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The Truth about Soy – Busting the Myths


The great debate… People seem to be either for soy, or against soy. And people seem to have some very strong opinions.

So we spent some time analysing the science and investigated further to find out why there’s so much conflicting opinion and confusion floating around about this humble bean.

Soy is one of the most researched foods on earth, so firstly let’s take look at some of the commonly believed “facts” about soy and compare this with the research…

#1 “Does Soy Contain Estrogen?”

No – none. Soya contains zero estrogen. (Side note: cow’s milk actually contains plenty of actual mammalian estrogen.[1])

Soya does contain phytoestrogens (plant hormones – not human hormones). Phytoestrogens in the human body are relatively weak and can actually bring benefits, such as a lowered risk of cancer, by ‘blocking’ actual estrogen.[2]

There is no evidence for soy disrupting sexual development in humans.

Although soya beans are amongst the richest sources of phytoestrogens, it’s worth noting that phytoestrogens are not only found in soya beans. Other beans, such as coffee beans, also contain phytoestrogens.

And phytoestrogens are found in many other foods as well, such as: apples, oats, sesame seeds, flaxseed, lentils, rice, carrots, mint, ginseng, beer, and pomegranates. Even if you completely avoid eating soy, you’re very likely still consuming phytoestrogens – but that’s not a problem.

(N.B. Isoflavones are phytoestrogens and powerful antioxidants. Antioxidants help remove free radicals before they can cause gene mutations potentially leading to cancer. Legumes, particularly soy beans, are the richest sources of isoflavones.)

Many people seem to think consuming phytoestrogens is “bad” but this certainly isn’t the case. The isoflavones contained in soy are actually powerful antioxidants (particularly genistein) and research has shown that they have very positive effects in protecting against cancers and other diseases.[3]

#2 “Will Soy Affect My Fertility?”

The 2003 Department of Health’s committee on toxicity report acknowledged that there was no evidence that people who regularly eat high quantities of soya, such as the Chinese and Japanese, have altered sexual development or impaired fertility. It should be remembered that China is the world’s most populous nation, with over 1.3 billion citizens, and who have been consuming soya for over 3,000 years.

For women, a large-scale study at a Boston fertility center showed female consumption of soy improved birth rates for couples undergoing fertility treatment.[4]

And for men, soy intake had no negative impact on fertility. A study at Harvard University found men’s soy intake was unrelated to the clinical outcomes on fertility. [5]

A 2010 meta-analysis (meta-analysis is a review of the results from many independent scientific studies) of fifteen placebo-controlled studies said that “neither soy foods nor isoflavone supplements alter the measures of bioavailable testosterone concentrations in men.”[6]. Furthermore, isoflavone supplementation has no effect on sperm concentration, count or motility, and it leads to no observable changes in testicular or ejaculate volume.

So men’s testosterone is not affected by consuming soy products.