The Use of Dietary Supplements in the Treatment of Diabetes

Thousands of dietary supplements are available for diabetes treatment, but an examination of available studies found that only three ingredients had consistent evidence to support their claims. 

In the United States, dietary supplements are a multi-billion-dollar industry, having generated more than $30 billion in sales in 2016, which is projected to double by 2024. The allure for investing in these products originates from a lack of government oversight by agencies like the US Food and Drug Administration. Unlike pharmaceuticals, the FDA does not require evidence of efficacy and safety before a supplement reaches the market. The result is countless products flooding the market with claims to promote health. Little regulation is in place to confirm the validity of these claims, aside from the FDA preventing such products from using statements claiming to treat, prevent, or cure a disease. Because of this, supplement use among Americans remains high, despite limited evidence supporting their use. A big challenge to determining which supplements are effective is finding well-designed studies providing strong evidence. As a result, the American Standards of Medical Care in Diabetes states there is insufficient evidence to support using dietary supplements to treat diabetes. However, several narrative reviews have been published highlighting positive outcomes among patients with diabetes taking various dietary supplements.   

Recently, a group of researchers published a systematic review to identify supplement ingredients commonly used for diabetes management and evaluate the evidence supporting their use. The team began by using the Dietary Supplement Label Database (DSLD), developed by the Office of Dietary Supplements at the National Institute of Health, to search approximately 76,000 commercially available products. From this, the study compiled a list of the top 100 ingredients used to treat diabetes based on the number of times each ingredient appeared on product labels. Next, a web-scraping program searched the PubMed database, automatically collecting articles on the top ingredients and diabetes. Articles underwent a two-phase screening process by members of the research team, requiring each study to examine diabetes-related outcomes such as glucose levels, insulin resistance, HbA1c, or diabetes-related complications. Finally, researchers assigned evidence grades to each study based on the type of study with meta-analysis receiving the highest grade of one and case reports receiving the lowest grade of four.    

A few supplement ingredients were shown to have positive effects on diabetes management, while most had conflicting results or no effect entirely. About half of the studies included ingredients which were minerals, such as chromium, potassium, and zinc. Of these, only zinc was found to have benefits such as improved fasting glucose, Hb1Ac, and insulin levels. Vitamin C was among the few beneficial supplements with a meta-analysis concluding supplementation may be associated with improved fasting glucose levels. Finally, fiber supplementation was found to have beneficial effects on Hb1Ac and fasting glucose.  

Of the top 100 ingredients included in the study, only three ingredients were determined to have consistent evidence to support their claims. Supplement use continues to rise among consumers due to perceived benefits and accessibility. It is estimated that in the United States, about 59% of individuals living with diabetes currently take some form of dietary supplement. Thus, healthcare providers must remain knowledgeable on the available evidence and advise patients on overall effectiveness. For most dietary supplements, the evidence is conflicting with poorly designed studies aimed at promoting the product rather than providing evidence for clinical use. There is a clear need for additional research with controlled study methods such as clinical trials before recommendations for supplements can be made.     

Practice Pearls: 

• It’s estimated that dietary supplements are used by 52% of adults living in the United States. 
• Many of these supplements have little to no evidence supporting their use and can be potentially harmful to patients taking them.
• Recent studies have found some dietary supplements like Vitamin C, zinc, and fiber are associated with positive outcomes in patients with diabetes, such as improved fasting glucose, Hb1Ac, and insulin levels. 

Hannon, Bridget A., et al. “Use and Abuse of Dietary Supplements in Persons with Diabetes.” Nutrition & diabetes, vol. 10, no. 1, 2020. doi:10.1038/s41387-020-0117-6. 

Stephen Rubano, PharmD. Candidate, USF Taneja College of Pharmacy 

See more about dietary supplements and diabetes.