A new study links a pesticide (organochlorine pesticides) used by farmers (until it was banned for commercial sale in the U.S. in 1988) to the development of Parkinson’s disease in people who were exposed to it.
Earlier studies found a link between the neurodegenerative disorder that affects motor neurons in the brain and the consumption of dairy products, but there was little evidence as to how milk, cheese, and other dairy products might increase a person’s risk for Parkinson’s. Scientists hypothesized that chemicals in cows’ milk might be responsible.
During the 1980’s, an environmental scandal was unfolding in Hawaii. An organochlorine pesticide used by pineapple farmers made its way into the milk supply when cows were fed a gruel made in part from the pineapple debris.
There was also a study occurring at that time of heart disease among Japanese-American men that involved more than 8,000 men who were followed from mid-life to death. Researchers gathered information about what the men ate, how much milk they drank, and some of the participants agreed to donate their brain to science after death.
The men were followed for more than 30 years and scientists and autopsies were performed after their death.
Robert Abbott, from Shiga University of Medical Science in Japan, and his colleagues examined 449 brains and recorded the density of the area that is known to be affected by Parkinson’s – the substantia nigra region of the brain
- Neuron density in the brains was found to be lowest among non-smokers who drank more than 2 glasses of milk a day (16 oz.), suggesting compromised function of these nerves compared to men who drank the least amount of milk.
- The milk drinkers also had residues of specific organochlorines called heptachlor epoxide.
- Researchers also discovered that heptachlor epoxide accumulated before the cell damage, which suggests that the chemical was responsible for triggering the changes associated with Parkinson’s disease.
Robert Abbott, from Shiga University of Medical Science in Japan, said his team couldn’t say for certain whether the milk was the source of the pesticides in the men’s brains because they didn’t have samples to analyze, but it’s a logical conclusion.
“We don’t have all the data yet, but we are close to finding the smoking gun here,” he says. “It’s not complete, but it’s very suspicious.”
“There are several possible explanations for the association, including chance,” said Honglei Chen of the National Institute of Environmental Health Sciences, who wrote an editorial accompanying the study, in the release. “Also, milk consumption was measured only once at the start of the study, and we have to assume that this measurement represented participants’ dietary habits over time.”
While heptachlor epoxide is no longer used as an insecticide in the U.S., it tends to linger in soil and water for many years. The chemical has been found in goat and cow milk in Ethiopia, and other organochlorines have been detected in the milk supply in Italy.
Heptachlor was used for termite control and was also sprayed on crops through the 1960’s and 1970’s, and use of the chemical steadily declined until it was finally banned in 1988. It is still permitted by the Environmental Protection Agency (EPA) to control fire ants in power transformers. The Food and Drug Administration (FDA) limits for residual heptachlor and heptachlor epoxide for most food crops is .01 or .02 parts per million, and .1 parts per million for milk solids.
It is not the only chemical that has been linked to Parkinson’s disease. Glyphosate, the blockbuster herbicide made by Monsanto, has also been shown to induce cell death.
The team says people shouldn’t be afraid to drink milk because of these findings. The data only suggests that diet and lifestyle factors should be considered more deeply when it comes to their role in the development of Parkinson’s.
“This adds to the literature that diet may indeed play a role in Parkinson’s,” says Abbott. “But it also tells us that there is more to food than just its nutritional value. There’s contamination, and what’s on that food.”
 Medical Daily
Julie Fidler is a freelance writer, legal blogger, and the author of Adventures in Holy Matrimony: For Better or the Absolute Worst. She lives in Pennsylvania with her husband and two ridiculously spoiled cats. She occasionally pontificates on her blog.