The exact causes of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, are unknown. ALS results in damage to motor neurons that are responsible for voluntary muscle functions. Although the true causes of ALS are a mystery, researchers have discovered that when there are changes or mutations in a certain gene, called superoxide dismutase (SOD1), the body doesn't produce enzymes that protect motor neurons, and eventually the neurons die. Other research has shown that people with ALS have too much glutamate in their blood. Glutamate is a chemical messenger that helps nerve cells in the brain and the spinal cord communicate with one another. Excess glutamate can damage motor neurons. It's speculated that ALS can be caused by an autoimmune response, in which the body mistakenly attacks its own motor neurons. Other possible causes of ALS include exposure to toxic substances or viruses, abnormalities of the immune system, a lack of certain nutrients in the diet, and physical trauma.
One common misconception is that consuming monosodium glutamate, a common flavor-enhancing food additive better known simply as "MSG," can lead to ALS or cause complications with the disease. There's no need to worry about a box of Chinese take-out leading to a diagnosis of ALS -- according to Dr. Jeffrey Rothstein, co-director of MDA/ALS research group at Johns Hopkins, the glutamate you eat does not affect your brain or your nervous system. The glutamate relevant to ALS is produced within your own body [source: ALS-MDA].
One thing is certain: Lou Gehrig's disease is rare. It affects about one in every 50,000 people, and it's estimated that only 20,000 to 30,000 people in the United States live with ALS at one time [source: ALSA]. ALS is most common in Caucasian men and usually starts when people are between 40 and 60 years old. In 5 to 10 percent of cases, the disease is passed down through families, and is called familial ALS. In most cases, however (90 to 95 percent), the causes are unknown and dubbed sporadic ALS. Nearly 5,600 Americans are diagnosed with Lou Gehrig's disease each year [source: ALSA].
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