According to Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies (Critical Reviews in Food Science and Nutrition, 2017, both vegan and vegetarian diets can be associated with better health outcomes:
This comprehensive meta-analysis reports a significant protective effect of a vegetarian diet versus the incidence and/or mortality from ischemic heart disease (-25%) and incidence from total cancer (-8%). Vegan diet conferred a significant reduced risk (-15%) of incidence from total cancer.
Next, in some studies: Milk and dairy products: good or bad for human health? An assessment of the totality of scientific evidence (Food and Nutrition Research, 2016, they have found association between milk/dairy consumption and reduced risk of some chronic diseases:
The totality of available scientific evidence supports that intake of milk and dairy products contribute to meet nutrient recommendations, and may protect against the most prevalent chronic diseases, whereas very few adverse effects have been reported.
Is it possible that in countries with lot of vegans but also with high milk consumption, the health effects of vegan diet have been overrated and should be actually ascribed to milk consumption? Is it possible to find out this by comparing countries with lot of vegans and countries with high per capita milk consumption and the incidence of various diseases in these countries?