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able to trigger synuclein accumulation in human nerve cells, at least in a petri dish, though the study has since been retracted so it’s unclear what the data actually showed.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:

Eating the Way Nature Intended

The Paleolithic period, also known as the Stone Age, only goes back about two million years. Humans and other great apes have been evolving for the last 20 million years, starting back in the Miocene era. We hear a lot about the paleolithic diet, but that only represents the last 10 percent of hominoid evolution. What about the first 90 percent?

During the Miocene era, the diet “is generally agreed to have been a high-fiber plant-based diet…” For the vast majority of our family’s evolution, we ate what the rest of our great ape cousins eat—leaves, stems, and shoots (in other words, vegetables), as well as fruits, seeds, and nuts. I explore this in my video Lose Two Pounds in One Sitting: Taking the Mioscenic Route.

“Anatomically, the digestive tracts of humans and great apes are very similar.” In fact, our DNA is very similar. So, what do our fellow great apes eat? Largely vegetarian diets with high greens and fruit consumption. Just largely vegetarian? It’s true that chimpanzees have been known to hunt, kill, and eat prey, but chimpanzees’ “intake of food of animal origin is still at a very low level…with only 1.7% of chimpanzee feces providing evidence of animal food consumption.” This is based on eight years of work collecting nearly 2,000 fecal samples. So, even the most carnivorous of great apes appears to eat about a 98 percent plant-based diet. In fact, we may be closest to the diet of bonobos, one of the less known great apes, who eat nearly exclusively plant-based diets, as well.

Even our Paleolithic hunter-gatherer ancestors must have done an awful lot of gathering to get the upwards of 100 grams of fiber a day they may have consumed. What would happen if researchers put people on an actual Paleolithic diet? Not a supermarket-checkout-aisle-magazine paleo diet or some caveman blogger diet, but an actual 100-grams-of-daily-fiber diet or, even better, a mioscenic diet, taking into account the last 20 million years of evolution since we split with our common great ape ancestors.

Dr. David Jenkins and colleagues gave it a try and “tested the effects of feeding a diet very high in fiber.” How high? We’re talking 150 grams of daily fiber, far higher than the recommended 20 to 30 grams a day. However, 150 grams is similar to what populations in rural Africa used to eat—populations almost entirely free from many of our chronic killer diseases, such as colon cancer and heart disease.

The high-fiber diet didn’t mess around. Lunch, for example, could include Brussels sprouts, okra, green peas, mushrooms, filberts, and a plum. And dinner? How about asparagus, broccoli, eggplant, carrots, and honeydew melon? Surely, simply eating a lot of fruits, veggies, and nuts can’t be very satisfying, right? Actually, it got the maximum satiety rating from every one of the ten subjects, unlike the starch-based and low-fat diets which scored lower. Why? “All of the diets were designed to be weight-maintaining,” meaning the researchers didn’t want weight loss to confound the data. So, to get a full day’s calories of whole plant foods, the subjects had to eat about 11 pounds of food a day! Not surprisingly, this resulted in some of the largest bowel movements ever recorded in the medical literature, with men on the high-fiber vegetable-based diet exceeding a kilogram of fecal weight per day. You know how some people on weight loss diets lose two pounds a week? Well, in this study, the subjects dropped two pounds in one sitting.

That wasn’t the only record-breaking drop: A 33 percent drop in LDL cholesterol within just two weeks was seen. Even without any weight loss, bad cholesterol levels dropped by one-third within two weeks. That’s one of the biggest drops I’ve ever seen in any dietary intervention—better than achieved on a starch-based vegetarian diet or  a low saturated fat American Heart Association-type vegetarian diet. This was a “cholesterol reduction equivalent to a therapeutic dose of a statin” drug. So, we need to take a drug to get our cholesterol levels down to where they would be normally were we to eat a more natural diet.

We’ve been eating 100 grams of fiber every day for millions of years. This diet is similar to what’s eaten by populations who don’t suffer from many of our chronic diseases. Maybe this shouldn’t be called a “very high fiber” diet. Maybe what we eat today should be considered a very low, extremely fiber-deficient diet.

