Living in a rural environment increases the statistical risk of Parkinson's disease, perhaps because of exposure to well water and agricultural chemicals. Some scientists think there may be protective substances in cigarettes and coffee. Others think that the substances themselves are irrelevant, and that people with addictive behavior have a brain chemistry that also makes them more resistant to Parkinson's disease. Certainly, no one should begin or continue smoking in order to protect themselves from Parkinson's disease. The role of diet has been examined many times, based on the hypothesis that anti-oxidants might protect against the disease.
Most studies show no significant role for diet.
As with other diseases, genes and environment interact. Of the 400 people who injected MPTP in the early 1980s, only a few developed Parkinson's disease. So, even in this extreme case, some people were resistant to environmental effects. All members of a family do not have the same height, weight, and face. Here again, it's genetic and environmental differences that explain differences in our appearance and health.