Presently general nutritional advice during chemotherapy is to eat a healthy balanced diet. Depending on which chemotherapy drug is being used individual appropriate nutritional advice might be given.
Chemotherapy may affect taste buds so dietary intake may change during the course. We recommend eating little and often as this can help reduce the feeling of sickness (if affected). There is information on the internet about what food types to eat to improve the immune system however I would recommend checking this with your healthcare team before making changes to your diet or taking any supplements.