Effects of Zinc supplementation on serum lipids: a systematic review and meta-analysis

Zinc is a mineral that plays a vital role in many biological processes and plays an important role in insulin action and carbohydrate metabolism. It may also have a protective role in the prevention of atherogenesis. Numerous studies have evaluated the effects of Zinc supplementation on serum lipids in humans and have demonstrated varying results. We systematically evaluated the literature and performed a meta-analysis on the effects of Zinc supplementation on serum lipids. A five staged comprehensive search of the literature was conducted in the following databases; PubMed, Web of Science and SciVerse Scopus for studies published before 31st December 2014. All controlled clinical trial in humans, that included a Zinc supplement intervention, either alone or in combination with other micronutrients and evaluated effects on serum lipids (total cholesterol [TC], triglycerides [TG], LDL cholesterol [LDL-c] and HDL cholesterol [HDL-c]). A meta-analysis of selected studies was performed using RevMan v5.3. The Jaded scale was used to assess the methodological quality of the trials included in the systematic review. A total of 24 studies were included in Meta analysis, which included a total of 33 Zinc interventions, in a total of 14,515 participants in the Zinc intervention or control group. The duration of Zinc supplementation ranged from 1 month to 7.5 years. The dose of elemental Zinc supplemented ranged from 15-240 mg/day. The pooled mean difference for TC between Zinc supplemented and placebo groups from random effects analysis was -10.92 mg/dl (95 % CI: -15.33, -6.52; p < 0.0001, I(2) = 83 %), while for HDL cholesterol it was 2.12 mg/dl (95 % CI: -0.74, 4.98; p = 0.15, I(2) = 83 %). The pooled mean difference for LDL-c between Zinc supplemented and placebo group from random effect analysis was -6.87 mg/dl (95 % CI: -11.16,-2.58; p < 0.001, I(2) = 31) and for TG it was -10.92 mg/dl (95 % CI: -18.56, - 3.28; p < 0.01, I(2) = 69 %). In conclusion, Zinc supplementation has favourable effects on plasma lipid parameters. Zinc supplementation significantly reduced total cholesterol, LDL cholesterol and triglycerides. Therefore it may have the potential to reduce the incidence of atherosclerosis related morbidity and mortality.