The potato is a starchy, tuberous crop from the perennial nightshade Solanum tuberosum L. Potatoes were introduced outside the Andes region four centuries ago, and have become an integral part of much of the world's food supply. It is the world's fourth-largest food crop, following maize, wheat and rice.
Following centuries of selective breeding, there are now over a thousand different types of potatoes. They contain vitamins and minerals, as well as an assortment of phytochemicals, such as carotenoids and natural phenols.
The potato is best known for its carbohydrate content (approximately 26 grams in a medium potato). The predominant form of this carbohydrate is starch. A small but significant portion of this starch is resistant to digestion by enzymes in the stomach and small intestine, and so reaches the large intestine essentially intact. This resistant starch is considered to have similar physiological effects and health benefits as fiber: It provides bulk, offers protection against colon cancer, improves glucose tolerance and insulin sensitivity, lowers plasma cholesterol and triglyceride concentrations, increases satiety, and possibly even reduces fat storage.
However, potatoes contain toxic compounds known as glycoalkaloids, of which the most prevalent are solanine and chaconine. This toxin affects the nervous system, causing weakness and confusion. These compounds, which protect the plant from its predators, are, in general, concentrated in its leaves, stems, sprouts, and fruits (ie the above ground plant). However; exposure to light, physical damage, and age increase glycoalkaloid content within the tuber (ie. the Potato); the highest concentrations occur just underneath the skin. Whilst cooking at high temperatures —over 170 °C (340 °F)— partly destroys these, this is the reason why we shouldn’t/don’t eat green potatoes.