Kanikah Mehndiratta, M.Sc., University of Glasgow
Vitamin C, also called ascorbic acid, was the first vitamin to be artificially synthesized. It is one of the most essential micronutrients that plays a role in tissue repair and enzymatically producing many neurotransmitters. It is widely used to prevent diseases such as Scurvy.
It has antioxidant properties and exhibits integral roles in immune system functioning. It has well-studied benefits in reprogramming at epigenetic level, redox imbalance, regulation of oxygen sensing, synthesis of collagen. All these processes show involvement in tumour angiogenesis, metastasis, immune invasion and thus support vitamin C’s anticancer potential. A recent study published in the BMC Medicine journal discusses the causal association between vitamin C concentration and different types of cancers.
Vitamin C and the risk of cancer:
Many studies have reported clinical benefits of Vitamin C, via intravenous dosing in pharmacological concentrations amongst cancer patients. Oral dosing of such vitamin supplements doesn’t show much effect on cancer related symptoms such as dysphagia, nausea, or taste impairment.
Though observational studies report an inverse correlation between vitamin C concentration and cancer, one cannot rule out reverse causality as a reason. Oxidative stress and formation of more reactive oxygen species, both cancer-induced, can result in more consumption of antioxidants. One such major antioxidant could be vitamin C whose more dietary consumption can trigger cancer related symptoms.
Research strategy adopted:
The methodology followed the use of mendelian randomization (MR) to analyze the inherent properties of common genetic mutations and helped establish causal relationships between various diseases and environmental exposure. A bi-directional MR was used to check whether the concentration of vitamin C in plasma was predisposing a risk of 5 common types of cancer in Europe. The bi-directional approach also helped analyze whether a genetic predisposition to risk of different types of site-specific cancers causally influenced vitamin C concentration in plasma.
The major cancers considered were of the breast, prostate, colon, lungs and bronchus, and cancers in the rectal region. A meta-analysis was done to summarize the result of such separate studies. Genome-wide association studies (GWAS) on a population of about 52,018 Europeans aided in identifying 11 plasma vitamin C-associated single nucleotide polymorphisms with a 1.87% of variance. Publicly available data from different cancer consortiums helped in replicating the findings from the study. The reverse MR used uncorrelated and strongly associated genetic variables. Linkage disequilibrium was calculated from 1000 Genomes phase 3 data of Europeans.
Conclusive findings:
The MR analysis didn’t depict an association between the concentration of vitamin C and any of the cancers under consideration. Smoking initiation, which was used as a positive control in reverse MR analysis, depicted an inverse relationship with its concentration. No substantial evidence was found for the association. An analysis of sensitivity also gave similar results. The MR results in the study also showed consistency with null findings from meta-analysis done to depict the risk association. Only a lower risk of lung cancer with a ratio of about 0.84 was observed with higher consumption of vitamin C in diet and not via supplementation.
Though one cannot rule out completely very small effects of vitamin C in the common types of cancers, a larger effect remains inconclusive.
Also read: Malnutrition & its long term effects on COVID-19 severity
References:
1. 1. Fu, Y., Xu, F., Jiang, L., Miao, Z., Liang, X., Yang, J., Larsson, S. C., & Zheng, J.-S. (2021). Circulating vitamin C concentration and risk of cancers: A Mendelian randomization study. BMC Medicine, 19(1), 171. https://doi.org/10.1186/s12916-021-02041-1
2. Vissers, M., & Das, A. B. (2018). Potential mechanisms of action for vitamin C in cancer: reviewing the evidence. Frontiers in physiology, 9, 809. https://doi.org/10.3389/fphys.2018.00809
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Author info:
Kanikah Mehndiratta is an avid researcher in the field of Genetics with a background in Biotechnology. She is a postgraduate from the University of Glasgow in their Medical Genetics and Genomics program. Currently, based in Chandigarh as a scientific writer, she involves herself mainly in projects related to neurological disorders. Outside of academics, she likes to read novels, travel and is involved in volunteer work mostly.
LinkedIn profile- https://www.linkedin.com/in/kanikah-mehndiratta-301830171
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