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. 2025 Jun 5:12:1601218.
doi: 10.3389/fnut.2025.1601218. eCollection 2025.

The association between serum vitamin C levels and respiratory infections in children and adolescents

Ci Li  1 , Zhiwei Zhu  1 , Shicai Jiang  1 , Xiang Feng  1 , Kaijie Gao  1 , Tiewei Li  1 , Liu Yang  1 , Panpan Fang  1 , Junmei Yang  1
Affiliations

The association between serum vitamin C levels and respiratory infections in children and adolescents

Ci Li et al. Front Nutr. .

Abstract

Objective: Respiratory infections (RIs) are a leading cause of morbidity and mortality, and vitamin C may play a vital role in the risk of RIs. However, high-quality evidence on the association between vitamin C and RIs in the younger population remains limited. This study aimed to investigate the association between serum vitamin C and RI risk in a nationally representative sample of children and adolescents.

Methods: Utilizing data from the National Health and Nutrition Examination Survey (NHANES) 2017-2018, this study included 1,344 children and adolescents aged between 6 and 19 years old. Serum vitamin C levels were obtained from laboratory tests, and RIs were determined based on a self-reported health questionnaire. The association between vitamin C and RIs was tested using multivariable logistic regression models, interaction tests, and smoothing curve fitting.

Results: A total of 238 participants (17.7%) reported a respiratory infection in the past 30 days. Serum vitamin C was significantly and negatively associated with the risk of RIs in all regression models. 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% (OR = 0.93, 95% confidence interval [CI]: 0.87, 0.99). Such an association remained consistently significant across subgroups with various demographical and health characteristics.

Conclusion: Our study shows a negative association between vitamin C and RIs among children and adolescents, highlighting the protective role of vitamin C against RIs. Our findings suggest that vitamin C supplementation may be potentially used for the prevention and treatment of RIs, which needs to be validated in future well-designed studies.

Keywords: NHANES5; adolescents; children; respiratory infection; vitamin C.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of participant selection. NHANES, National Health and Nutrition Examination Survey.
Figure 2
Figure 2
Associations between serum vitamin C and respiratory infection. The solid red line represents the smooth curve fit between the variables, while the blue bands denote the 95% confidence intervals of the fitted values. Age, sex, race, the ratio of family income to poverty, body mass index, asthma, tobacco smoke exposure, total energy intake, and vitamin C intake were adjusted.
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