When I made the decision to stop drinking cow’s milk, I wondered what alternatives there were as porridge has been my go-to breakfast all my life (at least the German version which is oats just soaked in milk and not actually cooked!). One of my flatmates at that point drank soy milk but I was suspicious as I’ve heard scary things about soy – for example that it causes cancer! So I alternated between almond milk and home-made oat milk for a while.
BUT I was heavily misinformed. This misinformation was in part to people getting confused about the action of isoflavones which are similar to estrogens and can act on the estrogen recepor. It seems to be more commonly known that overactivity of the estrogen receptor can lead to the development of cancer. That’s where the notion was derived from that soy could cause it, too!
Therefore I did some more research into the topic and these are 3 surprising things I found:
Isoflavones may actually protect against cancer. The concern of soy causing cancer came from an animal model with existing estrogen-sensitive tumours which grew when fed an isoflavone found in soy. This at least raised the concern that there may be a risk for breast cancer patients to consume soy but not for the general population.
However analysing this data carefully shows that circulating levels (amount of compound in the blood) of the isoflavone are important for tumour growth. Compared to humans, mice are not very good at reducing these circulating levels and therefore are high – in humans the isoflavone efficiently gets converted into a compound that does not affect estrogen signalling. Plus the dosage used in the model was 6-20 times higher than average human consumption. This means the concentration needed for these negative effects are unlikely to be present in humans.
Most importantly a study looking at the effects of soy foods and supplements did not increase breast cancer risk markers in healthy women or breast cancer patients. This coincides well with the data found in Asian populations reliant on a soy-based diet, which seem to show a reduced risk of breast cancer!
East Asians are adapted to high soy intake. The reason why many studies have been contradicting whether it is beneficial or not may be highly related to what ethnic group you belong to and your intake during childhood/adult life. For example in East Asians which have been consuming large amounts for many centuries are thought to have a different gut bacteria population that can produce a compound called equol from isoflavones. This compound may be the key to the beneficial effects seen in both breast and prostate cancer.
Increasing soy intake decreases cardiovascular risk. Modest direct effects of soy have been linked to reduction of cholesterol and has also been shown to have lipid lowering effects. The indirect effects that go hand in hand with increasing your soy intake as a vegan/vegetarian such as decreasing fat intake (dairy, eggs, meat) are more likely to be the key effectors.
Still concerned about the effects? Remember Bisphenol A is WORSE. So if you reguarly drink from plastic bottles, eat canned food and use tupperware that is not BPA free (or Bisphenol S or F for that matter!), there is no need to worry about ‘potential’ negative effects of soy considering the little exposure you will have to it. Plus most soy milks have around 6% soy – which really isn’t very much.
In light of this, I believe eating a whole-food plant-based diet that includes some soy products is probably still better than eating lots of highly processed foods on a regular basis. Have you been paying attention to all the food labels? Most processed foods contain soy in some shape or form!
Additionally I feel better drinking soy milk, because really – Cow’s milk is baby calf growth food – do we really want to be putting that in our bodies? The reason we don’t buy organic is that it is not fortified and being on a plant-based diet it is more challenging to get enough calcium and Vitamin D. Hence, fortified milk in your breakfast can supplement well, as different studies have shown that absorption of fortified milks is similar to cow’s milk (1, 2).