I know the safety of soy is question on the mind of a lot of people especially when transitioning to a plant-based diet or when raising children on a vegan diet.
I looked at the latest scientific literature to be able to give you the best answer on the subject.
First of all soy phytoestrogen is not the same as human oestrogen. Oestrogen is an animal hormone and soy only contains isoflavones also called phytoestrogens (as well as chickpeas and other legumes). These isoflavones have been shown to be 1000x weaker than animal oestrogen.
Also soy has been badly seen due to the one study which looked at the side effects of soy consumption for subjects consuming up to 12 serves of soy a day! This is definitely an unrealistic amount of soy consumed and when the subjects of the studies stopped this excessive intake of soy their health returned to normal. (1, 2)
The recent studies have actually found positive effects on consuming soy.
This study published a few weeks ago found a link between dairy and breast cancer whereas soy consumption was not associated with higher breast cancer rates. Also the lowest incidence of breast cancers are in Asian countries where soy consumption is the highest. (3)
The overall scientific opinion on soy is that is entirely safe to consume.
Everyone would actually benefit from consuming soy especially women with history of breast cancer in their families and avoid dairy. Soy is a great alternative for anyone including vegan children as it is high in protein and calcium and has a similar nutrient component to dairy which is why it is the best plant milk for children to consume.
Overall I recommend adding soy and soy milk to your diet but choosing organic â€“ non-gmo soy.
For children with hypothyroidism it is best to avoid soy close to the time of the medication as soy may affect the absorption of thyroid medications. However soy has been found to have only small effects on thyroid hormones for people with hypothyroidism and is 100% safe for people with healthy thyroids.
(If you have a soy intolerance or allergy avoid all soy products.)