Effects of Dose and Duration of Zinc Interventions on Risk Factors for Type 2 Diabetes and Cardiovascular Disease: A Systematic Review and Meta-Analysis

Abstract

No meta-analysis has examined the effect of dose and duration of zinc interventions on their impact on risk factors for type 2 diabetes (T2D) or cardiovascular disease (CVD). This study aimed first to compare the effects of zinc interventions dichotomized as low versus high dose (<25 mg/d and ≥25 mg/d, respectively) and short versus long duration (<12 wk and ≥12 wk, respectively) on risk factors for T2D and CVD. Second, it discusses the results from the low-dose and long-duration meta-analyses as a foundation for understanding what impact a zinc-biofortification intervention could have on these risk factors. The PubMed and Cochrane Review databases were searched through January 2020 for full-text, human studies providing zinc supplements (alone) at doses ≤75 mg/d and a placebo. Data on study and sample characteristics and several T2D and CVD risk factors were extracted. There were 1042 and 974 participants receiving zinc and placebo, respectively, from 27 studies. Low-dose zinc supplementation (<25 mg/d) significantly benefited fasting blood glucose, insulin resistance, triglycerides, total cholesterol, and LDL cholesterol. High-dose zinc supplementation (≥25 mg/d) benefited glycated hemoglobin and insulin resistance. Short-duration interventions (<12 wk) benefited fasting blood glucose, insulin resistance, and triglycerides, while long-duration studies (≥12 wk) benefited fasting blood glucose, triglycerides, and total and LDL cholesterol. Effect sizes for low-dose and long-duration interventions were of equal or greater magnitude to those from high-dose or short-duration interventions. Low-dose and long-duration zinc supplementation each improved more risk factors for T2D and CVD than high-dose and short-duration interventions, respectively. It is currently unknown whether low doses of zinc delivered over long durations via a biofortified crop would similarly impact these risk factors. However, this review suggests that low-dose, long-duration zinc intake from supplements, and potentially biofortification, can benefit risk factors for T2D and CVD.

Effect of Zinc Supplementation on Insulin Resistance, Lipid Profile, BMI in Type II Diabetic Patients

“…Another trial performed 30mg of zinc supplementation for 30 days in 28 obese women, found a reduction in serum insulin and HOMA-IR values [14] . Also our result come in line with 2 recent systematic reviews concluded that Zn supplementation improves insulin resistance in obese individuals [15,16] .The difference from finding of another trial [17] , might due to the severity of metabolic disturbances, the dose and type of supplementation .…”

Patterns and Associations of Essential Trace Elements (Cu, Fe and Zn) in Saudi Adults with Varying Levels of Glycemia

“…It is suggested that Zn deficiency could be associated with a defect in insulin secretion due to its insulin-like effects via inhibition of the glycogen-regulating enzyme GSK3, activation of post-receptor proteins Akt and PI3 kinase, and the reduction of cytokines IL-1b and NFĸB [ 35 ]. Furthermore, the reduction in the blood concentrations of Zn from these patients was linked with an increased urinary excretion of Zn [ 37 , 38 ]. Some studies demonstrated that Zn supplementation may provide an important protection against diabetes as complications of diabetes were highly linked with Zn deficiency [ 39 ].…”

The Role of Zinc Homeostasis in the Prevention of Diabetes Mellitus and Cardiovascular Diseases

“…Although the reasons of these discrepancies remain unresolved, dose and duration of zinc supplementation may affect the effect of zinc on the risk of CVDs. The latest recent meta-analysis revealed that low-dose zinc supplementation ( 25 mg/d) and long-duration (≥ 12 weeks) improved fasting blood glucose and serum lipids, including total cholesterol and LDL, more than high-dose (≥ 25 mg/d) and short-duration ( 12 weeks) interventions 112) . To determine the most effective dose and duration of zinc supplementation, further study seems to be necessary.…”