An acid contained in the endosperm of grains which reduces the availability of some minerals to humans during digestion.
Phytic Acid (Phytate)
Phytic acid — or inositol hexaphosphate (IP6) — is a naturally occurring compound found in the bran and germ of cereal grains, seeds, and legumes, where it serves as the plant’s primary phosphorus store, released during germination. In the human digestive tract, however, it behaves as an antinutrient: it binds tightly to mineral ions — particularly iron, zinc, calcium, and magnesium — forming insoluble complexes called phytates that pass through the gut unabsorbed and are excreted.
This matters enormously when we think about wholegrain bread. A loaf made with wholemeal flour contains far more minerals than one made with white flour, yet if that bread is made quickly — with commercial yeast and a short fermentation — much of that mineral wealth remains locked away, bound to phytic acid and nutritionally unavailable. It is one of the great paradoxes of modern bread: more wholesome-looking on the surface, but not necessarily delivering what the label implies
Long, slow sourdough fermentation changes this completely. As the dough acidifies — through the production of lacticand acetic acids by the lactic acid bacteria in the starter — the falling pH activates the grain’s own phytase enzyme, which progressively cleaves phosphate groups from the phytic acid molecule, releasing the bound minerals in a form the body can actually absorb. A fermentation of eight hours or more can reduce phytic acid content by 50–60%, with corresponding improvements in mineral bioavailability. For individuals at risk of iron or zinc deficiency, this mechanism alone makes the choice of a genuinely fermented sourdough bread a clinically meaningful one — not a lifestyle preference, but a nutritional intervention.
