In brief

B vitamins and homocysteine

A high homocysteine level is not something you want to have. Homocysteine is an amino acid in the blood, and elevated levels have been linked to dementia, heart disease, stroke, and osteoporosis. The good news: Homocysteine can be lowered easily and inexpensively with a trio of B vitamins — B6, B12, and folic acid.

Problem solved? Not so fast. Lowering homocysteine doesn't mean much unless those reduced levels translate into reduced risk for the problems that elevated levels are thought to cause. Otherwise, you're just treating a blood test.

In 2004, the Journal of the American Medical Association published a study of 3,680 people who had suffered mild strokes that concluded a high-dose formulation of the B vitamins (25 milligrams of B6, 400 micrograms of B12, and 2.5 milligrams of folic acid) lowered homocysteine levels as expected, but had no effect on vascular outcomes. A Swed-ish study published in the May 2005 American Journal of Clinical Nutrition was similarly disappointing. Four months of B vitamins lowered the homocysteine levels of the 209 elderly (median age: 76) people in the study by almost a third, but didn't affect performance on a battery of tests designed to measure movement and cognitive abilities.

These results aren't the last word. Often, larger studies are needed. Perhaps larger doses of the B vitamins for a longer period of time will pay off. Also, relatively few people in these studies had high levels of homocysteine to begin with. Some doctors aren't waiting for the final word and are recommending vitamin therapy when people have homocysteine levels of 20 micromoles per liter (mol/L) or above, especially if those people have or are at risk for atherosclerosis.