Ideal nighttime snack for prediabetic patients to manage blood glucose levels

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A recent study published Journal of Nutrition evaluated the effectiveness of pistachios in controlling morning blood glucose levels and improving vascular health in prediabetic patients.

Study: Eating pistachios as dinner has similar effects on short- and long-term glycemic control compared with education for 1–2 carbohydrate exchanges in adults with prediabetes: a 12-week randomized crossover trial. Image credit: nelea33/


Prediabetes is a medical condition characterized by elevated fasting blood glucose levels, elevated glycated hemoglobin A1c (HbA1c) levels, and impaired glucose tolerance. Prediabetes in midlife can significantly increase the 30-year relative risk of cardiovascular disease. In the United States, the prevalence of prediabetes is 38% among adults, of whom approximately 74% are at risk of developing type 2 diabetes in their lifetime.

Rigorous lifestyle and behavioral therapy, including diet, weight loss programs, and exercise, are the current treatments for preventing or delaying the onset of type 2 diabetes in adults with prediabetes.

Eating dinner after dinner but before bed has been shown to be effective in preventing hyperglycemia the next morning. Consequently, the American Diabetes Association and the Academy of Nutrition and Dietetics recommend a carbohydrate-rich meal as dinner to improve glycemic control in prediabetic and diabetic patients.

Pistachios are rich in dietary fiber and unsaturated fatty acids, which positively affect glucose control and cardiovascular health. Several randomized controlled trials have shown that pistachios can improve fasting blood glucose levels and insulin sensitivity.

In the current randomized controlled crossover trial, scientists compared the effectiveness of pistachios and a carbohydrate-rich meal as dinner in controlling fasting blood glucose levels, reducing cardiovascular disease-related risk factors, and improving diet quality in prediabetic adults.

Research design

The study population consisted of 51 prediabetic adults randomly divided into two groups. In the intervention group, participants were provided 57 g/day of dry roasted and unsalted pistachios as an evening snack for 12 weeks. In the comparison group, participants were provided with a carbohydrate-rich meal as dinner for 12 weeks.

Primary and secondary parameters including fasting blood glucose, HbA1c, insulin, insulin resistance, lipids/lipoproteins, vascular health and diet quality were assessed at the beginning and end of each diet period on two consecutive days.

Important observation

A total of 26 participants were randomized to the intervention group, while 25 participants were to the comparison group. Dietary adherence was 90% in the intervention group and 93% in the comparison group. The most commonly consumed carbohydrate-rich foods in the comparison group were crackers, popcorn, and pretzels.

No significant differences were observed in glucose metabolism-related and vascular health-related parameters between the study groups. However, the Healthy Eating Index-2015 (HEI-2015) score, which was estimated to assess diet quality, was higher in the intervention group than in the comparison group. More specifically, participants in the intervention group had higher HEI scores for seafood and plant protein, refined grains, and fatty acid ratios than the comparison group.

Although no significant difference in total energy was observed between the study groups, the percentage of total energy from monounsaturated fatty acid and potassium intake was higher in the intervention group. This group also reported greater intakes of dietary fiber, nuts and seeds, and oils, as well as lower intakes of refined grains.

Significance of the study

Pistachios as an evening meal may increase food quality in prediabetic patients; However, this food item had similar effects on glycemic control and vascular health as carbohydrate-rich snacks. Still, research findings suggest that prediabetic patients can eat pistachios as a healthy alternative to a carbohydrate-rich dinner to increase alignment with the Dietary Guidelines for US Adults.

Importantly, the trial suffered a significant attrition rate and missing data due to trial suspensions and participant withdrawals during the coronavirus disease 2019 (COVID-19) pandemic. After the start of the pandemic, a specific age inclusion criteria was introduced as part of the university’s approval process to restart the trial, which may have limited the generalizability of the study’s results to people aged 65 and over.

Journal Reference:

  • Riley, TM, Kris-Etherton, PM, Hart, TL, & Petersen, KS (2024). Eating pistachios as dinner has similar effects on short- and long-term glycemic control compared with education for 1–2 carbohydrate exchanges in adults with prediabetes: a 12-week randomized crossover trial. Journal of Nutrition. doi:10.1016/j.tjnut.2024.01.021.

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