What is Cao Guo?

Cao Guo is the dried, ripe fruit of Lanxangia tsaoko. The plant was once called Amomum tsaoko. It is a tall plant in the ginger family, grown in Yunnan, Guangxi and Guizhou in south-west China.

In Chinese medicine it is used on its own to warm and dry the gut. It is also an everyday kitchen spice, with a smoky, camphor-like smell. In English it is sold as tsaoko fruit or Chinese black cardamom.

Healers reach for it when the stomach feels heavy, full and sick. They call this a "cold and damp" stomach. Signs include poor appetite, loose stools and a thick coat on the tongue.

It was also a classic part of old formulas for malarial fevers with strong chills.

Here is the honest picture on evidence. Cao Guo has a long, well-recorded place in Chinese medicine and cooking. But almost all of its modern research is lab and animal work.

Long use tells you that people have used a thing for a long time. It is not the same as proof that it works. That point applies to everything on this page.

How does Cao Guo work?

No one has shown how Cao Guo works in people. So what follows is a fair idea, not a settled fact.

Most of its smell and taste come from a volatile oil (an oil that evaporates easily). Oils like this can relax the gut wall a little. They may help trapped gas move, which could explain the old use for bloating and a heavy stomach.

In traditional terms, Cao Guo is warm, sharp and drying. Healers use that language to explain why it suits a person who feels cold and waterlogged inside. It is also why they avoid it in someone who already feels hot and dry.

Lab studies report that its extracts act as an antioxidant (they protect cells), kill bacteria and lower blood sugar. Animal studies have looked at blood sugar and at inflammation (swelling and heat in the body).

These findings are early. What happens in a dish or a test tube often does not happen in a person on a normal dose.

What forms does Cao Guo come in?

Whole dried fruits are the usual form. They look like brown-black, ridged pods the size of a thumb. You crack them open before use, so the seed cluster inside is exposed.

You will also find it as:

A coarse powder or ground spice.

A roasted form (wei cao guo), warmed in ash or a dry pan. Tradition sees this form as gentler on the stomach.

Part of ready-made granule and pill formulas from Chinese pharmacies. These nearly always hold several other herbs too.

An essential oil, sold for scent and flavour rather than for swallowing.

In practice, Cao Guo is rarely taken alone as a medicine. It is normally one herb inside a formula. Or it is simply one spice in a braise or a hotpot broth.

Where it comes from:

Cao Guo shows up in Chinese herb texts from about the Song and Yuan periods onward. That is roughly the 12th to 14th centuries. It is listed in the modern Chinese Pharmacopoeia.

Old texts group it with herbs that "transform dampness" and warm the middle burner. Middle burner is the old name for the stomach and spleen area.

Its best-known old role was in formulas for illness with chills and fever that come and go. We would now call that malaria.

It is also a staple kitchen spice in south-west China, Vietnam and Laos. Cooks use it in pho broth, red-braised meats and hotpot bases. That is how most people in the world meet it.

What does Cao Guo help with?

• Bloating and a heavy, full feeling after eating: This is the main traditional reason people use Cao Guo, and it is the use with the most plausible reasoning behind it. Aromatic spice oils can ease trapped gas for some people. No human trial has tested Cao Guo on its own for bloating. Any relief you get is worth noting for yourself, but it has not been measured in a study.
• Poor appetite with nausea: Classical texts pair Cao Guo with a stomach that feels waterlogged and refuses food. Practitioners use it in formulas for exactly this picture. There is no controlled trial evidence in people. If your appetite has dropped for more than a couple of weeks, or you are losing weight without trying, that needs a doctor rather than a spice.
• Loose stools linked to cold, damp conditions in TCM: Tradition considers Cao Guo drying, so it is chosen when stools are loose and the person feels cold and sluggish. Evidence here is entirely traditional. Persistent diarrhoea has many causes, some of them serious, and self-treating it delays finding out which one you have.
• Belching and trapped wind: Used in cooking and in formulas for this purpose for centuries. The volatile oil is the likely reason, if there is one. No human studies. This is a low-stakes traditional use, and culinary amounts are normal food.
• Traditional use in malarial chills and fever (historical): This is a historical use recorded in classical formulas, and we report it because it is part of the herb's record — not because it works. Malaria is a life-threatening infection with proven drug treatments. Never use Cao Guo in place of malaria testing and antimalarial medicine.

Which foods are rich in Cao Guo?

1. Vietnamese pho broth: one of the classic aromatics in the simmering stock
2. Sichuan and Chongqing hotpot bases: cracked pods in the oil and broth
3. Chinese red-braised (hong shao) meat dishes: used with star anise and cassia
4. Yunnan and Guizhou stews and cured-meat dishes
5. Some regional five-spice and braising spice blends

Practical Tips:

Indian recipes calling for black cardamom usually mean a close relative, Amomum subulatum, not Cao Guo; the two are related but not the same spice.

What are the side effects of Cao Guo?

• Heartburn or a burning feeling in the stomach
• Dry mouth and increased thirst
• Nausea, especially on an empty stomach
• Mouth or throat irritation from the strong oil
• Allergic reaction: rash, itching or swelling — in people sensitive to ginger-family plants
• Worsening of hot, dry symptoms such as night sweats or a dry cough, as traditional texts predict

Good to know:

At cooking amounts Cao Guo is a normal food spice with no expected problems for most people.

At medicinal doses the reported effects are mild and mostly digestive — burning, dryness, nausea. They usually settle when you stop. There are no reports we could find of liver injury, bleeding problems or serious poisoning from normal use.

The honest limit is that no safety trial has ever been run on this herb, so rare effects would not yet be known. Stop taking it if something new and unpleasant starts after you begin.

How much Cao Guo should you take?

• Recommended daily: There is no dose established by modern trials. What follows is the traditional range used by practitioners, not a tested recommendation. Chinese pharmacopoeial texts give 3 to 6 grams of the dried fruit per day, cracked open and simmered in water as part of a formula. Some sources allow up to 9 grams for short periods. Amounts used in cooking — one or two pods in a pot of broth shared by several people — are far smaller per serving and are treated as food, not medicine. If you are taking a ready-made granule or pill product, follow the label and the advice of the practitioner who supplied it. Do not stack a formula on top of loose herb.
• Best time of day: Usually taken in two or three divided doses across the day, spaced around meals. There is no evidence that any particular time of day works better.
• With or without food: Take it with or just after food. The herb is warming and pungent, and taking it on an empty stomach makes stomach irritation more likely.
• Time to effect: For gas and fullness, any effect would be expected within an hour or two of a dose. Traditional use for appetite and stool consistency is judged over several days. None of this has been measured in a trial.
• How long to take it: Traditional use is short and targeted: days to a few weeks while the digestive symptoms last, not an ongoing daily supplement. If your symptoms have not clearly improved after about two weeks, stop and get the problem looked at properly. Long unsupervised use has not been studied for safety.