By Marie-Evè Caplette
Plant-based diets are becoming more and more popular because… they have many health benefits, including helping to prevent chronic diseases like diabetes and heart disease.
However, a common question or concern that people have is whether the consumption of soy is safe or whether it has a negative impact on our hormones or is it good for our health. Let’s look at what science is telling us.
What is soy?
Soy is a legume rich in protein and several nutrients such as phosphorus and magnesium. At the grocery store, we can find whole soybeans, better known as edamame. Soy is also processed in many ways to produce tofu, tempeh, texturized vegetable protein (TVP), miso and soy beverage to name a few examples.
Where do fears related to soy come from?
Soy is high in phytoestrogens, specifically isoflavones. These are molecules that are very similar to estrogen, the female hormone secreted by the ovaries. This hormone is also present in men, but in smaller quantities.
One would therefore think that phytoestrogens, given their similarity to human estrogen, could negatively impact our hormones. However, they do not behave exactly like the human estrogen hormone, and may even play a beneficial role in the prevention of heart disease and certain cancers.
Soy and breast cancer
The hormonal activity of soy phytoestrogens is very low: 100 times lower than that of estrogens. Thus, moderate consumption of soy does not increase the risk of breast cancer. Not only is the risk not increased, but soy phytoestrogens may have the effect of reducing the risk of breast cancer in women, and may even reduce the risk of recurrence and mortality for women with breast cancer.
This has been particularly observed among the Asian population, who traditionally eat soy foods from a young age and are less affected by breast cancer than North Americans. More studies are needed before drawing a clear conclusion about which quantity of phytoestrogens is needed to provide a protective effect.
According to the Canadian Cancer Society, eating up to three servings a day of soy foods is safe, even for women in remission. One serving is:
- 1 cup (250 mL) of soy milk
- 3/4 cup (175 mL) of tofu
- 1/2 cup (125 mL) of tempeh
- 3/4 cup (175 mL) edamame
As a precaution, the Canadian Cancer Society advises against using soy supplements, which have a very high content of isoflavones.
In short, soy does not increase the risk of developing breast cancer or breast cancer recurrence. Phytoestrogens in soy do not have the same effect as estrogen.
Soy and men’s health
Science is very clear about this: soy does not affect testosterone levels, libido or fertility in men.
These beliefs originated when studies showed that high doses of phytoestrogens decreased fertility in male rats. However, humans do not metabolize soy isoflavones the same way rats do, and therefore the conclusions drawn cannot be applied to humans.
Soy and GMOs
At least 60% of the soybeans grown in Canada are genetically modified (GM or genetically engineered). However, soybeans intended for human consumption are not. Only crops intended for feeding farm animals that can be. Furthermore, GMOs have been proven to be harmless to health and offer producers the possibility of using less water, fossil fuels and fewer pesticides to help produce more food. Click here to read more on this topic.
Soy and hormones: demystified!
The important thing to remember is that soy doesn’t negatively impact hormones. From a nutritional point of view, soy in its various forms is a food that contains many health benefits and can easily be used as a substitute if you want to reduce your meat consumption. So enjoy soy and add it to your plate!