When germ-free mice with normal motor skills were given fecal samples from humans with Parkinson’s, they began to show Parkinson’s symptoms. About 75 percent of people with Parkinson's have gut symptoms like constipation years before motor symptoms appear.

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When germ-free mice with normal motor skills were given fecal samples from humans with Parkinson’s, they began to show Parkinson’s symptoms. About 75 percent of people with Parkinson's have gut symptoms like constipation years before motor symptoms appear.