Significance of iron bioavailability for iron recommendations.

Recently, recommended dietary allowances (RDA) have been formulated by the Dutch Nutrition Council for minerals and trace elements, including iron (Fe). For some population groups in the Netherlands, it is questionable whether they easily meet the Fe recommendation. An increase in Fe intake is not always possible, but "manipulation" of Fe bioavailability ultimately may result in better Fe utilization. Various factors are known to affect Fe bioavailability. Generally, much attention is paid to diet-related factors, such as inhibitors and enhancers of Fe availability for absorption. Factors such as pH, oxidation potential, structure of food, and time of digestion often are overlooked. Of the diet-related factors, heme Fe and ascorbic acid have a strong positive effect on Fe availability for absorption, whereas oxalate and polyphenols seem to be strong inhibitors of Fe availability. Because of the many interactions that may occur simultaneously, the net effect of the various combined factors in a meal is not equal to the sum of the individual factors.