All grains contain phytic acid (an organic acid in which phosphorous is bound) in the outer layer or bran. Phytic acid can combine with calcium, magnesium, copper, iron especially zinc in the intestinal track and block their absorption. This is why a diet high in unfermented whole grains may lead to serious mineral deficiencies and bone loss.
The modern misguided practice of consuming large amounts of unprocessed bran often improves colon transit time at first but may lead to irritable bowel syndrome and, in the long-term, many other adverse effects. Soaking allows enzymes, lactobacilli and other helpful organisms to break down and neutralize phytic acid. As little as seven hours of soaking in warm acidulated water will dissolve a large portion of phytic acid in grains.
The simple practice of soaking cereal grains overnight will vastly improve their nutritional benefits.
Phytic acid is found within the hulls of nuts, seeds and grains. In-home food preparation techniques can reduce the phytic acid in all of these foods. Simply cooking the food will reduce the phytic acid to some degree. More effective methods are soaking them in an acid medium, lactic acid fermentation, and sprouting.