“You’re diagnosed, you’re getting treatment, what do you eat now?” asks University of Alabama at Birmingham cancer prevention and control expert Wendy Demark-Wahnefried, PhD, RD. Unfortunately, she says, “the data are really thin.” She is one of the authors of the latest guideline from the American Society of Clinical Oncologists (ASCO), “Exercise, Diet, and Weight Management During Cancer Treatment.” “We know that diet is important for prevention, for overall health and for cancer survivorship, but during the window of time you’re getting treatment, we can’t make a guideline supported by data,” she says. “It doesn’t mean it’s not important. We just really need more research.”
Popular approaches abound for people in treatment, to be sure. These include ketogenic diets, low-fat diets, intermittent fasting, plant-based diets, macrobiotic diets and more. But there are very few rigorous clinical studies to back them up—yet.
The ASCO guideline, based on 52 systemic reviews plus 23 randomized controlled studies, concludes, “There is currently insufficient evidence to recommend for or against dietary interventions.” But it also states, “Diet and weight management strategies that provide health benefits to the general population could also provide important benefits to people who are undergoing cancer treatment. The Expert Panel is not discouraging clinicians from discussing healthy diet and weight with their patients, but did refrain from making specific recommendations, given gaps in the evidence.”
Jennifer Ligibel, MD, a medical oncologist specializing in breast cancer at the Dana-Farber Cancer Institute in Boston who coauthored the ASCO guideline, was surprised by the research gaps. “It was eye-opening, reviewing the data, to see how little information about diet and dietary change for people in treatment there is,” she says. “Oncologists would like to be able to tell patients what they can do during treatment that would be helpful, and patients have really valid and important questions about what they should be eating during cancer treatment. But we just don’t have sufficient data…