In the 70s, Pauling and Cameron just with conventional treatment, carried out in patients with advanced cancer, intravenous infusions of 10 g of ascorbate daily. Apparently, the life of these was prolonged.
Later, the Mayo Clinic repeated the studies of Pauling and Cameron; this time orally, although they found no benefit. Pharmacokinetic differences in the different pathways are believed to have caused the data to be contradictory.
Currently, although the support of more clinical trials is necessary to support it, the data suggest that it could have a clinical use in cancer patients.
Vitamin C is extremely important for many biological functions. However, its status in cancer patients is not evaluated in clinical practice. Even so, there are studies that have shown that its plasma and tissue concentration (such as in white blood cells) is low. Although a correct diet can palliate this hypovitaminosis, it seems that higher amounts than normal dietary intakes and intravenously are necessary.
The most accepted anticancer mechanisms are the following:
- Hydrogen peroxide generation. Vitamin C is not a prooxidant agent, but it does have an indirect effect through the reduction of ferric and cuprous cations. It has been postulated that there is a greater quantity of these ions in the extracellular fluid of the tumor microenvironment, so that when they are reduced, they generate hydrogen peroxide by reducing oxygen to a superoxide radical. It has also been proposed that dehydroascorbic acid transport in tumor cells that overexpress GLUT1 may have an oxidative effect through glutathione oxidation.
- As a cofactor of enzymes for the stabilization of the collagen structure, increasing the encapsulation of tumors by collagen; as a regulator of the alpha subunit of hypoxia-inducible factor 1 (HIF-1α) as it is a cofactor of HIF hydroxylases, etc.
- Antioxidant and anti-inflammatory effect due to the decrease in oxidative stress markers such as malondialdehyde or F2 isoprostanes and proinflammatory cytokines.
Vitamin C could be an aid in cancer therapy because, in part, cancer patients have hypovitaminosis (below 23 μmol/L and some below 11 μmol/L) . There are many doubts that arise around the use of vitamin C as an adjuvant therapy.
IS THE INTRAVENOUS ROUTE PREFERRED TO THE ORAL?
When Cameron and Pauling and, later, the Mayo Clinic did their studies on vitamin C in the 1970s, they found different results due to the route of administration. In the 1990s, Mark Levine highlighted the pharmacokinetic differences between both routes. It seems that the IV route is more efficient since, orally, it is regulated by the sodium-dependent vitamin C transporter (SVCT1).
IS IT SAFE?
It appears that only 1% report mild side effects such as lethargy or fatigue. Even so, special care must be taken in patients with renal dysfunction since calcium oxalate crystals can accumulate and in those with glucose-6-phosphate dehydrogenase (G6PD) deficiency. It can, with some meters, give false positives of high blood glucose, so it is recommended to measure glucose in these patients by absorbance
DOES IT INTERFERE WITH CHEMOTHERAPY OR RADIOTHERAPY?
It seems that there would be no problem because many of the chemotherapeutic agents do not act through oxidative mechanisms.. Even so it is recommended that a period of 5 half-lives elapse between the administration of vitamin C and chemotherapy. With regard to radiotherapy, it seems that they could act synergistically, although more studies are needed.
DOES IT REDUCE THE TOXIC EFFECTS OF CHEMOTHERAPY?
Yes, they would reduce the toxic effects, reducing symptoms such as fatigue, nausea, vomiting, insomnia, loss of appetite, etc., improving physical, emotional, cognitive and social functioning.
DOSE, FREQUENCY AND DURATION
Although it is currently impossible to give an answer, many medical professionals were surveyed and the results showed an average of 28g per dose, a frequency of 2 times per week and 19 treatments per patient.
Finally, we clarify that it is not something that has been proven, but that we rely on the conclusions of different studies.
In Vitónica | Physical exercise in cancer patients: these are the recommendations of the Spanish Society of Medical Oncology
In Vitónica | Cancer Prevention: What Science Has Shown Works So Far
Images | istock
Studies | Carr, AC, & Cook, J. (2018). Intravenous vitamin C for cancer therapy–identifying the current gaps in our knowledge. Frontiers in physiology, 9, 1182. Vissers, M., & Das, AB (2018). Potential mechanisms of action for vitamin C in cancer: reviewing the evidence. Frontiers in physiology, 9, 809.