Sweet Potato. Moche Culture. 300 A.D. Larco Museum Collection, Peru. Sweet potatoes are native to the tropical parts of South America , and were domesticated there at least 5,000 years ago in Peru.

Drawings of sweet potatoes have been found in pre-Columbian ceramics when ancient tombs were discovered. The sweet potato was already widely established in the Americas by the time Europeans first arrived there. Later, it spread from there, to the Old World .

Sweet potato varieties exist in many colours of skin and flesh, ranging from white to deep purple, although white and yellow-orange flesh are the most common.

The first Europeans to taste sweet potatoes were members of Columbus ' expedition in 1492. Later explorers found many varieties under an assortment of local names, but the name which stayed was the indigenous Taino name of batata. This name was later transmuted to the similar name for a different vegetable—the ordinary potato, causing confusion from which it never recovered. The first record of the name "sweet potato" is found in the Oxford English Dictionary of 1775.

The sweet potato was also grown before western exploration in Polynesia , where it is known as the kumara . Sweet potato has been radiocarbon-dated in the Cook Islands to 1000 AD, and current thinking is that it was brought to central Polynesia circa 700 AD, possibly by Polynesians who had travelled to South America and back, and spread across Polynesia to Hawaii and New Zealand from there. It is possible, however, that South Americans brought it to the Pacific. Sweet potatoes are now cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth.

Today, China is the largest grower of sweet potatoes; providing about 80% of the world's supply, 130 million tons were produced in one year (in 1990; about half that of common potatoes). Historically, most of China 's sweet potatoes were grown for human consumption, but now most (60%) are grown to feed pigs . The rest are grown for human food and for other products. Some are grown for export, mainly to Japan. China grows over 100 varieties of sweet potato.

Good nutrition from a sweet source
Besides simple starches, sweet potatoes are rich in complex carbohydrates , dietary fiber , beta carotene (a vitamin A equivalent nutrient), vitamin C , and vitamin B6 .

In 1992, the Center for Science in the Public Interest compared the nutritional value of sweet potatoes to other vegetables. Considering fibre content, complex carbohydrates , protein , vitamins A and C, iron, and calcium , the sweet potato ranked highest in nutritional value.

Sweet potato varieties with dark orange flesh have more beta carotene than those with light coloured flesh and their increased cultivation is being encouraged in Africa where Vitamin A deficiency is a serious health problem. Despite the name "sweet", it may be a beneficial food for diabetics, as preliminary studies on animals have revealed that it helps to stabilize blood sugar levels and to lower insulin resistance.

This root vegetable qualified as an excellent source of vitamin A (in the form of beta-carotene), a very good source of vitamin C and manganese, and a good source of copper, dietary fiber, vitamin B6, potassium and iron.

Sweet potatoes have healing properties as an antioxidant food. Both beta-carotene and vitamin C are very powerful antioxidants that work in the body to eliminate free radicals.

Culinary uses
Candied sweet potatoes are a side dish consisting mainly of sweet potatoes prepared with brown sugar, marshmallows , maple syrup , molasses , orange juice , marron glacé , or other sweet ingredients.

Baked sweet potatoes are sometimes offered in restaurants as an alternative to baked potatoes . They are often topped with brown sugar and butter. In Dominican Republic sweet potato is enjoyed for breakfast. In China sweet potatoes are often baked in a large iron drum and sold as street food during winter.

Sweet potato fries or chips are another common preparation, and are made by julienning and deep frying sweet potatoes, in the fashion of French fried potatoes .

Sweet potato greens are a common side dish in Taiwanese cuisine, often boiled or sautéed and served with a garlic & soy sauce mixture, or simply salted before serving.

Steamed/Boiled chunks: for a simple and healthy snack, chunks of sweet potato may be boiled in water or cooked in the microwave.