Is best"cure"for disease to avoid illness in the first place with an intake of good diet?

Yes. Hippocrates stated over 1000 years ago"let food be your medicine".Outside of trauma, infectious or genetic related illnesses, the vast majority of diseases, esp the chronic ones, are related to poor lifestyle and diet.
Nutrient dense foods. Eat foods that are nutrient dense (like meat, fish, poultry, eggs, cheese, low starch vegatables and water) avoid foods that are not nutrient dense (like starches and sugars, including fruit) avoid sugars, fried foods, vegatable oils like canola & soy, meats that are cured wth nitrates & nitrites, aspartame, splenda, partially hydrogenated vegetable oils, maragarine, soy based products, sweetened.