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Base foodLow concern
Wholegrain
In plain words
The short version
Carries phytates in the bran, which bind iron, zinc and calcium and reduce how much is absorbed.
Why it's green
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Safety profile
Phytic acid, concentrated in the bran layer, binds iron, zinc and calcium into compounds humans cannot break down. This is why iron from porridge is absorbed far less readily than iron from meat. Soaking, fermenting and leavening all reduce phytate — sourdough bread noticeably more than unleavened.
The detail
Educational information only. Not medical or dietary advice.