In January 1998, the Food and Drug Administration (FDA) recommended that cereal grain products sold in the USA should be fortified with 140 micrograms of folic acid per serving, because it has been shown that increasing the dietary intake of this vitamin reduces the frequency of some birth defects. Folic acid is also known to reduce the blood levels of homocysteine, a naturally occurring chemical, which in high concentrations can damage the arteries and lead to heart disease.

In this study three groups of patients with known coronary heart disease were fed breakfast cereals fortified with three different amounts of folic acid, and a fourth group ate cereal without any added. The blood levels of folic acid rose in all three groups who were fed the supplements, and the two larger doses of folic acid (500 and 665 micrograms of folic acid per day) also lowered homocysteine. The lower dose (127 micrograms, which was very close to the FDA-recommended dose) did not affect homocysteine. The authors concluded that eating a single daily serving of cereal fortified with folic acid at the recommended FDA dose would not reduce elevated levels of homocysteine, but that taking additional amounts of folic acid would do so.

Doctor's comments

An elevated homocysteine level is associated with an increased risk of coronary heart disease and stroke and is found in about one-third of patients who have these conditions. There is evidence that homocysteine can damage the delicate inner lining of arteries (the endothelium) and also cause oxidation of LDL cholesterol to a more virulent form, both of which processes can accelerate the formation of atherosclerotic plaque. Homocysteine is a naturally occurring amino-acid in the body, which some people are slow to metabolize, so that the blood levels build up. Folic acid helps to get rid of homocysteine, as do two other vitamins (B6 and B12). While the damage associated with high homocysteine levels is well established, direct proof that lowering the homocysteine can reduce the damage is so far lacking. The message from this study is that if you have high homocysteine levels, eating cereal five times a week that is fortified with folic acid will not be enough to lower your homocysteine - you will have to take additional folic acid supplements.

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