Only through a controlled trial can scientists determine the real effects of any treatment. In addition to the lack of a controlled clinical trial, reasons that make scientists reluctant to endorse vitamin therapy for everyone the possible variation in individual responses to consumption of these vitamins. In some, intake of folic acid without vitamin B-12 may mask the presence of pernicious anemia. For these reasons, the American Heart Association advises that most individuals meet recommended dietary intakes for these vitamins by eating a healthy balanced diet and use supplements only when the diet is not adequate to achieve these intakes. For folic acid, the recommended daily value is 400 micrograms.
Good sources are citrus fruits, tomatoes, vegetables and grain products.
Beginning in January 1998 grain and cereal products will be fortified with folic acid to add an estimated 100 micrograms per day to the average diet. The richest sources of B-6 are chicken, fish, liver, pork, kidney and eggs. Other good sources are unmilled rice, soybeans, oats, and whole-wheat products. The richest sources of B-12 are animal products. The recent findings indicating a graded association of blood plasma homocysteine levels with cardiovascular risk suggest that the availability of a laboratory test to determine the level of homocysteine in a blood sample can improve the assessment of risk, particularly in people with a personal or family history of cardiovascular disease.