Type 2 Diabetes Risk Increased in Adults with Vitamin C Intake Below the Estimated Average Requirements

by | Nov 14, 2022 | 2022, Diabetes, Vitamin C

Written by Taylor Woosley, Staff Writer. Study findings show that dietary intake of VC in adults with type 2 diabetes (mean 75.5, 95% CI 72.5-78.4 mg/day) was significantly lower than in adults without diabetes (84.6, 95% CI 83.4-85.7). 

vitamin CDiabetes is a metabolic condition that is characterized by chronic hyperglycemia and results from an interplay of genetic and environmental factors1. The population with diabetes mellitus (DM) is predicted to be about 439 million worldwide by 20302. Type 2 diabetes occurs due to the decreased insulin sensitivity or peripheral tissues, accompanied by defective insulin secretion in pancreatic islet β-cells3. DM that is not well managed can have significant impact on morbidity and mortality, including a risk factor for stroke, renal dysfunction, and neuropathy4.

Vitamin C (ascorbic acid) is an essential nutrient that must be taken through the diet and plays an important role in the normal functioning of the immune system5. Observational evidence suggests that plasma vitamin C is inversely associated with the incidence of type 2 diabetes6. Vitamin C (VC) has a cytoprotection role, antimutagenic activity, vasodilatory action, and inhibitory effect on platelet aggregation, being useful in type 2 DM and high blood pressure7. Research has shown that supplementation with vitamin C can improve blood glucose, lipid profiles, glycated haemoglobin (HbA1C) and insulin in subjects8.

Sun et al. conducted an observational study to evaluate VC intake parameters as potential indicators of diabetes development, and mortality risk in the diabetic and non-diabetic US population using data from the National Health and Nutrition Examination Survey (NHASES) between 1999 and 2018. Mortality records of 52,150 adults (25,206 men and 26,944 women, aged 18 to 85) were included in the study. Further information pertaining to daily dietary and supplemental VC intake and glycohemoglobin A1c were obtained from NHANES. Dietary interviews were given by a trained dietary interviewer and dietary and supplemental VC of participants consumed in the previous 24 h before the interview were estimated.

Half of the cohort (24,468) had available fasting plasma glucose data and the serum VC data of 7246 adult men and 7736 adult women were obtained through select periods of the NHANES. Serum VC and plasma glucose were assayed at the NHANES laboratory. Demographic data, diabetes status, and body mass index (BMI) of participants were included in analysis. Statistical analysis included weighted means, odds ratios (ORs), hazard ratios (HRs), survival time, and 95% confidence intervals of all data. Four categories of total VC intake (dietary + supplement) were included in the study based on the estimated average requirement (EAR) levels of VC intake for adult men (75 mg/day) and for adult women (60 mg/day). Binary logistic regression was utilized to analyze ORs of diabetes. The dependent variable was diabetes status and the independent variables included two or three levels of VC intake, three levels of serum VC and five levels of VC supplement respectively. Cox proportional hazards model was used to analyze HRs of all-cause mortality excluding accidental death. Significant findings of the study are as follows:

  • 428 type 1 diabetes and 6807 type 2 diabetes were identified among the 52,150 participants. These analyses revealed the prevalence of type 1 diabetes at 6.4% (95% CI 5.6-7.4%) of the total diabetic population while type 2 diabetes consisted of 93.6% (95% CI 92.6-94.4%) of the total diabetic population.
  • Dietary intake of VC in adults with type 2 diabetes (mean 75.5, 95% CI 72.5-78.4 mg/day) was significantly lower than in adults without diabetes (84.6, 95% CI 83.4-85.7).
  • Serum VC levels were significantly lower in adults with type 2 diabetes (0.84 95% CI 0.81-0.87 mg/dl), but not significantly lower in adults with type 1 diabetes (0.92 95% CI 0.83-1.02) than in adults without diabetes (0.94 95% CI 0.93-0.96 mg/d).

Overall findings of the study show that type 2 diabetes risk increased substantially in adults with VC intakes below the EAR who do not supplement with VC compared to adults with VC intake above the EAR and who supplement with VC. Additionally, study results report an inverse relationship between dietary VC intake and serum VC level, fasting glucose, and A1c level. Limitations include the vulnerability of the study to sampling and inter-laboratory measurement errors in the NHANES databases. Further research should continue to explore the effects of VC on diabetes occurrence.

Source: Sun, Hongbing, Jonathan Karp, Kevin M. Sun, and Connie M. Weaver. “Decreasing Vitamin C Intake, Low Serum Vitamin C Level and Risk for US Adults with Diabetes.” Nutrients 14, no. 19 (2022): 3902.

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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Posted November 14, 2022.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

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