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

Study: Intake of pistachios as a nighttime snack has similar effects on short and longer-term glycemic control compared to education to consume 1-2 carbohydrate exchanges in adults with prediabetes: A 12-week randomized crossover trial. Image Credit: nelea33 / Shutterstock.com

Background

Prediabetes is a health condition characterized by impaired 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 incident cardiovascular disease. In the United States, the prevalence of prediabetes is 38% among adults, about 74% of whom are at risk of developing type 2 diabetes in their lifetime.

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

Consuming nighttime snacks after dinner but before bedtime has been found to be effective in preventing hyperglycemia the following morning. As a result, the American Diabetes Association and Academy of Nutrition and Dietetics recommend carbohydrate-rich foods as nighttime snacks to improve glycemic control in prediabetic and diabetic patients.

Pistachios are rich in dietary fiber and unsaturated fatty acids, which are known to positively impact glucose regulation 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 compare the efficacies of pistachios and carbohydrate-rich foods as nighttime snacks in controlling fasting blood glucose levels, reducing cardiovascular disease-related risk factors, and improving diet quality in prediabetic adults.

Study design

The study population included 51 prediabetic adults randomly divided into two groups. In the intervention group, participants were provided with 57 grams/day of dry roasted and unsalted pistachios as a nighttime snack for 12 weeks. In the comparator group, participants were provided with a carbohydrate-rich food as a nighttime snack for 12 weeks.

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

Important observations

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

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

Although no significant difference in total energy was observed between the study groups, the percentage of total energy from mono-unsaturated fatty acids and potassium intake was higher in the intervention group. This group also reported a greater intake of dietary fiber, nuts and seeds, and oil, as well as a lower intake of refined grains.

Study significance

Pistachios as nighttime snacks can increase diet quality in prediabetic patients; however, this food item had a similar effect as carbohydrate-rich snacks on glycemic control and vascular health. Nevertheless, the study findings indicate that prediabetic patients can consume pistachios as a healthier alternative to carbohydrate-rich nighttime snacks to increase alignment with dietary guidelines for U.S. adults.

Importantly, the trial suffered a significant attrition rate and missing data due to trial suspension and participant withdrawal during the coronavirus disease 2019 (COVID-19) pandemic. After the start of the pandemic, a specific age inclusion criterion was introduced as a part of the University approval process to re-start the trial, which could restrict the generalizability of the study findings to individuals 65 years of age and older.