Loss of appetite is a common side effect for people undergoing cancer treatment, and the reasons vary. A patient’s taste for food may change. Nausea can occur. But even as eating becomes more difficult for some patients with cancer, good nutrition remains critical to help them maintain their body weight and strength during treatment.
“Patients with cancer should receive evidence-based, individualized recommendations from a nutrition expert, based on a number of factors, including their type of cancer, stage of disease, planned treatment, nutrition history, weight history, and lab values,” explained Marnie Dobbin, MS, RDN, CNSC, a clinical research dietitian at the NIH Clinical Center who works with patients who have cancer.
Not all patients receive these recommendations, however, and many search for this information online. What they learn depends on which websites they visit, according to a survey of cancer center sites. Overall, recommendations across the sites were “consistently inconsistent,” Colin Champ, MD, of Thomas Jefferson University and his colleagues reported March 2013 in Nutrition and Cancer.
The researchers assessed the landscape of information available online by surveying the websites of 21 cancer centers in the National Comprehensive Cancer Network (NCCN), an alliance of major cancer centers in the United States, most of which are NCI-designated comprehensive cancer centers.
The lack of consensus in online sources, some researchers say, in part reflects a lack of sufficient scientific evidence to develop specific dietary recommendations.
Among the 21 NCCN institutions surveyed, only four (19 percent) provided dietary recommendations for patients undergoing cancer treatment. Another five institutions (24 percent) referenced external websites for such information. Among the nine external websites referenced by NCCN institutions for dietary information, only four (44 percent) provided recommendations specifically for patients during or following cancer treatment.
Of the four NCCN institutions that provided recommendations on their websites, two recommended diets containing equivalent proportions of carbohydrate-rich, protein-rich, and fat-rich foods, whereas the other two recommended diets consisting primarily of carbohydrate-rich foods. The dietary information on websites referenced by the NCCN institutions, which included the NCI website and those of the American Cancer Society and the American Society of Clinical Oncology, also lacked consistency, the researchers found.
“This study drives home the point that there’s really very little information about what patients with cancer should eat, especially during their treatments,” said Elena Ladas, PhD, RD, who directs the Center for Comprehensive Wellness at Columbia University and was not involved in the study.
Because there is a need for more scientific evidence, Dr. Ladas continued, it can be difficult to tailor dietary and nutritional recommendations for patients undergoing therapy. Most dietary recommendations for cancer patients are based on suggestions developed for the general public, she added.
“Online nutrition information for patients with cancer could not be individualized enough without some sort of complicated algorithm,” said Sara Bergerson, RD, CNSC, also of the NIH Clinical Center, who was not involved in the study. “In lieu of that, these patients should rely on recommendations from nutrition experts at their treatment facilities.”
Randomized clinical trials provide the gold standard of scientific evidence, and although none have been conducted in this area, some small studies have been completed recently. (See the box below.)
Different Cancers, Different Recommendations
As the field moves forward, dietary recommendations are unlikely to apply broadly to patients with different types of cancer, Dr. Champ and his colleagues noted. For example, patients with locally advancedhead and neck cancers, who can have great difficulty eating during treatment, are often encouraged to eat whatever they can to keep weight on.
But for patients with localized cancers, such as breast or prostate cancer, eating whatever they want could be detrimental to their health. These patients are likely to become long-term survivors, and weight gain may increase the risk of relapse.
There’s really very little information about what patients with cancer should eat, especially during their treatments.
—Dr. Elena Ladas
Moreover, “it may be difficult for some patients who are focused on gaining weight during therapy to transition to a healthy diet during survivorship,” Dr. Champ said.
Indeed, the growing number of cancer survivors around the world has created a need for new research on the optimal nutritional approaches for patients who have been treated for cancer in the past. Specific recommendations on certain foods and the types of nutrients within these foods are also needed, noted Dr. Ladas.
Ensuring that future recommendations are implemented could be a challenge, Dr. Ladas cautioned. “If a physician doesn’t believe in a particular recommendation it doesn’t matter what a website says,” she said. “The only way to advance the field forward is to support more research, because we need the evidence to change practice and physicians’ minds.”
Every week, Dr. Champ receives e-mail from patients who ask what they should eat as they start therapy. He shares the results of animal studies and nonrandomized clinical trials with his patients, but he also tells them what researchers do not yet know.
“We don’t have high-level data to answer their questions,” he said. “Without this information, it’s hard to know what the effects of a particular diet will be during treatment.”
Exploring the Effects of Diet on Cancer Growth
Many researchers are interested in exploring the effects of diet on the prevention and treatment of cancer. Last year, for example, Eugene Fine, MD, of the Albert Einstein College of Medicine and his colleagues reported that a low-carbohydrate, insulin-inhibiting diet is safe and feasible for patients with advanced cancer.
The study was small, with just 10 patients. But if the findings are confirmed in larger studies, then “dietary manipulation may have the potential to be used as a complementary non-toxic approach to improve the effectiveness” of standard therapy in selected patients with cancer, Dr. Fine and his colleagues wrote.
The authors of an accompanying editorial agreed. This pilot study “lays the groundwork for testing the hypothesis that a carbohydrate-restricted diet will slow cancer growth in patients by decreasing the secretion and circulating levels of insulin,” they wrote.