Nicotine from edible Solanaceae and risk of Parkinson disease.

OBJECTIVE: To test whether risk of Parkinson disease (PD) is associated with consumption of nicotine-containing edibles from the same botanical family as tobacco, Solanaceae, including peppers, tomatoes, and potatoes.
METHODS: In a population-based study with 490 newly diagnosed idiopathic PD cases diagnosed during 1992-2008 at the University of Washington Neurology Clinic or Group Health Cooperative in western Washington State and 644 unrelated, neurologically normal controls, we examined whether PD was associated with self-reported typical frequency of consumption of peppers, tomatoes, tomato juice, and potatoes during adulthood, while adjusting for consumption of other vegetables, age, sex, race/ethnicity, tobacco use, and caffeine.
RESULTS: PD was inversely associated with consumption of all edible Solanaceae combined (relative risk [RR] = 0.81, 95% confidence interval [CI] = 0.65-1.01 per time per day), but not consumption of all other vegetables combined (RR = 1.00, 95% CI = 0.92-1.10). The trend strengthened when we weighted edible Solanaceae by nicotine concentration (ptrend = 0.004). An inverse association was also evident for peppers specifically (ptrend = 0.005). The potentially protective effect of edible Solanaceae largely occurred in men and women who had never used tobacco or who had smoked cigarettes < 10 years.
INTERPRETATION: Dietary nicotine or other constituents of tobacco and peppers may reduce PD risk. However, confirmation and extension of these findings are needed to strengthen causal inferences that could suggest possible dietary or pharmaceutical interventions for PD prevention.