Two Views on Vitamins
Two studies report good news and bad news about supplements of folic acid, the stuff in leafy greens.
High-dose Vitamins and Heart Disease
In science, knowing what doesn't work is as important as knowing what does. Just ask researchers at Carolina and Wake Forest University about their search for a way to fight cardiovascular disease.
In recent studies, elevated levels of homocysteine, an amino acid in blood, correlated with an increased risk of cardiovascular disease. So maybe reducing homocysteine levels could reduce chances of a second stroke. To the disappointment of researchers, a new study did not support that theory. The project, known as Vitamin Intervention for Stroke Prevention (VISP), relied on high vitamin dosages of folic acid, vitamin B12, and vitamin B6 to lower patients' homocysteine levels.
The high vitamin dosages given to patients failed to decrease their likelihood of a second stroke. "It is a suggestion that high-dose folic acid may not prevent strokes and heart attacks," says Lloyd Chambless, director of Carolina's Collaborative Studies Coordinating Center.
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The
vitamins used in the VISP study, which found that high-dosage folic
acid may not prevent strokes. Photo by Jason Smith. Click
to enlarge.
The work studied more than 3,600 adults who had already suffered a stroke. Researchers gave a randomly chosen group a multivitamin containing high-dosage folic acid, vitamin B12, and vitamin B6. The other patients received a multivitamin containing smaller dosages of these three vitamins.
In fact, the study's monitoring board stopped the research project early because the vitamin therapy apparently did not significantly affect the two groups. "They saw no need in following the patients another year because the data already showed there was virtually no chance in the remaining time to show a difference," Chambless says.
However, Chambless cautions against completely ruling out the potential of high-dosage vitamins to treat cardiovascular diseases. "One has to admit that this treatment didn't show a significant difference for this sample group. There are several possibilities for this. The study was done only on older patients. Or possibly the treatment didn't last long enough, or the reduction in homocysteine was too small, or the study group did not have high enough levels of homocysteine."
Since new FDA regulations require that all enriched grain be fortified with folic acid, this also might account for the lack of impact. The fortified grain could have increased the total folic acid already consumed by the low-dose vitamin group. This could explain why VISP only moderately lowered the homocysteine level in the patient volunteers and thus why researchers could not detect a change in strokes.
In subsequent investigations of the role of homocysteine, researchers will use the knowledge gained during the VISP study to alter the experimental design. Chambless says, "I am sure other people will study the same question in different ways. We are already in the process of conducting another study that examines homocysteine lowering in a different type of patient."
The VISP study was funded by the National Institute for Neurological Disease and Stroke. Findings were published in the February 4, 2004, issue of the Journal of the American Medical Association.
Thanks for the Memories, Mom
Leafy greens, breakfast cereals, multivitamins. All of these are good sources of folic acid, an essential nutrient that's especially important for pregnant women.
If a mother doesn't get enough folic acid just before and during early pregnancy, her child can develop neural tube defects such as spina bifida, in which the spinal cord does not close properly. Folic acid's role in early brain development has been well established in recent years, says Steven Zeisel, professor and chair of nutrition.
"But don't stop there," Zeisel says. A new animal study conducted by Zeisel and colleagues shows that a mother's folic acid intake in later pregnancy may affect the way her baby thinks.
The scientists fed pregnant mice and rats healthful diets that included low, normal, or high amounts of folic acid, then examined the pups' brains in the last third of pregnancy, when forebrain structures are forming. "Stem cells get turned on, multiply, and turn into brain cells to colonize the brain's memory centers," Zeisel says.
Folic acid-deficient pups formed only half as many stem cells as pups in the normal and high groups, and twice as many of these cells had died. If fewer cells are available to form them, memory centers will be abnormal permanently, and a pup's memory performance will be affected, Zeisel says.
Do these findings apply to people, too? The researchers believe so, since human brain centers are similar to those in mice and rats. And Zeisel says that animal research on the nutrient choline, found in milk and eggs, has linked it to late-pregnancy brain development and memory. "Pups born to mothers with extra choline are smarter," Zeisel says. "They perform better on memory tests such as mazes and never go senile." Folic acid and choline are metabolically interrelated, and Zeisel says they appear to regulate gene expression — and affect memory — in the same way. "Maybe something your mother ate is the reason you can't find your car keys anymore," he says.
How much folic acid is enough? Just 400 micrograms, the amount included in any multivitamin, Zeisel says. And getting that much through foods or a supplement is essential for all women of childbearing age, since 50 percent of pregnancies are unplanned. "Every woman who could get pregnant should take it," Zeisel says. "It's not worth the risk of having a baby with lifelong birth defects or deficiencies."
The study was published in the January 2004 issue of the Journal of Nutrition. Other authors are graduate student Elliott Brown, research associate professor Craig Albright, research assistants Corneliu Craciunescu and Mei-Heng Mar, all of the Department of Nutrition in the Schools of Public Health and Medicine; and Marie Nadeau of Tufts University.
The work was funded by grants from the National Institute on Aging of the National Institutes of Health (NIH) and supported by NIH grants to Carolina's Clinical Nutrition Research Center and Center for Environmental Health Susceptibility.
