Bromelain, an enzyme found in pineapples can shed the lining of the uterus walls, which induces the menstrual cycle. This enzyme also relaxes the muscles, and having pineapples during periods can help in calming down menstrual cramps. Pineapple also has a good amount of manganese content, which helps in increasing blood flow during periods. Sipping down pineapple juice throughout your period days can help one survive them a bit better.