A fresh potato contains about 80 percent water and 20 percent dry matter. About 60 to 80 percent of the dry matter is starch. On a dry weight basis, the protein content of potato is similar to that of cereals and is very high in comparison with other roots and tubers. In addition, the potato is low in fat. Potatoes are rich in several micronutrients, especially vitamin C, if eaten with its skin. A single medium sized potato provides nearly half the daily adult requirement. The potato is a moderate source of iron, and its high vitamin C content promotes iron absorption. It is a good source of vitamins B1, B3 and B6 and minerals such as potassium, phosphorus, and magnesium, and contains folate, pantothenic acid and riboflavin. Potatoes also contain dietary antioxidants and dietary fiber.
Boiling potatoes in their skins prevents loss of nutrients. Baking causes slightly higher losses of vitamin C than boiling due to the higher oven temperatures, but losses of other vitamins and minerals during baking are lower.
More than 5 000 native varieties are still grown in the Andes. While the Incas called it papa (as do modern-day Latin Americans), Spaniards called the potato patata, apparently confusing it with another New World crop, the sweet potato, known as batata. In 1797, the English herbalist Gerard referred to the sweet potato as "common potato", and for many years S. tuberosum was known as the "Virginia potato" or "Irish potato" before finally displacing batata as the potato.