Adzuki Bean

Vigna angularis (Willd.) Ohwi & H.Ohashi

Sources

6 listed

Best forChosen as a nourishing, high-fibre pulse for everyday cooking and for feast days, from sweet red bean paste to porridge and red bean rice. Its place is the kitchen and the festival calendar, not the medicine cabinet.

Clinical evidence

Traditional

Real World Significance

52Established historical significance

Breadth 25 Depth 100 Density 27 Convergence 38 Continuity 80

SafetyUsually well toleratedAdzuki is a cooked food legume eaten very widely with no signal of harm at ordinary intake. The cautions are those for any pulse, cook thoroughly, never eat raw, introduce gradually, plus the usual prudence around concentrated extracts, no medicinal doses in pregnancy and the warning about the deadly rosary pea. That keeps it firmly in the safe band.

Tradition

TCMFolk medicine

Common preparations

Whole FoodCookedPasteExtract

In short

Summary of findings for quick reference

The adzuki bean is one of East Asia's oldest crops. Carbonised seeds from Xiaogao in Shandong, China, are directly dated to about nine thousand years ago, when the bean grew there beside millet, rice and soybean, and measurements from 41 sites show that it was domesticated gradually and in several regions of China, Korea and Japan. It has been eaten without a break ever since. Japan's eighth-century chronicles name it, sekihan and sweet anko bring it to Japanese celebrations, and Korean families still cook red bean porridge, patjuk, at the winter solstice. Its tradition is East Asian and comes from the kitchen, and it reached Europe only in modern times.

In Chinese medicine the small red bean is chi xiao dou. The Shennong Bencao Jing credits it with drawing off water and draining pus, Li Shizhen's Bencao Gangmu of 1578 adds that only the small, dark red beans are fit for medicine, and the Chinese Pharmacopoeia lists the dried seed today at 9 to 30 g, accepting adzuki and the rice bean alike as its source. These uses rest on tradition, not on clinical trials. In the kitchen adzuki is a nourishing pulse. 100 g of boiled beans supply 7.5 g of protein, 7.3 g of fibre and 121 micrograms of folate for 128 kcal, and the red seed coat holds polyphenols such as catechins and kaempferol. Research in people is thin. In ten healthy adults steamed adzuki had a glycaemic index of 21 to 29, against 83 for white rice. In one trial an extract raised HDL cholesterol after four weeks, back at baseline by week eight, and a 2024 review calls the effect of adzuki on diabetes in people undetermined.

In the European Union adzuki is an ordinary food. No health claim is authorised for it, and the only EMA herbal monograph for a bean covers the dried pods of the common bean (Phaseolus vulgaris), a different plant and plant part. As an everyday food adzuki is eaten by children, adults and older people, and in pregnancy, with no sign of harm at ordinary amounts. The one rule that matters is the rule for every dried bean. Cook it thoroughly and never eat it raw or half-cooked, because raw beans contain lectins that cause nausea, vomiting and diarrhoea. If you are not used to beans, increase the amount slowly to keep wind in check. Medicinal doses of chi xiao dou are another matter in pregnancy, as Chinese medicine sources warn that large doses can bring on miscarriage. And never mistake adzuki for the rosary pea, a glossy red seed with a black spot that is deadly poisonous.

Clinical evidence ↔ Historical significance

We display two separate evidence categories: clinical evidence from modern trials and historical significance from documented healing tradition. Both are valuable, but they answer different questions.

In every encyclopedia entry we evaluate two distinct categories of evidence. Clinical evidence as used in trials meets a narrower but scientifically essential bar. At the same time, the hundreds of thousands of plant species worldwide have only partially been captured and tested in modern studies.

Alongside the trial picture our researchers compile a comprehensive overview of where and since when a plant has been used across different traditions of natural medicine. When a plant has been used as a medicinal plant in many cultures across many generations, that historical significance deserves to be visible too.

