Phytic acid, a compound naturally found in whole-grain breads, reduces how much magnesium the body can absorb from those breads, meaning the total magnesium listed on nutrition labels may...
Mechanism
Synthesis from 1 study
The magnesium in whole-grain bread gets stuck to phytic acid in your gut, forming a compound your body can't absorb. So even though the bread has magnesium, most of it just passes through and leaves your body without being used.
Most probable mechanism
When you eat bread with natural phytic acid, the acid binds to magnesium in your gut, forming a solid compound that your body can't absorb. This bound magnesium passes through your digestive system and leaves your body in stool, so even though the bread has magnesium, you don't get much of it.
Phytic acid dissociates from food in the intestinal lumen under physiological pH conditions
Phytic acid chelates free magnesium ions to form insoluble phytate-magnesium complexes
The insoluble complexes remain in the intestinal lumen and are excreted in feces, preventing magnesium uptake by enterocytes
Evidence from Studies
Supporting (1)
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Phytic acid added to white-wheat bread inhibits fractional apparent magnesium absorption in humans.
Contradicting (0)
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Gold Standard Evidence Needed
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