A pesticide found in milk in Hawaii has been linked to signs of Parkinson's disease.
Professor Robert Abbott, MPH, PhD, at the Shiga University of Medical Science in Otsu, Japan, and his colleagues studied a group of 449 Japanese-American men living in Hawaii who'd been part of a larger study about aging and had donated their brains to science after they died.
The research team found that nonsmoking men who drank more than two cups of milk a day had 40 percent fewer brain cells in a certain area of the brain than men who drank less than two cups of milk each day. Loss of brain cells in that area, known as the substantia nigra, is what happens during Parkinson's development, and it can start decades before someone even starts to show symptoms of the disease. The researchers also found that 90 percent of the heavy milk drinkers had more traces of a pesticide called heptachlor epoxide than men who did not drink any milk.
Before Heptachlor was banned in the United States in 1988, it had been used by pineapple farmers. So, while the scientists weren't able to study actual samples of the milk the men drank, it's known that the pesticide was "found at excessively high levels in the milk supply in Hawaii in the early 1980s," according to the Neurology study.
Another surprising finding was that men who drank more than two cups of milk and also smoked showed no signs of brain cell loss.
"This study is unique because it brings together two critical but different pieces of information — environmental exposure and physical changes in the brain — to understand potential contributors of Parkinson's disease," said James Beck, vice president of scientific affairs at the Parkinson's Disease Foundation, in a statement to NBC News. "For people living with Parkinson's, understanding the impact of environmental factors is crucial as nearly 85 percent have no idea why they developed Parkinson's. There is no clear genetic link."
Parkinson's is a progressive disorder of the nervous system that affects movement and often results in tremors. The Parkinson's Disease Foundation estimates that 7 million to 10 million Americans have the condition.