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High intake of niacin, particularly from food sources, may reduce the risk of Alzheimer's disease and age-related cognitive decline, according to a report in the August issue of the Journal of Neurology, Neurosurgery, and Psychiatry.

Severe niacin deficiency is known to cause dementia. However, the researchers note that it is unclear if more subtle variations in niacin intake influence the risk of neurodegenerative decline.

"There have been no epidemiologic studies to look at the association between dietary niacin and Alzheimer's disease or cognitive decline," lead author Dr. Martha C. Morris, from the Rush Institute for Healthy Aging in Chicago, told Reuters Health. Moreover, "animal studies and other studies have really focused on the effects of very high therapeutic dose levels of niacin," not amounts found in a standard diet.

To investigate, the researchers administered food frequency questionnaires and cognitive tests to several thousand elderly people living in a Chicago community. The study focused on 815 randomly selected subjects who were free from Alzheimer's disease at baseline. After an average of 3.9 years, 131 of the subjects were diagnosed with Alzheimer's disease.

A high level of total niacin intake seemed to protect against both Alzheimer's disease and cognitive decline. The association was stronger for niacin intake from foods than for niacin intake from supplements.

"We were surprised to see a fairly strong association between niacin intake from foods and Alzheimer's disease," Dr. Morris said. "Compared with the lowest quintile of intake, the highest quintile was linked to an 80% reduction in risk."

In the overall study population, high niacin intake was also linked to a reduced risk of cognitive decline.

Although the finding are provocative, Dr. Morris concluded, they will require verification before any changes to current dietary guidelines can be recommended.

J Neurol Neurosurg Psychiatry 2004;75:1093-1099.

Reported by Reuters Health