Many people misunderstand yoga to be a “cult of the body”. However, whilst yoga does not see the body as evil, neither does it intend to glorify your physical body. Even hatha yoga practices are designed to remind you that your body is the vehicle of your soul. It is an instrument that works best when you keep it clean and strong. If your body breaks down, you won’t reach your goal.
As the first of the niyamas, saucha represents purification on all levels. It includes the physical cleanliness of washing your body, maintaining an orderly home, eating healthy food and drinking clean water. It is also mental clarity, as well as speech that refrains from emotionally-charged obsessions and addictions. Saucha enables you to find balance in your life; it is a pre-condition for experiencing the fullness of yoga and attaining enlightenment.
I'm starting some discussions on this - please have a look at: http://my.yoga-vidya.org/forum/topics/spring-cleaning-saucha