What helps the body grow and repair worn or damaged parts?

Not all "worn out" and "damaged parts can be repaired. But the building blocks to do so, if it is possible, come from good diet. What helps you grow can help you re-grow so protein, fats, minerals, vitamins, carbohydrate and water that you intake every day. Good rest helps greatly as does a positive frame of mind (poor mental health has been shown to increase recovery times from illness).