Conclusion

The aim of this paper was to determine whether DS people suffer zinc deficiency, what symptoms they exhibit which could be the result of zinc deficiency, whether zinc supplementation improves any of these symptoms, and what factors could cause zinc deficiency in DS. The conclusions have been drawn from a critical review of all the research papers available on the subject of DS and zinc.

It appears that the majority of DS individuals are zinc deficient, and that they exhibit symptoms classically associated with zinc deficiency:

• thyroid dysfunction

• immunodeficiency

• retarded growth

• faulty DNA repair

Supplementation will raise DS zinc status to normal. Correction of zinc deficiency seems to:

• improve thyroid function, though it is not clear yet what parameters are being affected

• raise active thymulin levels and concomitantly lower inactive thymulin

• possibly increase lymphocyte proliferation

• possibly restore delayed hypersensitivity

• improve neutrophil function

• possibly normalise lymphocyte subset distribution

• possibly minimise growth retardation

• regulate DNA repair

• regulate myeloid cell differentiation and apoptosis

There several possible reasons behind DS zinc deficiency, which are most likely to be working in some combination:

• over-expression of genes

• malabsorption

• dysfunction of transport proteins

• food choices

It is difficult to recommend an optimum strategy for zinc supplementation as researchers use different regimes. However dosing by os is the most common method and therefore known to be safe, and as effective as any other method. As it is possible for too much zinc to suppress the immune system it would be wise to regularly test an immune parameter, such as lymphocyte proliferation, or to alternate periods of supplementation and periods without. It is possible that zinc therapy could benefit DS babies from birth but at present it is not possible to recommend this as there is no evidence even as to its safety.

It may be that the typical DS diet is low in zinc-rich foods, and it is vital to find ways of preparing such foods so as to appeal to a DS person and to educate individuals to incorporate such food in their diet.

It could also be sagacious to investigate such potential sources of malabsorption as food allergies, hypochlorhydria, and pancreatic insufficiency.