Folic Acid Linked to Parkinson's Disease Jan. 17, 2002 -- It's thought that both genetic defects and environmental toxins conspire together to cause Parkinson's disease. But a new study shows that folic acid might help prevent this degenerative brain disease -- at least in mice.

Folic acid is already known to prevent birth defects of the nervous system. And there is a lot of evidence that it also can ward off heart disease in people with too much of an amino acid called "homocysteine." Folic acid decreases levels of homocysteine.

The latest research shows that mice on a low-folic-acid diet are much more likely to get Parkinson's disease than mice on a normal diet. The study appears in the January issue of the Journal of Neurochemisty.

Parkinson's disease, which affects about 50,000 Americans annually, is due to degeneration of brain cells that produce a chemical messenger called "dopamine." Without dopamine, people develop multiple movement problems, including very slow movements; tremors, especially in the hands; and muscle stiffness.

Researchers at the National Institute on Aging (NIA) put some mice on a low-folic-acid diet and others on a normal diet. As suspected, the mice on the low-folic-acid diet had an eight-fold increase in homocysteine levels.

And when given a small dose of a chemical that causes Parkinson's disease, the mice on the low-folic-acid diet developed muscle coordination problems as seen in people with Parkinson's. But the normal-diet mice were resistant to the effects of this toxic chemical. Folic acid deficiency by itself did not cause any Parkinson-like problems.

"This is the first direct evidence that folic acid may have a key role in protecting adult nerve cells against age-related disease," said senior author Mark Mattson, PhD, in a news release. He is chief of the NIA's laboratory of neuroscience.

The researchers were able to finger homocysteine as the likely culprit behind the loss of brain cells. When homocysteine was injected directly into the brains, the Parkinson's symptoms were much worse than in mice injected with a placebo.

In addition, in a separate part of the study, the researchers showed that human brain cells were more susceptible to damage when exposed directly to homocysteine.