A pesticide that was present in milk a few decades ago may be linked to Parkinson’s disease in people today, a new study suggests.
In the study – published December 9 in the journal Neurology – the researchers looked Japanese-American men who lived in Hawaii and found that the number of brain cells in men, who drank two cups of milk (or more) per day at the beginning of the study, was 40 percent lower about 30 years later in life, compared with those who drank less than two cups of milk daily.
Loss of brain cells in the area of the brain called substantia nigra may indicate early signs of Parkinson’s disease, also known as idiopathic or primary parkinsonism, paralysis agitans, or hypokinetic rigid syndrome. According to the researchers, the loss of brain cells can start even decades before any symptoms of the disease are seen.
Researchers found the residue of heptachlor epoxide (a type of pesticide) in the brains of 90 percent of the men who drank more than two cups of milk per day, and in 63 percent of those who did not drink as much milk.
In the early 1980s, high levels of pesticide were discovered in the milk supply in Hawaii. The chemical was actually meant to be used in the pineapple industry for insect control. The U.S. Environmental Protection Agency stated that by 1988, the sale of the pesticide in the United States was banned.
According to the Agency for Toxic Substances & Disease Registry, people still use a related compound to control fire ants.
Study author Robert D. Abbott, of the Shiga University of Medical Science in Otsu, Japan, said that there is no direct evidence that the milk was infested with the pesticide, but there is no other explanation for the presence of the heptachlor epoxide in the men’s brains (who consumed milk).
For the study, the researchers tracked approximately 450 Japanese-American men in Hawaii – whose average age was 54 at the start of the study – for more than 30 years until they died. Researchers performed autopsies on 116 of the men, and analysed the brain cells in the substantia nigra, as well as the amount of pesticide residue.
It is important to note that the results of the new study show that there is an association between the milk or pesticide and the development of Parkinson’s disease, rather than a cause-and-effect relationship between these specific factors.
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