By TAP Integrative

B vitamins potentially influence brain and cognitive function via several mechanisms, including regulation of DNA repair, support of methylation, and modulation of homocysteine. Observational studies and prevention trials have reported mixed results on the associations between B vitamin intake and risk of dementia. While some studies suggest a protective effect, harmful associations have been identified between high folic acid intake and cognition in individuals with low vitamin B12 status. Moreover, mandatory folic acid fortification of flour and cereal grains since 1998 in the United States has complicated the interpretation of population-based studies.

A prospective cohort study, published in Nutrients (2016), sought to evaluate the association between B vitamin intake and risk of dementia in France, a country not affected by folic acid fortification policy. Data from 1321 citizens, with a mean age of 76 years and no dementia at baseline, were included in this study. Food frequency questionnaires and 24-hour dietary recalls were collected, and participants were followed for an average of 7.4 years. The primary outcome was incident dementia.

Mean daily intakes of B vitamins were as follows: 1.5mg for B6, 278.3μg for folate, and 5.7 μg for B12. A total of 197 participants (15%) developed dementia during the follow-up period. After adjusting for other B vitamin intake, overall diet quality, and other potential confounders, higher intake of folate was significantly associated with a lower risk of dementia (p for trend ≤.02). Compared with individuals in the lowest quintile of folate intake, those in the highest quintile had a 47% lower risk of dementia over 10 years (HR=0.47; 95% CI, 0.28-0.81). No significant associations were observed between dietary intakes of vitamins B6 or B12 and the risk of dementia.

The median folate intake in the upper quintile for this cohort was 444μg, a value that is markedly lower than in similar studies conducted in the United States. A US study, reporting a median folate intake of 742μg/d found no association between B vitamin intake and risk of dementia. The authors of the current study suggest this may indicate that folate is protective for the brain in lower intake ranges but becomes inefficient or even detrimental at higher ranges. They conclude that a strong association exists between higher folate intake and lower risk of dementia in a population with no folic acid fortification and relatively low average intake.


Reference

Lefèvre-Arbogast S, Féart C, Dartigues JF, Helmer C, Letenneur L, Samieri C. Dietary B Vitamins and a 10-Year Risk of Dementia in Older Persons. Nutrients. 2016;8(12)


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