High doses of B vitamins failed to slow cognitive decline in people with Alzheimer's disease, say U.S. researchers in a new study published in the Journal of the American Medical Association.
The researchers gave 409 people with Alzheimer's disease daily doses of five milligrams of folic acid, one milligram of vitamin B12 and 25 milligrams of vitamin B6. They were compared to 591 people who also had Alzheimer's but received placebo pills.
(For adults over 50, the recommended daily intake for folate is 400 micrograms, 2.4 micrograms for vitamin B12, and 1.7 micrograms for vitamin B6.)
All study participants completed tests that assessed cognitive skills such as memory and language.
After 18 months of supplementation, people with Alzheimer's who took B vitamins did no better on the cognitive tests than their peers who were given a placebo.
The researchers had hoped that B vitamins may lower the risk of Alzheimer's disease - or slow its progression - because B vitamins are known for cutting circulating levels of the amino acid homocysteine. (Homocysteine levels are often elevated in Alzheimer's patients.)
These findings do not support increasing intake of B vitamins through supplementation to ward off Alzheimer's disease.
People can get folate, the natural form of folic acid, and other B vitamins in their diet through leafy green vegetables and fortified cereals.
One cup (250 ml) of black beans - our November 2008 Featured Food - provides 270 micrograms of folate and 125 micrograms of vitamin B6.
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