who had previously suffered from breast cancer. Those diagnosed with oestrogen-negative breast cancer, and who consumed the most soy isoflavones, had a 21% lower risk of dying from cancer compared with those who ate the least.

In addition, the Women’s Healthy Eating and Living Study indicates that soy may help protect breast cancer survivors. Women who ate the most soy reduced their risk of cancer returning by half.

But how?

Your cells have two different kinds of oestrogen receptors: alpha and beta. Estrone, the main oestrogen in women after menopause, binds mainly to the alpha receptor. Soy isoflavones preferentially bind to beta receptors – which are the receptors that can trigger the growth of cancer cells. This binding seems to help block the cell growth that’s part of the cancer process.

Men's prostate cancer risk reduced – and no effect on testosterone

Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals
Natto (fermented soybeans)

A meta-analysis published by the US National Institutes of Health showed that neither soy products nor soy isoflavone supplements affect testosterone levels in men.

Indeed, it showed that consuming more soy resulted in a 26% lower risk of prostate cancer.

Brain health positives

Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals
Sprouting soybeans

When you consume soy in any form, your gut produces a metabolite known as equol. And this may reduce the risk for dementia, according to a study published in the journal Alzheimer's & Dementia.

Researchers checked brain images for lesions in brain white matter which are associated with cognitive disease in almost 100 elderly participants and tracked their equol levels.

Those who produced more equol from dietary soy products had 50% fewer white matter lesions than those with lower equol levels.

Japanese populations have more gut microbes that help produce these soy metabolites, compared to Western populations, due to their higher consumption of dietary soy.

Soy benefits for inflammatory conditions and osteoporosis

The Shanghai Women’s Health Study – a long-term study of the diets of 1,005 middle-aged Chinese women – found that the more soy products the women consumed, the less inflammation they had. Inflammation is a major factor in arthritis, cancer, type 2 diabetes, and heart disease.

Finally, several studies published in journals including the American Journal of Epidemiology point to soy and soy isoflavones helping to reduce osteoporosis – and therefore potential bone fractures – by around 30%.

Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals
Oriental soy bean rice (featured in the Health Defence Cookbook)

Conclusion – Soy good!

You can use soy food products to help reduce or even eliminate red and processed meats from your diet – since these are linked to adverse health issues. And enjoy the fast-expanding range of soy-based meat substitutes, yogurts, and even cheeses.

In addition, comprehensive supplements like NutriShield are right to include soy isoflavones. Decades of research show them to have important health benefits.


Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals

Dr Paul Clayton designed NutriShield as a comprehensive health supplement with OPTIMUM levels of 43 essential nutrients including soy isoflavones, polyphenols and flavonoids from fruits, vegetables and other plants, Omega 3, betaine and green tea. 

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Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals

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Uni-Vite Healthcare has a range of combination anti-ageing and immune-supporting health supplements to buy online from a UK company.

Should I worry about eating too much soy? NutriShield Multi Vitamins and Minerals

Should I worry about eating too much soy? NutriShield Multi Vitamins and MineralsDr Paul Clayton's best-selling book Health Defence is available from bookstores or from Uni-Vite Healthcare here.

A free summary report and the opportunity to read the book online is available here.

Colin Rose's new book (2020) Delay Ageing is also available from bookstores or from Uni-Vite Healthcare here.



1. Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data. Messina M, Mejia SB, Cassidy A, et al. Crit Rev Food Sci Nutr. 2021;1-57. doi: 10.1080/10408398.2021.1895054

2. Associations of equol-producing status with white matter lesion and amyloid-β deposition in cognitively normal elderly Japanese. Sekikawa A, Higashiyama A, Lopresti BJ, et al. Alzheimer’s Dement. 2020;6:e12089-e12098.

3. Epidemiology of soy exposures and breast cancer risk. Wu AH, Yu MC, Tseng CC, Pike MC. Br J Cancer. 2008;98:9-14
Association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women: A meta-analysis of epidemiological studies. Chen M, Rao Y, Zheng Y, et al. PLoS ONE. 2014;9:e89288-e89298

4. Dietary isoflavone intake and all-cause mortality in breast cancer survivors: The Breast Cancer Family Registry. Zhang FF, Haslam DE, Terry MB, et al Cancer. 2017;123:2070-2079.

5. Soy isoflavones and risk of cancer recurrence in a cohort of breast cancer survivors: The Life After Cancer Epidemiology study. Guha N, et al; Breast Cancer Res Treat. 2009;118:395-405.

6. Soy protein isolate and protection against cancer. Badger TM, et al; Am Coll Nutr. 2005;24:146S-149S.

7. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: Results of a meta-analysis. Hamilton-Reeves JM et al, Fertil Steril. 2010;94:997-1007

8. Soy consumption and prostate cancer risk in men: A revisit of a meta-analysis. Yan L, Spitznagel EL ;Am J Clin Nutr. 20 0 9 ; 8 9 :1155 -116 3

9. Prospective cohort study of soy food consumption and risk of bone fracture among postmenopausal women. Zhang X, Shu XO, Li H, et al Arch Intern Med. 20 05;165:189 0 -1895