Adzuki beans, Vigna angularis, are not a kind of red kidney bean. They belong to the genus Vigna, with mung bean, while the kidney bean is Phaseolus vulgaris. The Japanese name 小豆 means “small bean”, a counterpart to 大豆, “large bean”, the word for soybean.
Most adzuki beans in East Asia are eaten sweet, as red bean paste called anko in Japanese. The purple color of good paste comes from pigments in the seed coats that wash out into the water as the beans boil. Cooked plain, 100 g has 128 calories and 7.3 g of fiber, and a cup (230 g) has 76% of the daily value for copper.
Human research on adzuki is small and mostly Japanese or Chinese. The trials below used juice, extracts or a processed bean food rather than a bowl of boiled beans, so they show what is possible, not what a serving does.
Health benefits of adzuki beans
The top findings from 11 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★★★Lower “bad” LDL cholesterol, from pulses in generalEating about 130 g a day of pulses lowered LDL a little (by 0.14 mmol/L across 38 trials). Adzuki beans were not singled out in the study.
- ★★Lower fasting blood sugar and insulinAcross 11 trials, pulses eaten alone lowered fasting blood sugar and insulin, but results varied widely between studies. These were pulses in general, not adzuki alone.
- ★Low blood sugar rise after cooked adzuki beansIn 10 healthy adults, cooked adzuki beans had a low glycemic index (a measure of blood sugar rise), unlike millet or black rice. Adzuki and lotus seed together scored 21 to 51, against 83 to 109 for the other foods.
- ★Lower triglycerides with adzuki bean juiceIn 33 healthy young Japanese women, 150 g a day of adzuki bean juice for one menstrual cycle lowered triglycerides by 15.4%. LDL and HDL cholesterol did not change, and it was a small trial of juice, not whole beans.
- ★No extra blood sugar benefit in diabetesIn 120 adults with type 2 diabetes, a processed adzuki bean food improved blood sugar control about as much as a low-glycemic diet. It was a processed product, not boiled beans.
All 11 studies, strongest evidence first
Pooled pulses, with adzuki not singled out, lowered LDL cholesterol by 0.14 mmol/L across 38 trials
Pooled pulses (beans, chickpeas, lentils and peas), not adzuki alone. Meta-analysis of 38 randomized trials (2,095 people) of whole dietary pulses, with a median of 6 weeks and 130 g a day (0.5 to 0.67 cup). Non-HDL cholesterol fell 0.22 mmol/L and HDL dipped by 0.03 mmol/L. Results were similar across pulse types, and for beans LDL kept falling with amounts up to 1 cup a day.
Pooled pulses eaten alone lowered fasting blood glucose and insulin in 11 trials, with results that varied widely
Pooled pulses (beans, chickpeas, peas, lentils and more), not adzuki alone. Meta-analysis of 41 randomized trials of at least 7 days in people with and without diabetes. Pulses in low-glycemic-index diets (19 trials) lowered HbA1c or fructosamine. Differences between studies were high and mostly unexplained, and the authors call for larger trials.
A 4-week diet built on extruded adzuki bean food lowered the inflammation marker TNF-alpha in type 2 diabetes but did not beat a low-glycemic diet for blood sugar
Randomized trial in 120 adults with type 2 diabetes (106 finished) that compared a processed, extruded adzuki bean convenient food with a standard low glycemic index diabetic diet. Blood sugar control improved in both groups with no significant difference between them. IL-6 rose slightly on the adzuki food. This was a processed product, not boiled beans.
150 g a day of azuki bean juice for one menstrual cycle lowered triglycerides by 15.4% in healthy young women
Randomized trial in 33 healthy Japanese women (10 on control, 11 on azuki juice, 12 on concentrated juice), using a juice made to a traditional Kampo recipe. Triglycerides fell 0.170 mmol/L on the juice, and the concentrated juice (17.9%) only tended to differ from control (p = 0.055). LDL and HDL cholesterol did not change. It was a small trial of juice, not whole beans.
An adzuki bean extract for 8 weeks kept HDL cholesterol from falling in people with moderate to high LDL
Randomized, double-blind, placebo-controlled trial of a polyphenol-containing adzuki bean extract. After 4 weeks HDL had risen 3.76 mg/dL on the extract against a 0.08 drop on placebo, and at week 8 it was back at its starting level on the extract (0.36) but 3.17 mg/dL below it on placebo. No adverse effects were seen. The abstract reports HDL only. This was an extract, and two authors work for a food company.
Cooked adzuki beans had a low glycemic index in 10 healthy adults, unlike millet or black rice
Randomized crossover trial in 10 healthy adults who ate pre-soaked adzuki beans, lotus seed and four other foods, each cooked for two lengths of time. Adzuki and lotus seed together fell in a glycemic index range of 21 to 51, while the other foods (83 to 109) did not differ from rice. In lab digestion tests, pre-soaking raised the starch that digests quickly and lowered resistant starch.
Mice fed 15% adzuki bean on a high-fat diet gained less fat and had better insulin sensitivity
Study in mice, not people. Mice ate a low-fat diet, a high-fat diet, or a high-fat diet with 15% adzuki bean for 12 weeks. Adzuki bean lowered obesity, blood fats and fatty liver, and moved gut bacteria back toward the normal pattern, including a lower Firmicutes to Bacteroidetes ratio.
