What is Kanzoto?

Kanzoto is a Kampo medicine made from one herb only: licorice root (Glycyrrhiza). It is used short-term for a sudden sore throat and for a dry, tickly cough with little or no phlegm.

The name means "licorice decoction". It is a single drug (Kampo) formula, which is unusual, since most Kampo medicines combine several herbs. Traditionally it is sipped slowly or held in the mouth so the sweet liquid coats the throat.

Honest verdict on the evidence: Kanzoto has a long and respected place in Kampo practice, but we could not identify published human trials testing this formula for sore throat or cough. Long traditional use tells you a preparation has been trusted for a long time; it is not the same as proof that it works, and this is the only place in this document we will say so.

One more thing to know before you read on. Licorice is not a bland herb. Taken in large amounts or for more than a short course it can push down your potassium, raise your blood pressure and affect your heart rhythm, so Kanzoto is meant for a few days of use, not as a daily tonic.

How does Kanzoto work?

Kanzoto is thought to soothe and coat an irritated throat, which may calm the urge to cough. This is the traditional explanation and it has not been confirmed in people.

Laboratory work shows that licorice constituents can reduce inflammation (swelling and irritation) and that they have some antiviral and mucus-soothing activity in cell and animal studies. Whether any of that happens at the dose you would actually swallow is unknown.

Glycyrrhizin, the main sweet compound in licorice, also blocks an enzyme in the kidney that normally protects the body from cortisol. That is the same action behind its side effects, so the helpful and the harmful effects come from one source.

What forms does Kanzoto come in?

Kanzoto usually comes in one of three forms. The choice is mostly about convenience.

Dried decoction: cut licorice root simmered in water and sipped warm, which is the classical method. Granules or fine powder: a dried extract sold in sachets in Japan and mixed into hot water. Tablets or capsules: less traditional, and they skip the throat-coating step that the liquid gives.

Strength varies a lot between brands, so the amount of licorice in one sachet is not a fixed number. Check the label for the raw-herb equivalent or the glycyrrhizin content before you decide on a dose.

Where it comes from:

Kanzoto is old. It appears as Gancao Tang in the Shanghan Lun, a Chinese medical text from roughly the third century, and it was carried into Japanese Kampo practice, where it is still a listed formula today.

Its classical indication was a painful throat, and later Kampo writers extended it to sudden dry coughing fits. Because it is a single herb, it was often the first thing tried before moving to a larger formula.

What does Kanzoto help with?

• Acute sore throat: This is the classical use and the reason the formula exists. Kampo practitioners choose it for a throat that has become painful quickly, and the sweet liquid is meant to be sipped slowly so it coats the sore area. We could not find human trials testing Kanzoto for sore throat, so this rests on tradition and on practitioner experience, not on measured results.
• Dry, tickly cough: Traditional use targets a cough with little or no phlegm, the kind that comes in fits and scratches the throat. Licorice has a long history as a cough soother across many cultures. Published human evidence for Kanzoto specifically is lacking, and it is not a treatment for a wet, productive or long-lasting cough.
• Hoarse or scratchy voice: Some Kampo practitioners use it for short-term hoarseness from overuse of the voice or a mild throat infection. This is an extension of the throat-soothing use rather than a separate tested indication. Hoarseness lasting more than about three weeks needs a doctor, not an herb.
• Sudden coughing fits: Tradition describes it as a quick, short-course remedy for a cough that arrives abruptly. It is not used as a background treatment for asthma, COPD (a long-term lung disease) or any ongoing lung condition. If you cough most days, the cause needs to be identified.

Which foods are rich in Kanzoto?

1. Licorice root tea: the same herb, so it adds to your total dose
2. Black licorice sweets made with real licorice extract: a common hidden source of glycyrrhizin
3. Some herbal cough syrups and throat lozenges: licorice is a frequent ingredient
4. Anise-flavoured sweets: usually contain no licorice at all, despite the taste

Practical Tips:

Count licorice sweets and teas as part of your dose, because the body does not tell them apart from the medicine.

What are the side effects of Kanzoto?

• Low potassium in the blood, which can cause muscle weakness, cramps or an irregular heartbeat
• Raised blood pressure
• Swelling of the face, hands, ankles or feet from fluid retention
• Weight gain from held fluid rather than fat
• Headache
• Muscle weakness or, rarely, muscle breakdown
• Nausea or stomach upset
• Reduced urine output
• Heart rhythm disturbances in severe cases

Good to know:

Most of these come from one known effect of licorice: pseudoaldosteronism (a state where the body acts as if it has too much of the salt-holding hormone aldosterone, so it keeps sodium and water and loses potassium).

The risk rises with the dose and with how long you take it. Short courses at normal doses are usually tolerated, but cases of dangerously low potassium and heart rhythm problems have been reported with high or prolonged licorice intake, including in people taking several licorice-containing Kampo formulas at once.

Older people, people with heart, kidney or liver disease, and anyone on water pills are more sensitive. Stop and seek advice if you notice swelling, unusual weakness or a fluttering heartbeat.

How much Kanzoto should you take?

• Recommended daily: There is no dose established by clinical research. Traditional Kampo practice uses roughly 2 to 8 grams of dried licorice root per day, simmered in water and split into two or three servings. Packaged extract granules are dosed by the label, usually one sachet two or three times a day. Follow the package, because extract strength differs between makers. Keep your total licorice from all sources in mind. Other Kampo formulas, licorice tea and licorice sweets add to the same load.
• Best time of day: Spread the doses through the day, typically morning, midday and evening. Many people take an extra sip when the throat flares. Traditional practice favours taking it warm and sipping slowly rather than swallowing it in one go.
• With or without food: Kampo practice usually takes it between meals or before food, on a fairly empty stomach. If it makes you feel queasy, take it with a small amount of food instead.
• Time to effect: Any soothing effect on the throat is meant to be felt within minutes of sipping it, and it fades as the coating washes away. There is no measured evidence for how quickly it changes the course of an infection. If nothing has improved within a few days, it is not working for you.
• How long to take it: Use it for a few days only. Most traditional guidance keeps Kanzoto to about three to seven days, and the risk of low potassium and raised blood pressure climbs with longer use or higher doses. If your throat or cough has not improved after about five days, stop and see a doctor. Do not take it continuously for weeks without medical supervision and, ideally, a potassium blood test.