Zinc supplementation in pre-diabetes: study protocol for a randomized controlled trial

Abstract

BackgroundThe number of people with diabetes is increasing worldwide, especially in developing South Asian countries. Therefore, preventing diabetes at the early stages has become an important issue. Recent clinical trials, systematic reviews, and meta-analysis have shown that zinc has beneficial effects on glycemic and metabolic control in those with diabetes. The present study is designed to evaluate the effects of zinc supplementation on glycemic control and other metabolic parameters in those with pre-diabetes.Methods/designThe study will be conducted as a randomized, double-blind, placebo-controlled clinical trial for a period of 12 months at the Faculty of Medicine, University of Colombo, Sri Lanka. The study has been approved by the Ethics Review Committee of Faculty of Medicine, University of Colombo (EC/11/189). A total of 200 adults (age 18–60 years) with pre-diabetes will be recruited for the study. They will be stratified according to age, gender, and body mass index and randomly assigned into the test and placebo groups on a 1:1 ratio. The zinc capsules, each weighing 456 mg, will contain the following ingredients:zinc sulfate monohydrate 55.096 mg (elemental zinc 20 mg), lactose monohydrate 399.504 mg, and stearic acid 1.400 mg. The placebo capsule with the same weight will be comprised of lactose monohydrate 454.600 mg and stearic acid 1.400 mg. The subjects will receive either zinc 20 mg capsules or placebo daily for a period of 12 months. The study drugs will be double blinded to both investigators and subjects. The visits and the evaluations will be done as follows: screening (visit 0), 1 month (visit 1), 3 month (visit 2), 6 month (visit 3), and 12 month (visit 4). The following primary outcome measures will be evaluated:fasting plasma glucose (FPG), post oral glucose tolerance test (OGTT), serum insulin, HbA1c, total/low-density lipoprotein (LDL)/high-density lipoprotein (HDL) cholesterol, triglycerides, serum zinc, and appetite using a visual analog scale. Secondary outcome measures include: blood pressure, anthropometry, and dietary assessment using a validated food frequency questionnaire. Data will be analyzed using SPSS v16.DiscussionThe present protocol will aim to establish the beneficial effects of zinc supplementation on disease progression in those with pre-diabetes and also establish its effectiveness in the prevention of diabetes mellitus.Trial registrationSri Lanka Clinical Trial Registry: SLCTR/2012/010

Zinc supplementation in prediabetes: A randomized double‐blind placebo‐controlled clinical trial

“…Inclusion and exclusion criteria have been described in detail elsewhere . Briefly, the inclusion criteria were age between 18 and 70 years and confirmation of prediabetes, as defined above, by a screening test.…”

“…The primary outcome was defined as change in glycemic control (assessed using FPG and 2‐h OGTT plasma glucose levels) from baseline. A full list of the secondary outcomes assessed at each time point has been described elsewhere, and includes development of diabetes during the follow‐up period (as indicated by either FPG >125 mg/dL and/or 2‐h OGTT plasma glucose levels >199 mg/dL confirmed during follow‐up visits), serum lipid levels (total cholesterol [TC], high‐density lipoprotein cholesterol [HDL‐C], low‐density lipoprotein cholesterol [LDL‐C], triglycerides [TG]), serum insulin, insulin resistance, systolic and diastolic blood pressure (SBP and DBP, respectively), anthropometric assessment (body weight, height, body mass index [BMI], waist circumference [WC], hip circumference [HC], and waist: hip ratio [WHR]). The participants also completed a questionnaire regarding physical activity and diet.…”

“…All anthropometric measurements (height, weight, BMI, WC, HC, and WHR) were made using standard calibrated equipment and following WHO guidelines . Details of anthropometric and clinical measurements have been described in detail elsewhere . Seated SBP and DBP were measured after a 10‐min rest using Omron IA2 digital BP monitors (Omron Healthcare, Singapore).…”

“…Inclusion and exclusion criteria have been described in detail elsewhere. 17 Briefly, the inclusion criteria were age between 18 and 70 years and confirmation of prediabetes, as defined above, by a screening test. The exclusion criteria were being on any other vitamin or mineral supplement, current use of a weight loss medicine or dietary modification, a history of diabetes mellitus or any metabolic disease, the presence of acute diseases or another untreated illness requiring treatment, impaired hepatic or renal function, and lactation, pregnancy or unwillingness to use an effective form of birth control for women of child-bearing age.…”

Pharmacokinetics of zinc in pre-diabetes: a pilot study

“…The inclusion and exclusion criteria for the clinical trial are described elsewhere. 13 In summary, to be included in the study the participants had to be:…”