Zinc plays a central role in the immune system and has been found to be significantly reduced in people with Down syndrome. The effectiveness of zinc supplementation in people with Down syndrome has been reported with discordant results. A comparison was made between a range of clinical and biochemical variables and zinc levels in 120 individuals with Down syndrome. Two groups of participants, one with normal zinc levels and the second with low zinc levels, were compared on the following measures: growth hormone secretion, IgA and IgG antigliadin antibodies, presence of coeliac disease, T3, T4, fT3, fT4, TSH, hypothyroidism, hyperthyroidism, CD4/CD8 ratio, total immunoglobulins G and subclasses. No significant difference was found between the two groups, except for IgG4 which was, unexpectedly, significantly decreased in the group with normal zinc levels. In conclusion, an impairment of zinc blood level in individuals with Down syndrome does not necessarily impact on the organs and systems evaluated here.