The Western diet is devoid of meaningful levels of micronutrients and as a result poor mineral status is common. Generally most people are unaware they have insufficient mineral intakes because clinical deficiencies never develop. Instead the poor mineral status maintains the individual in a hinterland somewhere between health and disease, and this produces subclinical symptoms that are often put down to aging, wear and tear, fatigue and other minor maladies. The difficulty in detecting mineral deficiencies without detailed clinical analysis makes diagnosis unlikely for the average man or woman. Indeed, the fact that multiple deficiencies may be present muddies the water further. For this reason, a high quality diet and a strong multivitamin and mineral formula supplement are a good insurance against developing poor micronutrient status. However, in the case of some minerals it could be argued that the intake is too great. For men particularly, iron is one such example, and this relates to the high intakes of red meat in Western nations.
The vast majority of the World obtains its dietary iron from plant foods, and this is because the vast majority of the World do not have access to large intakes of red meat. However, in Western nations, red meat is commonly consumed, and some would argue in too great an amount. Red meat contains the heam form of iron, and this iron is generally well absorbed. The ease of haem iron absorption no doubt contributes to the good iron status reported in frequent red meat eaters. Legumes are also a good source of iron and can contribute significantly to iron intake. However, the iron from plant foods appears to be poorly absorbed based on the studies which have looked at the absorption of non-haem forms of iron. For example, in one study1 the mean absorption from a range of legumes was only 0.84 (black beans) to 1.91 % (soybeans) with only small differences between the iron absorption from different legumes. For example, mung beans and split peas showed iron absorbances in healthy humans of 1.91 and 1.09 %, respectively.
It is interesting that legumes are a good source of iron and yet the iron within them is so poorly absorbed. The factors that inhibit the absorption of this iron have not been identified. It is suspected that high molecular weight polyphenols (such as tannins) in legumes may bind to iron and prevent its absorption. However, both mung beans and soybeans do not have high a tannin content and so other factors may also be inhibitors of iron absorption. Another possible candidate for this low iron absorption is the phytate content of beans. However, as with tannins, the ability of phytate to account for the low availability of iron from legumes is controversial because degradation of phytate using the enzyme phytase or its removal of phytate from processed legumes does not greatly improve iron availability. Therefore it is likely that multiple phytochemicals in legumes are responsible for the poor iron availability. Enhancers of iron availability, such as ascorbic acid, might improve the iron absorption rates significantly, however.
Dr Robert Barrington’s Nutritional Recommendation: For men at least, iron deficiency is not common if red meat is eaten, but vegetarians and women are more at risk. Therefore, a blanket recommendation for iron is not appropriate as iron status should be judged on an individual basis. It is very likely that enough iron can be obtained from the diet in the absence of red meat as long as a high quality diet is consumed and iron enhancers are consumed with plant sources of iron.
RdB
