Actually, there is some research which indicate that freed (not bound)
glutamine, casein and lactose is driving Parkinson type changes in the brain.
Sure, it was drinked for millenia, but the issues are:
- how much? so much as today? i'd bet no
- what type? goat, sheep, camel, cow milk?
- in what form? cheese, kefir, butter, raw milk?
- how were these animals rised? today they are fed hormones and all kinds of nasty stuff.
- pasteurized or raw?
- how much of todays dairy (yoghurt, ice cream) comes with added sweeteners, sugar, aspartame, etc?
As you can see, its very hard to do precise research in this field.
Especially when Parkinson is much more common as age progresses - you have to wait lots of time to draw conclusions.
Such incredibly high correlation among many different populations gives very strong indication whats going on, in my opinion.
Also, dairy intake is linked to autism spectrum disorders among other factors like heavy metals toxicity. Its also a brain disorder.
Do you know that dairy is very high in dioxins? There were much less dioxins in the soil and animal flesh a hundred years ago.