Folic Acid Supplementation and Cardiovascular Disease

Cardiovascular disease involves any disorder of the heart and blood vessels that comprise the cardiovascular system. Coronary heart disease occurs when blood vessels that supply the heart become clogged or blocked, increasing the risk of a heart attack. Vascular damage can also occur to blood vessels supplying the brain, causing a stroke.

Cardiovascular disease is the most common cause of death in industrialized countries and is on the rise in developing countries. The National Heart, Lung, and Blood Institute of the National Institutes of Health has identified many risk factors for cardiovascular disease, including an elevated LDL cholesterol level, high blood pressure, a low HDL cholesterol level, obesity, and diabetes. In recent years, researchers have identified another risk factor for cardiovascular disease, an elevated homocysteine level. Homocysteine is an amino acid normally found in blood, but elevated levels have been linked with coronary heart disease and stroke. Elevated homocysteine levels may impair endothelial vasomotor function, which determines how easily blood flows through blood vessels. High levels of homocysteine also may damage coronary arteries and make it easier for blood cells called platelets to clump together and form a clot, which may lead to a heart attack.

A deficiency of folate, vitamin B12, or vitamin B6 may increase blood levels of homocysteine, and folate supplementation has been shown to decrease homocysteine levels and to improve endothelial function. At least one study has linked low dietary folate intake with an increased risk of coronary events. The folic acid fortification program in the United States has decreased the prevalence of low levels of folate and high levels of homocysteine in the blood in middle-aged and older adults. Daily consumption of folic acid–fortified breakfast cereal and the use of folic acid supplements have been shown to be an effective strategy for reducing homocysteine concentrations.

Evidence supports a role for supplemental folic acid for lowering homocysteine levels; however, this does not mean that folic acid supplements will decrease the risk of cardiovascular disease. Clinical intervention trials are underway to determine whether supplementation with folic acid, vitamin B12, and vitamin B6 can lower risk of coronary heart disease.

It is premature to recommend folic acid supplementation for the prevention of heart disease until results of ongoing randomized, controlled clinical trials positively link increased folic acid intake with decreased homocysteine levels AND decreased risk of cardiovascular disease.