Educational information, not medical advice — ask your doctor or midwife.
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Sangchu is the Korean name for common lettuce (Lactuca sativa). It is eaten as a food, most famously as the leaf you wrap around grilled meat and rice at the table. It is valued as a cooling, watery green rather than as a medicine.
People look up sangchu for three reasons: gentle help with sleep, lighter digestion, and adding low-calorie bulk and vitamins to meals. Folk belief in Korea and across East Asia says a large plate of lettuce at dinner makes you drowsy.
Here is the honest verdict up front. Lettuce has a long, solid place in Korean cooking and folk habit, but there is almost no human trial evidence that eating it treats any condition. Traditional use tells you what people have done for a long time; it is not proof that something works.
Most of what sangchu does is simple nutrition. It is roughly 95% water with fibre, folate, vitamin A precursors and vitamin K, so it fills you up for very few calories and adds bulk to stool.
The sleepiness idea comes from lactucarium, a bitter milky sap in the lettuce genus. Wild lettuce (Lactuca virosa) carries much more of it than the mild garden lettuce on your plate. Animal studies suggest sedative (sleep-promoting) activity from concentrated extracts.
That is a reasonable idea, not a proven one. No good human study shows that a normal serving of sangchu changes how fast you fall asleep. Treat the drowsiness story as folklore until better evidence exists.
Fresh whole leaves are the usual form and the one Korean cooking assumes. They are washed, dried and served raw as ssam wraps.
Other common forms are quick-blanched lettuce in soups, lettuce kimchi (sangchu-geotjeori), and lettuce juice or smoothies.
Supplement shelves also sell lettuce seed oil and wild lettuce extract capsules or tinctures. These are not the same thing as sangchu. Wild lettuce is a different, far more bitter species with much stronger sap, and it should not be swapped in for the salad leaf.
Lettuce reached Korea from China centuries ago and appears in old Korean farming and food records as a common kitchen-garden green. Classical East Asian materia medica lists lettuce as a cooling vegetable that moves urine and eases the bowels.
Its firmest standing is culinary. Sangchu-ssam, the leaf wrap, is a defining part of Korean table culture rather than a recognised medical treatment.
See a doctor if you get bloody diarrhoea, a fever, or vomiting that will not stop within a day or two after eating raw salad, as this can be serious food poisoning. Get help straight away if your lips, tongue or throat swell, or you wheeze or feel faint after eating lettuce. Contact your anticoagulation clinic if your INR blood test result changes after a big shift in how many greens you eat. Also see a doctor if constipation or sleep problems last more than a few weeks.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Sangchu is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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