Phytate (inositol hexa phosphate) hydrolysis can occur during food preparation and production and in the intestine, either by phytase from plants, yeasts or other micro-organisms. This degradation is of nutritional importance, because removal of phosphate groups from the inositol ring results in an increased bioavailability of essential dietary minerals. To substantially improve iron absorption the degradation has to be virtually complete. Food processing techniques increasing the activity of the naturally occurring plant phytases are soaking, malting, hydrothermal treatment and fermentation. An alternative is addition of phytases or micro-organisms producing phytase. Phytate degradation in the stomach and small intestine occurs as a result of activity of dietary phytase of plant or microbial origin. The plant phytase is less stable than fungal phytase in the physiological conditions of the intestine. Biotechnologically produced phytases may be possible for use tomorrow in food processing as well as plant raw material and starter cultures with inserted phytase genes.