Cancer treatment affects appetite, metabolism, and body weight. During treatment because of chemotherapy or other radiations, cancer patients undergo some side effects like-

• Diarrhea
• Constipation
• Fatigue
• Loss of taste
• Vomiting
• Nausea

Under the doctor’s regular supervision and consultation, a cancer patient must eat an adequate and balanced diet.

Should Eat: 

• Plenty of water (at least 2 liters daily) to avoid dehydration. Because a cancer patient is already undergoing some side effects from cancer itself or cancer treatment and experiencing water loss (i.e., from diarrhea, nausea, vomiting, fever, medicines).  
• Fiber-rich foods like whole grains (i.e., pasta, wheat bread, oats), legumes (i.e., lentils, soybeans, chickpeas), fruits (i.e., apples, oranges, pears, berries), vegetables (e.g., green peas, carrots, broccoli), nuts (i.e., almonds, peanuts, pecans) to avoid constipation. 
• For calcium and iron: All green leafy vegetables, and for lowering blood sugar levels: Bitter gourd. 
• Yogurt so that beneficial bacteria can help regulate a cancer patient's regular bowel movement.
• Soups prepared with legumes and vegetables.
• Plenty of fresh salads are prepared with lettuce, tomato, cucumber, broccoli, green peas, pomegranate, pear, and so on. Fresh salad is a great source of nutrients such as folic acid, vitamin A, vitamin C, protein, calcium, and other antioxidants. These strengthen the body’s immune system and also help to fight against cancerous cells.

Shouldn't Eat:

• Sugary and carbonated drinks should be avoided. These cause bloating when someone is fasting for a long time. This may worsen for a cancer patient if pain accompanies it. 
• Saturated fats and excessive salt consumption may worsen cancer conditions. It is better to try baking, steaming, and grilling instead of frying. 
• Overly fatty and creamy soups should be taken.
• Tea and coffee consumption increases fluid loss and thirst.