Dietary niacin (vitamin B3 ) may protect against the development of Alzheimer's disease and the cognitive decline associated with ageing in older people, suggests research in the Journal of Neurology Neurosurgery and Psychiatry.

Rich sources of niacin include lean meat, fish, legumes, nuts, dairy products, enriched grains and cereals, and coffee and tea.

[Dietary niacin and the risk of incident Alzheimer's disease and of cognitive decline J Neurol Neurosurg Psychiatry 2004; 75: 1093-99]

The researchers base their findings on almost 4000 people aged 65 and older, who had no Alzheimer's disease. These participants completed a dietary questionnaire and were checked for any signs of decreasing mental agility (cognitive decline) three and six years after the start of the study.

At three years, a random sample of 815 people, who had not initially had Alzheimer's disease, were checked for clinical changes and their dietary niacin intake assessed by means of food frequency questionnaires.

Among this smaller group, 131 people were diagnosed with Alzheimer's disease. After adjusting the results for age, gender, race, educational levels, and the ApoE gene - all important risk factors for the disease - those with the lowest food intake of niacin (an average of 12.6 mg/day) were 80% more likely to be diagnosed with Alzheimer's disease than those with the highest intake (22.4 mg/day).

An analysis of the larger group showed that the rate of cognitive decline among those with the highest niacin intake was almost half (44%) that of those with the lowest intake.

Niacin has been prescribed to older people to prevent confusional states, and severe deficiency causes pellagra, a condition characterised by dementia, diarrhoea, and dermatitis, but its role in Alzheimer's disease has not been thoroughly explored, say the authors.

Previous research has indicated that niacin has an important role in DNA synthesis and repair, neural cell signalling, and acts as a potent antioxidant in brain cells, they say.

Dr Martha Morris, Rush Institute for Health Aging, Chicago, Illinois, USA.
Tel: +1 (312) 942 3350

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Source: British Medical Association
Caroline White
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