A folic acid deficiency that has been linked previously to an increased risk of Parkinsons has also been implicated in the development of Alzheimers Disease. National Institute on Aging researchers found that key nerve cells in the brains of mice fed a diet deficient in folic acid were unable to repair DNA damage. The findings were reported in the March 1, 2002, issue of the Journal of Neuroscience. In mice fed an adequate amount of the vitamin, the nerve cells were able to repair the damage from the stroke. Mice fed a low folic acid diet had a decreased number of neurons and high levels of homocysteine. Folic acid is found in green, leafy vegetables, citrus fruits and juices, and in whole wheat bread and dry beans. Vitamin supplements normally contain 400 micrograms of the B vitamin, which is considered to be 100 percent of the recommended daily allowance for adults.