This means no fatty, greasy, heavily processed foods. Try to eat as much plant based foods as you can in your diet ie: fruit, vegetables, nuts, juices, natural plant products rather than processed ones, etc.
Food is a fuel for body. If fuel is natural our body organs always remain energetic and work well. It depends on us only to provide our body with the right fuel.
Nature is best and most effective healer. Nature has provided us with its best doctors without any cost. No consultation is required from them, just benefits and healings. Why should people turn to medical doctors when they can seek solutions to their health problems?