Zinc is a cofactor to a large number of enzymes in human metabolism and is therefore an essential nutrient. Deficiency of zinc causes reproductive, immune and growth problems in mammals including humans. The role of zinc in the growth of mammals has been extensively researched, and depriving rodents of zinc has been shown to cause growth retardation during early life. Supplementation of animal with adequate zinc in contrast allows the animals to attain their full growth potential. A poor zinc status is therefore detrimental to health during the early growth phase of animals. In humans too, zinc deficiency has been shown to cause detrimental effects to correct growth patterns. This is concerning because increasingly it is being shown that the typical Western diet does not supply enough of the essential trace minerals including zinc. This is particularly true to the poorest socioeconomic groups in Western countries who have generally been shown to have poor mineral status.
In one study1 the effects of zinc supplementation were investigated in 40 children who were in the lowest growth percentiles for their ages. The children who were between 2 and 6 years of age, and who were in the 10th percentile for their growth, were supplemented with 5 mg of zinc sulphate as a cherry flavoured syrup two times per day for a period of one year. Some children received a similar cherry flavoured syrup but without any zinc. The results of the study showed that after 1 year of supplementation, the height of the zinc supplemented children was significantly greater than the height of the children receiving the placebo. This effect was largely because of the extra growth experienced by the boys receiving zinc supplements. Therefore the authors concluded that a poor zinc status in children of a poor socioeconomic status can be a limiting factor in the growth rates of the children and that supplementation is able to improve the growth potential of the children, particularly with regard to boys.
This study is interesting because it suggests that poor zinc status in boys is a limiting factor in their growth and development and that children may benefit from a zinc supplement if they have a poor zinc status due to a low quality diet. The fact that boys responded more than girls suggests that the mechanisms by which the zinc improved growth was hormonal in nature and therefore gender specific. Some evidence from animal studies suggests that the zinc requirement in young male animals is higher than that of young female animals. The mean height increase in the zinc supplemented group was 10 % greater than the control subjects. While this seems like a small increase, it should be remembered that the study only lasted for one year and so over a longer time period this effects may be larger. Another interesting consideration from this study was that the 10 % increase in growth was as a result of just a zinc supplement. It might be that these children had multiple deficiencies and that supplementation with other essential factors, and perhaps more protein, may have caused an even greater improvement in the growth rate.
Dr Robert Barrington’s Comments: That poor mineral status impedes growth rates in humans should not be surprising as minerals play important roles as cofactors to enzymes that are required for the metabolic regulation of growth including tissue repair and protein synthesis. The best way to ensure an adequate supply of essential nutrients is to eat a high quality diet and supplement with a suitable multivitamin tablet. Tablets suitable for children of all ages are commercially available and should be considered as part of the high quality diet that all children should receive.
RdB
