Produce Delivery and Parkinson’s Disease: Not all Fruits and Vegetables are Created Equal

Is fresh best?

There is a presumption that fresh is best. That organic produce is better than pesticide-laden produce, and food grown with love in a local permaculture farm is somehow more nutritious than the mass-produced monocrops harvested from depleted soil from around the world. These notions are informed a little bit by data and a lot by intuition/ bias. Scientifically, very little research has gone into determining if/how farming practices, packaging, and delivery affects the nutritional value of any particular food.

One of the most successful and frequently referenced nutrition studies in Parkinson disease (PD) comes from the Nurses’ Health Study (NHS). Researchers followed healthy adults for over a decade and found that individuals with the highest intake of fruits and vegetables (among other foods) were the least likely to be diagnosed with PD. [Gao X, et al, 2007] Since fruits and vegetable have also been shown to protect against Alzheimer’s disease, cardiovascular disease, and cancer and plants are a rick source of nutrition (polyphenols, glutathione, fiber, etc.) the findings from the NHS make sense. Apparently, there is something good about fruits and vegetables…

It’s much easier to package and deliver a pill than it is a diet.

I’m eager to make parkinsonism preventable and it seems obvious that a diet high in fruits and vegetables should be part of the prevention plan. While I’m happy to scream “eat more fruits and vegetables” from the mountaintops, some refinement is necessary to determine whether French fries and ketchup can be included alongside kale and currants.

In the NHS study, the researchers put fresh, frozen, and canned (tinned) produce in the same category, making it impossible to determine whether one is better than the other. Below is an example of a Food Frequency Questionnaire (FFQ) used in NHS; the way the questions are being asked, it is impossible to differentiate between canned and fresh, let alone organic or conventional.

To take this research a step further, I set out to answer two questions:

  • Once diagnosed, does intake of fruits and vegetables slow rate of progression?
  • Does it matter whether the produce is fresh, frozen, or canned?

My hypothesis was that the more fruits and vegetables a person eats, the slower their PD progression. I predicted all forms of produce would be good, but I thought they would have different levels of good, with fresh being better than frozen and frozen better than canned.

Since 2016, we have surveyed over 1700 people with idiopathic PD about their diagnosis, symptoms, and diet and it is safe to say we now have enough data to prove my hypothesis wrong: Not all produce is good for you, and in fact, it appears some of it may be bad for you!

The devil is in the details.

As you might expect, the more often people reported consuming fresh fruits and fresh vegetables, the fewer PD symptoms they reported over time. Frozen fruit fell on the beneficial side, but not enough to reach statistical significance. To my surprise, frozen vegetables, canned vegetables, and canned fruit were actually associated with faster rate of PD progression.

Individuals with idiopathic PD were surveyed about their diagnosis, symptoms and diet. (N=1742) All analyses were adjusted for age, gender, income, and years since diagnosis.

This type of study isn’t able to tell us whether the fruits and vegetables that are causing these changes in outcomes, or if you change your diet whether that will change your outcome. It only tells us that people doing the best over time are eating more fresh produce, while the most symptomatic people are more often eating from cans.

While some people reading this will find this information empowering, others may find themselves scared and frustrated. Food scarcity is a global problem and fresh produce is more expensive than canned. Not everyone has access to fresh produce and sometimes frozen or canned it the only food available. Beyond finances, some people live in food deserts with limited access to fresh produce or have mobility issues making it difficult to get to the market regularly. Make changes slowly and be easy on yourself— lifestyle modification comes in fits and starts. Do what you can with what you have and focus on getting more ‘good’ stuff in before worrying about eliminating the ‘bad’.  Notice what’s in season at the grocery store and start a list of all the dishes you enjoy that contain fresh fruits and fresh vegetables. Challenge yourself: how many enjoyable and affordable ways can you find to incorporate fresh fruits and fresh vegetables into your diet this week?

Side effects of fresh fruits and fresh vegetables:

Increasing your intake of fresh fruits and vegetables is likely to increase the frequency of bowel movements, reduce inflammation, and decrease risk dementia and cardiovascular disease.

Author: Laurie K Mischley, ND PhD MPH

Dr. Mischley developed the PRO-PD rating scale and the PD screening tool, ParK-9, using dogs to identify the scent of PD from ear wax. She is principal investigator of the “CAM Care in PD” study, designed to identify the relationship between lifestyle choices and risk of PD progression. She is an advocate for patient-centered care and research and has published on the role of diet, exercise, nutritional supplements, and social health as they relate to PD severity and progression. Dr Mischley is also the founder of the Online Parkinson’s School. You can access further resources at

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