Our position: a truly informative overview emerges only when both categories sit side by side. We communicate transparently what counts as what.

Overview

The adzuki bean, Vigna angularis, is an annual of the legume family whose small, glossy, mostly dark red seeds have been cooked in East Asia for around nine thousand years. The dried seed is the part used. It is simmered whole into soups and porridge, steamed with glutinous rice for the Japanese feast dish sekihan, or cooked down with sugar into anko, the sweet paste inside countless Japanese confections. It is first of all a food, with plenty of fibre, plant protein and folate, and its red colour carries meaning at New Year, at weddings and at the winter solstice in China, Japan and Korea.

Medicine took an interest early. Chinese materia medica has listed the small red bean, chi xiao dou, since the Shennong Bencao Jing as a remedy that draws off water and drains pus from boils, and today's Chinese Pharmacopoeia still lists the dried seed, accepting both adzuki and its close relative the rice bean (Vigna umbellata) as its source. In the European Union adzuki is simply a food, with no authorised health claim. Research has turned to its fibre, its slowly digested starch and the polyphenols of its red seed coat. The human studies are few and short. Steamed adzuki raises blood sugar far less than white rice, and in one trial an adzuki extract lifted HDL cholesterol for a few weeks, but no study has yet shown a lasting health effect from eating the bean.

History

Some of the oldest adzuki beans yet found come from Neolithic China. In 2025 a team led by Xuexiang Chen published carbonised adzuki seeds from Xiaogao, a settlement of the Houli culture in Shandong, radiocarbon dated directly to 8985 to 8645 years before present. The people there lived by hunting, fishing and foraging as well as farming, and they grew the bean beside broomcorn and foxtail millet, rice and soybean. Measuring beans from 41 sites across East Asia, the team found that seeds grew larger over the millennia, but along a different path in each region. Between about 6000 and 4500 years ago beans in Japan and Korea were already notably large, larger than Chinese beans from before and after that time. Their conclusion is a domestication that unfolded in several places. The wild ancestor still grows across East Asia, and Japan has older finds still. Charred beans of the same genus from the Tochibara rock shelter are dated to about 10,700 years ago, and waterlogged adzuki from the lake bed at Awazu on Lake Biwa are possibly ten thousand years old. The bean's story has more than one beginning.

Writing came later. The Shennong Bencao Jing, the oldest Chinese materia medica, places chi xiao dou in its middle class of drugs and says it drives down watery swelling and expels pus and blood from abscesses. Li Shizhen's Bencao Gangmu of 1578 reads in places like a farmer's notebook. The bean is sown after the summer solstice, grows about a foot tall with leaves like the cowpea, flowers in autumn and is picked when the pods are three parts green and two parts yellow, and it can be boiled or roasted and made into porridge, bean rice and dumpling filling. For medicine, he insists, only the small, firm, dark red beans will do, while the larger bright red ones cure nothing. He also retells an old story, that a worthless son of the water god Gonggong died at the winter solstice, returned as a plague demon and feared red beans, which is why red bean porridge was cooked on that day, and he dismisses it as a far-fetched tale.

In Japan the bean belongs to the oldest myths. The Kojiki of 712 tells how the storm god Susanoo killed the food goddess Ogetsuhime, and how the first crops grew from her body, rice, millet, barley and soybeans, and red beans from her nose. Over the centuries azuki became the colour of celebration. Sekihan, glutinous rice steamed with the beans and tinted red by them, is still the dish for weddings, birthdays and other auspicious days, and anko, the sweet bean paste, fills mochi, steamed manju and dorayaki. Because the bean is eaten almost always with sugar, a bean breeder from Hokkaido observed, Japan ate little of it while sugar was scarce. In 1970 Japan grew azuki on 90,000 hectares, almost half of them in Hokkaido, where the Tokachi plain has only about 134 frost-free days a year. The trade knew two grades, ordinary azuki and the larger, dearer Dainagon, plus a little white azuki, shiro shozu, for pale bean paste.

