The effects of long-term almond consumption on whole-body insulin sensitivity, postprandial glucose responses, and 48 h continuous glucose concentrations in males and females with prediabetes: a randomized controlled trial

PURPOSE: Findings concerning the effects of almond consumption on glucose metabolism are inconsistent which might relate to body weight gain. The effects of long-term almond consumption on glucose metabolism are investigated in a free-living setting without detailed dietary instructions in males and females with overweight/obesity and prediabetes. METHODS: Forty-three participants volunteered in this randomized, cross-over trial with a 5-months control and intervention period and a 2-months wash-out. In the intervention period participants daily consumed 50 g whole almonds. At the end of both periods insulin sensitivity was assessed by a hyperinsulinemic euglycemic clamp, and postprandial glucose responses, and 48 h continuous glucose concentrations were measured. RESULTS: Almond consumption significantly decreased insulin sensitivity (P = 0.002), and increased postprandial glucose concentrations (P = 0.019), as well as fasting insulin concentrations (P = 0.003) as compared to the control period. The AUCs for 24 h glucose concentrations were not significantly different between control and intervention (P = 0.066). Almond consumption also significantly increased BMI (P = 0.002), and waist circumference (P = 0.013), supported by the concurrent increased energy intake (P = 0.031). The effects on glucose metabolism could only partly be explained by the observed weight gain as the almond effect remained after correcting for BMI changes. CONCLUSIONS: In participants with prediabetes, long-term almond consumption showed adverse effects on insulin sensitivity and glucose metabolism. As almonds seemed not to have fully replaced other food items, it might be necessary to provide more supporting guidelines on how to incorporate energy-dense nuts into healthy diets to prevent type 2 diabetes development. CLINICAL TRIAL REGISTRATION: This clinical trial was registered in February 2018 as NCT03419702.