Japa is related to mind where contemplation of a deity is made. When contemplation is perfect, the deity descends on the body. How can we keep away the deity during those days? Can we stay away from God during certain number of days of a month? This perception is wrong and japa should not be discontinued during those days. If one is too religious, at the most they can dispense with nyāsa-s and mantra japa should never be stopped. One cannot ask God to stay away for a few days, who is always present within as the Self or Brahman.
As you know during those days bad blood will go out. Also extreme heat will be there in the body and hence they will be in need of proper rest. This is the reason why women were asked to stay away from all household works during those days.
Mantra recitation will generate heat in the body. If they recite mantras during those days body may not bear such high volume of heat (both mantra heat and period heat). That may lead to further physical problems.
Hence, it is better not to chant any mantras during that period but they can keep the thoughts of her upasana god (like reciting name of that god mentally) always.
From my professional standpoint i can't agree with your comment. by going through icse class 9th 10th biology book one can eradicate this wrong concept of bad blood and heat generation theory. please discuss with your nearest doctor. he will be able to make you understand why blood and mucus comes out. i do respect you for your knowledge in shastras but please do not explain everything with that. medical science is also started by bhagwan dhanwantari. don't ignore this.
as i have the impression that you have knowledge in tantra then you should have knowledge about golpuspa and kundapuspa. then also no comments against those days comes.
i hundred percent agree with ravi ji. those days are not bad days. if we think those days are bad days then we are telling that we also have originated from so called BAD
I have not said those days are bad days. Had I?
What I said is women require proper rest during those days. That is the reason why in ancient days and now also in some families, women will be out of regular household work. During that period in some families, women will not be touched by other people of that family. All this is for goodness of women only. Unfortunately, now a days that system is not following by many.
Next coming to BAD blood what I refer is not related to saastra or medical term. I have no knowledge of biology. Since my wordrobe in english is limited I could not describe that properly. Hope you understand it.
Next come to the rajaswal blood, I think you are aware of using that blood for some vaamachara purposes. That involves some abhichara prayoga with that blood. So in ancient times esp before Sri AadiSankaracharya, saadhakas were behind that blood. Ok, better to stop here on this point.