The validity of methods used to determine the heme and non-heme iron content in meat products

Introduction With iron deficiency being the most common nutritional deficiency in the world (Yip in Bowman and Russell, 2001), it comes as no surprise that iron is one of the most investigated micronutrients. Iron deficiency anaemia affects more than 1 billion people, mostly women of childbearing age and young children (Jacobson, 2008). Subsequently many national and international intervention programs have been developed to aid in the elevation of iron deficiency. These include iron fortification and supplementation programs, as well as promotions of the consumption of foods high in iron. Many foods are naturally high in total iron and many more are fortified with iron, often labelled and marketed as such. However, with varying absorption ratios a singular reference to the total iron content of a food has little value in context of nutrition (Strain and Cashman in Gibney, Vorster and Kok, 2002). The total iron content in a food can be present in two forms, namely either as heme or non-heme iron. The heme form, present in haemoglobin and myogobin of animal products is much more bioavailable than the nonheme iron form, present in the remaining portion of animal products and make up the total iron content of plant foods. The specific form of iron consumed has a major influence on the absorption of the mineral (Thompson & Manore, 2005). Upon consumption the nonheme portion of total iron enters a common non-heme iron pool in the gastric juice from which the amount absorbed depends on the iron status of the host, as well as other enhancing and inhibiting substances and factors that were consumed prior or with the meal (Strain and Cashman, in Gibney, Vorster & Kok, 2002). In general, the rate of nonheme iron absorption is related to its solubility in the upper part of the small intestine, thus the presence of solubility enhancers and inhibitors consumed during the same meal will have a significant effect on the amount of nonheme iron absorbed (Yip in Bowman and Russell, 2001). Heme iron constitutes a smaller portion of iron present in foods than nonheme iron, and as heme iron is only found in animal sources, it compromises a much smaller proportion of most diets. Although often consumed in smaller amounts, heme iron is 2-3 times more bioavailable than nonheme iron, and is much less affected by other dietary sources (Yip in Bowman and Russell, 2001).