BRIDGING THE GAP
RESEARCH and PRACTICALITY
Nutritional Support for Cancer Patients
Body composition and nutrition can positively influence survival duration and quality of life for clinically diagnosed cancer patients (2-4,13). Lifestyle modifications that optimize nutritional quality and maintain body weight can lessen many of the deleterious side effects experienced during treatment and recovery. Efforts to increase survivability in diagnosed patients require a thorough understanding of the risk factors associated with both prevention and promotion of this disease (5,8,12). The purpose of the following paper is to examine the detriments of chemotherapy and radiation therapy on health status, and 2) to assess the role of nutrition in mitigating the debilitating symptoms of advanced-staged cancers.
Surgery, radiation therapy, and chemotherapy can alter a patientís nutritional needs and interfere with the physiological processes of digestion and absorption (1-5,7,10). Chemotherapeutic agents, for example, exert destructive, nonspecific effects on both normal and cancerous cells. Consequently, patients often report symptoms of nausea, vomiting, diarrhea, pain, and anorexia in response to the toxicity of this pharmacological intervention (12). Prior to any clinical intervention, it is important to consider the increased incidence of unintentional weight loss, lean muscle mass loss, weight gain, or other nutritional alterations caused by the toxicity of the treatment.
Stable body composition indicates energy balance during which caloric intake is equal to total energy expenditure (10, 12). While energy intake is characterized by the composition of dietary macronutrients, total energy expenditure is the combination of resting metabolic rate (RMR), thermic effect of food (TEF) and nonexercise activity thermogenesis (NEAT) (5). Increased total energy expenditure in relation to decreased energy intake creates a negative energy imbalance, and thus, net weight loss; whereas, increased energy intake in relation to decreased total energy expenditure creates a positive energy imbalance, and ultimately, net weight gain.
Weight loss and malnutrition are major concerns for patients with advanced-stage diagnoses or tumors located along the gastrointestinal tract. Bosaeous et al. (2002) observed average weight loss in adult cancer patients (7.1%) and a clinically significant loss in more than 38% of the participants (3). In addition, many pancreatic cancer patients reported extreme weight loss with cancer cachexia present in approximately 80% of patients. This weight loss is attributed to diminished caloric intake in response to adverse side effects associated with cancer treatment (3). Side effects include pain or nausea during eating, early satiety, anxiety or depression. Malnutrition is also prevalent in the cancer patient population, ranging from approximately 40 to 80%, and is associated with reductions in survival, quality of life, tolerance to treatment, and increased mortality (12). Generally, a negative energy imbalance stimulates metabolic adaptations that lead to decreased energy expenditure. However, continued body mass reduction, in response to cancer treatment, can shift an individualís RMR from a hypometabolic state to a hypometabolic state, and consequently, lead to severe malnutrition.
Cachexia is a severe form of malnutrition that leads to a chronic, negative energy imbalance in response to reduced food intake and metabolic changes (2,3-6). The catabolic effects of cachexia result in muscle and lipid wasting, an abnormal response to the presence of tumors and tumor factors, and overall reduced functional capacity in the patient. For individuals at risk for extreme weight loss, patients and physicians should focus on increasing food intake and reducing total energy balance (13). To ensure patients obtain sufficient nutrient intake to combat disease, the World Cancer Research Fund/American institute of Cancer (2003) recommends a caloric requirements of 30-35 kcal/kg and 35-40 kcal/kg for individuals suffering from a slightly hypermetabolic state and individuals with advanced-staged cancer and malnutrition, respectively (13).
Making informed dietary choices that provide adequate amounts of carbohydrates, protein, and fat can ensure variety and nutrient adequacy in patients suffering from malnutrition. The American Institute of Cancer recommends a minimum of 5 portions (400mg) of fruit and no starchy vegetables and limited consumption of foods that are highly refined, processed, and very energy dense such as red meat and beverages high in sugar content (13). Patients that experience adverse side effects of treatment, such as reduced appetite or early satiety, are encouraged to eat smaller meals more frequently throughout the day to increase food intake. It is important to note, however, it is recommended that individuals suffering from extreme malnutrition and muscle wasting consume nutrient dense drinks that increase caloric intake when regular feeding habits cannot be sustained (5,13). Additionally, for individuals with poor appetite, weight loss, or both, consumption of foods rich in omega-3 fatty acids (such as walnuts) is highly encouraged due to an association between reduced risk of cardiovascular disease and reduced mortality rate. Unlike saturated and trans dietary fats, foods rich in omega-3 fatty acids are related to reduced risks of heart disease and various cancers (1,13).
Healthful food choices for cancer patients are very nutrient dense and contain high amounts of phytochemicals and dietary fiber (8). Whole grains, vegetables, legumes, and fruit should constitute the majority of the carbohydrate sources in the diet because consumption is positively associated with a lower incidence of colorectal cancer, lung cancer, and various cancers of the gastrointestinal tract. Vegetables are especially encouraged because they are more nutrient dense that most fruits. Micronutrients and vitamins within these whole-food sources act synergistically to reduce cancer risk and reoccurrence (8,12,13). A variety of colors ensure that diets include a variety of different phytochemicals, however, it is important to note that raw vegetables may increase the risk for infection in some patients whose immune responses have been compromised from chemotherapy. Steaming or cooking vegetables is an easy alternative to raw vegetable consumption because it increases absorption of many nutrients and phytochemicals and decreases the risk for infection (13).
Although there is a well-documented, decreased incidence of cancer among individuals who eat diets rich in fruits and vegetables, most dietary supplements do not elicit the same beneficial effects (8-10). The indirect therapeutic effect of radiation occurs indirectly via the ionization of water molecules into reactive oxygen species within the cytosol. These free radicals bind to nuclear DNA and can potentially elicit apoptosis. Antioxidants, however, can counteract free radicals and prevent them from creating tissue, and thus, organ damage. Although antioxidants are beneficial in reducing the oxidative DNA modification, the same mechanism can be used to protect cancerous tissue from cell death and elimination. For example, use of folic acid supplements is contraindicative to the actions of a chemotherapy agent, methotrexate, which functions by inhibiting folic acid metabolism (8). Additionally, vitamin supplements that contain high levels of Vitamin E and Vitamin C is strongly contraindicated because of high antioxidant concentrations that can potentially repair cellular oxidative damage of cancer cells during radiation or chemotherapy. Additionally, Satia et al. (2009) demonstrated that long term use of individual beta carotene, retinol, and lutein supplements were associated with increased incidences of lung cancer (10). Although vegetables and fruits are frequently associated with reduced risk of lung cancer, the Beta Carotene and Retinal Efficacy Trial (CARET) discovered significantly higher incidence of lung cancer in the experimental group taking 25,000 IU of retinyl palmitate and 30 mg of beta carotene (9). Due to the controversial research, cancer patients are advised to avoid antioxidant supplementation while undergoing chemotherapy or radiation therapy.Given the unfavorable prognosis and outcome associated with severe malnutrition, cancer patients are encouraged to adhere to a low fat, nutrient dense nutritional program to augment the anticancer effects of treatment and minimize its adverse side effects. It is plausible that nutritional guidance my reduce the risk of developing second cancers by physiological mechanisms such as reduced fat and improved antioxidant defenses from consumption of a whole food, plant-based diet.
Written by Rachel Safran, Occidental College, Los Angeles, CA.
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