Millet-based Diets for Managing and Preventing Diabetes

Alternative carbohydrate sources with lower glycemic indices like millets may have benefits for patients with diabetes or prediabetes.

Consuming carbohydrate sources with high glycemic indices (GI) such as refined rice, maize, and wheat, are associated with significant changes in postprandial blood glucose concentrations. Therefore, it is essential to consider alternative carbohydrates when trying to optimize diets for patients with diabetes mellitus. Millets are carbohydrates with low GI that come in various types and are available worldwide, especially in Asian and African countries. Several studies have been conducted on millet-based diets to view their effects on glycemic control. However, due to the heterogeneity of the data in most of these studies, it is difficult to determine the actual benefits of millet-based diets, especially when considering the various methods of preparation and types of millets. 

The authors conducted a meta-analysis to determine if millet-based diets can help manage type 2 diabetes and reduce progression from prediabetes to diabetes. All peer-reviewed studies published from 1950 to the last quarter of 2020 that looked at the effect of thirteen types of millet on one or a combination of prespecified key outcomes were included. Key outcomes include a glycemic index, fasting blood glucose, postprandial blood glucose, insulin index, and A1c. Review articles, animal studies, and studies with weak or incomplete information were excluded from the study. A total of 65 studies were included in the meta-analysis and regression analysis. Depending on the heterogeneity (I2) of the sample, a fixed-effect model or a random-effects model was used. Subgroup analyses looked at the type of control used (i.e., rice/bread/glucose), participant’s health condition (with diabetes, prediabetes, or without diabetes), and the type of millet. The investigators also looked at the effect of crop choice on dietary GI via regression analysis when considering the crop, cooking method, and methods to measure GI.

The results showed that when looking at the different types of millets overall, the mean GI of millets (52.7±10.3) was much lower than that of high glycemic index foods such as refined rice (71.7±14.4) and refined wheat (74.2±14.9). Millet types that have low GI (<55) are Job’s tears, fonio, foxtail, barnyard, and teff. Millet types with intermediate GI (55-69) are pearl millet, finger millet, Kodo millet, little millet, and sorghum. When comparing the GI of millets to other control foods (refined wheat, rice, maize, and glucose), all millet types except for little millet had significantly lower GI (p<0.01). However, the higher GI of little millet may have been due to a lack of research and the inclusion of one study that deviated highly from the other studies. For effects on fasting blood glucose, long-term consumption (≥7 days) of millets showed significant reductions by 12% (SMD -0.89 [-1.11 to -0.67]; p<0.01) regardless of health condition. Reductions in postprandial blood glucose were also observed in short-term studies (p<0.01) and long-term studies (SMD -0.95 [-1.46 to -0.44]; p<0.01), with long-term studies showing a 15% reduction in postprandial levels in patients with diabetes or prediabetes. However, millets did not show this effect in groups without diabetes (p<0.01). Analysis of six long-term studies showed reductions in A1c by 15% when compared to rice-based diets or baseline A1c levels for patients with prediabetes or diabetes (p<0.01). Reductions in fasting insulin level and insulin index were reported as significant but not included in the publication. Finally, the regression analysis showed that millet consumption was associated with significantly lower GI across all types than maize-based diets, except for pearl and little millet. To appreciate the magnitude of this reduction, foxtail millet, which had the most observations (12.4% of 267), reduced the GI of a meal by 30%. 

Millet-based diets, on average, are associated with improved glycemic control for patients with or without diabetes when compared to staple sources of carbohydrates. While millets may not be typically consumed in the United States, this study shows the potential benefit of including low GI foods into diet plans. These results are supported by other meta-analyses highlighting the effects of low-GI diets on reducing body weight and improving glycemic control in people with prediabetes or diabetes. Future studies could investigate the impact of other low-GI foods on glycemic control to determine additional methods of diet diversification.    

Practice Pearls:

• Overall, the glycemic index of millets is significantly lower than typical staples such as milled rice and refined wheat. 
• Long-term millet consumption can reduce fasting blood glucose, postprandial blood glucose, and A1c.
• Millets may be beneficial in preventing the development of diabetes mellitus or reducing disease progression. 

Anitha, Seetha, et al. “A Systematic Review and Meta-Analysis of the Potential of Millets for Managing and Reducing the Risk of Developing Diabetes Mellitus.” Frontiers in Nutrition, July 28, 2021.

Zafar, Mohammad Ishraq et al. “Low-glycemic index diets as an intervention for diabetes: a systematic review and meta-analysis.” The American journal of clinical nutrition

Andy Dao, PharmD Candidate, University of South Florida Taneja College of Pharmacy