You might want to hold off on leaving a glass of milk out with Santa’s cookies this Christmas.

A recent study done by Robert Abbott from the Shiga University of Medical Science in Japan has found a connection between frequent milk drinking and Parkinson’s disease. 

The phenomenon resulted after a pesticide which was widely used in the 80’s made its way into the United State’s supply of milk. Abbott and his team looked back into a similar case that involved Hawaii using the pesticide with pineapples during the same time period. Researchers found heptachlor epoxide pesticide, which was used to kill insects feeding on the pineapples, was able to leak into the gruel fed to the cows from the pineapple’s debris. This caused the pesticide to make its way into the milk supply.

A photo posted by @chickendinner83 on

Using this information, along with data from a study of heart disease in Japanese-Americans living in Hawaii at the time, Abbott was able to find detailed accounts of the food and milk 8,000 men drank from mid-life until death. Researchers analyzed 449 of the participants brains which were donated upon death, recording the density of the neurons in the portion of the brain that affects Parkinson’s disease. Using this information, the researchers were able to determine that men who drank two glasses of milk per day (16 oz) had the thinnest nerve networks, thus increasing the development of Parkinson’s disease in comparison to men who rarely drank milk.

According to TIME, the team was also able to find residue of heptachlor epoxide inside the body. The pesticide has accumulated before the neurons were damaged, thus hinting that the pesticide was responsible for the thinning nerves. It’s also important to note that the team was not able to test a sample of the milk, which leaves a big “what if” in terms of a definite culprit. Abbott explains, “[the data] is not complete, but it’s very suspicious.”

While the pesticide was banned from the United States in 1988, heptachlor epoxide has remained in the soil long after the pesticide has been used. Rather than avoiding milk all together, this study proves that we should instead focus on the impact chemicals could have on our health in the long term.

[via TIME]