Editorial prologue The diet of the citizens of postindustrial societies varies. Herbert Sandström, general practitioner and associate professor at the Department of Family Medicine, University of Umeå, reviews an article from Chicago, which compares the cognition of persons with different diets; the results are suprising. Previous papers in this series were written by Lena Strålsjö (evaluation15_eng.htm) and Karin Björkegren (publisher19_eng.htm).

Morris MC, Evans DA, Bienias JL, Tangney CC, Hebert LE, Scherr PA, Schneider JA. Dietary folate and vitamin B12 intake and cognitive decline among community-dwelling older persons.
Arch Neurol. 2005 Apr;62(4):641-5.

The interest for the association between vitamin B12 – folate and neurodegenerative diseases has increased in recent years. Except that it is well established that severe vitamin B12 deficiency leads to neurological symptoms, it has been observed in several cross-sectional studies that even a slightly lowering of serum folate and B12 is associated with cognitive impairment. Additionally, it is known that increased concentration of homocysteine may be associated with dementia. These observations, together with studies showing that low dietary intake of folate leads to increased frequency of neural tube defects, resulted in a requirement of fortification of grain products by the FDA in 1998.

The aim of the present study from Chicago was to evaluate possible association between dietary intake of folate and vitamin B12 and cognitive decline during a period of 6 years. Cognitive function was tested at baseline, and after 3 and 6 years. Dietary intake of folate and vitamin B12 and possible multivitamins during the last year was assessed using standardised food questionnaires. Patients (n=3718) 65 years and older were included in the study which was part of Chicago Health and Aging Project (CHAP). Mean age at baseline was 74 years.

When divided into quintiles persons with high intake of dietary folate tended to have a more favourable risk profile for cognitive change than persons with low intake, higher baseline cognitive score, higher education and greater intake of vitamin C and E. They were also less likely to have a history of cardiovascular disease.

Surprisingly for the research group, they found that high folate intake was associated with a faster cognitive decline adjusted for multiple risk factors. The cognitive decline in the highest quintile (median 742 µg/d) was more than twice that of those in the lowest ( 186 µg/d) after adjustment for age, demographic factors, education and vitamin supplentation. They also observed a slower decline in cognitive function among elderly persons with higher intake of vitamin B12.

This paper from Chicago reports that high intake of folate in an older population was associated with a faster rate of decline in cognitive function. One limitation of the study, which is also commented on by the authors, is that the folate intake is only based at diet questionnaires without knowledge about serum concentrations of folate and vitamin B12 or their biochemical markers, e.g. homocysteine. The authors are discussing the possibility that a high folate intake may be masking unrecognised vitamin B12 deficiency in persons with impaired cognitive function. Such concerns were also raised as a conceivable effect of general folate supplementation.

These results are interesting, but it should be observed that the cognitive decline appeared mainly in the highest quintile of self reported folate intake, i.e. the group with the highest cognitive function at baseline, and the decline was proportionately small in absolute numbers.

Published June 29, 2005