What is Tong Cao?

Tong Cao is the dried white pith from inside the stem of the rice paper plant (Tetrapanax papyrifer). It is a single herb used in Traditional Chinese Medicine. Practitioners use it mainly for trouble passing urine and for low breast milk supply.

It comes as light, spongy white sticks or slices. It is almost always cooked with other herbs in a formula. It is rarely taken on its own.

The honest evidence picture is thin. We could find no human trials of Tong Cao by itself. Its standing rests on long use in one tradition, and traditional use is not proof that something works.

How does Tong Cao work?

The short answer is that no one has mapped how Tong Cao works in people.

In the traditional model, the herb is bland and cool. Practitioners say it "drains damp" and clears heat from the bladder. That is a traditional idea, not a laboratory finding.

In modern words, it is used as a mild diuretic (something that makes you pass more urine). That effect has not been measured in good human studies. So we cannot tell you how strong it is, or whether it happens at all.

Early laboratory work has looked at the plant sugars in the pith. Test-tube work like this cannot show what happens in a person. Treat it as a starting point, not an answer.

Its traditional use for low breast milk has no tested mechanism. Tradition holds that it helps "open the channels" so milk can flow. No trial has checked this.

What forms does Tong Cao come in?

Tong Cao is sold in a few simple forms.

Dried pith sticks or slices, white and very light, for cooking into a tea (decoction).

Granules or powdered extract, to be stirred into hot water.

As one herb inside a ready-made Chinese patent formula.

There is no essential oil, no tincture in wide use, and no injectable form you should consider.

Where it comes from:

Tong Cao has been used in Chinese herbal medicine for centuries, and it is a standard item in modern Chinese pharmacopoeia.

The name has a messy past. In older texts, "Tong Cao" often meant Akebia stem, the herb now called Mu Tong. The name shifted to the rice paper plant pith in later centuries.

The same pith was also cut into thin sheets for the "rice paper" used in Chinese paintings. This name confusion matters for safety, and is covered below.

What does Tong Cao help with?

• Trouble passing urine: This is the main traditional use. Formulas with Tong Cao are given for scanty, slow or difficult urination. No human trial has tested the herb alone for this. Trouble passing urine can signal infection, a stone or a prostate problem, so get it checked first.
• Burning or painful urination: In TCM this is often read as "damp heat" in the bladder. Tong Cao is combined with cooling herbs for it. There is no trial evidence that it treats a urinary infection. Bacterial infections need proper medical care, and can reach the kidneys if left alone.
• Mild fluid retention and puffiness: Tradition uses it to move fluid and ease mild swelling. Any such effect is unmeasured in people. New or one-sided swelling can point to heart, liver or kidney problems. See a doctor before self-treating.
• Low breast milk supply: Tong Cao has a long traditional record here, usually cooked with pork trotter or fish soup. We found no human trials showing that it raises milk supply. If you are breastfeeding, speak to a doctor, midwife or lactation adviser first.

What are the side effects of Tong Cao?

• Passing urine more often
• Thirst or dry mouth
• Dizziness, if you become dehydrated
• Mild stomach upset or loose stools
• Rash or itching, in rare allergic reactions

Good to know:

Side effects appear to be uncommon at normal doses, but reporting is poor.

Most concerns come from fluid loss rather than from the herb itself. Older adults and people on water pills are more likely to feel it. Stop the herb and drink water if you feel dizzy or very thirsty.

A bigger risk comes from the wrong plant in the bag. See the section on who should avoid it.

How much Tong Cao should you take?

• Recommended daily: No dose has been set by human trials. Standard TCM practice uses about 2 g to 5 g of the dried pith per day. It is simmered in water with other herbs to make a tea. Some sources go up to 6 g. Granule and extract doses vary by brand. Follow the label, or the amount a qualified practitioner gives you.
• Best time of day: Split the daily amount into two warm doses, morning and early evening. Avoid a dose close to bedtime, since it may make you get up to pass urine.
• With or without food: Traditionally taken between meals. If it upsets your stomach, take it with food instead.
• Time to effect: Not known from trials. In traditional use, any change in urine flow is expected within a few days.
• How long to take it: Use it in short courses, not as a daily long-term supplement. Most traditional use runs for a few days to two or three weeks. Stop and reassess after two weeks if nothing has changed. Ongoing urinary symptoms need a medical opinion, not a longer course of herbs.