Nature's Answer to Summer Heat
When the thermometer climbs and the air turns thick with humidity, Chinese kitchens reach for one humble ingredient: the mung bean. Simmered into a pale jade broth and served warm, at room temperature, or chilled, mung bean soup (绿豆汤 / lǜ dòu tāng) is the classic cooling drink of the Chinese summer — a simple potion that has been poured for centuries to calm heat, quench stubborn thirst, and gently support the body's own cleansing.
In Traditional Chinese Medicine (TCM), mung bean soup belongs to a small, trusted category of cooling foods (凉性食物). It is traditionally used to address summer-heat (暑热 / shǔ rè): the flushed face, the dry mouth that no amount of iced water seems to fix, the restless irritability that comes with long hot days. Unlike an icy drink, which TCM considers a shock to the digestive system, mung bean soup cools from the inside out — gently, evenly, and without the crash.
TCM Properties of Mung Beans
In the TCM framework, every food carries a thermal nature, a flavour, and a set of meridians it travels through. Mung beans (Vigna radiata) are classified as follows:
- Thermal nature: Cold (凉 / liáng) — among the most cooling of common foods
- Flavour: Sweet (甘 / gān)
- Meridian entry: Heart (心 / xīn) and Stomach (胃 / wèi)
- Key actions: Clears summer-heat (清热 / qīng rè), quenches thirst (生津 / shēng jīn), and is traditionally believed to support detoxification (解毒 / jiě dú)
Because mung beans enter the Heart meridian, TCM holds that they can settle the agitation and irritability that heat tends to stir up. Their sweet flavour harmonizes with the Stomach, which is why the soup is easy to drink even when appetite is poor on a sweltering day. The thin, green broth is prized over thick preparations for hydration — in folk tradition it is often described as carrying the "cooling essence" of the bean while remaining light on digestion.
Traditional Uses Through History
Mung beans are one of the oldest cultivated legumes in China, and their medicinal reputation is documented in the classics. The Ben Cao Gang Mu (《本草纲目》 / Compendium of Materia Medica), Li Shizhen's monumental 16th-century pharmacopoeia, praises mung beans for clearing heat, dispelling summer-heat, and easing toxicity from spoiled food. Throughout Chinese history, mung bean soup has been used for:
- Summer-heat and mild heat stroke — dizziness, fatigue, and unquenchable thirst on hot days
- Heat rashes and skin flare-ups — including acne and small boils that worsen in warm weather
- Irritability and restless nights — when internal heat makes the mind feel wired
- Recovery after rich meals — as a gentle, light drink believed to help the body process heaviness
In many families, the soup is still the first thing made when someone comes home flushed from the sun — a small ritual of care passed down through generations.
Complete Recipe: Classic Mung Bean Soup (绿豆汤)
This is the everyday version — simple, quick, and endlessly adaptable. It makes about 4 cups of soup.
Ingredients
- 1 cup (200 g) dried mung beans (绿豆 / lǜ dòu)
- 8 cups (2 L) water — filtered water helps keep the broth green
- 1–2 tablespoons rock sugar (冰糖 / bīng táng) or honey, to taste
- Optional: 3–4 slices of dried tangerine peel (陈皮 / chén pí) to protect the Stomach
- Optional: a squeeze of lemon juice to preserve the green colour
Step-by-Step Instructions
- Rinse and pick over the beans. Place the mung beans in a bowl, cover with water, and swish with your fingers. Drain and repeat until the water runs clear. Remove any stones or shriveled beans.
- Soak (optional but helpful). Cover the rinsed beans with fresh water and soak for 1–2 hours. This softens the beans and shortens cooking time; if you are short on time, you can skip it and simply simmer 10 minutes longer.
- Bring to a gentle boil. Add the beans and 8 cups of filtered water to a large pot. Bring to a boil over medium-high heat, then immediately reduce to a low, gentle simmer. Avoid a violent rolling boil — vigorous boiling oxidizes the beans and turns the broth reddish.
- Keep the lid on. Cover the pot, leaving a small crack for steam to escape. Simmer for 25–35 minutes, until the beans have burst open and the liquid is fragrant and pale green.
