The Soy Scare: Should You Avoid Phytoestrogens?

A recent wave of anti-soya publications claim that we should immediately stop eating this popular legume – and especially stop giving soya milk to babies – do to the risks of phytoestrogens. But what are they?

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Plants too have hormones

Everyone knows that hormones are essential for human growth, development, and fertility. However, it may come as a surprise that plants have hormones too! Plants’ growth and fertility are modulated by the so-called phytoestrogens – hormones that are similar to the human female hormone estrogen, which regulates female fertility. The issue with phytoestrogens is that they can bound to the same receptors in our body as real estrogen and potentially mimic effect.

Phytoestrogens are found in legumes, carrots, apples, and coffee, but its richest source is soy, which has become one of the food staples in the West as well as inthe East, especially among vegetarians. Naturally, health concerns have arisen: is it dangerous to eat soy?

Phytoestrogens and babies

If phytoestrogens are dangerous, then up to 25% of all babies – who receive soy-based infant formula – are at risk. Apparently, phytoestrogen levels in a daily portion of soya formula, when translated into human estrogen equivalent, is equal to several birth-control pills! Some experts are concerned that it may negatively affect fertility and growth further on in life (more details here). Though, truth be told, millions of infants in the West have been fed soya milk for the past decades and have grown up absolutely normal, so more research is needed.

Fertility issues

Some studies done on animals suggest that a diet rich in phytoestrogens is bad for fertility: for example, Australian sheep that ate grass containg lots of this plant hormone, but also cheetahs in a zoo that were given soy (interestingly, fertility was restored once the diet was changed). These findings make many authors call upon women to stop eating soya; however, it has to be noted that animals metabolize phytoestrogens very differently from humans. So far, there is no proof that eating soya or other foods rich in phytoestrogens reduces human fertility – see this UK government report, for example.

What about cancer?

Some cancers (breast, ovarian, and prostate, in particular) are linked to hormonal disbalances. Thus, some suggest that an excess of estrogen (or its equivalent) can lead to a higher risk of cancer in younger women. By contrast, some studies suggest that in older, post-menopausal women, who have low levels of estrogen and need hormonal therapy, phytoestrogens actually act as a protective and preventive measure and should even be recommended as a diet supplement! As for younger people, the interaction between our bodies and phytoestrogens is so complex that so far there is really no proof one way or the other (more info here).

Where do the claims come from?

Interestingly, a lot of anti-soya slogans originate with a dubious U.S. organization called WAPF (Weston A. Price Foundation), which promotes “healthy” nutrition… based on raw milk and saturated animal fat (scientifically linked to increased risks of stroke and heart disease). WAPF’s claims are known to be unscientific and should never be taken as sound nutrition advice.

Whatever anti-soya activists say, there is no proof that phytoestrogens can really hurt you. If you concerned, stick with fermented soy products, such as tofu; and even if you are vegetarian, make sure to give your baby breast milk or formula based on cow milk. As for the real role of phytoestrogens in our health – only time will tell.


The pros and cons of phytoestrogens  –
Concerns for the use of soy-based formulas in infant nutrition –
Phytoestrogens –
Weston A. Price Foundation –

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