Phytates

What slows things down

The phosphorus reserve of seeds. It binds to the iron, zinc and calcium of the same meal and carries them away.

Effects

The phosphorus reserve of seeds has a downside: in the same meal, it grabs iron and zinc and carries them off. Removing phytates from a meal multiplied the iron absorbed by up to four in trials; the effect matters most when whole grains and legumes form the basis of the plate.

Phytic acid carries six phosphate groups that grab minerals like pincers. In the gut, the iron, zinc and part of the calcium of the same meal stay caught in these complexes, which we cannot undo: we lack the enzyme, phytase, that ruminants owe to their bacteria.

In trials, removing phytates from a soy-based meal multiplied the iron absorbed by four or five (Hurrell et al., 1992). For zinc, EFSA had to set needs that depend on the phytates eaten: from 9.4 to 16.3 mg a day for a man, from 7.5 to 12.7 for a woman, depending on whether the plate holds few or many (EFSA, 2014).

By sex and age: women before menopause, whose iron needs are the highest, and people who eat no meat are the first concerned. In a varied diet, the effect stays modest.

Sources: Hurrell et al., AJCN, 1992 · EFSA, 2014

The remedy

The remedy is cooking, not giving up: soak overnight and discard the water, sprout, choose sourdough bread, cook long. Legumes and whole grains remain the best there is for the microbiota.

Phytates

Effects

The remedy

Where to find it (72)

Also, in smaller amounts (148)