Cancer patients often ask what they should eat, but it’s just as important to know when they should eat, according to Dawn Lemanne, MD, of Oregon Integrative Oncology, Ashland, and the University of Arizona, Tucson. Dr. Lemanne tells host David H. Henry, MD, how cancer patients may benefit from fasting. The pair discuss immune system suppression, insulinlike growth factor I (IGF-I), and blood glucose monitoring. Fasting and the immune system Fasting before and after chemotherapy can put part of the immune system “to sleep,” thereby protecting it from the deleterious effects of treatment, Dr. Lemanne says. A study of patients on platinum-based chemotherapy suggested that fasting for at least 48 hours (divided pre- and post chemo) led to decreased DNA damage in leukocytes (BMC Cancer. 2016 Jun 10;16:360). Based on this study and preclinical results, Dr. Lemanne advises fasting in patients receiving emetogenic and immunosuppressive chemotherapies. Lemanne defines fasting as consuming no (or few) calories. Patients can drink water and caffeinated beverages such as coffee or tea, but the drinks can’t include additions like cream or sugar. IGF-I levels Several studies have linked the growth hormone IGF-I to cancer (Endocrinol Metab Clin North Am. 2012;41[2]:335-50). Lemanne says high IGF-I levels in middle age seem to increase the risk of cancer, and high IGF-I levels in patients who already have cancer may increase the risk of death. Overnight intermittent fasting of 13 hours or more can lower IGF-I levels, according to Dr. Lemanne. Although there are drugs that can lower IGF-I levels, Dr. Lemanne doesn’t recommend them because of potential side effects. Blood sugar Studies have suggested that metformin can improve survival in diabetics with cancer (Cancer Manag Res. 2019;11:3295-313). Researchers are investigating whether metformin provides the same survival benefit to nondiabetics with cancer. Lemanne says she checks cancer patients’ hemoglobin A1C and fasting insulin levels even if they are not diabetic. She even gives patients glucose monitoring systems so they can see how their blood sugar spikes after meals. If a patient’s blood sugar levels are high, Dr. Lemanne will try to lower them via dietary changes. If that doesn’t work, she will give patients low-dose metformin. Disclosures: Dr. Lemanne and Dr. Henry have no relevant disclosures. * * * For more MDedge Podcasts, go to mdedge.com/podcasts Email the show: podcasts@mdedge.com Interact with us on Twitter: @MDedgehemonc David Henry on Twitter: @davidhenrymd