There are many reasons why women planning to have a baby are advised to take folic acid supplements, rather than just increase their dietary intake of food containing folic acid. These include:
Diet
Cooking and processing
Body's absorption
Fortifying foods
Diet.While it is possible for a woman to have adequate intakes of folic acid through her diet, not everyone eats enough foods rich in folic acid on a consistent, daily basis (particularly green, leafy vegetables, which are the richest source). However, women who are
vegetarian or vegan usually eat an adequate amount of folic acid in their diet. If a woman drinks alcohol, this interferes with her body's absorption of folic acid. You can read more in
alcohol.
Cooking and processing. Heat used in cooking and processing can destroy some of the folic acid naturally available in foods. This will vary depending on the food, and the way it is cooked. In some cases, the loss of folic acid can be as high as up to 50%. For example, folate is present in flour, but may be depleted after being cooked as bread, or after pasta is boiled.
Body's absorption. The body does not readily absorb all the folic acid available in natural food sources, when compared to vitamin supplement tablets. It is thought that folic acid taken as supplements is absorbed at 100% of what is eaten, while foods containing natural amounts of folic acid are only absorbed at about 50 to 60%.
Fortifying foods. Because up to 50% of pregnancies are unplanned, many women will not benefit from taking folic acid supplements. This has brought about a dilemma for health care professionals and governments, aiming to address this issue. One possible suggestion is that
ALL women who are sexually active, and of childbearing age (15 to 45 years), should routinely supplement with folic acid 'just in case'. However, this is obviously not a realistic solution.
An alternative solution is to 'fortify' foods.