Zinc supplementation improves glycaemic control in persons with, at risk of diabetes
Zinc supplementation significantly lowers key glycaemic indicators, particularly fasting glucose (FG) in individuals with diabetes and in those who received an inorganic supplement, results of a systematic review and meta-analysis have shown.
“[Z]inc supplementation has beneficial effects with respect to glycaemic control in diabetics and in individuals with a high risk of developing diabetes,” researchers said.
Articles containing estimates for the outcomes of interest and published through 10 February 2019 were searched in PubMed, Embase and the Cochrane Library. A random-effects model was used to analyse the pooled results. In total, 32 placebo-controlled interventions were identified from 36 publications, including 1,700 participants in 14 countries.
Overall, participants who received zinc supplementation had a statistically significant reduction in FG (weighted mean difference [WMD], –14.15 mg/dL, 95 percent CI, –17.36 to –10.93 mg/dL), 2-h postprandial glucose (WMD, –36.85 mg/dL, –62.05 to –11.65 mg/dL), fasting insulin (WMD, –1.82 mU/L, –3.10 to –0.54 mU/L), homeostasis model assessment for insulin resistance (WMD, –0.73, –1.22 to –0.24), glycated haemoglobin (WMD, –0.55 percent, –0.84 to –0.27 percent) and high-sensitivity C-reactive protein (WMD, –1.31 mg/L, –2.05 to –0.56 mg/L) concentrations as compared with their respective controls. [Am J Clin Nutr 2019;110:76-90]
In subgroup analyses, diabetic status and the formulation of the zinc supplement significantly influenced the effects of zinc supplementation on FG.
“Taken together, these results indicate that zinc supplementation may be used as an adjunct therapy for preventing or managing diabetes,” researchers said.
In another recent meta-analysis, zinc supplementation was found to have significantly reduced total cholesterol, low-density lipoprotein cholesterol and triglyceride concentrations, but the overall role of zinc on preventing and treating diabetes remained inconclusive because the included studies had varying health status, dose, duration and formulation of the supplement, as well as genetic background of individuals. [Nutr Metab (Lond) 015;12:26; Atherosclerosis 2011;219:22-23]
Some studies that examined the effects of zinc supplementation in combination with other micronutrients reported the beneficial effects of combined supplementation, while others reported less pronounced effects on glycaemic control. [Saudi Med J 2006;27:1483-1488; Appl Physiol Nutr Metab 2018;43:565-570; J Trace Elem Med Biol 2018;48:166-171; Int J Obes 2010;34:1070-1077]
The inconsistent findings could be explained by the differences in the physiologic functions of the supplements and interactions, including variations in ingredients, according to the researchers.
“Therefore, we included studies that used zinc as single factor as well as studies that combined zinc with other supplements in our meta-analysis; moreover, we used studies that used zinc as a single factor in our subgroup analyses in order to examine in further detail the effects of zinc supplementation on glycaemic control,” they added.
Large, multinational, prospective, randomized controlled trials are warranted to help determine the ideal dose, duration and formulation of the zinc intervention specific to each individual patient’s health status, researchers said.