- Skim the foam. In the first 10 minutes, skim any foam that rises to the surface — this keeps the broth clean and clear.
- Sweeten to taste. Stir in rock sugar until dissolved, or let the soup cool slightly and stir in honey. Add the optional squeeze of lemon to lock in the green hue.
- Serve. The soup can be enjoyed warm, at room temperature, or lightly chilled. In TCM, avoid ice-cold servings — extreme cold is believed to shock the Spleen and Stomach.
Cooking Tips
- Green vs. red: The jade-green colour is a sign of minimal oxidation. Use filtered water, gentle heat, and keep the lid on. A drop of lemon juice also helps.
- Thick or thin: For a thinner, more hydrating drink, add another cup of water. For a heartier version closer to a dessert, simmer until half the beans break down into the liquid.
- Savoury option: Skip the sugar and add a pinch of salt and a few drops of sesame oil for a light summer broth.
- Batch ahead: The soup keeps for 2–3 days in the refrigerator. Reheat gently rather than boiling hard.
Delicious Variations
Mung Bean and Winter Melon Soup
Add 200 g of diced winter melon (冬瓜 / dōng guā) with the beans. Winter melon is even more cooling and is traditionally used to promote urination and drain dampness — a lovely pairing for humid, sticky days.
Mung Bean and Mint Cooler
After cooking, steep a handful of fresh mint leaves in the warm soup for 10 minutes, then strain. Mint adds a bright, aromatic lift that enhances the cooling effect of the soup on hot afternoons.
Mung Bean, Lily and Lotus Seed Soup
Add 20 g of dried lily bulb (百合 / bǎi hé) and 30 g of lotus seeds (莲子 / lián zǐ), pre-soaked, when you start simmering. Lily and lotus seeds are traditionally used to calm the spirit and support restful sleep — making this a soothing evening version for heat-frazzled nights.
Precautions and Who Should Drink Less
Mung bean soup is a therapeutic food, not an everyday drink for everyone. Because of its cold nature, TCM advises caution for certain patterns:
- Cold Spleen and Stomach: If you regularly have loose stools, poor appetite, cold hands and feet, or feel chilled easily, drink mung bean soup only occasionally — once or twice a week at most — and consider adding ginger or tangerine peel to warm it up.
- Pregnancy: Traditionally, pregnant women are advised to drink it sparingly and lightly sweetened. Check with your healthcare provider first.
- Medication timing: In folk tradition, mung bean soup is sometimes said to affect herbal formulas. If you are taking prescribed TCM herbs or medication, space the soup a few hours apart from your doses, and ask your practitioner.
- Raw beans are toxic: Never eat raw mung beans — they contain compounds that can upset the stomach and must be neutralized by thorough cooking.
When in doubt, listen to your body: if the soup leaves you feeling cold, bloated, or heavy, your system may be telling you it needs the warming foods instead.
Frequently Asked Questions
Is mung bean soup the same as mung bean porridge?
No. Mung bean soup (绿豆汤) is a thin, hydrating broth made from beans and water alone — a drink. Mung bean porridge (绿豆粥) adds rice and simmers into a thick congee — a meal. Both are cooling, but the soup is lighter and more focused on clearing heat and quenching thirst, while the porridge is more nourishing and filling.
Should I drink it hot or cold?
Traditionally, TCM recommends serving it warm or at room temperature. A lightly chilled version is acceptable on very hot days, but ice-cold servings are discouraged because they are believed to impair digestion and weaken the Spleen. The gentle warmth of the soup itself is part of its cooling magic — it helps the body release heat without shocking the system.
How long can I store it?
Mung bean soup keeps for 2–3 days in a covered container in the refrigerator. Reheat it gently over low heat rather than boiling it hard, which destroys the delicate green pigment. If it develops a sour smell or cloudy appearance, discard it.
Can children drink mung bean soup?
Yes, in small amounts and lightly sweetened, mung bean soup has long been given to children during heatwaves as a gentle, hydrating tonic. Serve it warm or at room temperature rather than chilled, and keep portions small — children's digestive systems are more sensitive to cold-natured foods.