I think I heard something about not doing this. It might’ve been water, rather than dry. And I think it was in Mindy Pelz’s more recent research into how the cycle’s affected - so you may need to watch a few of her vids before finding enough to go on. I know she’s no big guru on fasting, but she is at least doing to job of researching for women….even if it is all to sell her book. Good luck ;)
I’ve done it and been fine but I have a very regular, healthy period. I know many women who have irregular periods or are trying to get their periods back avoid during that time so you may just need to trial and error with your own body and see how it affects your period + period symptoms.
all i know is that in filonovs book at around day 7 or maybe 9 or something he says that your period may start independent of ur normal cycle timing due to an acidotic crisis and it’s not necessarily a bad thing or anything like that. so that kind of implies that despite having ur period in a time of fasting you should be fine