Ladies, unless you are menorrhagic (bleeding more than 120 milliliters each cycle) your period is not doing you wrong. If you have iron-deficiency anemia and your doctor is insisting it's because you slough off your endometrium from time to time without doing a single test to confirm it, you may want to insist on an endoscopy. It could save your life.
Apparently the common wisdom that menstruation causes anemia is common nonsense. Kate Clancy dispels this myth in the link above. Shockingly in one study 86% of women diagnosed with anemia due to menstruation actually had a gastrointestinal bleed, the first line of investigation for men.