Fermentation Frees Minerals in Grains and Beans.

A bowl of maize porridge or chickpeas can contain plenty of iron and zinc on paper, yet deliver less of those minerals than the nutrition label suggests. The main obstacle is phytate, or phytic acid: the phosphorus-storage molecule that plants pack into seeds. Its phosphate groups readily bind positively charged minerals, forming complexes that are harder to dissolve and absorb during digestion.

That does not make phytate a poison, nor does it mean every mineral in a bean is trapped. The effect depends on the amount of phytate, the mineral, the rest of the meal, and a person’s overall diet. It matters most when unrefined cereals and legumes provide a large share of daily calories and there are few alternative sources of easily absorbed iron or zinc.