B vitamins, iodine and the brain

OLYMPUS DIGITAL CAMERACan high dose B vitamins prevent Alzheimer’s disease?  Recent headlines suggested the answer is “yes”.  Unfortunately, the study in question didn’t really come to that conclusion.

Higher levels of the metabolic byproduct homocysteine are associated with atrophy in certain areas of the brain.  This atrophy is linked to Alzheimer’s disease progression.  Certain B vitamins play a role in the breakdown of homocysteine.  Would higher doses of those B vitamins impact brain atrophy?  The subjects for this study were 156 elderly people who already showed signs of mild cognitive decline.  They were divided into 2 groups and followed for 2 years.  One group took a B-vitamin supplement that included folate, B12 and B6, in doses higher than the minimum daily recommendation, but definitely not megadoses.

The subjects took cognitive tests and had their brains scanned before and after the 2 year study period.  The B-vitamin supplement seemed to slow the atrophy of certain brain regions, and the effect was most significant for those subjects who started the study with elevated homocysteine.  The placebo subjects with high homocysteine had much greater brain atrophy compared to those with low homocysteine.  As expected, brain atrophy was associated with loss of cognitive function.

What can we conclude about B vitamins and Alzheimer’s?  First, this study only used 3 key B vitamins, so taking large doses of other B vitamins might have no benefit.  Second, the supplements were not mega doses, at 100 or 1000 percent of the recommended daily intake.  More important, the study focuses on degrees of brain atrophy progression.  The B vitamins didn’t reverse the atrophy, they just slowed it.  And the effect was most significant for people who had elevated homocysteine.  So if you don’t have that particular risk factor, taking extra B vitamins might not provide any benefit.

Finally, this study looked at elderly people who already had signs of cognitive decline.  Giving a few B vitamins late in life might not be the best approach to a relentless disease like Alzheimer’s, which might begin decades earlier.  Obviously it would be better to prevent cognitive decline, than to try to treat it once the process of brain atrophy has begun.  But brain function is a tricky thing to research.  Brain scans can provide more meaningful data, but in order to investigate prevention, subjects would have to be followed for decades.  A study like that would be very complicated and extremely expensive to run.  We aren’t likely to see that data anytime soon.  At best, this study indicates that early screening for elevated homocysteine could be an important tool in the reduction of Alzheimer’s risk.

Brain function at the beginning of life was the focus of another recent study.  Pregnant women who don’t consume adequate iodine put their infants at risk for poor brain development, which can impact future IQ.  The effect of severe iodine deficiency on fetal development has been understood for a long time, and can cause newborns to develop cretinism, which is impairment of both neurological and physical growth.  This study examined the effect of mild iodine deficiency on childrens’ IQ.  Two-thirds of the mothers in this study had deficient intake during pregnancy.  When their children were tested at ages 8 to 9, the children of iodine deficient mothers were more likely to test in the lowest IQ groups.

In the US, iodine is added to table salt, to combat iodine deficiency, although not to all salt.  Salt added in to manufactured foods need not be fortified.  Prenatal supplements typically contain iodine, and good food sources include milk and ocean fish.  But milk consumption has declined, many people do not eat ocean fish, and many people are cutting back on salt, putting some people at risk for low iodine intake.

Excess iodine is a bad idea.  And taking extra iodine while pregnant will not make your baby smarter.  Pregnant women should consume adequate iodine from food and/or a prenatal supplement.

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