The study used data from the National Health and Nutrition Examination Survey (NHANES) to assess correlations between vitamin C levels and recent respiratory issues, reporting that the positive association remained consistently significant across various health and demographic subgroups.
“Our findings suggest that vitamin C supplementation may be potentially used for the prevention and treatment of RIs [respiratory infections], which needs to be validated in future well-designed studies,” wrote researchers at Children’s Hospital Affiliated to Zhengzhou University in China.
Vitamin C and respiratory illness
Previous research has demonstrated that vitamin C may help reduce the risk of respiratory illnesses.
For example, a UK study of 19,357 adults found that higher levels of vitamin C are associated with a reduced risk of both cancerous and non-cancerous respiratory illnesses. Another study reported that children consuming orange juice with 70 mg of vitamin C had fewer respiratory infections, research suggests that intravenous vitamin C may reduce the severity of pneumonia in children.
Other studies have shown that vitamin C deficiency can increase the risk of respiratory infections and extend hospital stays. Conditions such as irritable bowel syndrome, celiac disease and chronic infections may contribute to deficiency due to reduced absorption, increased nutrient losses and decreased food intake. This highlights the importance of the supplement for older populations and those with health conditions.
The mechanisms involved in vitamin C’s benefits include its antioxidant, immunoregulatory and anti-inflammatory properties.
The current study notes that vitamin C neutralizes free radicals and protects epithelial cells in the respiratory system. It helps immune cells clear pathogens, modulates cytokine production and inhibits inflammation, shortening the duration of respiratory infections.
Study details
The study drew data from the National Health and Nutrition Examination Survey (NHANES) 2017–2018, which included 1,344 children and adolescents between the ages of 6 and 19.
The researchers analyzed participants’ serum vitamin C levels, as determined by laboratory testing, and tracked incidence of respiratory infections based on self-reported health questionnaires.
They used appropriate statistical measures to investigate the associations between four vitamin C groups, allocated according to participants’ serum levels, and the risk of respiratory infections.
Almost 18% reported a respiratory infection in the past 30 days, and vitamin C was negatively associated with the risk of developing such an infection.
“After adjusting for all potential confounders, an increase of the vitamin C level by 10 units indicated a decrease of the RI risk by 7%,” the researchers wrote, noting that the association was consistently significant across all subgroups with different health and demographics.
In addition, individuals in the group with the highest serum vitamin C levels had a 50% lower risk of respiratory infections compared to those in the lowest group.
“Our findings highlight the protective role of vitamin C against RIs, which may provide useful guidance for future prevention and treatment of RIs among children,” the researchers concluded, calling for further studies to validate their outcomes.
Source: Front. Nutr., 05 June 2025, Sec. Nutritional Epidemiology; Volume 12 - 2025 | doi: 10.3389/fnut.2025.1601218; “The association between serum vitamin C levels and respiratory infections in children and adolescents.” Authors: C. Li et al.
