Its ration of carbohydrate to protein is such that anyone eating enough potatoes to satisfy their energy requirements will automatically obtain most of the protein they require. Furthermore, the "biological value" of potato protein (an index of the nitrogen absorbed from a food and retained by the body for growth and maintenance) is 73, second only to eggs at 96; just ahead of soybeans at 72, but far superior to corn (maize) at 54 and wheat at 53.
Potatoes also contain significant amounts of essential vitamins (the British, in fact, used to derive 30% of their vitamin C intake from potatoes.) Exceptional productivity is another virtue of the potato. A field of potatoes produces more energy per hectare per day than a field of any other crop. Potatoes grow well from sea level to 14,000 feet on a wider variety of soils, under a wider range of climatic conditions, than any other staple food. The potato matures faster in 90 to 120 days, and will provide small but edible tubers in just 60 days.
All in all, the potato is about the world's most efficient means of converting plant, land, water and labour into a palatable and nutritious food. John Reader, Man on Earth, 1998. ( Reader's latest book, Potato, A History of the Propitious Esculent, was published in 2009.)