Trace mineral are important constituents of the human diet because they are incorporated into enzymes as co-factors. They are necessary because they are charged, and their charge alters the shape of the protein, allowing it to perform important function in biochemical pathways. Without the necessary mineral, the enzyme has the wrong shape and is unable to function correctly. Zinc is particularly important amongst the minerals because it is functionally a part of hundreds of enzymes in the body, and without it metabolism is seriously impeded. Zinc may be of particular interest to those who find it hard to lose weight, because deficiency has been shown to decrease basal metabolic rate, which may cause serious problems for the maintenance of energy balance.
A study published in the journal of Nutrition in 19861 fed six healthy men 16.5 mg of zinc for 12 days, then 5.5 mg zinc for 54 days, then 16.5 mg zinc for 9 days. During the intake of the low (5.5 mg) levels of zinc, the basal metabolic rate of the subject fell significantly, suggesting that their metabolism had been adversely affected. In addition, the researchers also recorded a reduction in circulating thyroid hormones as has been previously shown in zinc-deficient rats. Metabolic rate and thyroid levels rose on return of the higher zinc levels. This was a relatively short study, but illustrates nicely the adverse effect of mineral deficient diets. It also illustrates that zinc optimises thyroid function.
The current RDA for zinc is 15 mg in both the United Kingdom and the United States. If you have read my other articles (here) about minerals in diets you will already know that the processing of grain removes much of the original zinc content from the plant material. Many other studies which directly analysed zinc levels in food or indirectly estimated intake from diet surveys, have consistently found intakes fall below the recommended levels. This mineral deficient highly refined diet consumed by the majority of the Western population is the cause of the widespread metabolic dysfunction and disease we now see in epidemic proportions. Therefore ensuring a high quality diet is important to provide optimal mineral levels, because it is likely that zinc optimises thyroid function in humans.
RdB
