Researchers have spent decades trying to unravel cancer’s causes. While the search has yielded as many questions as answers, the role of nutrition is one area that scientists are considering in light of newer data.
“Overall, current research indicates a correlation between nutrition, dietary components and cancer development,” says Gloris Xynos, a registered dietitian and education coordinator for community outreach with St. Luke’s Hospital. “Studies have examined the role of a diet high in plant foods in decreasing risk of certain types of cancer; and on the contrary, the role of a diet high in animal foods, fat and sugar with increasing risks of certain types of cancer.” However, she adds that “no single study can prove that any factor definitely is a cause of, or is protective against, any disease.”
In other words, experts agree that studies support the benefits of a plant-based diet featuring whole (not processed) foods, but there is no conclusive finding.
Lynn Ruesler, a registered dietitian and certified oncology specialist with Missouri Baptist Medical Center, provides a few rules of thumb based on current knowledge: Maintain a healthy body weight (body mass index no greater than 25), exercise regularly, limit consumption of sugar, focus on fruits and vegetables, increase fiber intake, limit alcohol to one drink per day for women and two for men, and eat less red and processed meat. Xynos adds that dietary supplements have not been shown to have proven cancer-preventive effects.
While cancer prevention through diet remains primarily speculative, nutritional needs of cancer patients are a concern that should be addressed as part of an overall treatment plan. “Every patient going through cancer treatment is different. Addressing their nutritional status depends on the type of cancer, treatment, current health status, past medical history, socioeconomic status and emotional health,” says Sharon Geekie, a registered dietitian with SSM DePaul Health Center.
“Every nutritional assessment and recommendations are individualized for that patient,” she continues. “Any significant diet changes or recommendations for weight loss are addressed after treatment and with the approval of their oncologist. There is evidence that overweight or obese women with certain types of breast cancer have higher incidence of recurrence and poorer outcomes.”
A diet that helps patients maintain stamina throughout treatment may include extra protein, fluids and, in some cases, calories, says Ruesler.
“The most important thing to understand about diet and risks associated with cancer is that nothing works in isolation,” Xynos says. “Although we may have been exposed to carcinogens, or may carry genes associated for specific types of cancer, there are many variables in our lifestyle that may exacerbate or decrease these risks. Following this model, we cannot hope to take one nutrient or even one single food and translate that into a cure for all. Nutrients need be examined as a composition of single foods, foods should be examined as a composition of meals, meals as a composition of diet, and diet as a component of lifestyle. Lifestyle is a variable that you have the power to influence in cancer development and treatment.”
You may have heard the buzz about ‘superfoods’—those foods that contain almost magical nutrients thought to protect against all manner of ills. Is it hype or evidence-based science?
“No, there is no ‘true superfood’ that has substantial evidence that it reduces the risk of cancer,” says Sharon Geekie, a registered dietitian with SSM DePaul Health Center. “However, it is recommended to consume five to nine servings of colorful fruits and non-starchy vegetables per day. There is probable evidence that these foods can decrease the risk of developing cancers of the head and neck, stomach, lung, colorectal, pancreas and prostate.”
Fruits and vegetables contain various combinations of vitamins, minerals and phytochemicals, Geekie explains, which can act as antioxidants, preventing oxidative damage to cells, proteins and DNA. “However, no one component in these foods can be identified in its association of lowering cancer risk as these foods contain multiple components and this may have a synergistic effect,” she adds.
Lynn Ruesler, a registered dietitian and certified oncology specialist with Missouri Baptist Medical Center, reviewed a list of foods that have been shown to contain compounds that may contribute to cancer prevention.
• Berries, especially strawberries and raspberries, contain ellagic acid, a phytochemical that may help prevent cancers of the skin, bladder, lung, esophagus and breast. “Research suggests that ellagic acid seems to utilize several different cancer-fighting methods at once: it acts as an antioxidant, it helps the body deactivate specific carcinogens, and it helps slow the reproduction of cancer cells,” she says. In addition, blueberries contain some of the most potent antioxidants found.
• Red and purple grapes contain resveratrol, an antioxidant that prevented the kind of damage known to trigger the cancer process in cell, tissue and animal models. “Other laboratory research points to resveratrol’s ability to slow the growth of cancer cells and inhibit the formation of tumors in lymph, liver, stomach and breast cells,” Ruesler notes. “Resveratrol has also triggered the death of leukemic and colon cancer tumors.”
• Cruciferous vegetables, including cabbage, kale, broccoli and Brussels sprouts, are rich in vitamins, minerals and phytochemicals that appear to decrease inflammation, a risk factor for some cancers.
• Tomatoes contain lycopene, a substance studied in particular relation to prostate cancer prevention. “Lycopene, a powerful antioxidant, together with a group of related compounds collectively called the ‘red family,’ has displayed anti-cancer potential in a variety of laboratory studies,” Ruesler notes. “In the laboratory, tomato components have stopped the proliferation of several other cancer cells types, including breast, lung and endometrial.”
• Curcumin is a substance found in the spice turmeric. “In the lab, curcumin modulates cell signaling pathways, suppresses tumor cell proliferation and induces apoptosis of cancer cells,” Ruesler says. “There is evidence that curcumin can suppress inflammation and inhibit tumor survival, initiation, promotion, invasion and metastasis. The findings from lab studies have led to clinical trials in humans, which are generally small but have generated promising findings.”