What is Da Suan?
Da Suan is garlic: the bulb of the plant Allium sativum. It is both a food and a single herb in Chinese medicine. There it is classed as warm and pungent.
In that tradition it is given for cold-type gut problems and for parasites (tiny pests that live in the body). Put on the skin, it is used for rashes and fungal problems. Today most people take it for heart health.
The evidence verdict: garlic has a long, wide record of traditional use. Human trials point to small but real effects on blood pressure and blood fats.
Those effects are modest, and the trials are mixed in quality. Standing in tradition and proof of effect are two different things. A long history of use does not by itself show that something works.
Garlic is safe as a food for most people in normal cooking amounts. Strong supplements are another matter. They thin the blood a little, and they clash with several prescription drugs.
How does Da Suan work?
Garlic's effects are thought to come from sulphur compounds. These form when you crush or chop a clove.
The compounds seem to relax the walls of blood vessels. That may explain the small drops in blood pressure seen in trials.
They also make platelets slightly less sticky. Platelets are the tiny cell bits that form clots. This is why bleeding risk goes up with drugs that act the same way.
In the lab, garlic also kills bacteria and fungi. Whether that treats an infection in a person is not known. Do not rely on it for one.
What forms does Da Suan come in?
Common forms include:
- Fresh raw cloves, crushed and eaten, or added to food at the end of cooking - Cooked garlic in food, which loses much of the allicin - Dried garlic powder in tablets, often coated to cut the smell - Aged garlic extract, taken as capsules or liquid - Garlic oil softgels - Garlic in TCM decoctions and pastes, sometimes put on the skin
Where it comes from:
Garlic is one of the oldest recorded medicines in the world. It appears in Egyptian, Greek, Roman, Indian and Chinese sources.
Workers and soldiers were fed garlic as a tonic. That was long before anyone knew what was in it.
Chinese medicine records Da Suan as warming the middle burner (the digestive centre). It is also said to move stuck food, kill parasites and dry damp skin problems.
It has stayed in daily use in kitchens and clinics in many cultures. That run of use goes back well over two thousand years.
Who should avoid Da Suan?
- Do not take garlic supplements if you are on warfarin or any other blood-thinning medicine, unless your prescriber has agreed to it.
- Do not take garlic supplements if you are on saquinavir or other HIV medicines, unless your HIV specialist has cleared it.
- Do not take garlic supplements in the 7 to 10 days before surgery, dental extraction or any procedure, and stop them if you are told to stop aspirin.
- Do not use garlic if you have a bleeding disorder such as haemophilia (a condition where blood does not clot properly).
- Never use garlic in any form if you are allergic to garlic, onions or other Allium plants.
- Never place raw crushed garlic directly on skin, in the ear or in the vagina; it commonly causes chemical burns and blistering.
- Do not take concentrated garlic supplements if you are pregnant or breastfeeding; garlic as food is fine, but supplement doses have not been shown to be safe.
- Do not give garlic supplements to children; garlic in food is fine, but supplement doses are not established for them.
- Avoid garlic supplements if you have a stomach ulcer (a sore in the stomach lining) or bad reflux, as they often make it worse.
When should you see a doctor?
See a doctor promptly if you notice unusual bruising, nosebleeds that will not stop, blood in your urine or stool, or black tarry stools while taking garlic.
Get emergency help if you have swelling of the lips, face or tongue, a spreading rash, or trouble breathing after taking garlic; that can be a severe allergic reaction.
Also see a doctor if raw garlic on your skin has caused a burn or blister, if you are relying on garlic for high blood pressure instead of prescribed treatment, or if you have a suspected parasite or infection that needs proper diagnosis.
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