In Korea the bean is pat, and its great day is Dongji, the winter solstice, once honoured as a little New Year. Families cooked patjuk, red bean porridge, set bowls of it at the house shrine and around the home and splashed it on walls and doors, trusting the red colour to keep away the spirits that spread disease. One rule shows how seriously this was taken. When the solstice fell early in the lunar month, a so-called Aedongji, no patjuk was made, because it was thought to bring bad luck to the children, and steamed rice cake was eaten instead. The bean itself is far older on the peninsula. Bean impressions on potsherds from Osanri on the east coast, identified with certainty only to the genus, are about seven thousand years old, and directly dated charred adzuki from Pyeonggeo-dong in the south nearly five thousand. Europe came to know the bean only in modern times, as a food from East Asia.

Mechanism

Adzuki works the way pulses do, through what it is made of rather than through a single active substance. 100 g of boiled beans bring 128 kcal, 7.5 g of protein, 7.3 g of fibre, 532 mg of potassium, 52 mg of magnesium, 2 mg of iron and 121 micrograms of folate, with almost no fat, and part of the starch resists digestion. The red seed coat is where the chemistry concentrates, in polyphenols such as catechin and its glucosides, kaempferol and other flavonoids, and anthocyanins, together with saponins and phytic acid. These compounds sit in the part that is eaten, and they are the reason researchers study the bean.

Most of what is known about how adzuki might act comes from the laboratory. Extracts, proteins and starch fractions of the bean inhibit alpha-glucosidase in the test tube, the gut enzyme that releases glucose from starch, and extruded adzuki inhibits it more strongly than raw beans. In mice with type 2 diabetes, hot-water extracts of the bean lowered blood sugar. In people, the one clear observation is that blood sugar rises only a little after a meal of steamed beans, which fits the enzyme findings and the bean's fibre and resistant starch. Whether this adds up to a lasting benefit for people who simply eat adzuki has not been tested.

Human research on adzuki is small but has grown beyond a single study. One trial, published by Tomoko Kitano-Okada and colleagues in 2019, gave adults with moderately to highly raised LDL cholesterol either a polyphenol-containing adzuki extract or a placebo for eight weeks, randomised and double-blind. After four weeks HDL cholesterol had risen by 3.8 mg/dL with the extract and fallen by 0.1 mg/dL with placebo, a statistically significant difference. By week eight the extract group was back at its starting value while the placebo group had slipped below it, and no effect on LDL, the reason the volunteers were chosen, is reported. No adverse effects were seen. The first author worked for a food company, Cosmo Foods, and the trial tested a concentrate, not the cooked bean.

Two studies have tested the bean as food. In a randomised crossover trial from China Agricultural University in 2019, ten healthy adults ate portions of several starchy foods, each with 50 g of available carbohydrate. Soaked overnight and steamed for 40 or 70 minutes, adzuki had a glycaemic index of 21 and 29, against 83 for white rice, and produced no typical blood sugar peak at all. In a 2018 trial at Peking Union Medical College Hospital, 120 people with type 2 diabetes ate either a convenience food made from extruded adzuki or a standard low glycaemic diet for four weeks. Blood sugar control improved in both groups, with no statistically significant difference between them. The adzuki group had lower levels of the inflammatory marker TNF-alpha, while another marker, interleukin-6, rose slightly. Both studies were short, and neither measured long-term outcomes.

The rest of the evidence comes from animals and the test tube. A 2024 review by Shu Hang Kwan and Elvira Gonzalez de Mejia at the University of Illinois found thirteen animal studies and two laboratory studies on adzuki and blood sugar but only one in people, the 2018 diabetes trial, and concluded that the effect of eating adzuki on type 2 diabetes in humans remains undetermined. In a 2008 study by Sato and colleagues, rats bred to develop high blood pressure ate a diet with 0.8 per cent adzuki polyphenol extract for eight weeks. Their blood pressure rose less, and their hearts and kidneys held fewer macrophages, the immune cells of inflammation. These results explain the scientific interest. They have not been shown in people.

