Zinc supplementation confers no benefit in prediabetes

Supplementation with zinc does not help with glucose control in individuals with prediabetes, according to data from the Zinc in Preventing the Progression of pre-Diabetes (ZIPPeD) study.

ZIPPeD included 98 individuals (mean age 60.8 years, 55 percent female) with prediabetes (haemoglobin A1c [HbA1c] 5.7–6.4 percent, 39–46 mmol/mol) across 10 practices in New South Wales in Australia. They were randomized to receive either 30-mg zinc gluconate or placebo, taken daily with breakfast.

Researchers collected blood tests at baseline and at months 1, 6, and 12. The primary outcomes were HbA1c and fasting blood glucose (FBG). Secondary outcomes were Homeostasis Model Assessment 2 (HOMA 2) parameters, lipids, body weight, height, waist circumference, blood pressure, and pulse.

At baseline, the mean body mass index of the population was 34.1 kg/m², and the mean waist circumference was largely above the healthy recommended limit of 88 cm in women and 102 in men. Fifty-two participants (53 percent) had never smoked, and around half consumed alcohol within recommended levels.

Compared with placebo, zinc had no significant effect on either HbA1c (baseline-adjusted mean difference, −0.02, 95 percent confidence interval [CI], −0.14 to 0.11; p=0.78) or FBG (baseline-adjusted mean difference, 0.17, 95 percent CI, −0.07 to 0.42; p=0.17) at 6 months.

Likewise, there were no significant between-group differences observed in any of the secondary outcomes.

In terms of safety, zinc was well tolerated, and compliance was high at 88 percent.

The findings are consistent with other Western clinical trial studies and do not support the use of supplemental zinc in prediabetic populations with a Western diet.