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Folic acid requirements defined

CHICHESTER, UNITED KINGDOM. The U.S. government has mandated the fortification of all cereal grains with 0.14 mg (140 micrograms) of folic acid per 100 grams of grain. The aim of this measure is to reduce the risk of women giving birth to babies with neural tube defects (spina bifida). The fortification would theoretically supplement a person's diet with about 0.1 mg (100 micrograms) of folic acid per day.

Folic acid supplementation has also been found useful in lowering homocysteine levels and thereby reducing the incidence and mortality from ischemic heart disease (angina and heart attack). A dosage of 1 mg (1000 micrograms) per day has been found to result in about a 25 per cent decrease in homocysteine concentration; this is estimated to correspond to a 15 per cent reduction in mortality from ischemic heart disease. Higher dosages (up to 5 mg/day) have not been found to have any greater effect than the 1 mg/day dose. British researchers have now addressed the question of how much folic acid (in supplement form) is needed to achieve the maximum homocysteine reduction. Their clinical trial involved 151 patients with ischemic heart disease who were randomized to receive 0.2 mg, 0.4 mg, 0.6 mg, 0.8 mg, 1 mg or a placebo daily for a three-month period. The participants' blood levels of folate and homocysteine were measured before the start of supplementation, at the end of the supplementation period, and three months later. The maximum median reduction in homocysteine levels (23 per cent) was observed at a supplementation level of 0.8 mg/day.

The currently recommended daily intake of 200-400 micrograms/day achieved only a 10 per cent reduction in homocysteine levels. Homocysteine levels returned to their pre-trial levels after three months without supplementation indicating that folic acid supplementation must be continuous and indefinite if homocysteine levels are to be kept in check. The researchers conclude "It would be reasonable for clinicians to consider advising patients with ischemic heart disease to take 0.8 mg (800 micrograms) of folic acid each day."
Wald, David S., et al. Randomized trial of folic acid supplementation and serum homocysteine levels. Archives of Internal Medicine, Vol. 161, March 12, 2001

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