I doubt it. I come from the South West of England (known for enormous consumption of dairy products) and people aren't tall. I'm just under 6ft and was tall there, whereas I'm short here in The Netherlands.

It's probably a combination of genetics, cycling everywhere and eating so many slices of brown bread and potatoes.

Basic statistics also plays a part: when comparing arbitrary groups you'll often see smaller groups as outliers. Both high and low. Dutch population isn't huge (16m) so that is also a contributing factor..