Evidence suggests that poor diet is a contributory factor in the development of not only poor cognitive function, but also age-related memory decline and dementia. Low levels of B vitamins have been linked to a number of cognitive problems, and this may relate to the use of B vitamins in many energy related pathways, particularly glycolysis and the citric acid cycle. Chronic low levels of these vitamin may therefore impair energy production in the central nervous system, leading to cognitive impairment. In addition, three of the B vitamins are required for the correct metabolism of the amino acid methionine, and low levels of folic acid, vitamin B6 and vitamin B12 may impair the metabolism of methionine and result in increased plasma concentrations of homocysteine. High levels of plasma homocysteine has been investigated for its ability to damage tissues through the generation of free radicals, and in this way high plasma levels of homocysteine may damage neurons in the brain.
The B vitamins may have important functions that help maintain the integrity of nervous tissue. Low levels of vitamin B12 have been associated with an accelerated rate of whole brain atrophy and with insufficient myelination of nerves. This can lead to damage to the white matter of the brain. High dose vitamin B treatment has also been shown to reduce the rate of grey-matter atrophy in Alzheimer’s Disease related regions of the brain. Good sources of vitamin B12 are eggs, red meat, shellfish, liver and cheese. Vitamin B12 is produced by microorganisms in animal tissues, but is not generally accepted not to be present in plant foods. For those that do not eat animal produce a supplement of vitamin B12 is therefore recommended. The B vitamins are water soluble and are generally safe as long as intakes remain realistic.
A number of studies have investigated the effects of low intakes of B vitamins of cognitive impairment. For example, in one study researchers divided a group of women into low and high vitamin B12 groups with the cut off point at 304 pmol/L (150 to 300 pmol/L is considered a low plasma concentration of vitamin B12). The women also underwent an auditory verbal learning test and had an MRI scan to assess any damage to the hippocampus area of the brain. The results of the study showed that subjects with lower plasma levels of vitamin B12 had significantly poorer learning ability compared to subject with higher plasma concentrations of vitamin B12. There was also a poorer microstructure integrity in subjects with lower plasma levels of vitamin B12 when compared to the subjects with higher plasma levels of vitamin B12. In particular, the cornu ammonis 4 and dentate gyrus region showed poorer integrity. Therefore lower intakes of vitamin B12 are associated with poorer cognitive function and changes to brain structure.
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