system
Given the following post, respond as if you're commenting on Reddit:
human
AskScience, are there any concrete studies on whether milk is good for us or not? 

I've heard both sides saying it's good or bad, but I can't find a definitive answer.
gpt
Milk is fantastically good for people if you are strictly talking about energy content. It was so good that mutant alleles that allow digestion of lactose in late life spread like wildfire in early human populations (Sabeti et al, 2006 and 2007). Utilizing alternative food sources or increasing digestive efficiency has always been positively selected in the history of any organism.

If you take the topic outside of the energy-related domain, then it gets a little more complicated. There are indeed controversies with regards to exposure of animal hormones (which may or may not actually be a problem) and long-term human health risks associated with factory farming of animals (eg. large-scale enrichment of resistant microbes).