Fasting for 24-48 hours during chemotherapy improves the response of the immune system against tumors and reduces chemotherapy toxicity through yet unknown mechanisms. The investigators have found that fasting induces the activation of p21, a protein that stops cell proliferation and plays important immune roles. The investigators hypothesize that p21 induction with short-term fasting enhances the immune anti-tumour response and reduces chemotherapy toxicity. To test this, half of the colorectal carcinoma (CRC) participants will follow 48 hours of fasting, 24 before and 24 after chemotherapy, under constant and specialized nutritional supervision. While the other half will follow a standard diet. A complete blood immunological profile at each chemotherapy cycle will be generated in collaboration with expert cytometrists, and gene expression, biochemical parameters, tumor evolution and toxicity markers will be measured. The investigators will (1) perform a complete analysis of immune cells to characterize the immune effects of fasting during chemotherapy; (2) analyze the effects of fasting on genes, metabolites and other molecules, to identify the responsible biological mechanisms, focusing on p21; (3) assess the reduction of chemotherapy toxicity in patients of colorectal carcinoma subjected to short-term fasting during chemotherapy.~Our project will further explore a safe, inexpensive, relatively unexplored and powerful nutritional intervention that can improve the quality of life and survival rates of millions of cancer patients: short-term fasting. Also, our project will have an important scientific impact, since previous reports have not yet described a clear mechanism explaining the beneficial effects of short-term fasting with chemotherapy
This study will evaluate the ability of short-term fasting to reduce chemotherapy toxicity and enhance anti-tumour response in patients with colorectal carcinoma subjected to chemotherapy.