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Bite on This: Fasting During Chemotherapy

Fasting is traditionally a religious practice utilized to establish self-control and purification. Scientists find that fasting may prove useful for certain medical conditions as well. Dr. Valter Longo and colleagues observed that fasting on chemotherapy days increased the ability of the drugs to target the cancer cells, making the drug more effective and decreasing the side effects to “healthy” cells. While these results are promising, the practice of fasting during chemotherapy should only be used in very specific circumstances until further research is available.


The Current Research:

To Fast… Currently, there are just a few, small human trials that have demonstrated the benefits of fasting 3-5 days around chemotherapy days (the day before, day of and for 2 days after chemotherapy). For people who were able to follow through with the studies and fast, the results were promising. Patients reported that fatigue and gastrointestinal side effects were reduced and that blood counts did not take such a hit. Also, there were beneficial hormonal changes (like decreased insulin like growth factor 1) that occurred in the patients.

Or Not to Fast? However, there are a number of contraindications to allow patients to safely fast. In the trials, some patients were not able to fast due to headache, hypoglycemia, hyponatremia and/or dizziness. Patients with extreme nausea, difficulty swallowing, significant weight loss, who are on medications that require food (like some oral chemotherapies), have malabsorptive diseases, have a history of an eating disorder, live alone without someone checking in on them, etc. should not fast during chemotherapy. By contrast, if someone is otherwise healthy and has a stable weight, fasting may be done safely under proper medical guidance. It is essential to consult the medical team as electrolyte and hydration levels need to be monitored closely.

That is the question Overall, larger human trials are needed before we can safely go ahead and recommend this protocol to more patients. Regardless, consult a Board Certified Oncology Dietitian or “CSO” to learn more about your nutrition needs during treatment.

Hillary Murray is a registered dietitian working in an outpatient radiation and chemotherapy center.  She uses evidenced based information to help patients minimize treatment related side effects and to guide survivors towards health and wellness.  Hillary received a BS in nutritional sciences from Cornell University; completed her dietetic internship at James J. Peters Veteran Affairs Medical Center; and earned an MS in Clinical Nutrition at New York University. 

Hillary Sachs, MS, RD, CSO, CDN

Hillary is a Registered Dietitian and Board Certified Specialist in Oncology Nutrition (CSO). She received her BS in Nutritional Sciences at Cornell University and MS in Clinical Nutrition at New York University, and completed her dietetic internship at the James J. Peters Bronx VA Medical Center. Hillary works as an outpatient dietitian at the North Shore-LIJ’s Cancer Institute, where she counsels patients and their families before, during and after cancer treatment. Additionally, Hillary counsels clients on nutrition through her private practice, Recipe for Health, L.L.C., and has been invited to present at several nutrition-related events including the Breast Cancer Update Symposium at North Shore-LIJ (2013) and Adelphi University’s Farm to Table lecture (2014). Hillary strives to translate the science behind health, nutrition and prevention into practical and easy-to-follow recommendations.

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