As a diet, it’s actually pretty healthful, if a little dull – although I’m sure it was enlivened with butter, onions, wild garlic, field mushrooms, young nettles, seaweeds such as dulse, and so forth whenever possible. Contemporary visitors to Ireland often remarked on Irish people’s healthiness, height, muscularity, and freedom from many markers of poverty such as skin eruptions, compared with the peasants of other countries.
Potatoes are comparatively easy to grow and prepare (no winnowing, threshing, grinding, baking, etc., required), and have a high calorific content. Note that, in The Martian, the hero decides to grow potatoes to survive (and waffles on about them for most of the book…) – not wheat, not quinoa, not sprouted alfalfa: the humble potato. You don’t even need much land, or decent soil. Stick a hairy spud from the back of the cupboard in some straw, and in 90 days or so you’ll have enough potatoes for a family Sunday roast. Keep covering up the leaves as they appear and you could potentially have spuds for dinner till the end of time.
So, when the zombie apocalypse starts, get your shovels out – one blow to the brain, ready-made growbags…