Lettuce

Lettuce is the world's most widely consumed raw vegetable. 100 g supplies approx. 102 µg vitamin K (about 85 % DV), 73 µg folate, 166 µg RAE vitamin A (from beta-carotene), 238 mg potassium and only 13 kcal — making it an ideal satiety vegetable with low energy density. The tender, water-rich leaves (95.5 % water) provide dietary fibre, support intestinal peristalsis and promote hydration. Consumed raw in salads, sandwiches, wraps or briefly braised — classic early-summer vegetable, often the first outdoor crop harvested in German-speaking regions.

[#src_usda_lettuce] [#src_wp_en_lettuce] [#src_wp_de_kopfsalat] [#src_nutritionvalue_lettuce]

Lettuce and other Lactuca varieties with dark green leaves are significant sources of beta-carotene (provitamin A). 100 g of butterhead lettuce supplies approx. 166 µg RAE vitamin A — comparable to butterhead types (Boston, Bibb). Beta-carotene is an antioxidant compound and precursor of vitamin A, essential for visual function, immune defence and skin integrity. Dark green outer leaves contain 4–8× more beta-carotene than pale inner leaves — these should be eaten rather than discarded.

[#src_nutritionvalue_lettuce] [#src_wp_en_lettuce] [#src_usda_lettuce]

Lettuce contains small amounts of the sesquiterpene lactones lactucin and lactucopicrin in its milky sap — the same bitter compounds concentrated in the related wild lettuce (Lactuca virosa) as lactucarium. In European folk medicine of the 17th–19th centuries, eating a head lettuce before bedtime was regarded as a sleep-promoting home remedy. Animal studies confirm sedative and analgesic effects of lactucin and lactucopicrin; at normal salad consumption levels, concentrations are too low for a pharmacological effect.

[#src_wp_en_lactucarium] [#src_pfaf_lactuca] [#src_wp_en_lactucopicrin]

In traditional phytotherapy (PFAF, Grieve), Lactuca species are described as mildly diuretic, slightly antispasmodic and calming (nervine). The milky sap (lactucarium) from flowering plants was sold in pharmacies in the 19th century as a cough remedy and mild sedative. Cultivated lettuce has very low lactucarium content compared to Lactuca virosa; the recorded uses refer primarily to wild species and flowering plants.

[#src_pfaf_lactuca] [#src_wp_en_lactucarium]

Lettuce is a relevant vitamin K source: 100 g of butterhead types supplies approx. 102 µg vitamin K1 — about 85 % of the daily requirement. Vitamin K is essential for blood coagulation (factors II, VII, IX, X) and bone mineralisation (osteocalcin activation). Dark-green lettuce varieties (unlike iceberg lettuce) supply significantly more vitamin K. Patients on anticoagulant therapy should keep their daily vitamin K intake consistently stable.

[#src_nutritionvalue_lettuce] [#src_usda_lettuce] [#src_wp_en_lettuce]

The flowering or bolting of lettuce is evaluated positively in folk medicine: in Central European folk belief, the milky sap of the bolting plant was considered especially valuable (bitter, concentrated). In everyday cooking, bolting plants are however usually discarded. Horticulturally important: harvest lettuce before bolting in cool weather with even watering, as bitterness and toughness of leaves increase.

[#src_wp_en_lactucarium] [#src_pfaf_lactuca] [#src_wp_de_kopfsalat]

Lettuce seeds can be sprouted and eaten as sprouts — they are rich in proteins and contain germination-active enzymes. In the traditional cooking of the Middle East and Central Asia, lettuce seeds are occasionally pressed for oil (lettuce oil). The oil is edible, but not economically significant due to small seed size (PFAF). Consume seed sprouts 3–5 days after sprouting at room temperature, then refrigerate.

[#src_pfaf_lactuca] [#src_wp_en_lettuce]