What is Vitamin C?
Vitamin C (ascorbic acid, ascorbate) is an essential micronutrient that must be delivered either with the diet or as a supplement, given that humans lost the ability to synthesize it due to mutations in the gene encoding a part of vitamin C.
This vitamin plays an important role in multiple processes as a cofactor for enzymes involved in process and effects important for cancer transformation, such as:
- Antioxidant defense.
- Regulation of gene expression.
- Immune system mediator and inflammation regulation.
Anticancer properties of vitamin C have been reviewed in recent papers. These studies suggest several potential targets of anticancer activation of vitamin C. Some of them are:
- Redox imbalance.
- Epigenetic imbalance.
- Epigenetic reprogramming.
- Oxygen sensing regulation.
- Host immunity.
- Collagen synthesis in regard to metastasis.
What is the Best Dose?
Doses of vitamin C up to 2,000 mg/day are considered safe for general consumption, but even so high doses are unlikely to result in a concentration in plasma higher than 80 μM. Studies suggest a higher bioavailability of natural vitamin C compared to synthetic one.
What have studies shown?
In a meta-analysis of 37 studies, it was concluded that the total (dietary and supplementary) intake of vitamin C reduced breast cancer risk by 15%, but dietary only intake reduced that risk by 23%. High vitamin C intake from food was associated with a decreased risk of breast cancer.
Many molecular studies suggest that vitamin C can act at least in two opposite ways: anti and prooxidant. Anticancer therapy with vitamin C remains under study. A group of researchers, Carr and Cook, concluded that cancer patients had lower concentration of vitamin C than healthy control, and that intravenous infusion is the optimal route for administration of high doses of this vitamin in order to obtain the antioxidant and anticancer effect.
Metastasis is responsible for most cancer related deaths (aprox. 90%). This process requires adhesion to and invasion of surrounding tissues and organs by cancer cells. Therefore, penetrating cellular and extracellular compartments is necessary for metastasis. One of the main components of the extracellular matrix and the connective tissue is collagen. Because vitamin C promotes collagen synthesis, it can affect cancer growth, invasion and metastasis. This is one of the important anticancer properties that the vitamin has.
The anticancer effects of dietary vitamin C are nonspecific because it acts as other low molecular weight antioxidants. More studies need to be conducted in order to take advantage of its anticancer properties and to standardize the dose needed to obtain the anticancer effect.
Pawlowska E, Szczepanska J, Blasiak J. Pro- and Antioxidant Effects of Vitamin C in Cancer in correspondence to Its Dietary and Pharmacological Concentrations. Oxid Med Cell Longev. 2019;2019:7286737.