Ethical Eating: nothing but potatoes and milk?

The Straight Dope: Could I survive on nothing but potatoes and milk?:

As I recall from Don Smith's Irish History class at Grinnell in the 70s, you can do just fine on potatoes, milk, and a few apples. The Straight Dope finds the same plus.....

"How did the Irish do on this diet? We can't be certain — nobody was conducting nutrition studies in those days. But there's reason to believe they were healthier than you might guess. In the century before the famine, Ireland had the highest birthrate in western Europe. Some credit potatoes, saying the availability of easy-to-grow, easy-to-cook spuds made it practical to raise large families. Telling evidence on this score, one historian writes, 'is that the Irish in general and Irish women in particular were widely described as healthy and good-looking.' I don't know about you, Josh, but any diet that gets results like that is good enough for me."