Intermittent Fasting and Cancer

Known in the West as intermittent fasting , the intermittent fasting diet is becoming a popular eating program. Unlike other diets, it focuses not on foods but on when to eat. Nutrition is important during cancer and chemotherapy, and eating may change: previously liked foods may become unappealing, and new foods may not be added. Loss of appetite and nausea sometimes limit intake. This may not be as harmful as assumed. New studies suggest treatment-related appetite loss should not always be viewed negatively, and occasional fasting may benefit appropriately selected patients.

Intermittent fasting involves little or no calorie intake for 16-48 hours. Models include 8 hours eating and 16 fasting, or 2 eating and 21 fasting. It is also called a fasting diet or periodic fasting.

These models are tested to improve mammalian physical and mental performance. Body fat decreases while muscle is preserved. Studies suggest intermittent and periodic fasting may sensitize cancer cells to chemotherapy and other anticancer treatments. Other research shows fasting triggers autophagy and activates CD8 cytotoxic T cells while inhibiting regulatory T cells, modulating immunity. It also helps modulate insulin, leptin, and adiponectin. Fasting was initially studied for diabetes and polycystic ovary syndrome control, but is now attracting attention for cancer prevention or treatment.

Rodent studies show fasting before chemotherapy prolongs survival and reduces metastasis and toxicity. Similarly, periodic fasting before tyrosine kinase inhibitors inhibited growth in cancer cell lines, including small cell lung cancer . Fasting from 24 to 72 hours was examined in 8 studies. Of these, % 63 (of 8 studies, 5) found inhibited tumor growth; the remaining 3 found no significant difference from animals eating normally.

A systematic review of animal experiments found reduced metastasis and tumor growth. Intermittent fasting before chemotherapy significantly reduced chemotherapy-induced adverse effects, improving tolerance.

No study has evaluated human cancer incidence after intermittent fasting, so prevention is unknown. Several human clinical trials have assessed chemotherapy efficacy and safety. A systematic review examined fasting cycles of 24 to 180 hours; adverse effects, including hematological (blood and bone marrow) effects, were lower than in non-fasting patients.

A case series published in 2009 followed patients fasting before or after chemotherapy for 24 to 72 hours, evaluating 6 patients; effects were lower when fasting. Another study involved neoadjuvant or adjuvant docetaxel, doxorubicin (adriamycin), and cyclophosphamide planned for HER2 -negative stage II / III breast cancer in 13 patients, divided into 2 groups: short-term fasting before and after chemotherapy or normal eating. At 7 days, the fasting group of 7 had significantly fewer hematological effects, higher average hemoglobin and platelets, but no difference in non-hematological effects. Immune-cell DNA damage repair was also faster in fasting patients.

Gynecological cancer patients, totaling 34, participated in a randomized trial with 36 hours fasting before and 24 after chemotherapy, a total 60 hours. Quality of life was assessed. Fasting patients had fewer effects, no significant weight change, and preserved quality of life.

Conclusion

Current human data suggest fasting may benefit chemotherapy outcomes, particularly by reducing adverse effects. It appears safe in appropriately selected patients, with low-grade fasting-related effects. However, it has not been studied in large randomized controlled trials, so definitive conclusions on safety and effectiveness for cancer prevention and treatment cannot currently be drawn.