Vegetables on display in grocery store

Written by Brooke Sawicki, MS, RDN, LDN, Tate Cancer Center at UM Baltimore Washington Medical Center

Most Americans tolerate the avalanche of conflicting nutritional advice in popular culture -- until the stakes become high. After considering cancer risk or being diagnosed, they want clear, evidence-based guidance. Registered dietitian nutritionists (RDNs) serve as a critical component of the multidisciplinary treatment team in the University of Maryland Cancer Network.

The Continuous Update Project

The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) collaborate on the Continuous Update Project, which summarizes the latest research on cancer prevention. The two organizations published their a report, "Diet, Nutrition, Physical Activity, and Cancer: a Global Perspective," in 2018. The AICR developed the "New American Plate," a cancer-prevention diet that calls for visually dividing your plate into thirds: Plant foods should make up two-thirds or more of your plate, and animal protein should make up one-third or less. The New American Plate is not necessarily a diet, but part of a healthy lifestyle.

According to the WCRF and AICR, one of the most protective factors against cancer is maintaining a healthy weight, as being overweight increases the risk for several types of cancer. Excess body fat can cause systemic changes in metabolic and endocrine pathways, dysregulate hormonal profiles, and create a chronic inflammatory state.

The WCRF and AICR recommend participating in at least 150 minutes of moderate or 75 minutes of vigorous physical activity per week and limiting sedentary behavior throughout the day. Physical activity helps prevent cancer in multiple ways, including regulate hormones, strengthen the immune system, regulate digestion, and reduce insulin resistance, oxidative stress and inflammation.

The WCRF and AICR recommend these healthy eating patterns:

  • Consume a diet rich in whole grains, fruits, vegetables and beans. Whole grains contain protein, vitamins, minerals, fiber and phytochemicals, which have anti-carcinogenic properties. Fruits and non-starchy vegetables contain potential anti-tumorigenic agents such as dietary fiber, vitamin C, vitamin E, selenium and phytochemicals. Consuming at least five servings of a variety of fruits and non-starchy vegetables daily is recommended. A recommended 30 grams of dietary fiber daily reduces the risk for colorectal cancer, specifically by decreasing intestinal transit time, increasing fecal bulk, reducing secondary bile acid production, reducing insulin resistance and helping to maintain a healthy weight.
  • Limit consumption of processed foods that are high in fat, starches and/or sugar. High in calories and low in nutrition, processed food can contribute to weight gain.
  • Limit intake of red meat (beef, veal, pork) to no more than three portions (or 12 to 18 ounces) per week and avoid processed meat (ham, salami, bacon, sausage and hot dogs). A high intake of red and processed meat increases the risk for colorectal cancer. Meats cooked at high temperatures can produce carcinogenic compounds. Processed meats also contain N-nitroso compounds, which have carcinogenic potential.
  • Limit consumption of sugar-sweetened beverages. Soda, sports drinks and juices contribute to weight gain, increasing the risk of cancer.
  • Avoid alcohol, or consume no more than two standard drinks per day for men and no more than 1 standard drink per day for women. Alcohol intake can increase cancer risk, disrupt cellular DNA synthesis and repair, act as a solvent for cellular penetration of carcinogens, and produce oxidative stress and inflammation.
  • Do not use high-dose dietary supplements. Aim to meet nutritional needs though diet alone. High-dose dietary supplements have not demonstrated a protective effect on cancer risk in randomized controlled trials. Some studies even show the potential for adverse effects.

Special Considerations for Cancer Survivors and Patients

For cancer survivors, some accommodations may be necessary, especially during and immediately following the acute stage of treatment.

One study found that malnutrition is prevalent in up to 80% of oncology patients throughout their cancer care, and associated with increased morbidity and mortality, recurrent hospitalizations, impaired quality of life, reduced response to treatment, and recurrence of disease. Nutrition-related symptoms such as unintentional weight loss, dysphagia, xerostomia, malabsorption, early satiety and dehydration can all contribute to malnutrition.

In oncology practice, RDNs are a critical component of the multidisciplinary treatment team to optimize a patient's nutritional status throughout cancer treatment and afterward. However, there is a lack of outpatient access to RDNs in the oncology setting nationwide. The National Cancer Institute (NCI) Comprehensive Cancer Centers found that there was an average of 1 RDN to 2,674 patients in 2014.

While the WCRF and AICR recommend that patients continue a cancer protective diet after diagnosis, this is not always feasible due to the course of treatment and side effects. Nutrition counseling and interventions should focus on prevention of weight loss, maintaining lean body mass, symptom management to improve oral intake, and use of oral nutrition supplements, pharmacologic therapies, and nutrition support in some cases, which requires coordination of care with the oncology team.

Want to learn more about how diet could affect your patient's predisposition to cancer or cancer treatment? Refer a patient.

About the UM Cancer Network

With the NCI-designated UM Marlene and Stewart Greenebaum Comprehensive Cancer Center as its hub, the UM Cancer Network offers patients access to nationally-renowned experts, cutting edge treatments and technologies, and the latest clinical trials. Learn more about the UM Cancer Network.