Tomatoes and Parkinson’s disease: An old hypothesis revisited

In 1989, Jacob Sage proposed that tomatoes might contribute to the etiology of Parkinson’s disease (PD) [1]. At the time, his hypothesis mainly served as a provocative, tongue-in-cheek illustration of the challenges in identifying the causes of PD. In our paper 2], we discuss why this hypothesis may have been less far-fetched than originally thought.

Specifically, evidence linking pesticide exposure to the etiology of PD is mounting fast [3, 4]. Various epidemiological studies have found associations between PD and certain pesticides, which is further supported by pre-clinical studies [5-7]. While most studies have focused on occupational exposure, emerging evidence indicates that people living near agricultural fields or consuming pesticide-treated products may also encounter risks [8, 9].

Interestingly, at least some of these very same pesticides are used in the cultivation of tomatoes. To gain insight into the pesticide profile used in tomato production, we analyzed pesticide use data from California — a major tomato-producing state [10]. We found that many of the most commonly used pesticides on tomatoes have been previously linked to PD (Table 1). Moreover, the increasing number of pesticides applied over the years raises concerns about cumulative or even synergistic neurotoxicity, where the combined effects of multiple pesticides could amplify neurotoxicity [11, 12]. In addition, countries with the highest growth in tomato cultivation, including China, India, and the United States, also have a rising prevalence of PD, which suggests that contaminated tomatoes could be contributing to the worldwide growth of PD.

We fully acknowledge that the evidence presented in our paper is circumstantial and that our hypothesis remains speculative. While we do not claim that tomatoes — or specifically the pesticides used on them — are an actual cause of PD, we believe that the growing use of pesticides in agriculture and their potential (cumulative) neurotoxic effects merit serious consideration. It is crucial to critically look at current pesticide regulations and risk assessments, which often do not consider the long-term neurotoxic effects of individual compounds, and especially the combined effects of multiple compounds [13]. Future research should focus on real-world exposures, including more adequate risk assessment, with a specific focus on interactions between environmental exposures, including the potential for cumulative and synergistic toxicity. Findings could help inform much-needed preventative measures to mitigate the growing burden of PD worldwide.

Table 1: Top pesticides applied on tomatoes across California by pounds applied (2010–2020).

Top pesticides used on tomatoes by total pounds of active ingredient applied each year from 2010 to 2020. Source: California’s Pesticide Use Report (PUR) database [10]. For each pesticide, it is indicated whether it has been previously linked to Parkinson’s disease (PD), along with its chemical class and whether it is systemic or non-systemic.

References 

1. Sage JI. Tomatoes and Parkinson's disease. Med Hypotheses. 1989;28(2):75-9. 
2. Bogers JS, Paul KC, Dorsey ER, Bloem BR. Tomatoes and Parkinson’s disease – an old hypothesis revisited. Medical Hypotheses. 2026;206. 
3. Atterling Brolin K, Schaeffer E, Kuri A, Rumrich IK, Schumacher Schuh AF, Darweesh SKL, et al. Environmental Risk Factors for Parkinson's Disease: A Critical Review and Policy Implications. Mov Disord. 2025;40(2):204-21. 
4. Su D, Cui Y, He C, Yin P, Bai R, Zhu J, et al. Projections for prevalence of Parkinson's disease and its driving factors in 195 countries and territories to 2050: modelling study of Global Burden of Disease Study 2021. BMJ. 2025;388:e080952. 
5. Tanner CM, Kamel F, Ross GW, Hoppin JA, Goldman SM, Korell M, et al. Rotenone, paraquat, and Parkinson's disease. Environ Health Perspect. 2011;119(6):866-72. 
6. Kab S, Spinosi J, Chaperon L, Dugravot A, Singh-Manoux A, Moisan F, et al. Agricultural activities and the incidence of Parkinson's disease in the general French population. Eur J Epidemiol. 2017;32(3):203-16. 
7. Betarbet R, Sherer TB, MacKenzie G, Garcia-Osuna M, Panov AV, Greenamyre JT. Chronic systemic pesticide exposure reproduces features of Parkinson's disease. Nat Neurosci. 2000;3(12):1301-6. 
8. Darweesh SKL, Vermeulen R, Bloem BR, Peters S. Exposure to Pesticides Predicts Prodromal Feature of Parkinson's Disease: Public Health Implications. Mov Disord. 2022;37(5):883-5. 
9. Krzyzanowski B, Mullan AF, Dorsey ER, Chirag SS, Turcano P, Camerucci E, et al. Proximity to Golf Courses and Risk of Parkinson Disease. JAMA Netw Open. 2025;8(5):e259198. 
10. California Department of Pesticide regulation (CDPR). Pesticide Use Report (PUR) data  Available from: https://www.cdpr.ca.gov/pesticide-use-in-california/. 
11. Paul KC, Krolewski RC, Lucumi Moreno E, Blank J, Holton KM, Ahfeldt T, et al. A pesticide and iPSC dopaminergic neuron screen identifies and classifies Parkinson-relevant pesticides. Nat Commun. 2023;14(1):2803. 
12. Braun G, Herberth G, Krauss M, Konig M, Wojtysiak N, Zenclussen AC, et al. Neurotoxic mixture effects of chemicals extracted from blood of pregnant women. Science. 2024;386(6719):301-9. 
13. Bloem BR, Boonstra TA. The inadequacy of current pesticide regulations for protecting brain health: the case of glyphosate and Parkinson's disease. Lancet Planet Health. 2023;7(12):e948-e9. 
14. Kamel F, Tanner C, Umbach D, Hoppin J, Alavanja M, Blair A, et al. Pesticide exposure and self-reported Parkinson's disease in the agricultural health study. Am J Epidemiol. 2007;165(4):364-74. 
15. Shrestha S, Parks CG, Umbach DM, Richards-Barber M, Hofmann JN, Chen H, et al. Pesticide use and incident Parkinson's disease in a cohort of farmers and their spouses. Environ Res. 2020;191:110186. 
16. Rhodes SL, Fitzmaurice AG, Cockburn M, Bronstein JM, Sinsheimer JS, Ritz B. Pesticides that inhibit the ubiquitin-proteasome system: effect measure modification by genetic variation in SKP1 in Parkinson׳s disease. Environ Res. 2013;126:1-8. 
17. Brouwer M, Huss A, van der Mark M, Nijssen PCG, Mulleners WM, Sas AMG, et al. Environmental exposure to pesticides and the risk of Parkinson's disease in the Netherlands. Environ Int. 2017;107:100-10. 
18. Gatto NM, Cockburn M, Bronstein J, Manthripragada AD, Ritz B. Well-water consumption and Parkinson's disease in rural California. Environ Health Perspect. 2009;117(12):1912-8. 
19. Narayan S, Liew Z, Paul K, Lee PC, Sinsheimer JS, Bronstein JM, et al. Household organophosphorus pesticide use and Parkinson's disease. Int J Epidemiol. 2013;42(5):1476-85. 
20. Manthripragada AD, Costello S, Cockburn MG, Bronstein JM, Ritz B. Paraoxonase 1, agricultural organophosphate exposure, and Parkinson disease. Epidemiology. 2010;21(1):87-94.