The Role of Pesticides in Parkinson’s Disease

In the original description of Parkinson’s disease by none other than Dr. James Parkinson himself, he described a characteristic feature of the disease: constipation, which may precede the diagnosis by many years. In fact, bowel movement frequency may be predictive. Men with less than one bowel movement a day were four times more like likely to develop Parkinson’s an average of 12 years later. This could be simply a really early symptom of the disease tied to decreased water intake, however. Many Parkinson’s patients report never really feeling very thirsty, and perhaps that led to the constipation. “Alternately, one may speculate that constipation also increases the risk of Parkinson’s disease as constipation results in a longer stay of the feces in the bowel and thus more absorption of neurotoxicants,” neurotoxins from the diet.

Two studies suggest an association between constipation and Parkinson’s, but, at the same time, 38 studies link the disease to pesticide exposure and by now more than 100 studies link pesticides to an increased risk of up to 80 percent.

Many of these studies are on occupational exposure, like that experienced by farmworkers, who may reduce their risk of Parkinson’s by wearing gloves and washing their clothes, but Parkinson’s has also been linked to ambient exposure. In the United States where approximately a billion pounds of pesticides are applied annually, just living or working in high-spray areas may increase Parkinson’s risk. It’s the same with using pesticides in the home. I didn’t realize how common household pesticide use was, and a study out of UCLA suggests it might not be such a good idea. 

Pesticides may cause DNA mutations that increase susceptibility for Parkinson’s or play a more direct role. Many neurodegenerative diseases appear to be caused by the buildup of misfolded proteins. In Alzheimer’s, it’s the protein amyloid beta; in Creutzfeldt-Jakob and mad cow disease, it’s prions; in Huntington’s, it’s a different protein; and in Parkinson’s disease, it’s a protein called alpha synuclein. A variety of pesticides—8 out of the 12 tested by researchers—were able to trigger synuclein accumulation in human nerve cells, at least in a petri dish, though the study has since been retracted so it’s unclear what the data actually showed.

The buildup of synuclein may play a role in killing off specialized nerve cells in the brain, 70 percent of which may be gone by the time the first symptoms arise. Pesticides are so good at killing these neurons that researchers use them to try to recreate Parkinson’s disease in animals. Is there any way to stop the process? As of this writing, there aren’t yet any drugs that can prevent this protein aggregation. What about flavonoid phytonutrients, natural compounds found in certain fruits and vegetables? Flavonoids can cross the blood-brain barrier and may have neuroprotective effects, so researchers tested 48 different plant compounds to see if any could stop the clumping of synuclein proteins into the little fibers that clog up the cell. And, indeed, they found a variety of flavonoids that can not only inhibit the spider web-like formation of synuclein fibers, but some could even break them up. It turns out flavonoids may actually bind to synuclein proteins and stabilize them.

In my video Berries vs. Pesticides in Parkinson’s Disease, you can see healthy nerve cells and the neurites, the arms they use to communicate to one another. After exposure to a pesticide, however, you can see how the cell is damaged and the arms are retracted. But, if you first incubate the nerve cells with a blueberry extract, the nerve cell appears better able to withstand the pesticide effects. So, this implies that flavonoids in our diet may be combating Parkinson’s disease as we speak, and healthy diets may be effective in preventing and even treating the disorder. However, these were all petri dish experiments in a laboratory. Is there any evidence that people eating berries are protected from Parkinson’s?

A study published quite a long time ago suggested the consumption of blueberries and strawberries was protective, but it was a tiny study and its results were not statistically significant. Nevertheless, that was the best we had…until now. In a more recent study, those eating a variety of phytonutrients were less likely to develop Parkinson’s disease. Specifically, higher intake of berries was associated with significantly lower risk. The accompanying editorial, “An Apple a Day to Prevent Parkinson Disease,” concluded that more research is necessary, but, until then, “an apple a day might be a good idea.” Of course, that’s coming from a man. Apples appeared protective against Parkinson’s for men, but not women. However, everyone appeared to benefit from the berries.

We may not want to have our berries with cream, though, as milk may be contaminated with the same kind of neurotoxic pesticide residues found in the brains of Parkinson’s disease victims.


I’ve produced other videos on Parkinson’s disease, including: 

Learn about other neurological muscular disorders, including essential tremor and ALS:

The same reason Parkinson’s may be related to constipation may also explain the breast cancer connection. For more on this, see my video Breast Cancer and Constipation.

What else can berries do?

But what about all the sugar in fruit? See my videos If Fructose Is Bad, What About Fruit? and How Much Fruit Is Too Much?.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

How to Boost DNA Repair with Produce

“In the light of strikingly consistent observations from many epidemiological [population-based] studies, there can be little doubt that the habitual consumption of diets high in fruits and vegetables helps to reduce the risk of development of degenerative diseases, including many types of cancers.” Not satisfied with merely telling people to eat their fruits and veggies, scientists want to know the mechanism. I discuss this topic in my Which Fruits and Vegetables Boost DNA Repair? video.

Not just vehicles for antioxidants, fruits and vegetables contain innumerable phytonutrients that can boost our detoxification enzymes, modulate gene expression, and even modulate DNA repair pathways. “Until fairly recently…it was generally assumed that functions as important as DNA repair were unlikely to be readily affected by nutrition,” but, if you compare identical twins to fraternal twins, only about half to three quarters of DNA repair function is genetically determined. We may be able to control the rest.

