Can fasting help fight cancer?

Author: Sandra Krstev Barać, Master of Nutrition

Fasting as a technique for physical, mental and spiritual purification has been present in many religions for centuries and is one of the oldest medical therapies. Many famous doctors throughout history have promoted fasting as a method of treatment, including the "father of medicine", Hippocrates, who believed that fasting was an excellent way to purify the body. Modern science also supports the thesis that periodic periods of fasting offer numerous benefits: from easier blood sugar regulation, reduced insulin levels and weight loss, to a beneficial effect on the risk of heart and blood vessel disease and a strong anti-inflammatory effect.

Fasting has also been an extremely interesting topic among oncology patients in recent years, thanks to the increasing number of studies (albeit mostly on animal models) that indicate the benefits of this practice in the prevention and treatment of malignant diseases. Some cancer patients view the idea of fasting favorably, because it gives them a sense of control over their own treatment. While the idea of fasting with cancer therapy should be considered seriously, it is important to be aware of the potential dangers of this approach, especially if undertaken without the knowledge and support of an oncology team.

Fasting may reduce the toxicity of therapy

Animal studies suggest that fasting with standard therapy may improve outcomes and reduce the toxicity of cancer treatment. This finding can be explained by the theory that cancer cells, unlike healthy cells, have difficulty “tolerating” conditions without a constant influx of nutrients. Therefore, the combination of fasting and therapy, in theory, makes cancer cells more susceptible to oxidative stress, in other words, the therapy destroys them more easily. In addition, the practice of fasting has been shown to support the immune system in the fight against cancer. However, what is true for mice does not necessarily apply to humans.

Thus, human studies on this topic are only sporadic and include a small number of subjects. A study published in 2015 in the journal BMC Cancer was conducted on 13 subjects with early-stage breast cancer. The subjects were randomly divided into 2 groups: in the first group, patients fasted for 24 hours before and after chemotherapy, while in the second group, women followed recommendations for proper nutrition. The results indicated that chemotherapy had a less toxic effect on the bone marrow in the subjects who fasted.

A study published in 2018 also in the journal BMC Cancer examined the impact of fasting on 34 subjects with breast or ovarian cancer. The subjects fasted for 36 hours before and 24 hours after therapy on different occasions, and the results showed that the practice of fasting reduced fatigue and improved the quality of life of patients. Although these studies provide some reasons for optimism, this is certainly not enough evidence to recommend fasting to patients in addition to standard oncology therapy. However, it is likely that we will hear a lot about the topic of fasting and cancer in the coming years, and until then, more high-quality clinical studies need to be conducted to confirm the effectiveness and safety of such a practice.

Can fasting be dangerous?

In the eyes of a healthy person, the greatest advantage of intermittent fasting, which leads to weight loss, can also pose the greatest threat to cancer patients. Insufficient intake of nutrients, especially protein, as well as even a small weight loss can quickly have a negative impact on the patient's health. The situation is even more dangerous for those patients who are already weak and malnourished or have difficulty maintaining their current body weight, because fasting will only worsen the condition, and thus probably reduce the tolerability of treatment and quality of life.

Fasting is also a bad choice in cases where chemotherapy drugs are taken orally, especially those that need to be taken with food for better absorption. In the presence of diabetes, insulin resistance, kidney or liver disease, fasting periods are not recommended. The same applies to people who have or have ever had eating disorders such as anorexia or bulimia.

If you decide to fast, consult a specialist!

Despite the expert opinion that fasting with cancer is not the best idea, statistics reveal that some patients are enthusiastic about this practice. Instead of rejecting the very idea of fasting, it is up to the oncology team to educate the patient and provide him with professional support. It is also in the patient's interest to warn his doctor about any changes in diet or taking supplements, in order to optimize therapy.

It is also important to keep in mind that not all patients with malignant diseases are malnourished or have other chronic diseases. If such a patient insists on fasting with oncology therapy, instead of doing it on their own, it is desirable for a specialist to assess their nutritional and health status, advise on which type of fasting to apply, and monitor them along the way so that timely action can be taken in the event of deterioration in health.

And finally...

The fact is that the use of fasting with standard therapy is an extremely interesting topic among cancer patients. However, real evidence that fasting is safe, reduces side effects, and improves the outcome of therapy is lacking. Therefore, it is advisable to avoid this idea, especially since we still have a long way to go before we know exactly how different types of fasting affect different types of cancer. Any patients who, despite the warnings, are considering fasting should consult a specialist first.

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