New research suggests that fasting, including intermittent low-calorie diets, may play a significant role in revolutionizing cancer treatments by potentially supercharging the immune system and making therapies more effective. Scientists believe this approach could be on the cusp of a major shift in cancer care.
Immune Cell Enhancement
A 2024 study published in the journal Immunity found that fasting can dramatically strengthen the function of natural killer (NK) cells, a type of immune cell crucial for destroying tumors. The research involved implanting mice with human colon and melanoma cancer cells. Mice subjected to a 24-hour fast twice a week showed tumors that were up to 70 percent smaller than those in control groups allowed to eat freely. Fasting led to a decrease in glucose and insulin levels and an increase in free fatty acids. NK cells, which typically rely on glucose that cancer cells consume, were observed to adapt to using fatty acids as an alternative fuel source during fasting periods, optimizing their anti-cancer response.
Furthermore, fasting promoted the migration of NK cells to the bone marrow, where they are primed to produce interferon-gamma, an immune-boosting substance that enhances their power. Experts suggest this effect could be beneficial across various cancer types, particularly when combined with immunotherapy.
Reprogramming Cancer Cells
Research also indicates that fasting can directly affect cancer cells, potentially reprogramming them from within, especially in estrogen-sensitive breast cancer. Current treatments for this type of cancer often involve drugs like tamoxifen, which block estrogen receptors. However, cancer cells can develop resistance over time, leading to recurrence.
A study in Nature explored how fasting might prevent this resistance. By combining tamoxifen treatment with a 48-hour weekly fast in mice with estrogen-positive breast cancers, researchers observed an increase in stress hormones like cortisol during fasting. This activated glucocorticoid receptors within tumor cells, switching on genes that inhibit tumor growth while suppressing those that promote multiplication. Consequently, tumors shrank, and tamoxifen remained effective.
Human studies using low-calorie diets designed to mimic fasting—developed by the company L-Nutra—showed similar results. Patients on these regimens experienced a surge in cortisol, leading to the activation of growth-inhibiting genes in tumors and a reduction in cancer-promoting hormones like insulin and leptin. This suggests that such diets could help prevent breast cancer proliferation by reprogramming the cancer itself.
Thomasina Miers, a MasterChef winner and founder of the restaurant chain Wahaca, revealed that she followed a fasting-mimicking diet alongside chemotherapy for breast cancer.
Potential Therapeutic Alternatives
While fasting shows promise, its application in cancer care presents challenges, as prolonged fasting can be difficult and potentially harmful for patients experiencing weight loss and muscle wasting (cachexia).
To address this, researchers have explored drug alternatives. Dexamethasone, a steroid commonly used to manage chemotherapy side effects, was found to activate similar glucocorticoid pathways as fasting in mice. Combining dexamethasone with tamoxifen significantly delayed tumor growth without causing weight loss. Researchers at the University of Basel also found that dexamethasone reduced liver metastases and prolonged survival in certain breast cancers.
However, dexamethasone may not be suitable for all cancer types. Glucocorticoid receptor activation could potentially worsen non-hormonal breast cancers, such as triple-negative and HER2-positive types. It is important to note that typical chemotherapy doses of dexamethasone have not been shown to negatively affect treatment or survival in patients with hormone-negative cancers.
Other strategies under investigation include extending overnight fasting periods, such as through time-restricted eating. A 2016 study in JAMA Oncology found that fasting for at least 13 hours overnight significantly reduced the risk of cancer recurrence.
Experts also speculate that GLP-1 drugs, like Mounjaro, could potentially mimic fasting effects in future cancer treatments. Despite encouraging early trial results, researchers emphasize that this field is still in its nascent stages and requires more data before widespread clinical application. Patients are advised to consult their oncologists and maintain a balanced diet, as certain supplements like vitamins C and E may potentially encourage cancer spread in some contexts.