Adzuki resistant starch lowered serum cholesterol in rats fed a cholesterol-rich diet
Study in rats, not people. Rats ate 15% adzuki resistant starch with a 0.5% cholesterol diet for 4 weeks. Total cholesterol and the VLDL, IDL and LDL fraction were lower than on the cholesterol diet alone, and bile acid in the feces and short-chain fatty acids were higher. The starch was a purified fraction, not whole beans.
A hot-water adzuki extract lowered blood glucose in mice with type 2 diabetes
Study in mice, not people. Diabetes-prone KK-Ay mice ate 5,000 mg of an extract fraction per kg of body weight a day, for 8 weeks to test prevention and 4 weeks in mice that were already diabetic. Serum insulin, urinary glucose and liver triglycerides were also lower. It tested an extract, not the beans.
An azuki bean extract lowered blood pressure in rats with hypertension
Study in rats, not people. Spontaneously hypertensive rats with a systolic pressure near 200 mm Hg ate a diet with 0.9% polyphenol-containing extract for 8 weeks. Their pressure ended lower than in untreated rats, and urinary nitrate and nitrite, a sign of nitric oxide production, was higher. It tested an extract, not the beans.
Four adzuki bean varieties ranged from low to medium glycemic index in a lab digestion model
Lab test, not a study in people. The in vitro glycemic index ranged from 39.00 to 56.76. Resistant starch made up 69.78 to 81.03% of the total starch, and the beans blocked alpha-amylase, an enzyme that digests starch.
Who should be careful with adzuki beans
Most people can eat adzuki beans freely. Take a little care if one of these applies:
- Sweet red bean paste and sweetened canned beans. The sugar is the issue, not the bean. USDA lists sweetened canned adzuki beans at 237 calories and 55.0 g of carbohydrate per 100 g, against 128 calories and 24.8 g for boiled beans without sugar.
- Irritable bowel syndrome or a gassy gut. Monash University names galacto-oligosaccharides as a main fermentable carbohydrate in legumes and says canned beans, or beans boiled and drained, tend to be lower in them. The Monash blog does not mention adzuki beans, so no tested serving size is given here.
- Legume allergy. Adzuki bean allergy is rare, but reports from Japan describe allergy to adzuki beans, including food protein-induced enterocolitis syndrome, a delayed gut reaction. People with a known legume allergy should ask their allergist before trying them.
How to choose, store and eat adzuki beans
- Boiled whole beans: 100 g has 128 calories, 7.5 g of protein and 7.3 g of fiber, and in a 10-person trial cooked adzuki beans had a low glycemic index. Extension guides soak most dry beans before cooking, while the authors of that trial advise keeping pre-soaking short for blood sugar.
- Sweet paste and sweetened cans: USDA lists 237 calories per 100 g for sweetened canned beans, nearly double the 128 of plain boiled ones, and 260 calories for yokan, a sweet made from adzuki beans and sugar.
- Juice, extracts and processed foods: the trials above used 150 g a day of juice, an 8-week extract and an extruded bean food. They are not the same as eating the beans, and none of them has been tested against a bowl of boiled beans.
Pick through dry beans and discard discolored or shriveled ones, then rinse them. Soak them with a hot soak (boil for 2 to 3 minutes, then stand up to 4 hours) or overnight in the fridge, and drain before cooking. Dry beans keep best away from oxygen and light, and in ordinary food-grade bags they hold up for about a year or more. No official pesticide residue data for adzuki beans turned up, so none is given here.
Sources
- Including legumes on a low FODMAP diet. Monash FODMAP blog.
- Kitamura K, Sato N, Nakamura M, et al. Identification of allergens in azuki (adzuki) bean allergy. J Investig Allergol Clin Immunol. 2024.
- Irahara M, Sato Y, Ohno T, et al. Food protein-induced enterocolitis syndrome caused by adzuki beans: a case report. Pediatr Int. 2025.
- Beans, adzuki, mature seeds, canned, sweetened (FDC 173729). USDA FoodData Central, SR Legacy.
- Yokan, prepared from adzuki beans and sugar (FDC 173730). USDA FoodData Central, SR Legacy.
- Beans, adzuki, mature seeds, cooked, boiled, without salt (FDC 173728). USDA FoodData Central, SR Legacy.
- Zhu R, Fan Z, Han Y, et al. 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.
- How to cook dry beans from scratch. University of Nebraska–Lincoln Extension.
- Storing dry beans. Utah State University Extension.
History of adzuki beans
Adzuki beans were first domesticated in Japan, according to a 2025 study in Science that used about 700 accessions from across Asia. It places the start of domestication 3,000 to 5,000 years ago in central Japan, in the Jomon period, followed by spread into China and crossing with wild Chinese populations. The same work traced the shift to red seed coats to a gene change, and suggests that early selection was weak.
