In the previous article, we discussed how fasting might be able to slow the ageing process, and at the very least appears to reduce the risk of age-related diseases. In this article we will focus on one of those diseases: cancer. Can fasting reduce your risk of cancer, help slow tumour growth, or even reduce the side effects of chemotherapy?
Disclaimer: This article is not intended to be health advice for cancer patients. If you are receiving cancer treatment, you should consult with your doctor before making any significant changes to your diet.
Cancer is a disease in which cells divide rapidly and uncontrollably because the genes that control growth and replication in these cells have become damaged. As a tumour grows, cancer cells acquire more mutations that help them to divide faster in a process not dissimilar to evolution by natural selection.
Because of this rapid growth and division, cancer cells are vulnerable to nutrient deprivation, as they are very energy-hungry. Cancer cells also tend to mutate to acquire resistance to anti-growth signals, and are therefore bad at adapting to nutrient scarcity. This raises the possibility that low nutrient intake could help to slow tumour growth, and evidence in cell culture and animal models seems to support this.
As we discussed in the previous article, long term fasting, intermittent fasting and calorie restriction can reduce levels of various growth factors and encourage cells to repair themselves. DNA damage, inflammation and defective autophagy (the cell’s waste disposal system) – factors that are heavily implicated in cancer development – are all reduced by fasting. It therefore seems probable that fasting would reduce the risk of cancer development. This, too, seems to be supported by scientific studies.
Another area of interest when it comes to fasting is the interaction between nutrient deprivation and chemotherapy. Chemotherapeutic drugs are, by necessity, toxic to human cells. While chemotherapy primarily kills cancer cells, it can damage and kill healthy cells as well, resulting in side effects. However, studies have shown that fasting can protect normal cells, but not cancer cells, against damage from chemotherapy. This is probably due to the fact that nutrient deprivation activates stress resistance and repair pathways in normal cells. Cancer cells, as touched on above, mutate to acquire resistance to anti growth signalling, and therefore do not activate these pathways in response to fasting.
Despite everything discussed so far, most dietary advice for cancer patients receiving chemotherapy is to increase calorie intake. This is because loss of appetite due to chemotherapy, potentially in addition to the effects of the cancer itself, can cause unhealthy amounts of weight loss. If fasting is to be used as a means to enhance cancer treatment, its safety needs to be verified. Recent evidence is promising in this regard, and appears to suggest that short term fasting prior to chemotherapy, as well as the use of less extreme nutrient deprivation such as the fasting-mimicking diet, are safe and effective adjuvants to chemotherapy. However, we need to remember that there are many different types of cancer, and many different forms of chemotherapy. We are still going to need more research to establish whether fasting is truly worthwhile, and under what conditions.
Could Intermittent Energy Restriction and Intermittent Fasting Reduce Rates of Cancer in Obese, Overweight, and Normal-Weight Subjects? A Summary of Evidence: DOI: 10.3945/an.115.011767
Fasting and cancer: molecular mechanisms and clinical application: doi: 10.1038/s41568-018-0061-0.
Starvation-dependent differential stress resistance protects normal but not cancer cells against high-dose chemotherapy: doi: 10.1073/pnas.0708100105
Fasting cycles retard growth of tumors and sensitize a range of cancer cell types to chemotherapy: doi: 10.1126/scitranslmed.3003293
Autophagy and intermittent fasting: the connection for cancer therapy?: DOI: 10.6061/clinics/2018/e814s
Fasting and Caloric Restriction in Cancer Prevention and Treatment: DOI: 10.1007/978-3-319-42118-6_12
Fasting mimicking diet as an adjunct to neoadjuvant chemotherapy for breast cancer in the multicentre randomized phase 2 DIRECT trial: https://doi.org/10.1038/s41467-020-16138-3
Safety and feasibility of fasting in combination with platinum-based chemotherapy: doi: 10.1186/s12885-016-2370-6