Evidence

5 Outcomes evaluated. Sorted by grade.

Outcome	Class	Grade	Effect	Studies
Nourishing food legume and culinary stapleChildren, adults and the elderly eating the cooked bean	Traditional	D	Traditional food use
Traditional use for fluid balance and mild swelling (chi xiao dou)Traditional East Asian medicine practice	Traditional	D	Traditional use only
Blood lipids (HDL cholesterol), concentrated extractAdults with moderately to highly raised LDL cholesterol	Emerging	I	One small trial	1 study
Blood sugar after meals and glycaemic controlHealthy adults and adults with type 2 diabetes, plus laboratory and animal models	Emerging	I	Two short food studies	2 studies
Blood pressure (azuki polyphenol extract)Spontaneously hypertensive rats (animal model)	Insufficient	I	Animal model only

Key studies

The studies that matter.

Randomised controlled trial · 2018
In Beijing, 120 people with type 2 diabetes ate either a daily convenience food made from extruded adzuki or a standard low glycaemic diet for four weeks, and 106 finished. Blood sugar control improved in both groups with no statistically significant difference between them. The adzuki group had lower TNF-alpha, an inflammatory marker, while interleukin-6 rose slightly. The largest human study of the bean, but short and without a placebo, so it shows adzuki holding its own against a good diabetic diet rather than beating it.
Liu Y, Wang Q, Li S, Yue Y, Ma Y, Ren G. Liu Y, Wang Q, Li S, Yue Y, Ma Y, Ren G. Convenient food made of extruded adzuki bean attenuates inflammation and improves glycemic control in patients with type 2 diabetes: a randomized controlled trial. Ther Clin Risk Manag. 2018;14:871-884. doi:10.2147/TCRM.S161649 doi:10.2147/TCRM.S161649
Randomised controlled trial · 2019
In a randomised crossover trial, ten healthy adults ate portions of six starchy foods, each with 50 g of available carbohydrate, and white rice for comparison. Adzuki, soaked overnight and steamed for 40 or 70 minutes, had a glycaemic index of 21 and 29, against 83 for white rice, and produced no typical blood sugar peak. A small single-meal study, but a direct measurement in people of how the cooked bean behaves.
Zhu R, Fan Z, Han Y, et al. Zhu R, Fan Z, Han Y, Li S, Li G, Wang L, Ye T, Zhao W. Acute effects of three cooked non-cereal starchy foods on postprandial glycemic responses and in vitro carbohydrate digestion in comparison with whole grains: a randomized trial. Nutrients. 2019;11(3):634. doi:10.3390/nu11030634 doi:10.3390/nu11030634
Randomised controlled trial · 2019
Adults with moderately to highly raised LDL cholesterol took a polyphenol-containing adzuki extract or a placebo for eight weeks, randomised and double-blind. After four weeks HDL cholesterol had risen by 3.8 mg/dL with the extract and fallen by 0.1 mg/dL with placebo, a statistically significant difference, but by week eight the extract group was back at its starting value. No adverse effects were seen. One small extract trial with a first author from a food company, so it counts for little on its own and says nothing about the cooked bean.
Kitano-Okada T, Nagata R, Han KH, et al. Kitano-Okada T, Nagata R, Han KH, Mikami N, Satoh K, Nishihira J, Sasaki K, Ohba K, Fukusima M. Safety and efficacy of adzuki bean extract in subjects with moderate to high LDL-C: a randomized trial. Biosci Biotechnol Biochem. 2019;83(5):933-941. doi:10.1080/09168451.2019.1574553 doi:10.1080/09168451.2019.1574553
Review · 2024
This narrative review gathered the research on adzuki and type 2 diabetes and found one human trial, thirteen animal studies and two laboratory studies. Extracts, proteins and fibre of the bean lowered blood sugar in animals and inhibited alpha-glucosidase in the test tube. The authors conclude that the effect of eating adzuki on type 2 diabetes in people remains undetermined and call for randomised human trials. A useful map of the evidence rather than evidence of benefit.
Kwan SH, Gonzalez de Mejia E. Kwan SH, Gonzalez de Mejia E. The potential of the adzuki bean (Vigna angularis) and its bioactive compounds in managing type 2 diabetes and glucose metabolism: a narrative review. Nutrients. 2024;16(2):329. doi:10.3390/nu16020329 doi:10.3390/nu16020329
2025
Archaeobotanists reported carbonised adzuki seeds from Xiaogao, a Houli culture site in Shandong, directly radiocarbon dated to 8985 to 8645 years before present, and measured adzuki seeds from 41 sites across East Asia. Seeds grew larger over time but along different regional paths, which the authors read as domestication in several regions. The strongest evidence for the bean's age and history, though it says nothing about health.
Chen X, Sun Z, Zhang S, Lee GA, Nasu H, Zhang F, et al. Chen X, Sun Z, Zhang S, Lee GA, Nasu H, Zhang F, et al. The discovery of adzuki bean (Vigna angularis) in eastern China during the 9th millennium BP and its domestication in East Asia. Proc Natl Acad Sci U S A. 2025;122(39):e2510835122. doi:10.1073/pnas.2510835122 doi:10.1073/pnas.2510835122

