It doesn't have to be potatoes, you know. I mean, one can theoretically live off potatoes and potato dishes (just look at Steve), but that seems more like poor farmer than a national food. There's carrots, lettuce, tomatoes, radishes, etc. But don't just think of vegetables. Fruits, such as apples and oranges, contain vitamins and other nutrients not found in vegetables. Like Vitamin C. They are also sweeter and are better for beverages compared to veggies. So, unless you want your populous to be scurvy-ridden potato farmers (like Steve), I recommend you add some fruits in there as well. Bananas, grapes, tomatoes, watermelons, you get the gist. And don't forget grains, like rice and wheat!
But it's not just about the food, it's about where the food is.
If the climate tends to be warm and sunny, citrus fruits are a must. For bitter, harsher climates (like Ireland), vegetables that are in the resistant soil are your best bet. More moderate climates are home to the majority of fruits and veggies, though, so you might need a greenhouse or nursery for cold and hot climates, respectively.
Enough about all this vegan crap, though.
Meat from livestock (or monsters, if you're like that) are a vital source of Protein. You can't live off nuts and seeds, after all. Eggs can also be a great source. There's also Calcium from various sources of milk, though the cow seems to be th most popular. Beef, chicken, pork, etc. Meat makes you stronger. People who tend to eat ONLY meat, though, end up fatter and more likely to end up sick or dead.
Anyway, one should find a balance between these to make wonderful dishes. Veggie soup with bread, Beef with veggie sauce and wine, or a simple serving of mashed potatoes and apple juice. Be sure to never have one area (village or otherwise) entirely dependent on one source of food. Those are few and far between.
