Menstrual Iron Loss Drives Highest Needs in Young Women

Steps:

• Identify that iron requirements vary by age, sex, and life stage due to blood loss and physiological demands.
• Recognize young women (15-49 years) have the highest Recommended Dietary Allowance (RDA) for iron at 18 mg/day.
• Link this to menstruation, which causes average monthly blood loss of 30-40 mL, containing 0.5-1 mg iron.
• Compare to other groups: men and postmenopausal women need only 8 mg/day without menstrual losses.

Why B is correct:

• Menstruation leads to iron depletion via hemoglobin loss in blood; RDA compensates to prevent anemia, per WHO guidelines on iron deficiency.

Why the others are wrong:

• A: Iron stores build for pregnancy, but peak RDA reflects ongoing menstrual losses, not future storage alone.
• C: Iron primarily supports oxygen transport in hemoglobin, not direct protein synthesis.
• D: Milk production increases iron needs during lactation, but a non-lactating 20-year-old's requirement stems from menstruation.

Final answer: B