I have heard that tying hair in braids rather then in ponytail keeps hair healthy and reduces hair loss.is it true?

Braids: Depends. Tight braids are bad because all the strain goes on the few hairs at the front of the braid and this causes traction alopecia. (which is baldness where the hair root gets pulled out) tight small curlers will have a similar effect.

Not really: Many women get worse traction alopecia from braids. Avoid any style that pulls too much on the hair & scalp. Braids can be helpful for some people when done properly, but it depends on the cause of your hair loss.