Dataset Information

Evaluation of an 8-Week Vegan Diet on Plasma Trimethylamine-N-Oxide and Postchallenge Glucose in Adults with Dysglycemia or Obesity.

ABSTRACT:

Background

Trimethylamine N-oxide (TMAO), a metabolite generated by the gut in response (in part) to meat consumption, is linked to poor cardiometabolic health.

Objectives

We investigate the effect of an 8-week vegan diet, followed by a 4-week period of unrestricted diet, on glucose tolerance and plasma TMAO in human omnivores with obesity or dysglycemia.

Methods

This interventional single-group prospective trial involved 23 regular meat eaters with dysglycemia [glycated hemoglobin ≥ 5.7% and ≤8% (39-64 mmol/mol)], or obesity (ΒΜΙ ≥ 30 kg/m2) aged 57.8 ± 10.0 years. Participants [14 men (60.9%) and 9 women (39.1%)] were supported in following a vegan diet for 8 weeks, followed by 4 weeks of unrestricted diet. The primary outcomes (plasma TMAO and glucose) were assessed at baseline, during the vegan diet (weeks 1 and 8), and after the unrestricted diet period (week 12). TMAO was assessed after fasting and glucose was measured as a time-averaged total AUC using a 180-minute oral-glucose-tolerance test. Generalized estimating equation models with an exchangeable correlation structure were used to assess changes from baseline, adjusting for age, sex, ethnicity, and weight.

Results

TMAO levels (marginal mean) were reduced after weeks 1 and 8 of a vegan diet compared to baseline, from 10.7 (97.5% CI, 6.61-17.3) μmol/L to 5.66 (97.5% CI, 4.56-7.02) μmol/L and 6.38 (97.5% CI, 5.25-7.74) μmol/L, respectively; however, levels rebounded at week 12 after resumption of an unrestricted diet (17.5 μmol/L; 97.5% CI, 7.98-38.4). Postprandial glucose levels (marginal means) were reduced after weeks 1 and 8 compared to baseline, from 8.07 (97.5% CI, 7.24-8.90) mmol/L to 7.14 (97.5% CI, 6.30-7.98) mmol/L and 7.34 (97.5% CI, 6.63-8.04) mmol/L, respectively. Results for glucose and TMAO were independent of weight loss. Improvements in the lipid profile and markers of renal function were observed at week 8.

Conclusions

These findings suggest that a vegan diet is an effective strategy for improving glucose tolerance and reducing plasma TMAO in individuals with dysglycemia or obesity. This study was registered at clinicaltrials.gov as NCT03315988.

SUBMITTER: Argyridou S

PROVIDER: S-EPMC8245890 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundTrimethylamine-N-oxide (TMAO) is a compound that is present in seafood and produced through human gut microbial metabolism of its precursors. Previous studies have suggested that elevated TMAO concentrations are associated with an increased risk of cardiovascular events. However, the association between diet and TMAO concentrations in free-living adult populations has not been adequately described.ObjectivesThe objective of this study was to identify dietary predictors of plasma TMAO concentrations.MethodsTMAO concentrations were assessed in 2 fasting plasma samples collected 6 mo apart among 620 healthy men. Short-term and long-term dietary intakes were assessed during the same time-frame of blood collections via repeated 7-d dietary records (7DDRs) and a semiquantitative food-frequency questionnaire (SFFQ), respectively. We grouped individual food items into 21 groups and regressed against averaged TMAO concentrations. We also assessed the association between dietary scores and TMAO concentrations.ResultsIn models adjusted for demographic characteristics and mutually adjusted for food groups, SFFQ-assessments of fish and egg intakes were significantly associated with increased TMAO concentration (β = 0.082; 95% CI: 0.021, 0.14; P = 0.009 for fish; β = 0.065; 95% CI: 0.004, 0.13; P = 0.039 for egg). The positive association between fish consumption and TMAO concentration was replicated in the 7DDR-assessments (β = 0.12; 95% CI: 0.060, 0.18; P < 0.001). There was no association between red meat intake and TMAO concentrations. The unhealthful plant-based diet index (uPDI) was inversely associated (β = -0.013; 95% CI: -0.021, -0.005; P = 0.001) and healthy dietary scores were positively correlated with TMAO concentration.ConclusionsTMAO concentration was significantly associated with fish intake, but not with red meat consumption. uPDI, an unhealthy dietary pattern, was inversely related to TMAO concentration. As such, this study suggests that in free-living populations, higher circulating concentrations of TMAO cannot simply be interpreted as a marker of unhealthy food intake or an unhealthy dietary pattern.

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