Is soy milk bad for you?

The brief history of soy

Soy milk is made from beans (or legumes) that are just like peanuts, chickpeas, black beans and kidney beans. Soy is a versatile, cheap, high quality source of protein, and a rich source of many other nutrients. They are also high in choline, magnesium, omega 3, zinc and iron. In fact, soy is nutritionally quite close to chicken.

Soy has been a staple human food for thousands of years – and a central part of Asian diets since it’s domestication in 1100BC.

Soy is one of the most researched foods on earth. A large and growing body of evidence indicate that soy is safe for everyone, and is beneficial for disease prevention and recurrence. Nonetheless, fear remains about soy foods. Those who have heard the stories about breast development in men often don’t realise that these are anecdotes, not science.

Anti-soy arguments


Some people claim that soy crops destroy more forest and rainforest land than grazing cattle. This is misleading. While current rates and methods of rainforest destruction for soy crops is utterly devastating, it is important to understand that 75% of that soy goes to feed animals used for food. Tragically, 88-93% of soy grown on Earth is for livestock feed – soy for human consumption accounts for only a small portion of the remainder. The rest is used for industrial purposes, such as biofuel. Most omnivores who are opposed to soy for perceived health or ethical reasons generally don’t realise that it’s in the animals they eat.


The chemical structure of isoflavones is similar to oestrogen, hence the name”phyto-estrogen”. Many plant foods contain isoflavones, but soy is the richest common source . Isoflavones have a mild estrogenic effect because they can bind to human oestrogen receptors. In reproductive tissues, soy has anti-oestrogenic effects which may reduce the risk of cancer. However, these mechanisms are still not well understood.

Those concerned about the hormonal effects of soy should also consider the oestrogen in cow’s milk. Unlike isoflavones, this is a mammalian hormone, and as such, it may have significant effects on human health.

The science is clear and settled – soy doesn’t cause breast development in men. It does not contain oestrogen. It does not cause infertility or cancer.


Soy is an allergen for some people, however, soy allergies are uncommon compared to milk and dairy allergies.

Genetic modification

Many people are concerned that soy is genetically modified, however this only relates to some, non-organic soy. Organic soy that is produced for humans (at least in Australia) is not genetically modified…and most non-organic soy isn’t either. Check the label if you want to be sure. However, soy grown to feed cattle, chicken and pigs is almost always genetically modified.

What does the science really say?

Benefits of soy

Studies have shown that higher soy intakes are associated with increased fertilization and live births in women having IVF. Others have shown similar results using soy supplementation, suggesting that a modest in increase in soy may increase fertility for couples experiencing difficulty.

Additionally, there is emerging evidence that soy may protect bone density in post menopausal women. This may be due to its oestrogen modulating effects.

There is evidence that soy is protective from cardiovascular disease. It’s also been shown to decrease the risk of mortality and cancer reoccurrence in breast cancer survivors.

Soy milk is nutritionally superior to other plant milks

Soy is naturally higher in protein and micronutrients than other plant milks and is nutritionally comparable to cow’s milk – except for B12. Assuming all are calcium fortified, soy is more nutrient dense, providing more bang for your buck.


Research shows that estrogen modulation from soy is not a bad thing. In fact, soy appears to have the opposite impact on cancer risk to what we hear about.

So, yes – the science is clear. Soy milk is safe and healthy…and it is unquestionably better for the animals.

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