Shri Sai Nathaya Namah
"The God is beyond consciousness and unconsciousness. Chanting the name of Baba will always liberate you."
"If unknowingly you step on the fire, it will never happen that it will not burn you. Similarly, chanting God's name with any intention will free you from your sins."
Thus, it purifies your body, your senses and makes them more alert. Also, it keeps diseases away from you. After starting the Japa you will definitely feel the difference. You may do it as an experiment for some days. I am of the opinion that you should not believe it unless you experience it.
How to do a Japa (how to chant a mantra)?
You may chant the mantra at any time and all the time while eating, working, walking, travelling, inside the house, outside the house,while using toilet. You should chant the mantra to yourself and think about it. It is not necessary to have faith in the mantra. This is a science and you will get the results after the prescribed number is complete.
Thus, there is no restriction of time, cleanliness etc. in regard to mantra chanting. Ladies are also allowed to chant at any time. Draupadi, who was having 'periods' at the time of her tragedy in the Mahabharata, was chanting "Krishna-Krishna". Thus, menses should not be treated as a bad or impure period for chanting as it is a natural phenomenon. Chanting the mantra is a Golden means to achieve moksha. For your own sadhana there are absolutely no restrictions.
You will definitely be benefited by the Japa (chanting). It may be stated here that this technique is beneficial to people irrespective of their religion. Muslims, Christians, Jews, Parsis, Buddhists etc. will be equally benefited by Hindu mantras as well as their own mantras. Likewise, Hindus will also benefit from their own mantras as well as those of other religions.
Shri Sai Nathaya Namah...................