Martha Clare Morris, PhD, of the Rush Institute for Health Aging in Chicago, and colleagues studied 3,718 65-and-older residents of three south Chicago neighborhoods for more than five-and-a-half years. They also performed clinical tests on 815 of these people over four years.
They found that those who got the least niacin were 70% more likely to develop Alzheimer's disease than those who got higher amounts. Those who got the most niacin in their diets had much slower mental decline than those who got the least niacin.
"We observed a protective association of niacin against the development of Alzheimer's disease and cognitive decline within normal levels of dietary intake," Morris and colleagues conclude. Their report appears in the August issue of the Journal of Neurology, Neurosurgery, and Psychiatry.
Foods rich in niacin include:
Meat and fish
Beans and lentils
Fortified grains, whole-wheat bread, and fortified cereals
People who get dangerously little niacin in their diets develop a disease called pellagra. Pellagra usually isn't seen in people who get at least 11 mg of niacin a day. In the Morris team's study, the group at the lowest niacin level was getting a median 14 mg a day in diet and in vitamin supplements. The current recommended daily allowance for niacin is 16 mg per day for men and 14 mg per day for women.
Benefits of higher niacin intake began in men and women at a median intake of 17 mg per day. Those at the study's highest niacin level were getting 45 mg per day in diet and supplements.