The arteries of animals injected with homocysteine showed changes that may lay the groundwork for the buildup of atherosclerotic plaques. There is also evidence suggesting that homocysteine stimulates proliferation of blood vessel cells that help form plaques and that it encourages clotting. Folic acid is thought to protect against heart disease because it breaks down homocysteine and allows it to be cleared from the blood stream. The University of Washington review referred to 11 studies of folic acid's effects on homocysteine levels. Among these was the Tufts research, which showed for the first time that inadequate intake of the vitamin is the main determinant of the homocysteine-related increase in the risk of carotid blockage.
New studies suggesting a protective role for folic acid continue to appear.
There is even evidence that high risk patients have the most to gain. In 1995, a University of Utah study compared over 160 men and women who had evidence of early familial coronary artery disease with a comparable group who did not have the disease. Growing evidence that folic acid may prevent heart attacks has led to recommendations that people consume 400 mcg. This amount has been shown to maintain low homocysteine levels and also to prevent neural tube defects in the unborn. One way to insure adequate folic acid intake is to eat five daily servings of fruits and vegetables.