Usage

Forms and preparation

Adzuki is cooked like any dried bean, only faster. Rinse the beans, soak them for a few hours or overnight, then simmer them in fresh water until soft, which takes roughly 45 minutes to an hour and a quarter depending on the beans and the soak. Being small, adzuki cooks relatively quickly and is often used without a long soak. Eat the beans whole in soups, stews and porridge, steam them with glutinous rice for sekihan, or cook them down with sugar into anko, smooth or chunky, to fill mochi, steamed buns and pastries. Li Shizhen listed much the same uses in 1578, boiled or roasted beans, porridge, bean rice and dumpling filling. Beyond the kitchen, adzuki is also sold as flour, as canned cooked beans and as a concentrated polyphenol extract in some supplements, usually promoted for its polyphenol content. An extract is a concentrate, not a meal, so the label and the intended use matter, and the one trial that raised HDL cholesterol for a few weeks tested such an extract, not the cooked bean. As a food, adzuki needs nothing beyond soaking and thorough cooking.

Dosage

There is no official dose for adzuki as a food. It is eaten as part of meals, in portions like any other cooked bean. For medicinal chi xiao dou the Chinese Pharmacopoeia gives 9 to 30 g of the dried seed, and the powdered seed is also applied to swellings and sores. That is a traditional reference, not a modern recommendation. The extract that raised HDL cholesterol for a few weeks in one trial was a study protocol, not a serving size. Follow the label of any concentrated extract, and there is no reason to go beyond ordinary kitchen amounts of the cooked bean.

Special populations

As an ordinary cooked food, adzuki is eaten by children, adults and older people and during pregnancy and breastfeeding as part of a normal diet. The usual notes for any pulse apply. Introduce beans gradually if you are not used to them, since the fibre can cause wind, and always cook them thoroughly. Medicinal chi xiao dou is a different matter in pregnancy. Li Shizhen's Bencao Gangmu of 1578 used it to ease difficult labour and to expel the afterbirth, and a modern Chinese medicine reference warns that large doses can bring on miscarriage. This concerns medicinal doses, not a bowl of red bean soup, but in pregnancy leave medicinal preparations and concentrated extracts alone unless your doctor or midwife agrees. Extracts have not been assessed in pregnancy or breastfeeding.

