While it’s no cure, it may help improve the health of those at greater risk for severe Covid-19.
Vitamin C was the nutrient researchers tried to pinpoint as the cure for scurvy in the early 1900s. It works because vitamin C deficiency causes scurvy. As people with scurvy usually died from pneumonia, people started thinking that vitamin C might help fight pneumonia as well.
While vitamin C is essential in tissue repair, it also acts as an antioxidant and supports the nervous and immune systems. Thus, it’s logical to believe that increased vitamin C intake would aid the immune system in countering pneumonia. While that’s true in animal models, results are inconsistent in human clinical trials with the consensus that vitamin C may be beneficial in preventing or supporting recovery from pneumonia, the common cold, or other infections, especially in those deficient in vitamin C or under heavy physical stress such as athletes, soldiers, or marines.
So vitamin C is never a cure for any infections, but it may help in certain cases. This brings us to a question: how can vitamin C help in times of Covid-19?
Vitamin C overlap with Covid-19 risk factors
The answer lies in improving the health of persons at risk for severe Covid-19, argued a research review published in October in the Frontiers of Immunology. First, the review mentioned that the major risk factors of more severe and lethal Covid-19 include obesity, diabetes, and cardiovascular diseases. These conditions are known to cause and sustain a state of chronic inflammation that weakens the immune system’s ability to fight infections. And herein lies a potential solution.
Despite already having adequate intake or blood levels of vitamin C, clinical trials have shown that extra vitamin C supplementation lowers systemic inflammation in people with obesity, diabetes, and hypertension.
For instance, a randomized placebo-controlled trial (RCT) in 2008 found that oral vitamin C supplementation (1,000 mg/day for two months) reduced blood levels of C-reactive protein (CRP) in overweight-to-obese participants by about 25%. CRP is a biomarker of systemic inflammation that also predicts severe and fatal Covid-19. Notably, these participants already had elevated CRP and sufficient vitamin C levels at baseline.
In another RCT in 2015, oral vitamin C treatment (1,000 mg/day for two months) lowered markers of inflammation (including CRP) and fasting blood glucose in 64 people with obesity, hypertension, or diabetes. A 2017 meta-analysis of 22 studies also found that vitamin C supplementation improved blood sugar control among people with diabetes. As high blood glucose levels injure blood vessels, it’s also a biomarker of increased Covid-19 severity.
In senior citizens, vitamin C and other nutritional deficiencies are common, especially in situations with limited access to nutritionally dense foods. And vitamin C deficiency is a strong predictor of all-cause mortality among older adults, especially from cardiovascular diseases. Plus, older adults given vitamin C supplements (200 mg/day for four weeks) in an RCT had better clinical outcomes than the placebo group from respiratory infections.
“Based on the above, vitamin C supplementation…could potentially be able to improve the health of these individuals [at risk for Covid-19] and reduce the susceptibility to infections,” the review authors suggested. “Investigations are strongly encouraged to establish a possible correlation between an extra intake of vitamin C and a possible decrease of incidence, severity, and mortality for Covid-19.”
Current recommendations
Preliminary data from case reports and case series (of 17 patients) have advocated using intravenous vitamin C in aiding recovery from Covid-19. Yet case series (of 15 patients) from a separate research group did not find much of a benefit from vitamin C in treating Covid-19. Thus, the therapeutic potential of vitamin C in Covid-19 still needs examination.
Presently, Covid-19 clinical trials are testing intravenous. All trials are on-going, so none has been published yet. Owing to insufficient data, the National Institutes of Health remains neutral in their recommendations for or against vitamin C in treating Covid-19 patients.
However, as vitamin C is safe even at high doses — although minor risks such as diarrhea may exist — its benefits may outweigh the risks (if any). This is particularly true for those with comorbidities that up the risk of severe Covid-19, where vitamin C may help dampen their state of chronic inflammation. Besides, vitamin C deficiency is rather widespread globally at about 10–20% in high-income countries and 50–70% in middle- and low-income countries.
Short abstract
While vitamin C cures scurvy, it does not cure infections. But vitamin C may still aid recovery from infections in some people, particularly those with inadequate vitamin C intake and those under heavy physical stress. Interestingly, vitamin C may also improve health status in senior citizens and people with comorbidities like obesity, diabetes, and cardiovascular diseases. This would indirectly lessen the risk of severe infections, including Covid-19. The bonus is that this benefit can apply even to those who already have sufficient intake or blood levels of vitamin C. So, while not proven, ensuring proper vitamin C nourishment can go a long way.
This article was originally published in Microbial Instincts with minor modifications.