Kristina Petkova, Marchela Koleva, Mirela Dacheva, Bozhidar Murdzhev, Nikolay Tsigarovski, Samuil Katov, Adriana Andreeva, Petya Balikova, Yordan Hristov
Medical Oncology Department, Sv. Sofia Multiprofile Hospital for Active Treatment – Sofia
SPECIALIZED JOURNAL OF SCIENCE AND INNOVATIONS IN MEDICINE
MedicPlus
YEAR VI, June 2024
Abstract: Healthy eating habits in combination with a balanced intake of varied and healthy nutrients, absence of unhealthy habits and good physical activity are key factors both for reducing cancer risk and improving the quality of life during anti-tumor treatment. Timely diagnosis and correction of malnutrition in cancer patients is essential for improvement of their general condition and nutritional status. There are recommendations for macronutrient intake in a specific ratio tailored to the respective disease and a patient’s calorie demands.
Goals of a balanced diet
A balanced diet related to getting the necessary nutrients and calories is usually not a problem in healthy individuals. Most dietary standards emphasize the importance of consuming a variety of vegetables, fruits and whole grains, on the one hand, and reducing the use of red meat, especially processed or high-fat meats, trans fats, sugar, alcohol and salt to maintain a healthy weight. These things alone can be difficult to reach in the treatment of cancer patients, particularly, when patients experience treatment-related adverse events or are prevented from food intake due to a mechanical barrier resulting from the disease (head and neck, esophageal, thyroid and other tumors).
The nutritional requirements of cancer patients may vary according to a patient’s individual demands. A balanced diet is necessary in cancer patients so that they may:
• Feel better;
• Maintain their strength and vitality;
• Maintain a healthy weight and nutrient stores in the body;
• Improve tolerance to treatment-related adverse effects;
• Boost immunity and reduce the risk of infection;
• Contribute to faster and longer lasting recovery of the body after administration of antitumor therapy.
Malnutrition – causes and classification
Tumors may have systemic or local effects that affect nutritional status, including hypermetabolism, malabsorption, dysmotility and obstruction. Malnutrition and loss of muscle mass are common in cancer patients and have a negative effect on clinical outcome.
Catabolic changes in cancer patients are often associated with insufficient and unbalanced nutritional intake, resulting in weight loss. For practical reasons, inadequacy of food intake is considered to be present if a patient cannot eat for more than a week or if the estimated energy intake is <60% of what is required for more than 1 to 2 weeks.(1, 2) The causes of impaired intake are complex and multifactorial. A reduced food intake is caused by primary anorexia (i.e., at central nervous system level) and may be combined with secondary impairments of oral intake, some of which are reversible with appropriate medical treatment. The main secondary causes of reduced intake include oral ulceration, xerostomia, poor dentition, intestinal obstruction, malabsorption, constipation, diarrhea, nausea, vomiting, decreased intestinal motility, hemosensory change, uncontrolled pain and side effects of drugs.
A recent analysis of an international sample of over 11 thousand advanced cancer patients provided a framework for assessing the depletion of body reserves.(3) When body mass index (BMI) and weight loss are entered into a multivariate analysis accounting for age, sex, tumor site, stage and performance status a classification system based on combinations of BMI and weight loss can be developed differentiating groups of different median survival (grade 0 = longest survival, grade 4 = shortest survival).
Nutritional status may also be compromised in direct response to tumor-induced changes in metabolism (i.e., cachexia). Tumor-induced weight loss is common in patients with solid lung, pancreatic or upper gastrointestinal tumors and less common in patients with breast or lower GIT cancer.
Cachexia is more common in a more advanced disease. It is defined as a multifactorial syndrome caused by ongoing loss of skeletal muscle mass that cannot be entirely reversed with conventional nutritional support and leads to progressive functional damage.
There are three stages in the development of cachexia that correspond to the following diagnostic criteria:
• Precachexia: early (clinical and metabolic) signs that precede significant weight loss;
• Cachexia: presence of significant weight loss or sarcopenia in the absence of fasting:
◦ Weight loss >5% in the last 6 months,
◦ Body mass index <20 kg/m2 and weight loss rate >2%,
◦ Sarcopenia and any weight loss rate >2%;
• Refractory cachexia: cachexia that is clinically refractory, usually associated with advanced cancer or rapid progression of a disease that is not responsive to treatment.
