Effects of fiber, phytic acid, and oxalic acid in the diet on mineral bioavailability.

Studies on effects of fiber, phytic acid, and oxalic acid on mineral bioavailability are reviewed. It is difficult to separate the effects of fiber and phytic acid when cereal products are fed, because they occur together in these foods. However, even the combination of fiber and phytic acid does not appear to affect mineral balances unless unrefined cereal intakes are high and mineral intakes are low. Also, the body may be able to adjust to the decreased availability by increased absorption of the available mineral. Oxalic acid may result in decreases in mineral bioavailability if consumed with a high fiber diet, but the decrease may also be transient.