There is no one food that can give you all nutrients that your body needs. Thus, 3 important keys to healthy eating are: Variety, Balance and Moderation.
Eat a variety of foods from each food group to obtain all the nutrients required by the body. Your daily food selection should consist of carbohydrate, vegetables & fruits, protein and fat. And do not forget to drink at least 8 glasses of water daily.
Practise balance in your daily food selection. Too much or too little are both bad for your diet. Use the food guide pyramid to help you understand how much you need to consume from each group.
There is no good or bad food! The key is eating in moderate portions. Eating the amounts of foods according to your needs allow you to enjoy your favourite food.