All these adverse effects of cancer could be prevented or at least minimized by creating eating habits to accompany and be part of patients’ lives.
A healthy diet involves consumption of a wide variety of meals that provide the body with all nutrients it needs to fight cancer. Proteins, lipids, carbohydrates, water, vitamins and minerals are among these nutrients.
Guidelines for a balanced diet in the course of cancer development and treatment
Energy requirements. If not individually measured, total energy expenditure should be assumed to be similar to healthy individuals and usually ranges between 25 to 30 kcal/kg/day. There is no evidence that adequate nutritional support increases tumor growth in humans.(4) To estimate total energy expenditure (TEE) in cancer patients, it is necessary to consider resting energy expenditure (REE) and energy expenditure related to physical activity. While REE is elevated in many cancer patients, when TEE is taken into account, this value is lower in advanced cancer patients compared to estimated values for healthy individuals (5, 6); the main reason appears to be reduction in daily physical activity.
In leukemia patients and weight-losing bedridden patients with gastrointestinal tumors TEE is about 24 and 28 kcal/kg/day, respectively.(7, 8) TEE is overestimated in obese patients and underestimated in severely malnourished patients.
To preserve a patient’s muscle mass, protein intake should be at least 1 to 1.5 g/kg/day or the protein ratio should be increased to 20 to 30% of total energy intake. The recommended proportion of carbohydrate is 40 to 50% of total energy intake and the recommended fat proportion is 25 to 35%.
Daily protein intake: Most healthy people can easily get enough protein in their diet, but surgery and cancer treatment can increase the body’s protein demands and make the process of getting it more difficult. Protein intake is recommended to be above 1 g/kg/day and, if possible, up to 1.5 g/kg/day, especially if systemic inflammation is also present.(9-12) Older age, lack of physical activity and systemic inflammation are known to induce anabolic resistance, i.e. reduced sensitivity of protein synthesis to anabolic stimuli.(13) Recommendations in older, chronically ill people are for increased protein intake of 1.2 to 1.5 g/kg/day.(14, 15) The dose of amino acids capable of maintaining a positive protein balance in cancer patients may be close to 2 g/kg/day. This is in agreement with the recent study by Winter et al. (16) who showed that moderately cachectic lung cancer patients had significant insulin resistance, including impaired glucose utilization and whole-body protein anabolism, but that the normal anabolic protein response could be restored by increased protein consumption (2 g/kg/day).
Protein intake should be tailored to renal function as excessive protein intake in patients with kidney disease may further damage the kidneys causing hyperfiltration. In patients with normal renal function protein intake at doses up to and above 2 g/kg/day is safe.(17) In patients with acute or chronic kidney disease protein supply should not exceed 1.0 or 1.2 g/kg/day, respectively.(18)
Many of the dietary strategies recommended by NCI include ways to increase protein, such as consuming protein foods first or adding additional protein to the diet (milk in hot cereal, beans in salad). Consuming foods high in protein and calories (yogurt, eggs, beans and meat) is recommended. If protein powder is consumed in addition to the main meal, the dietary supplement should not contain high levels of lead, cadmium, arsenic and BPA. Supplements of neutral taste are recommended for a supplementary meal, as needed, at about 24 to 45 g a day divided into two or three daily intakes.
Daily carbohydrate intake: The recommended proportion of carbohydrates for cancer patients is 40 to 50% of total daily energy intake. There are many conflicting opinions regarding carbohydrate consumption in cancer. It is important to know that the main role of carbohydrates is to provide energy. Understanding the role of carbohydrates in a healthy diet is especially important for cancer patients, as cancer cells require a lot of energy. Effective management of the body’s preferred fuel intake, carbohydrates, will help control the fuel available to cancer cells as well. This is why a balanced intake of macronutrients is essential. Cancer cells need a lot of glucose for energy – more than normal cells. This is because cancer cells metabolize or break down sugars using a different and less effective process than normal, healthy cells. Cells normally use oxygen to burn glucose for energy. Since cancer cells grow in excess and become tightly packed, however, they often survive in а low-oxygen environment and have adapted to breaking down sugars in the absence of oxygen, a process called anaerobic metabolism. Unfortunately, anaerobic metabolism is much less effective than breaking down sugars aerobically or with oxygen. As a result, cancer cells may need up to 40 times more glucose than normal cells that function with sufficient oxygen levels to generate the same amount of energy. One of the goals of the eating habits in cancer patients is to limit the amount of excess glucose available to the growing cancer while providing enough energy for the brain and other vital functions. This can take place by maintaining steady blood sugar levels and avoiding glucose spikes providing additional sugars that can be used by the cancer. Here are some guidelines for blood sugar management:
Consumption of low glycemic index foods: The glycemic index (GI) is a measure of how quickly carbohydrates in food raise blood sugar levels. It is a 1 to 100 scale; 100 corresponds to pure glucose. Higher glycemic index foods are those that cause blood sugar levels to rise faster. Foods with a GI of 70 or more are considered high GI foods. Foods with a GI of 55 or less are considered low GI foods. Carbohydrates in low GI foods do not cause a big blood sugar spike.
