The high phytate content of soy and plant-based diets might help to prevent the development of cancer. That speculation could be drawn from the publication of a case report in Melanoma Research describing cancer remission in response to phytate supplementation.1

First, some background.

Phytate (inositol hexaphosphate, IP6) is found in all whole grains and legumes including soybeans. Myo-inositol (inositol) is a parent compound of IP6; foods containing the highest concentrations of inositol include fruits, beans, grains, and nuts.2

Despite being found in abundance in healthy foods, IP6 is generally viewed as an anti-nutrient because it inhibits the absorption of divalent cations, which include minerals such as calcium, iron and zinc. The effect of phytate on mineral absorption is one reason the iron RDA is 80% higher for vegetarians than for nonvegetarians. So potentially impactful is phytate on mineral absorption, the European Food Safety Authority set dietary zinc requirements for adults based on four levels of dietary phytate.3

However, there appears to be adaption to the inhibitory effects of phytate.4 In 2015, researchers found that the inhibitory effect of phytate on iron absorption was mitigated by the chronic consumption of a high-phytate diet. If this result holds true for the other divalent cations, it means the effect of phytate on mineral status in individuals consuming plant-based diets is a lot less than commonly thought.