A recent study of older adults found that those with high intakes of folate, a common B vitamin, may have a faster rate of mental decline than others their age.
The study, which followed adults aged 65 and older, found that those whose daily folate intakes were near or higher than the recommended level generally had a faster rate of mental decline than those with lower folate intakes. This finding was unexpected and it's not completely clear that it was the folate that caused the quicker cognitive deterioration.
However, the results do suggest that older men and women should use caution in supplementing their diets with folic acid -- the synthetic form of folate used in vitamin pills and added to foods such as cereals and other grains. Folate is naturally found in lentils, spinach, asparagus, artichokes and sunflower seeds.
Adults require 400 micrograms of folate a day, through supplements, fortified foods or natural sources such as leafy greens, beans and oranges. In this study, participants in the top fifth of folate intake -- who typically consumed more than 700 micrograms in a day -- had twice the rate of mental decline over six years as those who with the lowest folate intake.
Rates of decline were also faster among men and women who got more than 400 micrograms of folate a day specifically in the form of supplements, and among those whose typical intake of folate from food was nearly 400 micrograms. Folate is an important nutrient needed to produce and maintain healthy cells. Along with vitamins B12 and B6, folate also helps the body break down a protein called homocysteine, a byproduct of metabolism that, at high levels in the blood, is thought to be a risk factor for heart disease and stroke.
Studies are looking into whether the three B vitamins can lower the risk of cardiovascular disease by cutting homocysteine levels.
A possible explanation of these study findings, according to researchers, is that high folate intake is "masking" a deficiency in vitamin B12 in some people. Older adults are at greater risk of B12 deficiency because their bodies are less efficient at absorbing the vitamin from its natural food sources, which include red meat, fish and poultry. Left untreated, a B12 deficiency can cause mental function to deteriorate.
High folate intake from supplements could cause B12 deficiency to go undetected and untreated, which could in turn contribute to mental decline.
According to researchers very little is known about the potential health effects of this trend for older people. More research is needed to investigate the questions raised by this study.
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