Maybe it’s normal to eat 100 grams of fiber a day. Maybe it’s normal to be free of heart disease. Maybe it’s normal to be free of constipation, hemorrhoids, diverticulitis, appendicitis, colon cancer, obesity, type 2 diabetes, and all other the diseases of Western civilization.


How do we know our ancient ancestors ate more than 100 grams of fiber a day? We can examine their fossilized fecal matter, as I discuss in my video Paleopoo: What We Can Learn from Fossilized Feces.

For more evidence on what our natural diet is, see my What’s the Natural Human Diet? video.

Other popular paleo videos include:

Excited to share what you’ve learned about diet? Well, it turns out you can share more than my videos. Check out How to Become a Fecal Transplant Super Donor.

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:

Do Flaxseeds Offer Sufficient Omega-3’s for Our Heart?

According to two of perhaps the most credible nutrition authorities, the World Health Organization and the European Food Safety Authority, we should get at least half of a percent of our calories from the essential omega-3 fat ALA. That’s easy: Just have about one tablespoon a day of chia seeds or ground flaxseeds and you’re all set.

Our body can then take the short-chain ALA from our diet and elongate it into the long-chain omega-3s, EPA and DHA. The question, however, has long been whether our bodies can make enough EPA and DHA for optimal health. How would one determine that? Take fiber, for example. “A convincing body of literature showed an increased [heart disease] risk when diets were low in fiber,” so the Institute of Medicine came up with a recommendation for about 30 grams a day, which is an intake observed to protect against coronary heart disease and to reduce constipation. “Thus, just as [cardiovascular disease] was used to help establish an [adequate intake] for dietary fiber,” it was also used as a way to develop a recommendation for EPA and DHA, as I discuss in my video Should We Take EPA and DHA Omega-3 for Our Heart?.

With reviews published as late as 2009 suggesting fish oil capsules may help with heart disease, nutrition authorities recommended an additional 250 mg per day of preformed EPA and DHA, since, evidently, we were not making enough on our own if taking more helped. So, in addition to the one or two grams of ALA, it was suggested we should take 250 mg of preformed DHA/EPA, which can be gotten from fish or algae.

Fish is a tough one. On one hand, fish has preformed DHA and EPA, but, on the other hand, our oceans have become so polluted that seafood may also contain various pollutants, including dioxins, PCBs, pesticides like DDT, flame-retardant chemicals, and heavy metals, including mercury, lead, and cadmium, all of which can negatively affect human health. Dietary exposure to PCBs, for example, is associated with increased risk of stroke in general and an almost three times higher risk of hemorrhagic stroke. Unless you live next to a toxic waste dump, the major  source of exposure to PCBs is fish consumption. Salmon may be the worst.

This may explain why studies in the United States have shown that just a single serving of fish a week may significantly increase one’s risk of diabetes, emphasizing that even levels of these pollutants once considered safe may “completely counteract the potential benefits of [the omega-3] fatty acids and other nutrients present in fish,” and lead to the type of metabolic disturbances that often precede type 2 diabetes. Now, one could get their daily 250 mg of preformed DHA/EPA from algae oil rather than fish oil. Algae oil is free of toxic contaminants because it is manufactured without pollutant exposure. 

Then, one could get the best of both worlds: the beneficial nutrients without the harmful contaminants. However, it was demonstrated recently that these long-chain omega-3s don’t seem to help with preventing or treating heart disease after all. Since that was the main reason we thought people should get that extra 250 mg of preformed EPA and DHA, why do I still recommend following the guidelines in my Optimum Nutrition Recommendations? Because the recommendations were not just based on heart health, but brain health, as well. See my video Should We Take DHA Supplements to Boost Brain Function?.


Other omega-3 videos include:

If the no-heart-benefit surprised you, check out Is Fish Oil Just Snake Oil?.

Surprised by the link with diabetes and want to learn more? See:

Food Sources of PCB Chemical Pollutants has more on PCBs, and here are additional videos on other pollutants:

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: