Monday, March 15, 2010

Vitamin D and Memory

A general rule regarding memory and nutrients is that most dietary supplements are without effect unless a person has an inadequate diet. One nutrient of special interest is vitamin D. Vitamin D is synthesized in the skin from exposure to sunlight, but many people don't get enough sunlight every day. Sun-tan lotions, designed to reduce the risk of skin cancer, also reduce the likelihood that the skin can make enough vitamin D. Particularly vulnerable populations include Blacks and elderly who are confined indoors. Also the ability of skin to synthesize vitamin D declines with age.

Vitamin D and its receptors are found throughout the body. In recent years, scientists have learned that it contributes to normal cognitive function, including memory. Vitamin D increases the brain neurotransmitter chemical called acetylcholine, which is the most important transmitter for creating conscious arousal and attentiveness. Vitamin D also stimulates synthesis of nerve growth factor, which can promote growth of nerve terminals.

A recent study has confirmed results from another lab suggesting that normal brain function requires vitamin D. Participants, 1,766 adults aged 65 years and older, were evaluated to compare blood levels of vitanim D precursor and cognitive ability. Lower levels occurred in the subset of people who were cognitively impaired, compared to the normal subjects.

Another independent study reports similar findings. The study examined 3,133 men aged 40 to 79 at eight test centers across Europe. Men who had a better memory and were quicker to process information had higher levels of vitamin D. Men with 35 nanomoles per litre or less of vitamin D in their blood performed poorly.

These are only correlational studies, but they do suggest that increasing dietary vitamin D can improve memory in people who are vitamin D deficient. This idea awaits experimental verification. In the meanwhile, taking modest doses of vitamin D (use the D3 version, about 1,000-2,000 I.U. per day) is probably a good idea.

Sources:

Llewellyn. D. J. 2009. Journal of Geriatric Psychiatry and Neurology, Vol. 22, No. 3, 188-195 OI: 10.1177/0891988708327888

Lee, D. M. et al. 2009. J Neurol Neurosurg Psychiatry 2009;80:722-729 Published Online First: 21 May. doi:10.1136/jnnp.2008.165720

1 comment:

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