Elderly patients frequently are seen at the doctor’s office because they are “feeling poorly”. Concerned family members mention that there is lack of energy, and mental impairment may also be present. Immediately there may be the question, whether these are symptoms of Alzheimers disease. The other observation may be that the older person is not eating properly. Family physicians will order laboratory tests including vitamin B12 levels. If a deficiency is shown, patients will be advised to take a vitamin supplement, and they may receive injections of vitamin B12.
The unfortunate fact is that vitamin B 12 levels are notoriously unreliable in the diagnosis of deficiency. As early as 1988 a publication in the New England Journal of Medicine showed that neuropsychiatric disorder due to vitamin B12 deficiency can be present in a patient who had normal blood levels and no other findings. It does take some other avenues to detect the deficiency. The blood can be tested for the metabolite called MMA (methylmalonic acid) which is raised with vitamin 12 deficiency. A second test is the measurement of HTC (holotranscobalamin), which is the fraction of vitamin B12 bound to the plasma protein transcobalamin, which delivers the vitamin to the tissues of the body.
Dr. Cherie McCracken and colleagues from the department of psychiatry at Liverpool University, England studied 42 men and 42 women ages 69 to 93.They were tested for cognitive functions like orientation, language, attention and memory. In addition researchers took measurements of the MMA and HTC, the tests mentioned above. None of the test persons had dementia due to the selection criteria, but 31% were cognitively impaired. Mental scores indicating cognitive impairment were associated with increasing age and MMA, and the areas of language comprehension, language expression and ideation practice (translating an idea into an action) were affected.
The reason for the correlation of MMA with impairment of brain function can be explained by the fact that MMA is toxic to the oxidative function of mitochondria. The process is like a chain reaction: when mitochondria are poisoned, the nerve cells will lack energy for proper function.
Despite this sophisticated interplay of blood levels and cell function in the brain, the message that comes from the researchers is very simple. The MMA has to be ordered as a test in elderly persons, and the next important step is supplementation with vitamin B12 to prevent deterioration in mental functioning.
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Reference: The Medical Post, January 16, 2007, page 27
Last edited November 2, 2014