Irvine, Calif. -- Adults who eat the daily recommended allowance offolates -- B-vitamin nutrients found in oranges, legumes, leafy greenvegetables and folic acid supplements -- significantly reduce theirrisk of developing Alzheimer's disease, according to results from along-term National Institute on Aging study of diet and brain aging.
The study also found that folates appear to have more impact onreducing Alzheimer's risk than vitamin E, a noted antioxidant, andother nutrients considered for their effect as a brain-aging deterrent.
Maria Corrada and Dr. Claudia Kawas of UC Irvine's Institutefor Brain Aging and Dementia led the effort, which analyzed the dietsof non-demented men and women age 60 and older. They compared the foodnutrient and supplement intake of those who later developed Alzheimer'sdisease to the intake of those who did not develop the disease. It isthe largest study to date to report on the association between folateintake and Alzheimer's risk and to analyze antioxidants and B vitaminssimultaneously.
Results appear in the inaugural issue of the quarterly peer-reviewed research journal, Alzheimer's & Dementia: The Journal of the Alzheimer's Association.
"Although folates appear to be more beneficial than othernutrients, the primary message should be that overall healthy dietsseem to have an impact on limiting Alzheimer's disease risk," saidCorrada, who like Kawas started with the study while at Johns HopkinsUniversity in Baltimore.
The researchers used data from the Baltimore Longitudinal Studyof Aging to identify the relationship between dietary factors andAlzheimer's disease risk. Between 1984 and 1991, study volunteersprovided detailed dietary diaries, which included supplement intake andcalorie amounts, for a typical seven-day period.
Ultimately, 57 of the original 579 participants developedAlzheimer's disease. But the researchers found that those with higherintake of folates, vitamin E and vitamin B6 shared lower comparativerates of the disease. And when the three vitamins were analyzedtogether, only folates were associated with a significantly decreasedrisk.
In turn, no association was found between vitamin C,carotenoids (such as beta-carotene) or vitamin B-12 intake anddecreased Alzheimer's risk.
"The participants who had intakes at or above the 400-microgramrecommended dietary allowance of folates had a 55-percent reduction inrisk of developing Alzheimer's," said Corrada, an assistant professorof neurology. "But most people who reached that level did so by takingfolic acid supplements, which suggests that many people do not get therecommended amounts of folates in their diets."
Folates have already been proven to reduce birth defects, andresearch suggests that they are beneficial to warding off heart diseaseand strokes. Although folates are abundant in foods such as liver,kidneys, yeast, fruits (like bananas and oranges), leafy vegetables,whole-wheat bread, lima beans, eggs and milk, they are often destroyedby cooking or processing. Because of their link to reducing birthdefects, folates have been added to grain products sold in the U.S.since 1998. But even with this supplement, it is thought that manyAmericans have folate-deficient diets.
Recent research is beginning to show relationships betweenfolates and brain aging. Earlier this year, Dutch scientists showedthat adults who took 800 micrograms of folic acid daily had significantimproved memory test scores, giving evidence that folates can slowcognitive decline.
"Given the observational nature of this study, it is stillpossible that other unmeasured factors also may be responsible for thisreduction in risk," said Kawas, the Al and Trish Nichols Chair inClinical Neuroscience. "People with a high intake of one nutrient arelikely to have a high intake of several other nutrients and maygenerally have a healthy lifestyle. But further research and clinicalstudies on this subject will be necessary."
Judith Hallfrisch of the U.S. Department of Agriculture, Denis Mullerwith the National Institute on Aging and Ron Brookmeyer with JohnsHopkins collaborated on the study, which was originally undertaken atthe Gerontology Research Center of the NIA and the Department ofNeurology at Johns Hopkins. Study funding came from the ExtramuralPrograms of the NIA.
Begun in 1958 by the NIA, the Baltimore Longitudinal Study ofAging is America's longest-running scientific study of human aging.BLSA scientists are learning what happens as people age and how to sortout changes due to aging from those due to disease or other causes.More than 1,400 men and women are study volunteers. For moreinformation, see: www.grc.nia.nih.gov/branches/blsa/blsa.htm.
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