Does it work?

Numerous human studies report that adding soy protein to the diet can moderately decrease blood levels of total cholesterol and low-density lipoprotein ("bad" cholesterol). Small reductions in triglycerides may also occur, while high-density lipoprotein ("good" cholesterol) does not seem to be significantly altered.

Dangers and possible side effects.....

Avoid if allergic to soy. Breathing problems and rash may occur in sensitive people. Soy, as a part of the regular diet, is traditionally considered to be safe during pregnancy and breastfeeding, but there is limited scientific data. The effects of high doses of soy or soy isoflavones in humans are not clear, and therefore are not recommended.

References

https://www.drugs.com/npp/soy.html

http://www.webmd.com/vitamins-supplements/ingredientmono-975-soy.aspx?activeingredientid=975