You may feel as though your body needs extra energy to power uterus contractions and make up for blood loss, but you don't actually burn more calories than usual during your period. You do, however, burn more calories in the days leading up to your period because your metabolism increases with hormone changes.
Calories and Menstruation
Your metabolism is typically highest in the the two weeks leading up to your menstrual period. According to a paper presented at a meeting of the Society for the Study of Ingestive Behavior in 1999, women burn about 4 percent more calories during the luteal phase, or the second half of the cycle, due to increased progesterone levels. To maintain your weight during this time, you need to eat 4 percent more calories than during your period and in the two weeks following it.
Nutrition and Menstruation
You may not need extra calories during menstruation, but you do need adequate iron every day to make up for mineral loss from your period, according to the Centers for Disease Control and Prevention. The CDC recommends that women of childbearing years get 18 milligrams of iron per day, which is 10 milligrams more than the recommended daily allowance for men and postmenopausal women. Good iron sources include clams, white beans, pumpkin and spinach.