FDA regulations for nutritional supplements differ in important ways from those for prescription or over-the-counter drugs. For one thing, pharmaceutical companies have to gather data showing that a new drug is safe and effective in order to get the FDA's approval to market the drug. Makers of dietary supplements don't have to show that sort of proof. Be sure to let your doctor know about any nutritional supplement you plan on taking so you can discuss whether it's right for you and the appropriate dose.
The U.S. Public Health Service recommends that all women of childbearing age consume 400 mcg of folic acid (a B vitamin) daily to reduce their risk of having a pregnancy affected with spina bifida or other neural-tube defects. Women who are actively trying to get pregnant should consume 600 mcg, and lactating women should consumer 500 mcg. Women of childbearing age should also take care to meet the daily requirements for calcium, fiber, iron, protein and vitamin D. Discuss supplements with a health care professional, however. Iron and vitamin D in particular can be dangerous in high amounts.
For instance, foods rich in vitamin E and beta-carotene are healthy and can help reduce cancer risk. However, the U.S. Preventive Services Task Force (USPSTF) and the American Academy of Family Physicians (AAFP) recommend against taking vitamin E or beta-carotene for the prevention of cardiovascular disease. People who smoke or are at risk for lung cancer also should avoid beta-carotene. It can increase their risk of lung cancer.