Homocysteine is an amino acid that has shown to be linked to heart disease and osteoporosis. Homocysteine is normally converted by the body to cysteine and eventually taurine; amino acids that do not have the same negative implications. The conversion reactions that change homocysteine to the more benign amino acids are dependent on vitamins B6, B12 and folic acid. Taking these nutrients can lower homocysteine levels.
Now, according to research published in the February 14, 2002New England Journal of Medicineshows high homocysteine levels can also double the risk of dementia and Alzheimer’s disease. The data was taken from the Framingham Study and published in a report from scientists from Boston University. The researchers were able to follow a large number of patients over several years, beginning long before any of the subjects showed any signs of memory-loss or dementia.
Homocysteinelevels higher than 14 mmol/liter doubled the chance that a subject would develop Alzheimer’s Disease and each additional 5 mmol/liter elevation increased the risk of Alzheimer’s Disease by 40 %. People with consistently high levels of homocysteine throughout the period of the study were at highest risk for dementia and Alzheimer’s.
“The evidence is beginning to mount regarding homocysteine’s role in dementia,” according to Neil Buckholtz, Ph.D., chief of the Dementias of Aging program at the NIA. “The good news is that we may have found a potential risk factor for AD (Alzheimer’s Disease) that is modifiable. We don’t know yet whether reducing homocysteine levels will reduce dementia risk, but this is something that can and will be tested in clinical trials.”
This is supported by to two studies published in the May 28, 2002issue of Neurology, the scientific journal of the AmericanAcademyof Neurology. Both brain atrophy and vascular disease are related to the development of dementia, including Alzheimer’s disease. Brain atrophy and vascular disease are also associated with elevated blood levels of the amino acid homocysteine.
There is also a possible connection between Parkinson’s disease and low folic acid levels. Scientists at the National Institute on Aging have conducted experiments with mice that suggest that folic acid deficiency could increase the brain’s susceptibility to Parkinson’s disease. This finding was published in the January 2002 issue of the Journal of Neurochemistry. The scientists found that mice with low amounts of dietary folic acid had elevated levels of homocysteine in the blood and brain. They suspect that increased levels of homocysteine in the brain caused damage to the DNA of nerve cells in the substantianigra, an important brain structure that produces dopamine. “This is the first direct evidence that folic acid may have a key role in protecting adult nerve cells against age-related disease,” said Mark Mattson, Ph.D., chief of the NIA’s Laboratory of Neurosciences. “It is clear from this study that a deficiency of this vitamin is associated with increased toxin-induced damage to the dopamine-producing neurons in the mouse brain.”