# Dietary Choline and Betaine Are Not Associated With the Risk of Type 2 Diabetes. A Systematic Review and Meta‐Analysis of Observational Studies

## TL;DR

This study finds no strong evidence that dietary choline or betaine affects the risk of developing Type 2 diabetes.

## Contribution

A systematic review and meta-analysis reveals no significant association between dietary choline/betaine and Type 2 diabetes risk.

## Key findings

- High dietary choline intake showed a borderline non-significant increased risk of Type 2 diabetes (RR: 1.15, 95% CI: 1.00-1.33).
- Dietary betaine intake showed no significant association with Type 2 diabetes risk (RR: 0.99, 95% CI: 0.90-1.10).
- The certainty of evidence for both choline and betaine was rated as very low due to inconsistency and imprecision.

## Abstract

The link between dietary choline/betaine and Type 2 diabetes (T2D) has been shown in several studies. However, the findings are controversial. This meta‐analysis evaluated the connection between dietary choline/betaine and the incidence of T2D.

A thorough and organized search was conducted through PubMed, Scopus, and Web of Science up to September 2024. All reported effect sizes and their 95% CIs for risk of T2D were used to estimate log RRs with their standard errors (SEs). The overall combined effect size was obtained via a random effects model. The variability among the studies was examined using Cochrane′s Q test and the I‐squared statistic.

A total of five studies, including 76,678 subjects, provided data on the relationship between dietary choline and T2D risk. Compared with the lowest category of dietary choline, the combined RR for the diabetes incidence was 1.15 (95% CI: 1.00, 1.33; p = 0.058; I
2 = 63.1%) for the highest category of dietary choline. The pooled analysis of three studies, with 65,725 subjects, indicated no significant link between dietary betaine and T2D incidence. Compared with the lowest category of dietary betaine, the combined RR for the diabetes incidence was 0.99 (95% CI: 0.90, 1.10; p = 0.871; I
2 = 58.1%). The certainty of the evidence was rated very low for choline intake and T2D incidence as well as betaine intake and T2D incidence, with a downgrade for risk of bias, inconsistency, imprecision, and indirectness.

The findings of this study do not advocate the role of dietary choline/betaine in T2D incidence. Due to the limited number of primary studies and high heterogeneities among them, more rigorously designed prospective studies are required to confirm our results.