“The link between dairy products and Parkinson’s disease has been found in other studies,” said study author R. D. Abbott, PhD, with the Shiga University of Medical Science in Otsu, Japan. “Our study looked specifically at milk and the signs of Parkinson’s in the brain.”
The research participants consisted of 449 Japanese-American men who participated in the Honolulu-Asia Aging Study and were followed for more than 30 years until death. Autopsies and tests investigated whether participants had lost brain cells in the substantia nigra area of the brain, which occurs in Parkinson’s disease. The amount of pesticide residue (heptachlor epoxide) was measured in 116 brains.
Heptachlor epoxide was found at very high levels in the milk supply in the early 1980s in Hawaii, where it was used in the pineapple industry. It was used to kill insects and was removed from use in the US around that time. The pesticide may also be found in well water.
Heptachlor epoxide were found in 90 percent of people who drank the most milk, compared to 63 percent of those who did not drink any milk. The research participants who drank more than two cups of milk per day had 40 percent fewer brain cells in that area of the brain than people who drank less than two cups of milk per day.
“There are several possible explanations for the association, including chance,” said Honglei Chen, MD, PhD, with the National Institute of Environmental Health Sciences and a member of the American Academy of Neurology, who wrote a corresponding editorial. “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.”
1.R. D. Abbott, G. W. Ross, H. Petrovitch, K. H. Masaki, L. J. Launer, J. S. Nelson, L. R. White, C. M. Tanner. Midlife milk consumption and substantia nigra neuron density at death. Neurology, 2015; DOI: 10.1212/WNL.0000000000002254