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Intermittent fasting (IF) has garnered significant attention in recent years for its potential health benefits, including weight loss, improved metabolic function, and possibly even cancer prevention. However, a new study in mice, published in Nature, suggests there may be a trade-off, potentially increasing the risk of cancer.
What is Intermittent Fasting?
Intermittent fasting is a dietary pattern that alternates between periods of eating and fasting, without focusing on what to eat but rather when to eat. Popular schedules include the 16/8 plan, where individuals eat within an eight-hour window and fast for the remaining 16 hours, and the 5:2 diet, where normal eating occurs for five days and calorie restriction for two.
Research has linked poor diet to a wide range of diseases, including coronary heart disease, stroke, type 2 diabetes, and various cancers. Intermittent fasting has been seen as a possible solution to improve metabolic health and reduce these risks by influencing how the body processes food and energy.
The New Study’s Findings
The recent study explored how intermittent fasting affects the body at the cellular level. In particular, it found that gut stem cells—crucial for intestinal repair—become more active after refeeding, compared to mice that were either continuously fasting or eating normally. This heightened stem cell activity may help repair damage and maintain gut health.
However, there’s a catch. If the cells contain genetic mutations, this burst of regeneration after fasting could promote cancer development. The study identified polyamines, small molecules involved in cell growth, as the drivers of this regeneration, highlighting that while the refeeding process has healing benefits, it could also increase cancer risk, particularly when repeated fasting and refeeding cycles occur.
Although these findings are specific to mice, they raise important questions about the potential risks of intermittent fasting for humans.
Mixed Evidence on Intermittent Fasting and Cancer
The relationship between intermittent fasting and cancer risk in humans remains complex. Numerous animal studies suggest that intermittent fasting may reduce weight, improve blood pressure, and lower blood sugar levels—factors linked to reduced risks of diabetes, heart disease, and potentially cancer.
Human research also shows that intermittent fasting can reduce body weight, enhance metabolic health, reduce inflammation, and stimulate cellular repair processes, which might prevent damaged cells from turning cancerous. However, other studies argue that similar benefits can be achieved through simple calorie restriction, casting doubt on whether intermittent fasting offers any additional protection against cancer.
Fasting and Cancer Patients
For individuals already diagnosed with cancer, research has shown that intermittent fasting might protect against chemotherapy’s side effects, improving treatment outcomes by minimizing damage to healthy cells. Some studies suggest prolonged fasting could even reduce tumor growth.
On the other hand, caution is advised. Animal studies indicate intermittent fasting might weaken the immune system, potentially impairing the body’s ability to fight infections. While there is no conclusive evidence that fasting increases infection risks in humans, these findings emphasize the need for further investigation.
Is Intermittent Fasting Safe?
Intermittent fasting is generally regarded as safe for healthy individuals, with short-term benefits such as weight loss and improved overall health well-established. However, experts agree that more research is needed to fully understand the long-term effects, particularly on cancer risk and immune health.
Given the variety of intermittent fasting methods and the differing responses among individuals, it is difficult to offer blanket recommendations. Moreover, most studies have focused on people who are overweight or have pre-existing health conditions, so the applicability of the findings to the broader population remains unclear.
People with certain medical conditions, pregnant or breastfeeding women, and those with a history of eating disorders should approach intermittent fasting with caution and consult a healthcare provider before starting any fasting regimen.
Conclusion
Intermittent fasting shows promise as a health-improving dietary approach, but emerging research like the recent Nature study indicates there may be risks, particularly concerning cancer development. While fasting may enhance gut repair, it could also inadvertently promote cancerous growth if genetic mutations are present. As the research evolves, individuals considering intermittent fasting should weigh the potential benefits against the unknown long-term risks and seek medical advice tailored to their health circumstances.
For further reading: Shinya Imada et al, “Short-term post-fast refeeding enhances intestinal stemness via polyamines,” Nature (2024). DOI: 10.1038/s41586-024-07840-z