Safety

Safety profile

Adzuki is an everyday food and generally very well tolerated. The central safety point is the one shared by all dried beans. Soak them, cook them thoroughly and never eat them raw or undercooked. Raw beans contain lectins, phytohaemagglutinin among them, that cause nausea, vomiting and diarrhoea, and as few as four or five raw kidney beans can be enough. The US Food and Drug Administration advises boiling red kidney beans, the richest source, for at least 30 minutes and warns that slow cookers do not get hot enough, and that rule is the safe one for adzuki too. There is no regulator monograph and no official list of contraindications for adzuki, so this guidance comes from food safety science. A few more notes. A large helping of beans can cause wind and bloating if you are not used to them, which eases as the gut adjusts and with gradual introduction and good cooking. Concentrated polyphenol extracts are a different product from the cooked bean. The one extract trial saw no adverse effects over eight weeks, but extracts have not been broadly assessed, so follow the label and tell your doctor if you take critical medicines. Keep decorative red seeds out of the kitchen, because the rosary pea, scarlet with a black spot, is deadly poisonous. People with a known bean or legume allergy should avoid adzuki.

Drug interactions

There is no regulator interaction list for adzuki, and as an ordinary cooked food it has no known drug interactions of practical concern. As with other high-fibre foods, a very large helping of beans could slow the absorption of some medicines taken at the same time, so anyone who wants to be careful leaves a gap. Concentrated polyphenol extracts are less studied than the food, so anyone on medicines with a narrow safety margin who wants to take such an extract should mention it to their doctor. All of this is general prudence, not a documented interaction.

Contraindications

There are no formal contraindications for adzuki, because it is a food and not a registered herbal medicine. Known bean or legume allergy: anyone who reacts to beans should avoid adzuki. Raw or undercooked beans: not to be eaten because of their natural lectins, so always soak and cook them thoroughly. Concentrated extracts: anyone on critical medicines or with a health condition uses them with the usual prudence, since extracts are not the cooked food and have not been broadly assessed.

Side effects

At ordinary food intake adzuki has no known undesirable effects and is well tolerated. What people notice most is the wind and bloating common to any pulse, and both ease if you increase the amount gradually and cook the beans thoroughly. Allergic reactions are possible but uncommon. Raw or undercooked beans can cause nausea and digestive upset because of their lectins, which is why they are always cooked. If any unexpected reaction occurs, stop eating them and seek advice.

Look-alikes

Botany

Family

Fabaceae

Native regions

East Asia (China, Japan, Korea), centre of origin and domestication, Cultivated across Northeast Asia and the Himalayas, Grown worldwide as a food crop, including in North America and parts of Europe

Harvest window

Pods harvested when mature and dry in late summer to autumn; seeds threshed and dried

Habitat

A warm-season annual legume of cultivated fields and gardens, native to and domesticated in East Asia, grown for its dry seed across temperate and subtropical regions with a warm growing season.

Identification & foraging

An erect to twining annual of the legume family, usually half a metre to a metre tall, with leaves of three leaflets and small yellow pea-type flowers. The smooth, cylindrical pods hold several small seeds. These are short and barrel-shaped, about 4 to 6 millimetres across, glossy and dark brownish red, with a thin white line along one side, the hilum, which lies flat rather than standing proud. White, black and mottled cultivars also exist. The part used is the dried seed, soaked and cooked.

Similar plants and look-alikes

Unpleasant

Rice bean (Vigna umbellata), the second chi xiao dou species

The rice bean is the second species the Chinese Pharmacopoeia accepts as chi xiao dou, so in Chinese medicine the two beans share one name. The rice bean is longer and slightly flattened, 5 to 8 millimetres long, purplish red and only faintly glossy, with a raised white hilum that runs along about two thirds of the seed. Adzuki is shorter and barrel-shaped, dark brownish red and glossy, with a flat hilum. Neither is toxic, but they are different species, so check the botanical name on a pack of medicinal chi xiao dou or in a study.

