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Down Syndrome Abstract
of the Month: Feb 2008

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Zinc nutritional status in adolescents with Down syndrome.

Marques RC, et al.
Biol Trace Elem Res. 2007 Winter;120(1-3):11-8.

Universidade Federal do Piauí, Teresina, Piauí, Brazil.

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Studies have evidenced that zinc metabolism is altered in presence of Down syndrome, and zinc seems to have a relationship with the metabolic alterations usually present in this syndrome. In this work, the Zn-related nutritional status of adolescents with Down syndrome was evaluated by means of biochemical parameters and diet. A case-control study was performed in a group of adolescents with Down syndrome (n = 30) and a control group (n = 32), of both sexes, aged 10 to 19 years. Diet evaluation was accomplished by using a 3-day dietary record, and the analysis was performed by the NutWin program, version 1.5. Anthropometric measurements were performed for evaluation of body composition. The Zn-related nutritional status of the groups was evaluated by means of zinc concentration determinations in plasma and erythrocytes, and 24-h urinary zinc excretion, by using the method of atomic absorption spectroscopy. The diet of both groups presented adequate concentrations of lipids, proteins, carbohydrates, and zinc. The mean values found for zinc concentration in erythrocytes were 49.2 +/- 8.5 microg Zn/g Hb for the Down syndrome group and 35.9 +/- 6.1 microg Zn/g Hb for the control group (p = 0.001). The average values found for zinc concentration in plasma were 67.6 +/- 25.6 microg/dL for the Down syndrome group and 68.9 +/- 22.3 microg/dL for the control group. The mean values found for zinc concentration in urine were 244.3 +/- 194.9 microg Zn/24 h for the Down syndrome group and 200.3 +/- 236.4 microg Zn/24 h for the control group. Assessment of body composition revealed overweight (26.7%) and obesity (6.6%) in the Down syndrome group. In this study, patients with Down syndrome presented altered zinc levels for some cellular compartments, and the average zinc concentrations were low in plasma and urine and elevated in erythrocytes.

My comments:

I'm reviewing this paper because I haven't seen a study on nutritional status in DS for a while now. Zinc has been studied probably in more detail than other nutrients in people with DS, and studies have indicated that zinc supplementation may help with thyroid and immune function. This study focused on blood and urine in adolescents with DS.

Zinc levels in red blood cells were higher in the subjects with DS than controls. Almost all the zinc in red blood cells is bound to the enzyme carbonic anhydrase, which is known to be higher in people with DS. The plasma zinc, however, is more important to the zinc-dependent metabolic processes of the body, and it is this zinc that is vulnerable to dietary changes. The authors report that the plasma zinc levels in subjects with DS were lower than the lab's reference levels; but the levels were not statistically significantly different from the subjects tested without DS.

It's an interesting study that, again, highlights the need of parents and caregivers to be aware that zinc deficiency is a possibility in people with DS. However, what we really need are more studies showing the correction of specific disease conditions by the addition of specific nutrients.
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