Final answer:
The daily recommended dose of folic acid is 400 mcg because it meets the daily requirement for adult humans and helps prevent birth defects in women who might become pregnant.
Step-by-step explanation:
The daily recommended dose of folic acid is 400 mcg. This recommendation is based on the daily requirement of folic acid, which is about 300-400 µg for adult humans. Folic acid is important for women who might become pregnant because it helps prevent certain birth defects. Therefore, the Food and Nutrition Board of the Institute of Medicine recommends that all women who might become pregnant consume at least 400 µg/day of folate from supplements or fortified foods.