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Martha Morris and Jacob Selhub examine computer display of data. Link to photo information
Based on a population study, seniors with normal folate levels fared better than those with high folate levels under certain conditions. In photo, epidemiologist Martha Morris and biochemist Jacob Selhub examine apparent associations between B vitamin status and cognitive test results. Click the image for more information about it.

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When It Comes to Vitamins, More Is Not Always Better

By Rosalie Marion Bliss
November 16, 2007

Researchers funded by the Agricultural Research Service (ARS) looked into links between dietary intakes of two B vitamins—folate and vitamin B12—and mental agility among seniors. Folate and B12 are important nutrients for the development of healthy nerves and blood cells. ARS is the U.S. Department of Agriculture's chief scientific research agency.

The study, published in 2007, was led by epidemiologist Martha Morris and colleagues at the ARS Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) in Boston, Mass. It was based on an analysis of data collected from the U.S. population for the National Health and Nutrition Examination Survey between 1999 and 2002. Blood tests were used to determine the volunteers' folate and vitamin B12 levels.

U.S.-enriched cereal grain products have been fortified with the synthetic form of folate (folic acid) since 1998. The HNRCA's Paul Jacques and Jacob Selhub, coauthors on the 2007 study, had previously published papers with Silvina Choumenkovitch, reporting that folate levels have become extremely high in the U.S. population since fortification began.

The researchers found an interesting association among seniors aged 60 and older whose vitamin B12 blood levels were low. Aging and taking stomach-acid blockers can contribute to a gradual lessening of B12 absorption in the body.

People with high folate and low B12 status were found to be at a disadvantage when compared to those with normal folate and low B12 status; the former group was more likely to exhibit both anemia and cognitive impairment, according to Jacques. A single cognitive function test was used to assess aptitudes such as response speed, sustained attention, visual-spatial skills, associative learning and memory.

Scientists have long known that being seriously deficient in vitamin B12 leads to impaired cognitive function caused by neurological complications. The researchers recommend future studies that look into the implications of having too much folic acid, due to fortification, and too little vitamin B12, due to poor absorption.

Read more about this research in the November/December 2007 issue of Agricultural Research magazine.