Seed remains from Japan’s Central Highlands, dated to 6,000 to 4,000 years ago, suggest that use of adzuki, and larger seeds, began there earlier than in China or Korea. A separate 2025 find complicates the picture. At the Xiaogao site in Shandong, China, adzuki beans dated to about 9,000 to 8,000 years ago sat alongside millet, rice and soybean in an early mixed-crop system, and the authors describe domestication as a complex, multiregional process.
The plant has had several names. Willdenow described it in 1802 in the genus Dolichos, and botanists moved it to Vigna in 1969. Its section of the genus also holds the rice bean, while mung bean and black gram sit in a neighboring section. In Chinese the everyday names are hóngdòu and chìdòu, both meaning “red bean”.
Sweet paste is the main use across East Asia. Japanese cooks make tsubuan, with whole beans boiled in sugar, and koshian, sieved smooth, the most common kind. The paste goes into anpan, dorayaki, taiyaki and daifuku in Japan and into mooncakes and tangyuan in China.
Adzuki also colors a festive dish. Sekihan is sticky rice steamed with adzuki beans until it turns reddish, and red is believed to stand for happiness in Japan. It is served at birthdays, weddings and holidays such as Shichi-Go-San. A lab study found that the red pigment forms as the bean’s procyanidins change during cooking with the rice.
Sources
- Chien CC, Seiko T, Muto C, et al. A single domestication origin of adzuki bean in Japan and the evolution of domestication genes. Science. 2025.
- Chen X, Sun Z, Zhang S, 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.
- Takahashi Y, Nasu H, Nakayama S, Tomooka N. Domestication of azuki bean and soybean in Japan: from the insight of archeological and molecular evidence. Breed Sci. 2023.
- Takahashi Y, Tomooka N. Taxonomic history, morphology, evolution, gene pool and stress tolerances of azuki bean and its related wild Vigna genetic resources. Breed Sci. 2024.
- Yoshida K, Kawahara M, Takayama Y, Asano T. Purple pigments, catechinopyranocyanidins A and B, in the seed coats of red adzuki beans elute during processing to yield purple-colored an-paste. Proc Jpn Acad Ser B Phys Biol Sci. 2025.
- Takahama U, Hirota S, Morina F. Procyanidins in rice cooked with adzuki bean and their contribution to the reduction of nitrite to nitric oxide in artificial gastric juice. Int J Food Sci Nutr. 2020.
- Adzuki bean. Wikipedia.
- Red bean paste. Wikipedia.
- Sekihan. Wikipedia.
Frequently asked questions about adzuki beans
Are adzuki beans good for you?
Probably, as part of a normal diet. A cup (230 g) of boiled adzuki beans has 17.3 g of protein and 16.8 g of fiber, plus 70% of the daily value for folate and 76% for copper. Human evidence on adzuki itself is small, though: no finding here reaches strong evidence, and pooled pulses lowered LDL cholesterol by 0.14 mmol/L across 38 trials.
How many calories and how much protein are in adzuki beans?
Boiled adzuki beans without salt have 128 calories, 7.5 g of protein and 7.3 g of fiber per 100 g, or 294 calories in a cup (230 g). Protein supplies about 26% of the calories. Dry beans have about three times as much per 100 g because they hold no water, so do not mix dry and cooked numbers.
Are adzuki beans the same as red kidney beans?
No. Adzuki beans are Vigna angularis and red kidney beans are Phaseolus vulgaris, two different species. Per 100 g boiled, adzuki beans have 128 calories, 7.5 g of protein and 7.3 g of fiber, and kidney beans have 127 calories, 8.7 g of protein and 6.4 g of fiber.
Is sweet red bean paste healthy?
It depends on the sugar. USDA lists sweetened canned adzuki beans at 237 calories and 55.0 g of carbohydrate per 100 g, against 128 calories and 24.8 g for plain boiled beans. None of the studies above used paste, so their results do not apply to it.
Are adzuki beans good for blood sugar and diabetes?
They may fit, but the evidence is thin. Cooked adzuki beans had a glycemic index of 21 to 51 together with lotus seed in 10 healthy adults. In 120 adults with type 2 diabetes, a 4-week diet built on an extruded adzuki bean food lowered TNF-alpha but did not beat a low-glycemic diet for blood sugar. Check portions and choices with your care team.
Do adzuki beans lower cholesterol?
Pulses as a group do, a little, but adzuki trials are few. In 38 pooled trials pulses lowered LDL by 0.14 mmol/L. Of the adzuki trials, juice lowered triglycerides by 15.4% in a 33-woman trial and an extract kept HDL from falling, and the extract trial reported no LDL result.
Do adzuki beans cause gas?
They can, as other beans do, and no trial here measured gas from adzuki. Monash University names galacto-oligosaccharides as a main fermentable carbohydrate in legumes and says canned beans, or beans boiled and drained, tend to be lower in them. Its blog does not mention adzuki beans, so try small servings.
Can you eat adzuki beans if you have gout?
Probably in moderate amounts, but ask your clinic. A 2026 lab paper calls adzuki beans high in purines, and acid-assisted heat treatment removed 49 to 72% of them in the lab. In 47,150 men followed for 12 years, purine-rich vegetables were not linked to a higher risk of gout, while meat and seafood were.