Unpleasant

Mung bean (Vigna radiata)

Another small Asian Vigna bean, often sold on the same shelf. Mung beans are smaller, olive green, and yellow once hulled, and they play a different part in the kitchen, often sprouted or cooked into a pale paste or soup. They are a separate species with their own flavour and chemistry, so one cannot stand in for the other in a recipe or a study.

Unpleasant

Pigeon pea (Cajanus cajan, mu dou)

A Taiwanese survey of seed drugs found pigeon pea sold under the name chi dou, the Chinese name for adzuki, alongside true adzuki and rice bean. Its seeds are flattened globes of a similar size, 4 to 6 millimetres, dark red, with a conspicuous raised, oblong white hilum, and chewed they taste of raw bean. Pigeon pea belongs to a different genus and replaces neither adzuki nor rice bean, so check seed shape and botanical name when you buy loose red beans for a particular purpose.

Deadly

Rosary pea (Abrus precatorius), deadly poisonous

A glossy scarlet seed with a black patch at one end, a little larger and more oval than adzuki, sold as beads and called love bean (xiangsi dou) in China. It contains abrin, and the US Centers for Disease Control and Prevention warn that swallowed seeds can cause bloody vomiting and diarrhoea and, over several days, failure of the liver, spleen and kidneys. Adzuki has no black patch, only a thin white line along one side. Never cook with decorative seeds, and get medical help at once if any have been swallowed.

FAQs

What is an adzuki bean and what part is used?

The adzuki bean (Vigna angularis) is a small legume from East Asia with glossy, mostly dark red seeds about half a centimetre long. The part used is the dried seed, simmered until soft and eaten whole in soups, porridge and rice, or mashed with sugar into anko, the sweet red bean paste of Japanese confectionery. It is first of all a food, rich in fibre and plant protein.

Is the adzuki bean approved by the European regulator for any health use?

No. In the European Union adzuki is an ordinary food, no health claim is authorised for it, and a pack may not promise a health effect. The EMA's only herbal monograph for a bean covers the dried pods of the common bean (Phaseolus vulgaris), a different plant and plant part. In China, by contrast, the dried seed is an official medicinal herb listed in the Chinese Pharmacopoeia.

Is the adzuki bean the same as the medicinal chi xiao dou in Chinese medicine?

Yes, in part. The Chinese Pharmacopoeia defines chi xiao dou as the dried ripe seed of either the rice bean (Vigna umbellata) or the adzuki bean (Vigna angularis), and uses it to promote urination, ease swelling and drain pus. So adzuki is an official source of the medicinal herb and shares the name with a close relative. On a medicinal pack or in a study, the botanical name tells you which bean is meant.

Do adzuki beans need to be cooked, and are raw beans safe?

Yes. Like all dried beans, adzuki must be properly cooked and never eaten raw or half-cooked. Raw beans contain lectins that can cause nausea, vomiting and diarrhoea. The best known of them, phytohaemagglutinin, is at its highest in red kidney beans, and the US Food and Drug Administration advises boiling those for at least 30 minutes, because the gentle heat of a slow cooker is not enough. The same rule is the safe one for any dried bean, and adzuki needs 45 minutes or more to turn soft anyway.

Can adzuki be confused with a poisonous red bean?

Yes, and it has happened. The rosary pea (Abrus precatorius), called xiangsi dou or love bean in China and strung into bracelets, is a glossy red seed with a black patch at one end, a little larger and more oval than adzuki. It contains abrin, and the US Centers for Disease Control and Prevention warn that swallowing the seeds can cause bloody vomiting and diarrhoea and, over several days, failure of the liver, spleen and kidneys. In 2016 a young woman in Hangzhou added two of them to her rice porridge and ended up in intensive care. Buy red beans for cooking only as food, and never cook with decorative seeds.

Is there scientific proof that adzuki beans lower blood sugar or cholesterol?

