Vitamin C is an essential antioxidant necessary for our wellbeing, but ongoing research shows it may be an even more potent ally in our quest for health.
Unlike most animals, humans cannot synthesise vitamin C and the only source of the essential vitamin is our diet. When we are ill, injured or infected our needs increase and we can quickly use up our body stores. Increased intake via our diet may help address those increased needs, but due to the limited amount the body can absorb orally, people are increasingly turning to intravenous doses to maintain optimal health.
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We spoke with Dr Anitra Carr who studies the role of vitamin C in health and disease at the Department of Pathology and Biomedical Science, University of Otago, Christchurch.
What effect does vitamin C have on our bodies?
Vitamin C is an antioxidant, which means it can scavenge free radicals and other reactive oxygen species, and thereby protect our tissues from damage by the reactive chemicals generated in our bodies as part of our normal metabolism or are present in the form of environmental toxins or pollution.
Another important function of vitamin C is to act as a cofactor for specific enzymes in our bodies, which are responsible for making important compounds such as neurotransmitters and hormones and for regulating our DNA. This means vitamin C promotes numerous vital functions in the body, helping the cardiovascular, neurological and immune systems to work properly.
Why can’t we store vitamin C?
Vitamin C is water-soluble so any excess the body doesn’t need is excreted through urine. Therefore, we need to make sure we consume adequate amounts of vitamin C on a daily basis.
Why is the use of intravenous vitamin C controversial?
In the 1970s Linus Pauling and colleague Ewan Cameron reported that administration of intravenous vitamin C (10 g/day) prolonged the life of cancer patients compared to those who hadn’t received any vitamin C. The controversy originates from two subsequent Mayo clinic trials, which tried to reproduce Pauling and Cameron’s findings and found no effect of vitamin C administration. However, it turns out that they administered 10g per day of oral vitamin C and we now know that intravenous vitamin C gives much higher blood levels of the vitamin than oral administration. The issues these days are around the main anti-cancer mechanism(s) by which vitamin C is working and the appropriate doses required for its effects. There is currently much research going on around these areas.
Why can’t we get the same benefits from diet and/or supplementation?
Our requirements for vitamin C increase when we have acute and chronic illnesses such as infections and cancer. Although dietary amounts of 200mg per day are sufficient to replete the blood of healthy people, when someone gets a severe infection, such as pneumonia and sepsis, their requirements for the vitamin can increase at least tenfold, so they need at least 200mg per day. So although dietary vitamin C may be able to prevent or at least help decrease the risk of acute and chronic diseases, higher doses are required for the treatment of severe illnesses.
Is it looking like—or perhaps clinically proven—that vitamin C can help with illness and disease?
There are a number of plausible mechanisms by which vitamin C can mitigate various different illnesses, primarily through its activities as a cofactor for different enzymes with important functions in the body. For example, vitamin C is a cofactor for the enzymes, which make the hormones noradrenalin, and vasopressin (antidiuretic hormone), which are vital for restoring blood pressure during septic shock. Some recent studies have shown that administering around 6-7g per day of vitamin C to people with septic shock may save their lives. Vitamin C is also a cofactor for epigenetic enzymes, which modify and regulate DNA and thus may have a role to play in certain cancers. Vitamin C is well known to improve the quality of life of cancer patients, particularly those undergoing chemotherapy.