B Vitamins Avert Stroke, Coronary Disease, Death

B Vitamins Avert Stroke, Coronary Disease, Death

LONDON, Ontario—Taking B vitamins may lower homocysteine levels, thereby reducing the risk of ischemic stroke, coronary disease and death, according to an efficacy analysis of the Vitamin Intervention for Stroke Prevention trial (VISP).

Published in Stroke (36, 11:2404-09, 2005) (http://stroke.ahajournals.org), the analysis outlined researchers’ criticisms of VISP: participants in VISP may have been administered folate-fortified grain products, the low-dose arm of the study may have been given the recommended daily intake for B12, low-B12 patients in both study arms may have been treated with parenteral B12, test subjects with malabsorption may have been administered an excessively low dose of B12, study participants may have been taking vitamins outside of the study, and patients with significant renal impairment may have failed to respond to vitamin therapy.

In the efficacy analysis of VISP, researchers excluded patients with very low and very high B12 levels at baseline (less than 250 pmol/L and greater than 637 pmol/L, respectively, representing the 25th and 95th percentiles), in order to eliminate test subjects with B12 malabsorption, ongoing B12 supplementation outside the study and significant renal impairment. The resulting subgroup was comprised of 2,155 patients, 37 percent female, with a mean age of 66 plus or minus 10.7 years. There was a 21-percent reduction in ischemic stroke, coronary disease and death in the high-B12 dose group compared with the low-B12 dose group. Kaplan-Meier survival analysis of the four groups indicated patients with B12 levels at the median or higher at baseline who were randomized to the high-B12 dose showed the best overall outcome, whereas those with baseline B12 levels lower than the median who were assigned to the low-B12 dose had the worst general outcome.

In the era of folate fortification, B12 plays a key role in vitamin therapy for total homocysteine, the researchers concluded, and higher doses of B12, and other treatments to lower total homocysteine may be needed for some patients.

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