Has to be spuds with the skin still on (vitamin C lives just under the skin and usually gets peeled off), whole raw milk (vitamins A & some Bs and some protein and a lot of fat) OR butter, and a supplemental protein source - such as oily fish (vitamin D) or meat or cheese. If you peel the spuds, you'll need a supplement such as fruit. The classic Irish diet that the potato famine of 1840s pretty much wiped out and triggered mass migration to USA and here.

potatoes are excellent foods for vitamins