Are soy products healthy?

There has been a lot of bad press about soy – cancer scares, phytoestrogen concerns, GM fears, anti-nutrient effects and thyroid problems to name a few. Negative articles and blog posts can often be traced back to particular organisations with links to the meat and dairy industries. They are either completely unsupported by published research or else based on small pieces of information taken out of context. Nonetheless, bit by bit, the vague idea that soy is “unhealthy” and has “hormone-like side effects” has become a social contagion infecting the public and even health professionals (who should be basing their advice on scientific evidence not blog posts or newspaper articles).

Traditional soy foods have been consumed in Asia for thousands of years. They include tofu, tempeh, edamame, miso and soy milk. These were added to rice-based meals as condiments rather than being the central feature of the meal, which is often the case when one orders a tofu dish at an Australian restaurant.

Our food industry has created many highly processed meat, egg and dairy ‘replacement’ foods out of soy protein. There are also soy based ‘protein’ bars and ‘protein’ shakes. These processed foods often have added salt, sugar and fat and may provide unnaturally large amounts of soy protein. However, there is some merit in these products as a means of providing meat-like foods to consumers without the heavy environmental impact of animal agriculture.

The truth about soy:

  • The consumption of traditional soy products is associated with lower risks of a number of diseases including breast and prostate cancers.
  • The phytoestrogens in soy have both weak estrogenic effects and anti-estrogen effects. Soy products do not feminize males and soy phytoestrogens, even when artificially concentrated, are not strong enough to be effective hormone replacement therapy in post-menopausal women. Ironically, cow’s milk contains significant amounts of real full strength cow estrogens.
  • Genetically modified soy is not an issue in Australia if you are eating a whole food plant-based diet. Most GMO soy crops are fed to livestock. Foods in Australia with GM ingredients must be labelled as such, although if they are in highly refined ingredients (e.g. oils) they may not be – but we don’t recommend processed foods with highly refined ingredients. It is easy to buy soy milk, tofu and tempeh that is clearly labelled non-GMO.
  • Soy products do not significantly inhibit the absorption of iodine or other minerals.
  • Very high intakes of soy protein may have similar adverse effects to consuming animal protein. For example causing elevated levels of IGF-1, the cancer and acne promoting hormone.
  • Soy beans (along with peanuts) have a much higher fat content than the other legumes.

Recommendations:

  • It is not necessary to include soy foods in your diet, but they can be a health supporting addition to a whole foods plant based diet along with other legumes.
  • Choose mainly traditional soy products such as edamame, tofu or tempeh and use them as an accompaniment or condiment to starches and vegetables rather than making them the focus of your meal.
  • Soy milk should be based on whole soy beans (check the carton as some brands are not) and only used as an ingredient or as an addition to hot drinks or cereals. There is no need to drink soy (or any other milk) by the glassful as once weaned humans have no nutritional need to consume milk.
  • Avoid heavily processed foods containing isolated soy protein (e.g. soy chips, soy burgers and soy-based protein supplements).
  • If you are trying to lose weight then be aware that soy beans (and peanuts) are higher in fat than other legumes and so it would be wise to eat less of them.

Resources

Peer-reviewed articles:

 

Last updated 7 April 2016