Educational information, not medical advice — ask your doctor or midwife.
Kahoo is the Persian and Unani name for garden lettuce, Lactuca sativa — the same leafy salad plant sold in food shops. Both the leaf and the seed (called tukhm-e-kahu) are used. Healers give it as a cooling food and a gentle calming remedy for restlessness, trouble sleeping and thirst.
In Unani theory the plant is "cold and moist", so it is used to settle a body seen as too "hot" or too dry. The seeds are crushed into milk or drinks, or pressed into an oil that is taken by mouth or rubbed on the head at night.
Here is the honest verdict. Kahoo has a very long and well-documented traditional record, but almost no modern human trial evidence for the calming and sleep uses. Traditional use is not proof that something works, and that applies to everything below.
Nobody has shown clearly how Kahoo works, and the most likely answer for the leaf is "mostly as food".
Much of the sedative reputation of lettuce comes from lactucarium, the bitter milky sap of wild lettuce species. Garden lettuce contains only small traces of the same bitter compounds. That gap between the famous folk story and the mild plant on your plate is worth knowing.
The seed and seed oil contain fats and small amounts of bitter plant compounds that have shown mild calming effects in animal studies. Animal results do not reliably carry over to people. Any settling effect you notice may also come from a warm milky drink and a bedtime routine.
Fresh leaf is the everyday form, eaten raw in salad or lightly cooked. Fresh leaf juice is also used.
Seed forms are the traditional medicinal ones. These include whole or powdered seed stirred into milk or water, and cold-pressed seed oil taken in drops or applied to the scalp.
You may also meet it inside compound Unani formulas alongside poppy seed, purslane seed or coriander. Read the label of any such blend, because the other ingredients carry their own cautions.
Lettuce has been grown and eaten for at least 4,000 years, with images of it in ancient Egyptian tombs. Greek and Roman writers described it as a sleep-friendly supper food.
Persian and Arabic physicians took it up firmly. Avicenna's Canon of Medicine and later Unani texts list Kahoo and its seed as cooling agents for fever heat, thirst, sleeplessness and irritability. It has stayed a household staple in Unani practice ever since.
See a doctor if you get a rash, swelling of the lips, face or throat, or any trouble breathing after eating lettuce — call emergency services for breathing trouble or throat swelling.
Book an appointment if you take warfarin and your INR results start moving up and down, or if you get unusual bruising, nosebleeds or blood in your urine or stool.
Also get checked if sleep problems last more than four weeks, if a cough lasts more than three weeks, or if you get sickness and diarrhoea after raw salad that does not settle in two days.
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 Kahoo 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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