Not yet. The human studies are few and short. Steamed adzuki raised blood sugar far less than white rice in ten healthy adults, a convenience food made from adzuki did about as well as a standard low glycaemic diet over four weeks in 120 people with type 2 diabetes, and a concentrated extract raised HDL cholesterol for a few weeks in adults with high LDL. A 2024 review rates the effect in people as undetermined and asks for proper randomised trials. Adzuki earns its place as a good pulse, not as a treatment.

Why is the adzuki bean important in Japanese and Korean culture?

Red has long been the colour of celebration and protection in East Asia, and the bean carries it. In Japan sekihan, glutinous rice steamed with adzuki and tinted red by it, is served at weddings, birthdays and other happy occasions, and sweet anko fills countless confections. In Korea families cook patjuk, red bean porridge, at the winter solstice and once splashed some on walls and doors to keep evil spirits out. Japan's oldest chronicle, the Kojiki of 712, already has red beans growing from the body of a food goddess.

References

6 sources.

Kitano-Okada T, Nagata R, Han KH, et al.. Kitano-Okada T, Nagata R, Han KH, Mikami N, Satoh K, Nishihira J, Sasaki K, Ohba K, Fukusima M. Safety and efficacy of adzuki bean extract in subjects with moderate to high LDL-C: a randomized trial. Biosci Biotechnol Biochem. 2019;83(5):933-941. doi:10.1080/09168451.2019.1574553. 2019. doi:10.1080/09168451.2019.1574553
Liu Y, Wang Q, Li S, Yue Y, Ma Y, Ren G. Liu Y, Wang Q, Li S, Yue Y, Ma Y, Ren G. Convenient food made of extruded adzuki bean attenuates inflammation and improves glycemic control in patients with type 2 diabetes: a randomized controlled trial. Ther Clin Risk Manag. 2018;14:871-884. doi:10.2147/TCRM.S161649. 2018. doi:10.2147/TCRM.S161649
Zhu R, Fan Z, Han Y, et al.. Zhu R, Fan Z, Han Y, Li S, Li G, Wang L, Ye T, Zhao W. Acute effects of three cooked non-cereal starchy foods on postprandial glycemic responses and in vitro carbohydrate digestion in comparison with whole grains: a randomized trial. Nutrients. 2019;11(3):634. doi:10.3390/nu11030634. 2019. doi:10.3390/nu11030634
Kwan SH, Gonzalez de Mejia E. Kwan SH, Gonzalez de Mejia E. The potential of the adzuki bean (Vigna angularis) and its bioactive compounds in managing type 2 diabetes and glucose metabolism: a narrative review. Nutrients. 2024;16(2):329. doi:10.3390/nu16020329. 2024. doi:10.3390/nu16020329
Chen X, Sun Z, Zhang S, Lee GA, Nasu H, Zhang F, et al.. Chen X, Sun Z, Zhang S, Lee GA, Nasu H, Zhang F, et al. The discovery of adzuki bean (Vigna angularis) in eastern China during the 9th millennium BP and its domestication in East Asia. Proc Natl Acad Sci U S A. 2025;122(39):e2510835122. doi:10.1073/pnas.2510835122. 2025. doi:10.1073/pnas.2510835122
Sato S, Mukai Y, Yamate J, et al.. Sato S, Mukai Y, Yamate J, Kato J, Kurasaki M, Hatai A, Sagai M. Effect of polyphenol-containing azuki bean (Vigna angularis) extract on blood pressure elevation and macrophage infiltration in the heart and kidney of spontaneously hypertensive rats. Clin Exp Pharmacol Physiol. 2008;35(1):43-49. doi:10.1111/j.1440-1681.2007.04743.x. 2008. doi:10.1111/j.1440-1681.2007.04743.x

Legal notice: The depiction of historical significance and traditional use is context within our encyclopedia and not a health claim for any product, not a treatment promise, and not a substitute for medical advice. What may be stated on product labels, product pages, or in advertising is governed by the applicable legal requirements.