“It is estimated that, on average, there are 800 incidents of DNA damage [in our bodies] per hour,” which is about 19,000 hits to our DNA every day. What’s more, “that DNA damage can cause mutations and give rise to cancer, if not repaired.” Thankfully, “the regulation of [DNA] repair can be added to the list of biological processes that are influenced by what we eat—and, specifically, that this might constitute part of the explanation for the cancer-preventive effects of many plant-based foods.”

Any plants in particular? Nine fruits and vegetables were tested to find out which ones were better able to boost DNA repair: lemons, persimmons, strawberries, oranges, choy sum (which is like skinny bok choy), broccoli, celery, lettuce, and apples. Which ones made the cut? Lemons, persimmons, strawberries, broccoli, celery, and apples all conferred DNA protection at very low doses.

Lemons, for example, were found to cut DNA damage by about a third. Was it the vitamin C? No. Removing the vitamin C from the lemon extract did not remove the protective effect. However, if you first boiled the lemon for 30 minutes, the protective effect was lost.


If it’s not the vitamin C, what might it be? That’s the subject of my video Citrus Peels and Cancer: Zest for Life?

Surprised that the lemon benefit was abolished by cooking? Find out which vegetables it may be best to eat raw in Best Cooking Method.

What about cooked versus raw garlic? See my video Inhibiting Platelet Activation with Garlic and Onions.

For more on DNA protection and repair, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Plant-Based Diets Put to the Test for Diabetes

My Why Is Meat a Risk Factor for Diabetes? video shows how meat may play a role in increasing the risk of diabetes, and How May Plants Protect Against  Diabetes? and Plant-Based Diets and Diabetes discuss the potential protective role of healthy plant foods. But plant-based diets not only appear to guard against getting diabetes in the first place, they may successfully treat the disease better than the diabetic diets patients typically are placed on, benefiting both weight and cholesterol.

Diets based on whole plant foods can result in significant weight loss without limiting portion size or counting calories, because plant foods tend to be so calorically dilute. In my video Plant-Based Diets for Diabetes, you can see the volume of 100 calories of broccoli, tomatoes, and strawberries compared to 100 calories of chicken, cheese, or fish. People just can’t seem to eat enough of the plant foods to compensate for the calorie deficit, so they lose weight eating whole plant foods.

Most importantly, a plant-based diet works better. A plant-based diet beat out the conventional American Diabetes Association diet in a head-to-head, randomized, controlled clinical trial, without restricting portions and without calorie- or carb-counting. A review of all such studies found that those following plant-based diets experience improved reductions in blood sugars, body weight, and cardiovascular risk, compared with those on diets including animal products.

Cardiovascular risk is what kills diabetics the most. They’re more likely to get strokes, more likely to suffer heart failure. In fact, “[d]iabetes has been proposed as a coronary heart disease risk equivalent, which means diabetic patients without a history of coronary disease have an equivalent risk to that of nondiabetic individuals with confirmed heart disease.”

A newer study used a technique to actually measure insulin sensitivity. It improved on both diets in the first three months, but then the vegetarian diet pulled ahead. The researchers also found that the LDL cholesterol fell significantly in the vegetarian group. Indeed, that’s what we see when people are put on plant-based diets: Cholesterol comes down so much it can actually reverse the atherosclerosis progression—that is, reverse the progression of heart disease.

We know about the beneficial effect of a vegetarian diet on controlling weight, blood sugars, cholesterol, insulin sensitivity, and oxidative stress compared to conventional diabetic diets, but what about quality of life and mental health? How did people feel after making such a dramatic change in their diets? In a randomized, controlled trial, study subjects were assigned either to a plant-based diet group or a control group. The plant-based group ate vegetables, grains, beans, fruits, and nuts with animal products limited to a maximum of one daily portion of low-fat yogurt. The control group followed an official diabetes diet.

Quality of life improved on both diets in the first three months, but, within six months, the plant-based group clearly pulled ahead. The same results were seen with depression scores: They dropped in both groups in the first three months, but started to rebound in the control group.

The bottom line is that the more plant-based diet “led to a greater improvement in quality of life and mood. Patients consuming a vegetarian diet also felt less constrained than those consuming the conventional diet.” People actually felt the conventional diabetic diet was more restrictive than the plant-based diet. Disinhibition decreased with a vegetarian diet, meaning those eating vegetarian were less likely to binge, and the subjects in the vegetarian group tended to feel less hungry. All of this helps with sustainability in the long term, which is, of course, critical for any dietary change. So, not only do plant-based diets appear to work better, but they may be easier to stick to. And, with the improvement in mood, patients may exhibit desired improvements not only in physical, but also in mental, health.


For those seeking a deeper understanding of what diabetes really is and what causes it, check out How Not to Die from Diabetes and this series of videos:

Thankfully, not only can diabetes be reversed, but so can some of its complications. See Can Diabetic Retinopathy Be Reversed? and, for diabetic neuropathy, my live annual review From Table to Able: Combating Disabling Diseases with Food.

Of course, preventing it is better:

There are some foods that may increase the risk:

And others that may help:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: