This is the VOA SpecialEnglish Science Report.

Medical researchers say a new study shows a link between themental condition Alzheimer's disease and high levels of thesubstance homocysteine (ho-mo-SIS-teen) in the blood.

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Homocysteine is an amino acidpresent in proteins that are normally produced in the body.Homocysteine levels

Researchers at Boston University and Tufts University inMassachusetts carried out the new study. It is the first to find alink between high homocysteine levels in healthy people and thelater development of Alzheimer's disease. The researchers reportedtheir work in the New England Journal of Medicine.

They examined the medical records of people who took part in theFramingham, Massachusetts Heart Study. That study examined thehealth of several thousand people who live in a town near Boston.They have had medical tests every other year sinceNineteen-Forty-Eight.

More than ten years ago, researchers measured the homocysteinelevels of more than one-thousand healthy people taking part in theFramingham study. All the people were sixty-eight years old orolder. Eight years later, ten percent of them had developed themental and memory problems of Alzheimer's disease.

The researchers found that those with the highest homocysteinelevels had two times the risk of developing Alzheimer's disease asthose with lower levels. They said even a small increase inhomocysteine levels appeared to increase the chance that the personwould later develop Alzheimer's.

The study does not prove that high levels of homocysteine causeAlzheimer's. But, the researchers say homocysteine can damage bloodvessels and nerves. High levels of homocysteine have also beenlinked to strokes and heart attacks.

Experts say some vitamins and folic acid in fruits and vegetableshelp change homocysteine into amino acids that do not harm the body.The researchers say people can reduce their homocysteine levels byeating more fruits and vegetables. Or they can take folic acid andvitamin B in pills. Scientists are planning to continue their workto find out if the vitamins can prevent or delay Alzheimer's diseasein healthy people.

This VOA Special English Science Report was written by NancySteinbach.