Sangchu (lettuce)

Lettuce (Lactuca sativa) is an annual or biennial of the daisy family (Asteraceae), thought to have originated in Europe and western Asia and cultivated since antiquity. It probably reached Korea by way of China, though when is not known. The Sino-Korean names are wageo and wachae.

Korean lettuce earned a reputation abroad early. A Chinese text, Tianlu shiyu, reports that lettuce seed brought by Goryeo envoys was so prized it could be had only for a fortune, earning the name "thousand-gold vegetable" (cheongeumchae). The Yuan-dynasty poet Yang Yunfu praised Goryeo lettuce above fragrant mushrooms and noted that Goryeo people wrapped rice in raw greens; a story holds that Goryeo women taken to the Yuan court planted lettuce in the palace gardens and ate rice wrapped in it to ease their homesickness, starting a fashion among the Mongols. The late-Joseon cookbook Siui jeonseo describes washing lettuce, coating the leaves with a little oil, and serving them with gochujang cooked with minced beef and fish, accompanied by thin green onions and crown daisy. The custom of bokssam, wrapping rice in leaves "to wrap up good fortune," recorded in Dongguk sesigi, echoes the same idea.

In Korea lettuce is grown in spring and autumn on the plains, in summer in the highlands, and under cover in winter, so it is available year-round. Koreans mainly eat leaf lettuces rather than heading types; long-leaved chima sangchu and frilly green and red chukmyeon types are typical, picked leaf by leaf as the plant grows.

Sangchu-ssam is the essential use: a leaf in the palm, a spoonful of rice, a slice of grilled pork or bulgogi, a little ssamjang or doenjang, garlic or green chili, folded into one bite. Lettuce is also tossed with chili flakes, soy sauce and sesame oil as a quick geotjeori, and a milky sap in the stems was long believed to make one drowsy, a folk belief recorded in Korean sources.

• Light leafy green: Raw leaf lettuce is mostly water, about 20 kcal per 100 g, and provides vitamin K, vitamin A (as beta-carotene), folate and potassium (Korean Food Composition Table).
• Balancing the meal: Wrapping grilled meat and rice in lettuce adds fresh vegetables and volume to a rich meal, though the ssamjang and marinades bring sodium.
• Vitamin K and warfarin: Lettuce, especially green leaf types, contains significant vitamin K. MedlinePlus advises people on warfarin not to eat large amounts of leafy greens and to keep vitamin K intake consistent week to week.
• Raw-produce safety: The CDC notes that foodborne illness outbreaks have been linked to leafy greens eaten raw, including lettuce. Rinse leaves under running water, discard damaged outer leaves and keep cut greens refrigerated.
• Folk belief: The idea that lettuce makes you sleepy comes from Korean folk tradition about the milky sap in its stems, not from established evidence.