 Short-term food withdrawal during chemotherapy may begin to solve the long-standing problem with most cancer treatments, how to kill the tumor without killing the patient. Short-term fasting, for example, for 48 hours before chemo and 24 hours afterwards, may reduce side effects, reduce chemotherapy-induced toxicity. However, the potential tumor suppressing effects of fasting, for example, its influence on tumor growth, metastasis, and prognosis have not been evaluated until now. No, actually, sadly, they mean have not been evaluated until now, meaning have not been evaluated yet, period. So, in answering the question to fast or not to fast before chemotherapy, it should be emphasized that the evidence provided by human studies is still very limited. Some argue that reducing the side effects alone could improve efficacy since patients could withstand higher doses. For example, the heart and kidney damage associated with widely prescribed anti-cancer drugs limit their full therapeutic potential. It's not clear, though, that maximizing the tolerated chemo dose would achieve longer survival or better quality of life. For now, I think we should just be satisfied with the fewer side effects for fewer side effects' sake. Some cancer docs urge caution, a concern about malnutrition. That concern is echoed in official guidelines on nutrition and cancer patients. Because of the risks of malnutrition, and yeah, maybe a day or two might not hurt, but because patients might be tempted to prolong fasting episodes without firm evidence of a benefit, they feel fasting during chemotherapy cannot be recommended. Fasting proponents agree that patients with severe weight loss, muscle wasting, or malnutrition, probably not good candidates for even short-term fasting. But of the hundreds of patients that have been trying, there's no evidence of severe adverse events in terms of malnutrition, or weight loss with short-term fasting, or fasting-mimicking diets. And those patients who did experience a weight loss during fasting typically recovered their way before the subsequent cycle of chemo without detectable harm. But like, I mean, even if there is a risk, we're talking about cancer here, I mean, accepting trade-offs is kind of the name of the game. People are willing to put up with the risks of severe, even life-threatening side effects all the time. And even if it just helped alleviate some of the side effects, it might be worth a try. Of course, meanwhile, big farmers, busy trying to come up with drugs, aimed at reproducing the beneficial effects of fasting, although fasting-mimicking drugs may be preferred by patients who would rather pop a pill than go without eating, it will be years before they'll ever be on the market. And it's hard to imagine drugs will be developed that are both as effective and as safe as fast. So is there anything we can tweak in our diet to get similar benefits without having to fast? The way fasting works is by reducing the levels of a cancer-promoting growth hormone known as insulin-like growth factor 1. It's the reduced levels of IGF-1 that mediates the difference or protection of normal and cancer cells in response to fasting, and improves chemo's ability to kill cancer, but spare normal cells. How do we know this? Because restoration of IGF-1 was sufficient to reverse the protective effect of fasting. Check it out. Here's the growth of two cancer cell lines, breast cancer and melanoma, in a petri dish after being exposed to chemotherapy. Survival rates dropped down into the 60s or even 20s, but the same dose in starved cells works even better. Same dose, same starvation, but dripped back a little IGF-1 and the starvation benefit banishes. So reducing IGF-1 signaling may provide the dual benefits by protecting normal cells while reducing tumor progression and even help prevent the cancer in the first place, as I explained before. In my How Not To Die From Cancer video and an important video about animal protein, which kind of gives away the punchline, but fasting isn't the only way to drop IGF-1 levels. Yes, a few days of fasting can cut levels in half, but that's largely because you're cutting your protein intake. Protein is a key determinant of circulating IGF-1 levels in humans suggesting that reduced protein intake may become an important component of anti-cancer and anti-aging dietary interventions, particularly a reduction in animal protein. If you compare those eating strictly plant-based diets, this is getting about the recommended daily intake of protein, 0.8 grams per kilogram of body weight, and compare them to people just slender, but eating more typical American protein intake. Going on a calorie-restricted diet may lower IGF-1 a little, but eating a plant-based diet can lower it more. So not only may a diet centered around whole plant foods down regular IGF-1 activity, potentially slowing the aging process, but may be a way of turning anti-aging genes against cancer.