Evidence suggests that trace mineral intakes in developed nations are declining. This relates partly to the increasing consumption of the typical Western diet that is naturally high in mineral poor processed foods but naturally low in the types of foods that contain essential nutrients. In addition, the fall in the intake of minerals relates partly to the use of poor quality agricultural soils that are devoid of minerals. The combination of these two factors creates a population that has poor mineral status. Although actual mineral deficiencies amongst such populations are rare, the chronic low mineral intakes of many people has lead to a new classification of the mineral insufficiency. Such a status reflects borderline deficiency that does not result in the classic deficiency symptoms, but which leads to many difficult to diagnose subclinical disorders that may take decades to manifest as disease. Many idiopathic diseases and Western lifestyle diseases have been attributed by some researchers to such mineral insufficiencies.
As mineral intakes fall, efficiencies in mineral absorption may increase while excretion rates may fall. This is the natural response in order to maintain adequate mineral status for essential metabolic function. However, some minerals are also lost through sweat and this loss can be substantial. For example, one study1 the whole body losses of the trace minerals zinc, copper and iron were measured using healthy subjects in a metabolic chamber. Volunteers lived in a controlled environment for 4 to 9 months and during this time a mean of 88 samples of sweat were taken from the subjects. Analysis of the sweat revealed that losses of zinc, copper and iron were 0.50, 0.34. 0.33 mg per day, respectively. These values represented 3.9, 26 and 2.1 % of the mean dietary intakes of the subjects for zinc, copper and iron, respectively. The authors calculated that the surface losses of iron, zinc and copper should result in an 5 and 3 and 25 to 30 % increase in the daily requirement of zinc, iron and copper, respectively.
Recommended intakes for minerals use mineral balance studies, but often these do not take into account losses from sweat. As can be seen from this study, these can be substantial, particularly for copper. The loss of copper in sweat would increase the risk of a deficiency if intakes were marginal. High losses of copper have been reported in other studies, and this loss would likely increase with increased perspiration, which may make athletes particularly susceptible to poor copper status if intakes are not adjusted to compensate. The ~5 % loss of zinc and iron in sweat could easily be made up through incorporation of additional small quantities of meat, organ meat or seafood, which are good sources of dietary zinc and iron. The losses of copper would be more difficult to counteract through the diet however. The average American Western diet may only contain around 1 mg of copper per day, suggesting that losses from sweat would required a supplement of copper to maintain adequate mineral status.
RdB
