Among people seeking treatment for mood disorders, there may be a lot of undiagnosed subclinical vitamin B12 deficiency.
B12 is stored in the liver and used up in various metabolic transactions, particularly stress. It helps clean out toxins, homocysteine, and repair nerve cells.
As we age, our bodies absorb B12 poorly. But it's not just seniors who might have low B12! Anyone taking a stomach acid blocker is also blocking B12 absorption. Older people taking stomach acid blockers are doubly at risk for low B12.
Since B12 is generally found in animal products, vegetarians sometimes have difficulty getting enough. There are other factors that might cause B12 levels to be low, but show up as normal on regular blood tests -- that's why it's called subclinical B12 deficiency.
Subclinical B12 deficiency may cause low mood for which many people might seek an antidepressant. Many psychiatric symptoms may very well be just low B12.
Over the long run, subclinical B12 deficiency can be as destructive as frank B12 deficiency.
Researchers believe that a lot of people who have been institutionalized for dementia or Alzheimer's actually had longstanding subclinical B12 deficiency; low B12 is very common among people who have been diagnosed (or misdiagnosed) with Alzheimer's.
Here's a recent post from Dr. Andrew Weil's blog about the neurological effects of low B12:
Vitamin B12 and Senior Moments
As we get older, our bodies don’t absorb vitamin B12 as readily as they did during our younger years (B12 is found in animal foods - meat, poultry, fish, eggs and dairy products). And this decreasing absorption may help explain why brain size shrinks with age and seniors develop problems with thinking. Researchers in Chicago checked blood levels of B12 in 121 seniors taking part in the Chicago Health and Aging Project. The investigators also measured vitamin B12 in five metabolites that are considered markers for B12 activity; a protocol, which they said, could give a fuller picture of B12 status. The seniors were asked to complete 17 tests to assess their memory and thinking skills. More than four years later, the study participants underwent MRIs to measure brain volume and to look for other signs of brain atrophy. The research team found that low levels of B12 in the metabolites were associated with poorer thinking skills and smaller brain volume. Because the study was a small one, the investigators said their results must be confirmed by additional research, and cautioned against making dietary changes based on their results. The study was published in the September 27 issues of Neurology.
My take? It is interesting that these researchers concluded that testing B12 levels in the blood isn’t enough to assess its activity in the body, but this is not the first study to associate low levels of B12 with negative changes in brain anatomy and function. A study published in 2008 suggested that seniors with the highest levels of B12 were six times less likely to exhibit brain atrophy than participants whose B12 levels were lower....."