Nutrition and Cancer: Challenges and Recommendations

A cancer diagnosis brings numerous challenges, including in daily life. One of the biggest difficulties is food intake, which can be affected by side effects such as loss of appetite, digestive issues, or impaired nutrient absorption. Estimates suggest that up to 50% of cancer patients in hospitals suffer from malnutrition.

The gut microbiome, which can promote nutrient absorption, strengthen the immune system, and reduce inflammation, has increasingly become a focus of oncological research. There is evidence that it may influence the response to cancer therapies.

Nutrition in Oncology

A balanced diet plays a crucial role, especially in cancer treatment, as it supports therapy, improves quality of life, and helps maintain physical and mental functions. The body needs sufficient nutrients and energy to sustain vital functions, strengthen the immune system, and effectively support healing processes.

Common Nutritional Issues in Cancer Patients

During the course of the disease, various challenges arise that often lead to reduced food intake and, consequently, weight loss, affecting both muscle and fat tissue. In many cases, this can result in severe malnutrition. Significant weight loss and underweight can impair the body’s ability to tolerate cancer treatment, weaken the immune system, and reduce physical strength.

The main causes of malnutrition include:

• Systemic inflammatory processes and metabolic changes (catabolic processes) that affect energy and nutrient balance.
• Gastrointestinal issues such as appetite loss, taste changes, nausea, diarrhea, constipation, or dry mouth, which can be caused by the tumor itself, surgeries, or cancer treatments.
• Psychological and social burdens such as depression, anxiety, stress, exhaustion, or chronic fatigue, which negatively impact eating habits.
• Pain that reduces appetite and makes eating difficult.
• Limited physical activity, leading to muscle loss and a sluggish metabolism.
• Impaired nutrient absorption, making it difficult for the body to take in essential vitamins and minerals.

Primary Nutritional Goals for Cancer Patients

Through targeted nutritional therapy, the following goals should be achieved:

• Maintaining body weight and muscle mass
• Supporting cancer therapy through appropriate nutrition
• Improving quality of life through a balanced diet

Nutritional Recommendations

Since metabolic changes make it harder for cancer patients to maintain their weight and muscle mass, the following strategies can help achieve nutritional goals despite individual challenges.

These recommendations are general and do not replace individual dietary counseling. If you have specific nutritional needs or ongoing issues, consulting a qualified nutrition expert is recommended.

1. Eat What You Enjoy

The most important point: choose nutritious foods and meals that you like and enjoy. Try not to overly restrict your diet. “Cancer diets” are not recommended.

2. Energy-Rich Foods

For cancer patients with a normal weight, the energy requirement is the same as that of healthy individuals:

• Mobile patients: 30 kcal/kg body weight per day
• Bedridden patients: 25 kcal/kg body weight per day

Since many patients eat less due to gastrointestinal issues, pain, or psychological stress, it may be helpful to increase energy intake with smaller, high-calorie meals.

Tips:

• Enrich meals with nuts, seeds, nut butters, avocado, olive oil, hard cheese, or olives.
• Choose easy-to-eat options like soups, smoothies, milkshakes, and juices.
• Divide meals into 5-6 smaller portions instead of 2-3 large ones.
• Snack on calorie-dense foods like peanut butter and banana on bread, cheese with grapes, nuts, Greek yogurt with berries and seeds.
• Meal prep: Prepare larger portions of your favorite meals in advance and store them in the fridge or freezer.
• Regular physical activity can help stimulate appetite.

3. Protein-Rich Diet

Due to inflammatory processes in the body caused by the disease, protein needs are higher:

• Recommended intake: 1.2–1.5 g of protein per kg of body weight per day
• For severe inflammation: Up to 2 g per kg of body weight per day

Tips for meeting protein needs:

• Include protein in every meal – sources: lean meat, fish, eggs, legumes (lentils, chickpeas, beans), soy products (tofu, tempeh).
• Protein-rich snacks – nuts, cottage cheese with steamed vegetables, boiled eggs with mustard, whole-grain bread with smoked tofu and hummus, chia pudding, roasted chickpeas.
• Protein supplements – protein powders or shakes can help. Look for natural ingredients and avoid artificial sweeteners like aspartame, acesulfame K, sucralose, and saccharin.

4. Food Safety

Cancer therapy weakens the immune system, making patients more susceptible to foodborne illnesses. It’s essential to follow food safety measures:

• Hygiene: Wash hands before and after handling food.
• Avoid raw foods: No raw or undercooked meats, fish (e.g., sushi), eggs, or unwashed fruits and vegetables.
• Prevent cross-contamination: Keep raw and cooked foods separate.
• Maintain cold chain: Store perishable foods properly.
• Check expiration dates and avoid expired products.
• Choose pasteurized products for milk, juice, and eggs.

The Gut Microbiome and Cancer Treatmen

The gut is home to trillions of microorganisms, mainly bacteria, known as the gut microbiome. This community not only influences digestion but also affects the immune system and inflammation levels.

Studies suggest that the gut microbiome plays a crucial role in cancer development and treatment. An imbalanced microbiome can contribute to cancer by causing DNA damage, inflammation, and a weakened gut barrier. Conversely, a healthy microbiome can strengthen the immune system and improve the effectiveness of cancer treatments such as immunotherapy, chemotherapy, and radiation. This is especially relevant in colorectal cancer.

Nutrition and the Microbiome – Recommendations

To maintain or improve gut health, consider the following tips:

1. Increase Fiber Intake

Fiber improves stool consistency, feeds beneficial gut bacteria, and can help with both diarrhea and constipation. High-fiber foods: Vegetables, fruits, whole grains (whole wheat pasta, whole-grain bread, oats, quinoa, brown rice), nuts, seeds, legumes.

2. Eat Fermented Foods

Fermented foods contain probiotic, live bacteria that can positively influence the gut microbiome and improve nutrient absorption. Examples: Kefir, yogurt, sauerkraut, kimchi, miso, apple cider vinegar, fermented bread drinks, tempeh.

3. Increase Dietary Variety

A diverse microbiome is a healthy microbiome. Try to eat a wide range of foods: Rotate your bread, cheese, and vegetables regularly. Try foods from different cuisines to increase variety naturally. Experiment with spices to enhance flavor and digestion. Avoid restrictive diets that eliminate too many food groups.

4. Stay Hydrated

Your digestive system needs sufficient fluids to function properly. Drink 1.5–3L of water or unsweetened tea per day. Hydrating foods: Cucumbers, melons, tomatoes, zucchini, oranges, soups.

5. Reduce Artificial Sweeteners and Processed Foods

Studies suggest that artificial sweeteners, sugar substitutes, and preservatives can negatively impact the gut microbiome. Common in: diet products, protein bars, candies, packaged baked goods, ready meals, sauces, and light drinks.

Gut Microbiome Test

The myBioma Gut Microbiome Test uses advanced DNA analysis to provide scientific insights into gut health. It assesses microbial diversity, immune system interactions, and inflammation levels. After testing, you receive a personalized report with dietary and lifestyle recommendations.

More info: myBioma Gut Test

Final Thoughts

A nutrient-rich, balanced diet can prevent malnutrition, support cancer therapy, and improve healing. A gut-friendly diet, adequate hydration, and physical activity may enhance treatment outcomes and reduce complications.