Effects of lacto-vegetarian and vegan diets on glycemic responses and metabolite profiles in healthy adults: A randomized trial using continuous glucose monitoring and targeted metabolomics

Abstract

Background: Our previous studies have demonstrated that dairy products protect against type 2 diabetes (T2D) and improve cardiometabolic health outcomes. Given that continuous glucose monitoring (CGM) and metabolomics analysis capture different aspects of T2D, this study investigated the effects of dairy and non-dairy products on the glycemic and metabolite profiles in healthy adults following lacto-vegetarian and vegan diets.

Methods: A parallel randomized feeding trial with 30 participants compared isoenergetic vegan and lacto-vegetarian diets. All participants wore CGM sensors for 14 days to track glucose concentrations. Anthropometric and biochemical characteristics were also measured. In a subgroup of 13 individuals, fasting and postprandial blood samples were collected on days 1 and 15 for metabolomics analysis.

Results: Our CGM data showed higher mean glucose concentrations in the vegan group over 14 days compared to the lacto-vegetarian group (p = 0.0399), after adjusting for age, sex, body mass index, and baseline glucose concentrations. Metabolomics analysis from day 1 to day 15 showed increased postprandial phenylalanine (Phe; p = 0.0189) in the vegan group, while the lacto-vegetarian group showed increased acetyl carnitine (C2; p = 0.00704) and decreased argininosuccinic acid (p = 0.0149).

Conclusions: Our pilot CGM data suggest a lacto-vegetarian diet may offer better glycemic control, potentially explained by our preliminary metabolomics findings. The increased Phe observed in the vegan group may be explained by a hypothetical mechanism in which higher glucose induces oxidative stress, whereas the increased C2 from dairy in the lacto-vegetarian group may protect against oxidative stress, contributing to lower glucose concentrations. However, larger, longer-term studies with more diverse populations, along with in vitro investigations into biomolecular mechanisms, are needed to confirm these findings.

Keywords: Acetyl carnitine; CGM; Dairy; Metabolomics; Phenylalanine.