Phytate (phytic acid) in seeds, grains, and legumes binds calcium and other minerals in the gut, lowering their absorption. Soaking, fermenting, and cooking reduce it to varying degrees depending on the grain.

Which grains Peat flagged

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Asked about the safest grain choices, Peat singled out oats specifically for high phytate interfering with calcium absorption, and ranked alternatives by how they're processed:[1]

Masa harina (best), white rice or oats. The phytic acid in the oats block absorption of much of the calcium; cooking the oats much longer than usual might improve its nutritional value.

— Ray Peat[2]

Masa harina (nixtamalized corn: corn soaked and cooked in an alkaline solution, traditionally calcium hydroxide) ranked best because that processing measurably increases calcium content and digestibility, not just because corn is the base grain: a controlled lime-cooking study found phytic acid dropped about 35% while ionizable calcium rose 400-478% and ionizable iron rose 52-77%.[3][4] Asked whether soaking oats the same way would help similarly: boiling to start the process, rather than just soaking, matters for retaining the added calcium.[4]

Practice

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Do not build a diet around raw bran and unprocessed seed/grain meals. Where grains are eaten, prefer nixtamalized corn or well-cooked white rice over oats; long-cook oats if using them, and pair grain-heavy meals with dairy or other easy calcium sources. See Calcium, Iron, Zinc, Magnesium.

See also

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References

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  1. ↑ Ray Peat Forum Q&A, "Safe Grain Hierarchy," collected in Ephemera: Ray's Email Exchanges.
  2. ↑ Ray Peat Forum Q&A, collected in Ephemera: Ray's Email Exchanges
  3. ↑ Urizar Hernández AL, Bressani R, "The effect of lime cooking of corn on phytic acid, calcium, total and ionizable iron content," Arch Latinoam Nutr. 1997;47(3):217-23. PMID 9673675.
  4. ↑ 4.0 4.1 Ray Peat Forum Q&A, "Nixtamalizing Oats," collected in Ephemera: Ray's Email Exchanges.