Great article, I'm a little skeptical about the sourcing though. Most of the information seems to come from general literature (as opposed to something more objective, like say taxation records). What people choose to write about isn't necessarily what's most common in practice. For example a visitor from France would probably be more likely to write about some strange kind of cheese he's never seen before than the bread that looks more or less similar to what he's been eating everyday.

I don't doubt the importance of dairy but I doubt it accounted for the majority of people's calorie intake.

They actually have a pretty good idea of what they ate. Interesting article on it here:

http://www.ravensgard.org/prdunham/irishfood.html

The TLDR of their diet is "mostly pottage and soups, heavy on meat and dairy. Some oats and barley were grown, but a lot of that ended up being made into alcoholic beverages."