@Saniz,
Rickets is a disease that is caused due to lack of vitamin D.Even defciency of calcium also cause rickets.So to prevent rickets it is necessary to have a balanced diet that contain plenty of vitamin D and calcium.Sources of vitamin D are oily fish,egg,fortified breakfast cereal.Sources of calcium are diary products like milk,green vegetables,nuts etc.Sun is also a good source of vitamin D.So exposure to sun is also necessary.