Vitamin CNEW2026-09

Dietary vitamin C intake and the risk of islet autoimmunity and type 1 diabetes: The Environmental Determinants of Diabetes in the Young (TEDDY) Study.

Mattila Markus, Mramba Lazarus K, Niinistö Sari, Erlund Iris et al. — European journal of nutrition

Summary

This study investigated the link between dietary vitamin C intake and the risk of developing early signs of type 1 diabetes, known as islet autoimmunity, or type 1 diabetes itself, in children at genetic risk. Overall, vitamin C intake was not consistently associated with the development of these conditions. However, the research suggested that moderate vitamin C intake might be associated with the lowest risk for some early markers, indicating a complex relationship that warrants further investigation.

AI-generated summary — read the original

Key points

This study investigated if vitamin C intake affects the risk of developing early signs of type 1 diabetes or the disease itself in children.
Overall, no consistent link was found between vitamin C intake and the development of islet autoimmunity or type 1 diabetes.
However, the research suggested that very low or very high vitamin C intake might be associated with a higher risk for some early markers compared to moderate intake.
More research is needed to understand the complex relationship between vitamin C and type 1 diabetes risk.

What the study looked at

What question the study asked: Researchers wanted to know if the amount of vitamin C children consume through their diet affects their risk of developing islet autoimmunity (early signs of type 1 diabetes) or type 1 diabetes itself. They also looked at genetic factors related to vitamin C metabolism. How it was studied: This study followed 8,478 children who were at a higher genetic risk for type 1 diabetes. Participants in the TEDDY cohort had their diets and health monitored every few months throughout their childhood. Vitamin C intake was carefully measured over time using age-appropriate methods. What it found: The study did not find a consistent, straightforward link between vitamin C intake and the overall risk of developing islet autoimmunity or progressing to type 1 diabetes. However, for specific early markers of islet autoimmunity, the findings suggested a non-linear relationship: both very low and very high vitamin C intakes appeared to be associated with a higher risk compared to moderate intakes. Genetic factors related to vitamin C metabolism did not show a clear link to type 1 diabetes outcomes in this study.

Dietary takeaway

While this study didn't find a simple link, it hints that extremely low or high vitamin C intake might not be ideal for certain early markers of type 1 diabetes. For general health, it's usually recommended to get vitamin C from a balanced diet rich in fruits and vegetables like oranges, strawberries, and bell peppers. Remember, this is just one study, and more research is needed to fully understand vitamin C's role in type 1 diabetes prevention.

Abstract

PURPOSE: We explored the associations between vitamin C intake and the risk of islet autoimmunity (IA) and/or type 1 diabetes in genetically at-risk children. Furthermore, we explored associations between vitamin C metabolism-related single nucleotide polymorphisms (SNPs) and type 1 diabetes outcomes. METHODS: The current study within Environmental Determinants of Diabetes in the Young (TEDDY) cohort included 8478 children followed up every 3-6 months for relevant autoantibodies and diet. Dietary vitamin C intake was assessed longitudinally throughout childhood using age-specific dietary assessment methods and analysed using repeated measurements. Cox regression was used for the primary analyses and Bayesian joint longitudinal-survival models as sensitivity analyses. RESULTS: A total of 777 (9.2%) children developed IA, including 292 (3.4%) with IAA-first and 337 (4.0%) with GADA-first autoimmunity; 319 (41.0%) progressed to type 1 diabetes. Mean (SD) vitamin C intake was 60.7 (38.8) mg/1000 kcal. Higher vitamin C intake was associated with an increased risk of IAA-first autoimmunity (adjusted hazard ratio 1.04; 95% confidence interval 1.00-1.07, per 10 mg/1000 kcal increase) while lowest and highest tertiles of intake were associated with increased risk of GADA-first autoimmunity as compared to mid-tertile [(1.65; 1.20-2.27) and (1.42; 1.02-1.98), respectively]. Sensitivity analyses using Bayesian joint longitudinal-survival models supported the primary findings and suggested nonlinear associations between vitamin C intake and the risks of IA and multiple IA. Associations between vitamin C-related SNPs and study outcomes did not withstand correction for multiple testing. CONCLUSION: Vitamin C intake was not consistently associated with IA or progression to type 1 diabetes. However, the observed nonlinear association, with lowest risk for moderate intakes, merits further investigation. TRIAL REGISTRATION: NCT00279318, 06/09/2004.

View on PubMed →DOI: 10.1007/s00394-026-04116-2