Higher Vitamin C blood serum levels are associated with a reduction of respiratory infections according to a new Chinese study.
The study, which focused on children and adolescents, corroborates numerous other studies highlighting the immune benefits of Vitamin C.
According to the findings, published in Frontiers in Nutrition in June 2025, the people with the highest Vitamin C levels had an astounding 50% reduction in respiratory infections.
The study was conducted by researchers at Children’s Hospital Affiliated to Zhengzhou University in Zhengzhou, China.
The Children’s Hospital Affiliated to Zhengzhou University is touted as the world’s largest hospital, with over 10,000 beds. The enormous hospital facility serves more than 21,000 patients daily, so finding ways to curtail respiratory infections is a top priority.
Writing in the study summary, the researchers noted: “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.”
*Study details
To conduct the study the researchers used data from the National Health and Nutrition Examination Survey—a national database that collects data about the health of adults and children in the United States.
The researchers analyzed the 2017–2018 data, 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. The researchers then tracked incidence of respiratory infections based on self-reported health questionnaires.
The researchers applied industry-standard statistical measures to investigate the associations between risk of respiratory infections and four different Vitamin C groups (i.e. Vitamin C blood serum level).
The researchers learned almost 18% of survey subjects reported a respiratory infection in the past 30 days, and low Vitamin C level was consistently 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 in the study summary.
The researchers further noted that the association between low Vitamin C and respiratory infection risk was consistently significant across all subgroups of different health status and demographic grouping.
Most astonishing of all the findings, the researchers found individuals in the group with the highest serum Vitamin C levels had a 50% lower risk of respiratory infections compared to those with the lowest measured levels of Vitamin C.
*Corroboration
Vitamin C, one of the first vitamins to be identified and isolated, is critical in almost all aspects of human health; however, the support it provides in regards to immune health is perhaps where it is most widely recognized and studied.
The pinnacle of this recognition occurred during the Covid-19 pandemic when Vitamin C was actually used as a treatment in countries outside the U.S., especially in Asia.
In fact, as early as 2020 China had observed Vitamin C supplementing reduced Covid severity so drastically that the government added it to their official “treatment protocol.”
( https://blog.optimalhealthsystems.com/blog/vitamin-c-just-a-vitamin-in-the-us-but-a-treatment-for-coronaviruses-in-asia/ )
Other Vitamin C studies during the past decade include:
• A 2017 study that found Vitamin C supplementation reduced the risk of pneumonia by up to 80%.
( https://blog.optimalhealthsystems.com/blog/vitamin-c-deficiency-linked-to-pneumonia-in-three-separate-trials/ )
• A 2018 study that found a Vitamin C and probiotic combination reduced kids’ school absence by 30%.
( https://blog.optimalhealthsystems.com/blog/vitamin-c-and-probiotic-combination-reduces-kids-school-absence-by-30/ )
• A 2019 meta-analysis that found providing a Vitamin C fortification to patients in ICU reduced the time in hospital by an average of 8%.
*Final word
In the current Chinese study the researchers noted the profound way Vitamin C works in the immune system—by neutralizing free radicals and protecting epithelial cells in the respiratory system. They further noted that Vitamin C “helps immune cells clear pathogens, modulates cytokine production and inhibits inflammation, shortening the duration of respiratory infections.”
In the study summary the researchers specifically touted the benefit to young people: “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.”
Hopefully parents are paying attention.
