A new study has confirmed a relationship between consuming large
amounts of dairy products and an increase in the rate of Parkinson's
disease in men, but the reason for this relationship remains a
puzzle.
Researchers found that among more than 130,000 US adults followed
for nine years, those who ate the largest amount of dairy foods had
an increased risk of developing Parkinson's disease, a disorder in
which movement-regulating cells in the brain die or become impaired.

There was a clear pattern seen among men, whose Parkinson's risk
increased in tandem with consumption of dairy, particularly milk.
The results were more ambiguous among women, however.

The findings, which appear in the American Journal of Epidemiology,
echo those of earlier studies that found a link between dairy
consumption and Parkinson's in men, but not women.

For now, it's not clear what effect, if any, dairy foods might have
on women's risk of the disease. Nor is it known why there is a
relationship seen in men, lead study author Dr Honglei Chen, a
researcher at the National Institute of Environmental Health
Sciences, Research Triangle Park, North Carolina, told Reuters
Health.

Larger studies are needed to find out which dairy products might be
responsible, and why, according to Chen.

The findings are based on detailed dietary and lifestyle information
collected from 57,689 men and 73,175 women who took part in a cancer
prevention study. Over nine years, 250 men and 138 women were
diagnosed with Parkinson's disease.

Men with the highest levels of dairy consumption were 60 percent
more likely to develop the disease than those who consumed the least
amounts of dairy, the study found.

Men in the highest-intake group consumed an average of 815 grams of
dairy per day, which is roughly equivalent to three to four glasses
of milk; those in the lowest-intake group consumed 78 grams of dairy
per day, on average.

Milk, rather than dairy products like yogurt and cheese, explained
most of the association, according to Chen's team.

This study and previous ones indicate that calcium, vitamin D and
fat are not responsible for the link between dairy foods and
Parkinson's disease.

One theory is that pesticides or other nerve-damaging toxins present
in milk could contribute to Parkinson's disease over time.

However, dairy foods would likely be only a small part of most
people's exposure to these chemicals, according to Chen.

Furthermore, pesticide residues may also be present in other foods,
but no other foods were related to Parkinson's disease risk in this
study, the researcher noted.

For now, Chen said there is no reason to shun dairy because of the
potential relationship to Parkinson's disease.

"Given some of the potential health benefits of dairy foods, people
can still enjoy their moderate amounts."

However, the researcher added, since the dairy-Parkinson's link has
now been seen consistently in different studies, further research is
needed to understand why.

Sydney Morning Herald)