Scientific Study

Objectives: Pistachios contain unsaturated fats, fiber, and phytosterols that can influence glycemia, cardiometabolic health, and may alter the gut microbiota. The aim was to assess the effects of pistachio consumption on the stool microbiota of adults with prediabetes (fasting plasma glucose [FPG] >100 mg/dL < 125 mg/dL). Methods: A secondary analysis of data from a single-blind, 2-period (12 weeks each), randomized crossover trial was conducted. Participants were provided with 57 g/d of dry roasted unsalted pistachios (319 kcal; fat 26 g; CHO 16 g; protein 12 g; saturated fat 3.4 g; fiber: 6 g;] to consume as a nighttime snack or provided education to consume 1-2 carbohydrate (CHO) exchanges (usual care; CHO 15-30 g) as a nighttime snack. Fecal samples were collected at the beginning and the end of each diet period and analyzed with 16S rRNA sequencing. Linear mixed models were used to examine between-condition differences in community richness (α-diversity) assessed by Faith's Phylogenetic Diversity, Observed Features, and Pielou's Evenness metrics. Community dissimilarity (β-diversity) was evaluated with the Bray-Curtis Dissimilarity index. Bacterial abundance (center log2-ratio normalized) differences by condition were tested using linear mixed models with Benjamini-Hochberg correction for false discovery. Results: The analytical sample included 51 participants (37% female, 49±10 y, 31.5±4 kg/m2, FPG 102±10 mg/dL) who completed the trial. Diversity metrics (α- and β-diversity) were similar between the conditions. After the pistachio condition, Roseburia (LSM±SE; 3.2±0.9, p< 0.01) and Hydrogenoanaerobacterium (0.87±0.31, p=0.04) abundance were higher compared to the usual care. The abundance of Porphyramonas_Asaccharolytica (-0.7±0.2, p=0.02), Eubacterium (-0.39±0.1, p=0.03), Ruminococcus (-1.02±0.2, p=0.01), and Peptococcaceae (-0.56±0.17, p=0.01) were lower after the pistachio vs. usual care condition. Conclusions: In individuals with prediabetes, intake of 57 g/d of pistachios as a nighttime snack enriched butyrate-producing bacteria compared to a carbohydrate-rich snack. Additional research is needed to better understand how microbial changes influence cardiometabolic markers. https://doi.org/10.1016/j.cdnut.2024.103486