Study under review: Zinc supplementation in prediabetes: A randomized double-blind placebo-controlled clinical trial.
Prediabetes is a condition of elevated blood glucose that is above normal, healthy levels but not so high as to meet criteria for type 2 diabetes. Two definitions of prediabetes are summarized in Figure 1. Currently, the World Health Organization defines prediabetes as having a fasting blood glucose level of 110-125 mg/dL (6.1-7.0 mmol/L) or a two-hour blood glucose value of 140-200 mg/dL (7.8-11.1 mmol/L) during an oral glucose tolerance test. The American Diabetes Association has similar criteria, with the the additional parameter of HbA1c being 5.7-6.4%.
Figure 1 - Two definitions of prediabetes
The Center for Disease Control reports approximately one in three U.S. adults to have prediabetes. The prevalence increases with age, to about 48% of adults 65 years or older. Rising levels of blood sugar have also been noted worldwide in both developed and developing countries. Ultimately, about 70% of people with prediabetes will progress to develop type 2 diabetes, making prediabetes a critical period for intervention.
Lifestyle interventions for prediabetes primarily target fat loss, but improvements to diet and increases in physical activity are also key for preventing progression to diabetes. Although effective and cost-efficient, lifestyle interventions can be difficult for some people to adhere to.
Treatment with zinc may provide a cost-effective alternative. Zinc is thought to have multiple effects, summarized in Figure 2, that could help with both diabetes and prediabetes. It plays an important role in beta-cell function, insulin signal transduction, and is involved in insulin biosynthesis. Moreover, some people with type 2 diabetes have low zinc absorption and high urinary zinc excretion. This may, in part, explain why people with type 2 diabetes have lower levels of serum zinc.
A meta-analysis of zinc supplementation studies in participants with type 2 diabetes reported significant benefits for glycemic control and blood lipids. These findings were supported by a separate meta-analysis involving primarily patients with type 2 diabetes, but also insulin resistant and healthy adults. However, a systematic review looking only at people with insulin resistance without diabetes reported no significant benefit from zinc supplementation. Limited research looking specifically at adults with prediabetes exists. One pilot study reported that zinc supplementation benefits glycemic control in this population. The study under review sought to build upon this research to determine the effects of zinc supplementation in a large group of people with prediabetes over a 12-month period.
Prediabetes represents an important checkpoint on the path to type 2 diabetes. Zinc is involved in proper glucose metabolism and supplementation has been shown to benefit glycemic control in people with type 2 diabetes. Less certainty exists regarding its effects in people with prediabetes. The study under review sought to address this knowledge gap.
Other Articles in Issue #40 (February 2018)
Interview: Gabrielle Fundaro PhD, CISSN
In this interview, we chat with researcher and weightlifter Gabrielle Fundaro about her health routine, the challenges of teaching complex biological concepts, the microbiome, and nutrition.
Interview: Andrew Gelman, PhD
In this interview, we chat about important aspects of statistics and study design with one of the luminaries in the field.
A progress report on supplements for osteoarthritis
There are a lot of supplements that are supposed to improve aspects of osteoarthritis. But what's the evidence that they actually help?
A look under the hood at carbohydrate intake during exercise
Higher carbohydrate intake during submaximal exercise can help boost performance. This study explores why.
Some TLC from ALC in depression
Acetyl-L-carnitine can pass through the blood-brain barrier more easily than L-carnitine. This meta-analysis takes a look at whether it can help with depression.
Can curcumin reduce cardiovascular risk factors?
Curcumin is thought to have multiple possible health benefits. This meta-analysis zeros in on its effects on cardiovascular risk factors.
Can whole eggs help make swole legs?
Getting enough protein is essential to help stimulate muscle growth. But the type of protein-containing food can also play a role.