Can Vitamin C Help Cancer Patients?

Check out this answer from Consensus:

The current evidence on the use of vitamin C in cancer treatment is mixed. While some studies suggest potential benefits, particularly with intravenous administration, the overall quality of evidence is low, and more rigorous research is needed. Vitamin C appears to be safe for use in cancer patients, but its efficacy as a cancer treatment remains inconclusive. Future studies should focus on identifying specific patient populations that may benefit from vitamin C and optimizing the administration protocols.

Vitamin C, also known as ascorbic acid, has been a subject of interest in cancer research for many years. Its potential role in cancer treatment has been explored through various studies, with mixed results. This article aims to review the current evidence on the efficacy and safety of vitamin C in cancer therapy, focusing on both oral and intravenous administration.

Mechanisms of Action

Vitamin C is a water-soluble antioxidant that plays a crucial role in various metabolic functions. It acts as an electron donor, which can lead to the production of hydrogen peroxide (H2O2) in high concentrations, potentially exerting cytotoxic effects on cancer cells4. Additionally, vitamin C can target cancer cell vulnerabilities such as redox imbalance, epigenetic reprogramming, and oxygen-sensing regulation5.

Clinical Evidence

Systematic Reviews and Meta-Analyses

A systematic review assessed the effectiveness and safety of vitamin C administration in cancer patients. The review included 19 trials and found no clinically relevant positive effect of vitamin C supplementation on overall survival, clinical status, quality of life, or performance status. However, the studies were of low quality, and the interventions and patient groups were diverse, suggesting that specific patient groups might benefit from vitamin C1.

Another meta-analysis focused on vitamin C and survival among women with breast cancer. The study found that post-diagnosis vitamin C supplement use was associated with a reduced risk of total mortality and breast cancer-specific mortality. Dietary vitamin C intake also showed a statistically significant association with reduced mortality risks10.

Randomized Controlled Trials

Several randomized controlled trials (RCTs) have investigated the effects of high-dose vitamin C in cancer patients. One study involving patients with advanced colorectal cancer found no advantage of high-dose vitamin C over placebo in terms of disease progression or patient survival2. Another controlled trial with 150 advanced cancer patients also reported no therapeutic benefit of high-dose vitamin C treatment3.

Intravenous Vitamin C

Intravenous vitamin C (IVC) has been explored as an adjunctive cancer therapy. A systematic review of human studies found that IVC might improve time to relapse, reduce tumor mass, and enhance survival when combined with chemotherapy. IVC was also associated with improved quality of life and reduced chemotherapy-related toxicities8. However, the evidence is preliminary and requires more rigorous studies to confirm these findings.

Safety and Side Effects

Vitamin C treatment, whether oral or intravenous, is generally considered safe with minimal side effects. Studies have reported no significant increase in toxicity or interference with standard cancer therapies1 7. However, the safety profile and potential benefits of high-dose vitamin C need further investigation through well-designed clinical trials.

Can Vitamin C help cancer patients?

Andrew Das has answered Uncertain

An expert from University of Otago in Cancer, Leukemia, Biochemistry, Genetics

The question as it stands is very broad, and it would be helpful to break it down into two questions:

1. a) Does treatment with vitamin C (ascorbate) confer a benefit of any kind for cancer patients (for example, improved quality of life)?
2. b) Is there an impact of ascorbate treatment on the prognosis of cancer (for example, extending survival)?

With regards to question (a), there are a number of studies showing that treatment with ascorbate can improve a patient’s quality of life. It is important to note that these studies are hard to carry out in this patient population and the results difficult to interpret. A second point to note is that in any given population, there will be a percentage of people who have low levels of ascorbate. Interestingly, this percentage increases in cancer patient populations, particularly in blood cancer patients. Because ascorbate is an essential co-factor for many enzymes (and therefore, many biological processes) supplementing ascorbate for these patients who are low will undoubtably result in some benefit. These biological processes include epigenetic pathways, hormone synthesis, and collagen synthesis to name a few. Do those who have sufficient ascorbate in these populations receive a benefit from further supplementation? Uncertain. A third important point to note is, how is ascorbate being delivered? If orally, then there is a maximum threshold that is reached because our body is so good at clearing it out through the kidneys. To get around this, ascorbate can be delivered intravenously (IV). Whether or not benefits such as increased quality of life require higher doses of ascorbate is also uncertain.

The big question on most people’s mind when considering cancer and ascorbate is question (b). Does ascorbate go some ways towards targeting the cancer itself? I think it is important to say upfront that ascorbate (whether oral or IV) clearly does not cure all cancer. There have been multiple large studies done over the years that show this. However, this is not an issue confined to ascorbate. Firstly, cancer is not a single entity. There is heterogeneity at multiple levels. Cancer can arise from many different tissue types. Secondly, even in a given cancer we now know that the underlying mutations that give rise to the cancer can vary greatly between patient to patient. For example, genetic sequencing of a large cohort of acute myeloid leukaemia (AML) patients has shed light on at leat 11 different subtypes of this blood cancer. In practice, this results in AML patients responding differently to the same treatment, chemotherapy for example. Many new drugs are being developed to target these specific subtypes.

So the next question is, could ascorbate benefit patients with specific subtypes of some cancers? Sometimes mutations arise in genes that code for proteins that use ascorbate as a cofactor. For example, 10% of patients with AML have a mutation in the gene TET2. Studies with cell culture and mouse models have shown a benefit (extended survival) when treated with ascorbate. These benefits have not yet been tested in a human patient cohort and a clinical trial specifically designed to do this would be timely. Until that point, the answer to this question is also “uncertain“.

Can Vitamin C help cancer patients?

Margreet Vissers has answered Uncertain

An expert from University of Otago in Vitamin C, Biochemistry, Cancer Immunology

This is a very complex question, with limited evidence available, despite patients continually trying this. The latest evidence suggests that some patients may benefit, but we have yet to determine which patients and also the correct dose they would need. There are too many unanswered questions in this area.

Can Vitamin C help cancer patients?

Anitra Carr has answered Likely

An expert from University of Otago in Vitamin C

Yes – vitamin C can help cancer patients. Many patients with cancer have depleted vitamin C status, including those undergoing chemotherapy and radiation therapy (reviewed in [1]). Vitamin C has been shown to improve the quality of life of cancer patients, particularly those undergoing chemotherapy, e.g. decreasing fatigue, nausea, pain and insomnia and improving appetite (reviewed in [2, 3]). Vitamin C has a number of recently-discovered functions that could help patients with cancer; these include its gene-regulatory roles whereby it can help up- and down-regulate thousands of genes in the body, including those involved in various cancer-related processes [1].

References:

1.         Carr AC, Cook J. Intravenous vitamin C for cancer therapy – identifying the current gaps in our knowledge. Front Physiol. 2018;9:1182.
2.         Carr AC, Vissers MCM, Cook JS. The effect of intravenous vitamin C on cancer- and chemotherapy-related fatigue and quality of life. Front Oncol. 2014;4(283):1-7.
3.         Carr AC, McCall C. The role of vitamin C in the treatment of pain: new insights. J Transl Med. 2017;15(1):77.

Can Vitamin C help cancer patients?

Gerard Bos has answered Unlikely

An expert from Maastricht University Medical Center+ in Cancer, Immunology, Hematology

No there is no evidence that vitamin C can help patients with cancer in the doses used thus far, mostly oral dosing.