Consumption of milk is usually considered healthy. For years, slogans like "Drink more milk," "Milk. It does a body good," and "Got Milk?" have promoted the beverage.

For those drinking more milk in Hawaii before the 1980s, there were ingredients that were not doing the body any good. The milk was found to contain heptachlor epoxide, an organochlorine pesticide that had been identified at high levels in the milk supply in the early 1980s. It had been used extensively in the pineapple industry to eradicate insects and was discontinued in the United States during that period.

This milk intake had long-term consequences on those who drank it, as identified in a study recently published in Neurology. The data related to milk intake had been collected for a period of three years in men ages 45-68 who later had postmortem brain examinations.

The substantia nigra brain region was examined to determine the levels of heptachlor epoxide residue, and neuron density was measured. The substantia nigra showed degeneration present in Parkinson's disease.

Robert D. Abbott, Ph.D., with the Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, Japan, headed the team. The researchers found a correlation with lower neuron density and higher consumption of milk.

However, the association only held for those who did not smoke. Smoking has been shown to be protective of having Parkinson's disease in other studies.

Other studies have also linked pesticides to a greater risk of later developing Parkinson's disease.

A recently published systematic review of studies on neurodegenerative disorders linked to pesticide exposure found an association with Parkinson's disease. Also, farmers and those working closely with pesticides, such as exterminators, have a higher rate of Parkinson's disease.

Genetics also plays a role. Jeff M. Brontstein, M.D., reported in a study looking at variables related to Parkinson's disease that certain genetic variations came into play when there was a pesticide exposure. A conclusion was that many cases of Parkinson's disease are likely due to gene-environment interactions.

"The link between dairy products and Parkinson's disease has been found in other studies," Abbott said of the environment and milk exposure in his study. "Our study looked specifically at milk and the signs of Parkinson's in the brain."

Milk and dairy were a concern to health. But those exploring the alternatives to cow's milk need to ask what is being sprayed on the soy or almonds used in those milks.