MUC5AC and cancer: We suggest that unlike DR, acute fasting entirely depletes protein and sugar provision for resident microbes (including Lactobacillus) that rely on dietary sources of nutrition.29 This is in contrast to microbes that increased following acute fasting (e.g. Ruminococcus) that primarily utilize endogenous/host nutrient sources such as mucin.30,31 Despite these discrepancies, it is clear that manipulating the microbiota in a manner that does not detrimentally affect body composition is likely to be a fundamental step in better managing the complications of cancer treatment.