What is Heiisan?

Heiisan is a traditional Japanese Kampo stomach remedy, taken for a heavy, bloated, sluggish feeling after eating. Its Latin-style name translates as "level stomach", meaning it was meant to settle and calm the stomach. It is usually sold as a powdered or granulated extract you dissolve in hot water.

This entry is filed under a single Kampo (Japanese) heading, but Heiisan is not one herb. It is a fixed blend, and the herb that matters most for safety is kanzo (licorice root). Licorice is why this remedy has real drug interactions and a real list of people who must not take it.

What is it used for? Mild everyday digestive complaints: fullness after meals, bloating, poor appetite, loose stools and a coated tongue in the Kampo way of assessing patients.

Evidence verdict: Heiisan has deep classical standing across East Asian medicine, but we could not identify good published human trials of this formula, so its benefit is not proven. Long traditional use tells you a remedy has been trusted; it does not tell you it works, and that distinction applies to everything below.

How does Heiisan work?

The honest answer is that nobody has shown how Heiisan works in people. The explanations below are proposals, not proven mechanisms.

In Kampo theory, Heiisan is said to dry "dampness" in the stomach and get stalled digestion moving again. That is a traditional model of the body, not a description of measurable biology.

In laboratory terms, the bitter and aromatic herbs in the blend may stimulate digestive juices and ease spasm in the gut wall, and ginger may help with nausea. This work is mostly in test tubes and animals.

Licorice root is the one part with well-documented effects in humans, and they are mostly unwanted ones. Its main compound acts on the kidneys and can raise blood pressure and lower potassium.

What forms does Heiisan come in?

Granulated extract sachets are the standard form in Japan. You stir the granules into hot water and drink them.

Other forms you may meet:

Loose powder, the classical preparation, mixed with hot water.

Tablets or capsules of dried extract.

Raw dried herb packs for decoction (simmering in water), usually dispensed by a practitioner.

Products vary a lot in how much licorice they contain. Check the label for kanzo or glycyrrhizin content before you take it alongside anything else.

Where it comes from:

Heiisan comes from the Chinese formula Pingwei San, recorded in the Song dynasty pharmacy manual Taiping Huimin Hejiju Fang around the year 1110.

It passed into Japanese Kampo practice and has stayed in routine use there for centuries. It is also used in Korean medicine. Today it is a licensed Kampo preparation covered by Japanese national health insurance.

What does Heiisan help with?

• Bloating and fullness after meals: This is the classical target of Heiisan and the reason most people are given it in Kampo practice. Traditional standing here is strong. Published human trial evidence for this specific formula is what we could not find, so treat any benefit as unproven.
• Poor appetite: Kampo practitioners use Heiisan when appetite is dulled by a heavy, damp-feeling stomach rather than by illness. Bitter aromatic herbs have a long reputation for stirring appetite. No trial has tested Heiisan for this. Appetite loss that lasts more than a couple of weeks, or comes with weight loss, needs a doctor rather than a remedy.
• Indigestion with a heavy, sluggish feeling: Heiisan is chosen for the specific picture of a heavy stomach, a coated tongue and a dull ache, not for burning heartburn. That pattern-matching is central to Kampo. It is a traditional selection rule, not a tested one.
• Loose stools linked to overeating or rich food: Traditionally used for short bouts of loose stools after heavy or greasy meals. There is no trial evidence for this use. Diarrhoea lasting more than a few days, or with blood, fever or severe pain, is a reason to see a doctor, not to keep taking a remedy.
• Mild nausea after eating: Ginger, one of the usual ingredients, has reasonable evidence for nausea on its own. That does not transfer automatically to a blend containing a small amount of it. Heiisan itself has not been tested for nausea.

Which foods are rich in Heiisan?

1. Licorice sweets and licorice tea - contain the same glycyrrhizin as the kanzo in Heiisan, and count toward your total
2. Dried citrus peel used in cooking - the same chinpi ingredient, though in tiny culinary amounts
3. Fresh and dried ginger - shares the shokyo ingredient

Practical Tips:

Heiisan is not found in food, but licorice confectionery and licorice tea add to the same load on your blood pressure and potassium.

What are the side effects of Heiisan?

• Nausea or stomach upset
• Loss of appetite
• Skin rash or itching
• Swelling in the ankles, face or hands
• Raised blood pressure
• Low potassium in the blood, which can cause muscle weakness, cramps and tiredness
• Irregular or fast heartbeat, rarely
• Muscle pain with dark urine, a sign of muscle breakdown, very rarely

Good to know:

Most people who take Heiisan for a short course have no trouble, and mild stomach upset or rash is the usual complaint.

The serious effects all trace back to the licorice. Long use or high doses can cause pseudoaldosteronism (a reaction to licorice in which the body holds on to salt and water, blood pressure rises and blood potassium falls). Warning signs are swelling, headache, muscle weakness and cramps.

Very low potassium can disturb the heart's rhythm, and in rare cases licorice has caused muscle breakdown. These are documented, not theoretical. They are more likely at high doses, over long periods, or when several licorice-containing products are combined.

How much Heiisan should you take?

• Recommended daily: No dose has been established by research. What follows is the standard Japanese Kampo practice dose, not a proven amount. Adults commonly take 7.5 g of the granulated extract per day, split into two or three doses. Follow the label on your product, because strength differs between makers. Do not combine Heiisan with another Kampo formula that also contains kanzo (licorice) unless a practitioner has checked the total licorice for you.
• Best time of day: Traditionally taken two or three times a day, spaced through the day so doses fall before or between meals.
• With or without food: Kampo practice is to take it on an empty stomach, about 30 minutes before a meal or between meals, with hot water. If it upsets your stomach that way, taking it with food is acceptable.
• Time to effect: If it helps you, most people notice a difference in digestive comfort within a few days to two weeks.
• How long to take it: Heiisan is meant for short courses. Two to four weeks is a reasonable trial. If your symptoms have not improved after about two weeks, stop and get checked rather than continuing. Long continuous use raises the risk from licorice. If you want to use it for more than a month, you need a practitioner or doctor monitoring your blood pressure and blood potassium.