Low glycemic index foods contain plant fiber, which improves insulin production and provides the body with vitamins and minerals. Such food products are: spinach, olives, cucumbers, brown and black rice, bulgur, quinoa, carrots, tomatoes, green beans, red lentils, mushrooms, zucchini, pumpkin seeds, asparagus, cabbage, sugar-free peanut butter, fat-free cottage cheese, dark chocolate (containing more than 70% cocoa), fresh fruits (blueberries, passion fruit, strawberries, pear, peach, plums, apple, quince, pomegranate), ginger, raw nuts. High glycemic index foods contain high absorption rate simple carbohydrates that cause a serum glucose spike. Such food products are: white bread, sweets, jams, stewed fruits, honey, mashed potatoes, granola, white rice, milk chocolate, melon, pumpkin, white and brown sugar. It is recommended to consume more cooked and steamed food and less fried, too salty and spicy food, as well as consume balanced food of a mixed nutritional composition. A meal rich in complex carbohydrates and fiber will slow the release of food from the stomach, thus slowing the release of glucose from the food. Consumption of sweet tasting foods and drinks on an empty stomach should be avoided. This includes sweet tasting fruit and vegetable juices, fruits, carbonated drinks, sweetened refined cereals, honey or any liquids sweetened with any form of sugar. It is recommended to consume whole unprocessed foods and avoid foods that are highly processed and/or refined, foods high in preservatives, added sugar and those made with refined flour.
Following the said rules provides cancer patients with a nutritious diet that ensures intake of slow-burn, unrefined, complex carbohydrates.
Daily fat intake
The recommended fat proportion is 25 to 35% (in some cases up to 40%) of total daily macronutrient intake. In weight-losing cancer patients and in the presence of insulin resistance it is recommended to increase the ratio of energy from fats to energy from carbohydrates. This is intended to increase the energy density of a diet and reduce the glycemic load. The optimal carbohydrate-to-fat ratio in the diet of cancer patients has not been estimated but can be derived from various pathophysiological mechanisms. In insulin resistance patients glucose uptake and oxidation by muscle cells is impaired, but fat utilization is normal or increased (19), which suggests a benefit of a higher fat-to-carbohydrate ratio. Most dietary recommendations for patients with malnutrition-related cancer are aimed at increasing the energy density of a diet. In 1971 Waterhouse and Kemperman demonstrated that fats were effectively mobilized and used as a fuel source in cancer patients.(20) Similarly, several authors later demonstrated very effective mobilization and oxidation of endogenous fat in postabsorptive state ranging from 0.7 to 1.9 g/kg/day (i.e., up to 60-80% REE) in both stable-weight and weight-losing cancer patients.(21-27) Compared to healthy subjects, the metabolic clearance of various lipid emulsions is increased in stable-weight patients and even more in weight-losing cancer patients.(27)
Fat emulsions supply essential fatty acids. However, the use of large amounts of standard soy-based lipid emulsion has been questioned because of its high N-6 PUFA content, which is associated with an increase in the production of proinflammatory eicosanoids.(28)
Omega-3 fatty acids (Ω-3 fatty acids) regulate production of prostaglandin E (PGE 2), inhibit activation of genes involved in the inflammatory process (29), and thus may act toward reduction of inflammatory activity in cancer patients. Long-chain Ω-3 fatty acids (1-2 g/day) reduce inflammatory reactions in cancer patients since they lead to reduction in inflammatory markers: IL6 (interleukin 6 and C-reactive protein) and resting energy expenditure.(30-34)
It is recommended:
• To obtain most fats from nutritional sources that are rich in polyunsaturated and monounsaturated fatty acids. Such sources of healthy fats are: most nuts, olive oil, peanut butter, rapeseed oil, avocado, tuna and salmon;
• To limit excessive and unbalanced consumption of saturated fatty acids. Sources of saturated fatty acids include certain oils (palm and coconut), high-fat meat and other animal products such as butter, cheese and milk, except skimmed milk;
• Not to consume trans-fatty acids.
