Lower circulating levels of vitamins C, D, and E are detected in patients with diabetic retinopathy (DR) than in patients who do not have DR, according to a study published in the American Journal of Ophthalmology.

Investigators conducted a cross-sectional study and meta-analysis to evaluate the association between vitamins A, C, D, E, and carotenoids and risk of DR. They enrolled 517 participants with diabetes mellitus who were at least 40 years of age, performed fundus photography, obtained demographic information, and collected blood samples for serum analysis. Fundus photography and an initial diagnosis of diabetes mellitus determined the presence of DR. 

The researchers identified diabetic retinopathy in 159 participants (25.17%). The mean age of the participants was 60.9±0.73 years, and 51.3% of the participants were women. 


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After adjusting for confounding factors, the researchers found that only serum vitamin C was associated with a lower risk of DR (OR=0.60; 95% confidence interval [CI]: 0.38 to 0.95), representing a 40% reduction in risk for each standard deviation increase in serum level of vitamin C. They also noted participants with vitamin C deficiency had a 7 times higher risk of DR than those without the deficiency (OR=7.41; 95% CI: 1.43 to 38.34).

The researchers included 35 studies in the meta-analysis, and observed a pooled weighted mean difference of -11.01 (95% CI: -19.35 to -2.67) for vitamin C, -3.06 (95% CI: -5.15 to -0.96) for vitamin D, and -3.03 (95% CI: -4.24 to -1.82) for vitamin E after comparing 1056 patients with DR to 920 healthy controls. No associations were found between DR and circulating vitamin A or carotenoids.

“This study demonstrated a significant inverse association between circulating vitamin

C level and DR using a population-based dataset,” according to the investigators. They further advise, “Consumption of foods rich in vitamins C, D and E is thus recommended in the general diabetic population to prevent DR risk.”

Limitations of the study included an inability to infer causation due to the cross-sectional design, inability to perform subgroup analyses due to lack of data, inclusion of only cross-sectional studies in the meta-analysis, single measurements for circulating micronutrients, and inability to assess a dose-response relationship between circulating micronutrients and the severity of DR due to lack of data. 

Reference

Xiong R, Yuan Y, Zhu Z, et al. Micronutrients and diabetic retinopathy: evidence from the National Health and Nutrition Examination Survey and a meta-analysis. Am J Ophthalmol. Published online January 13, 2022. doi:10.1016/j.ajo.2022.01.005