Patients may develop a vitamin C deficiency over the course of their COVID-19 illness, since vitamin C is consumed at a more rapid rate if an infection is active.
A recent study has found that high doses of vitamin C for treating coronavirus disease 2019 (COVID-19) may benefit specific populations, although researchers say that key factors in efficacy include levels of a natural transporter needed to get the vitamin inside cells.
The factors of efficacy of vitamin C therapy may include age, race, gender, and expression levels, as well as genetic variations of vitamin C transporters that make them less efficient. The researchers recommend that those factors be considered in the design and execution of clinical trials and when the trial results are analyzed for COVID-19 and other conditions.
There are at least 30 clinical trials underway in which vitamin C, alone or in combination with other treatments, is being evaluated for COVID-19, some with doses up to 10 times the recommended 65 to 90 milligrams daily of vitamin C.
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Whether or not vitamin C can get inside the cell is a factor in the efficacy the therapy ultimately shows, according to the study authors. Without adequate transporters on a cell’s surface to get the water-soluble vitamin past the lipid layer of cell membranes, particularly large doses may enable the vitamin to cluster around the outside of cells where it actually starts producing oxidants, such as damaging reactive oxygen species, rather than helping eliminate them, according to the study authors.
The researchers suspect low transporter expression is a factor in the mixed results in the use of vitamin C in a variety of other conditions. Clinical trials for conditions such as osteoarthritis have produced mixed results, with its use in other viral-induced problems showing benefit in reducing organ failure and improving lung function in acute respiratory distress syndrome.
Further, part of the concern of COVID-19 is that it affects those at risk of mostly having both lower levels of vitamin C before they get sick and fewer transporters to enable the vitamin to be of benefit if they get more, according to the study authors. Many individuals who are older, Black, male, and with chronic medical conditions, such as osteoarthritis, hypertension, and diabetes tend to have lower levels of vitamin C, according to the study authors.
It was also noted by the study authors that patients may develop a vitamin C deficiency over the course of their COVID-19 illness, since vitamin C is consumed at a more rapid rate if an infection is active.
Transporter expression can be measured using PCR technology, a method that has been used for novel COVID-19 as well as influenza testing. The research goals are to find a drug or other method to directly increase expression, which should improve the health of older individuals, as well as those with other medical conditions that compromise those levels.
Further, the reduced transporter levels that occur naturally with age are a factor in the reduced immune function that also typically accompanies aging. Reduced immune function in older individuals is known to put them at an increased risk for problems such as cancer and COVID-19.
According to the study authors, low vitamin C levels have also been correlated with higher mortality in older individuals from causes such as cardiovascular disease. High oxidative stress is also associated with significantly reduced expression of the vitamin C transporter.
Vitamin C’s effectiveness against COVID may hinge on vitamin’s natural transporter levels. EurekAlert! https://www.eurekalert.org/pub_releases/2020-11/mcog-vce111020.php. Published November 11, 2020. Accessed November 11, 2020.