The main source of industrially produced trans-fatty acids are partially hydrogenated vegetable oils, which are used in the food industry to produce a large number of foods. They are present in large amounts in crisps and snacks, biscuits, wafers, cakes and other savory and sweet baked goods, frozen potatoes, frozen dough and pizza;
• Advanced (stage IV) cancer patients undergoing chemotherapy, being at risk of weight loss or malnourished, are recommended to take a dietary supplement with long-chain Ω-3 fatty acids or fish oil to stabilize the body and improve appetite, optimize food intake and improve lean body mass and body weight.
Guidelines for micronutrient intake in the form of foods and supplements in cancer patients
The overall idea of the recommended dietary practice is to provide all patients with an adequate diet that includes all classes of micronutrients, especially those that are essential in a human diet.(36)
Approximately 50% of all cancer patients consume supplemental or alternative medicinal products.(36) Here are some recommendations related to the use of micronutrients included within nutrients or taken as dietary supplements:
• Vitamins and minerals are recommended to be supplied in amounts approximately equal to recommended daily intake;
• High doses of micronutrients should not be consumed in the absence of specific deficiencies;
• The use of single high doses of micronutrients should be avoided;(38)
• The use of dietary supplements including vitamins and minerals in physiological doses, i.e. amounts of nutrients that are approximately equal to the recommended daily allowance, is helpful (38, 39) and safe (40). This also applies to cancer patients during chemo- and radiation therapy;(40)
• Vitamins and micronutrients should usually be added to parenteral feeding because of lack of sufficient amounts of them unless contraindicated;
• Vitamin and micronutrient supplementation is mandatory after parenteral feeding for more than 1 week.
Physical activity guidelines for cancer patients
Cancer patients generally report low levels of physical activity. Inactivity, on the one hand, and cancer treatment, on the other hand (41, 42) have serious adverse effects on muscle mass (43, 44). Data from published randomized studies, summarized in several meta-analyses, provide relatively convincing evidence that physical activity is well tolerated and safe at various stages of cancer (45) and that patients with advanced diseases are able and willing to engage in physical activities (46, 47). However, most of the studies included patients with early breast cancer (during and after therapy) and a small proportion included patients with advanced cancer (e.g., advanced lung cancer, oncohematological diseases, etc.). Physical activity in cancer patients is associated with maintenance or significant improvement of aerobic capacity, muscle strength, health-related quality of life and self-esteem, and with reduction in fatigue and anxiety (48-50) (meta-analysis and RCT, high-quality evidence). Here are some key recommendations that can improve the quality of life of patients and make them feel better and more fulfilled:
• Daily walks in the fresh air are recommended. They reduce the risk of muscular atrophy due to inactivity;
• In addition to aerobic exercises, individualized resistance exercises are suggested to maintain muscle strength and muscle mass;
• Resistance exercises in turn improve upper and lower body muscle strength more than usual care and there are some indications that resistance exercises may be more effective in improving muscle strength than aerobic exercises (49) (RCT, high level of evidence);
• Such resistance exercises can use self-weight, such as abdominal crunches and plank position exercises, and may also include the use of bands of varying resistance, dumbbells (not very heavy) or a medicine ball;
• All exercises should be tailored to the individual abilities, comorbidities, general condition, type of cancer and surgical interventions performed;
• Physical exercises should strengthen body’s tone and improve a patient’s general condition without causing overexertion;
• Physical activity should be integrated into multimodal patient treatment programs;
• One of the easiest ways to reach healthy physical activity is to walk daily and use a pedometer to track results;
• About 90 minutes of walking a day is recommended, which equates to an average of 7 to 8 thousand steps. Walking, on the other hand, should not be high-intensity, should not cause fatigue or shortness of breath and should not raise the heart rate above 115 beats/min.
