Many integrative oncology clinicians advise following this circadian rhythm practice of fasting from after an early-evening dinner until breakfast.
Fasting every day is part of our normal circadian rhythm, occurring naturally when we sleep. The first meal of the day is called breakfast (break fast) for this reason.
Many integrative oncology clinicians—including BCCT advisors Keith Block, Lise Alschuler and Dwight McKee—advise following this circadian rhythm practice of fasting from after an early-evening dinner until breakfast. A fast between 13 and 16 hours is considered optimal. An investigation of whether duration of nightly fasting predicted recurrence and mortality among women with early-stage breast cancer found that those who fasted less than 13 hours each night had an increased risk for breast cancer recurrence compared with fasting 13 or more hours per night.1
Treating the Cancer
Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action
Intermittent fasting may provide many of the same benefits as calorie restriction without the high level of challenge.
Research suggests that periodic fasting around the time of chemotherapy may sensitize cancer cells to chemotherapy, while protecting normal cells in patients with HER2-negative, stage 2/3 breast cancer.4 A number of clinical trials are underway to see if these early findings from small studies are replicated.5
Lab and Animal Evidence
Multiple cycles of fasting reduced the immunosuppression and mortality caused by chemotherapy and promoted regenerative effects of fasting on stem cells in cell and animal studies.7
In animal studies, intermittent fasting has been as effective as chemotherapy in delaying the progression of a wide range of cancers and can protect normal cells from the toxic effects of chemotherapy drugs while sensitizing cancer cells to the treatment.8
Managing Side Effects and Promoting Wellness
Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being
Integrative oncologist and BCCT advisor Dwight McKee, MD, has advised some of his chemotherapy patients to follow intermittent fasting during chemotherapy. “I have had some patients who nearly died from their first cycle of treatment, but then fasted for three days with their second cycle and breezed through it.”10
Women with early-stage breast cancer who fasted less than 13 hours each night had an increased risk for breast cancer recurrence compared with fasting 13 or more hours per night.11
In a case series, limited intermittent or periodic fasting was used safely in patients undergoing chemotherapy to reduce side effects of treatment and did not prevent the chemotherapy-induced reduction of tumor volume or tumor markers.12
Naturopathic oncologist and BCCT advisor Lise Alschuler notes that "a prolonged fast is not an appropriate detox program for someone just completing chemo."
Note: Additional evidence shows value from fasting in cancer types beyond breast cancer; we will be adding that evidence here soon.
- For patient-friendly information on intermittent fasting and cancer, see Dr. Lise Alschuler’s and Karolyn Gazella’s I-Thrive Plan: Diet—Overnight Fasting.
- Dwight McKee, MD, editor: Clinical Pearls
- Barbara MacDonald, ND, LAc: The Breast Cancer Companion: A Complementary Care Manual: Third Edition
- Block KI, Block PB, Gyllenhaal C: Integrative Treatment for Colorectal Cancer