Zinc is an essential mineral found in many foods and is vital for our growth. It plays a role in the regulation of the immune function of the body, DNA synthesis, and metabolism function. Since it is an essential mineral, it cannot be produced by the body.
Zinc deficiency is associated with growth retardation, impaired immune function, and lesions in the skin and the eye. Short stature associated with zinc deficiency can be treated with zinc supplementation. In fact, multiple studies have been performed to study the benefits of zinc supplementation. Although most studies have not been able to determine the effect of zinc supplementation on systemic aspects of zinc-deficient individuals, some of them do show that the benefits far outweigh the risks. One such study was performed on school children in Thailand, an endemic area for zinc deficiency.
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Method of study and data collection
The study performed by Drs Rerksuppaphol aimed to prove the benefits of zinc supplementation on the height and overall health of school-aged Thai children. This double-blind, randomized controlled trial was performed over the course of 6 months in 2013 and the effects of supplements were assessed.
Initially, 186 subjects were chosen and assessed if eligible. This sample size was narrowed by the researchers based on certain criteria. Children with any health issues like congenital heart problems, metabolic, or neurological problems were excluded from the sample. Furthermore, any child that was taking any supplements or was found to be allergic to supplements was removed from the sample. In the end, only 140 subjects were chosen for the study.
The entire sample population was then divided equally into two groups, the placebo group, and the intervention group. The intervention group was given a 15mg sachet of zinc supplements, only on school days. Whereas the placebo group was given a sachet that looked exactly like the sachet given to other groups and had the same odor and taste, also on school days.
The data collected from the subjects, at the beginning of the study was the weight, height, waist circumference, and hip circumference, along with middle-upper arm circumference(MUAC), skinfold thickness, and fat composition. While the height and weight were measured each month, during the course of the study, the rest of the data was measured again at the end of the study, by the same staff and methods.
The weight and height were measured using an electric scale and a height rod respectively. Waist circumference was measured using a non-stretch tape at the midpoint of lower costal margin and top of iliac crest while standing. Hip circumference was measured over the buttock, also while standing. The skinfold thickness was measured for biceps and triceps over the respective muscles using the Lange skinfold caliper. MUAC was measured at the midpoint of the olecranon process and the acromion process of the left arm.
The sample size changed for both groups by the end of six months with 4 subjects withdrawing from the intervention group, and 6 from the placebo group.
The researchers found a clear increase in the linear growth of subjects receiving zinc supplementation when compared to placebo. However, they did not see any effect of zinc supplementation on the rest of the anthropometric data when compared to placebo.
Limitations of the study
It is important to note however that there are two limitations to this study, that the researchers have mentioned. Firstly, they did not consider the dietary intake of the subjects in either group, which could have altered the results seen in their study. Secondly, they also did not measure the plasma zinc levels in their study. There is no way to know if the plasma levels increased in response to zinc supplementation. This limitation was not because the researchers did not consider it, but rather because venipuncture or taking of blood is an invasive procedure that the legal guardians and parents would not let the doctors perform on their children.