---
topic: "Adzuki Beans"
title: "Adzuki Beans: Blood Sugar, Cardiovascular, and Gut Health"
order: 1
description: "How adzuki beans lower triglycerides, help maintain HDL cholesterol, affect blood sugar and inflammation in type 2 diabetes, shift gut bacteria in mice, and deliver an exceptional concentration of plant protein, prebiotic fiber, and seed-coat polyphenols."
question: "Do adzuki beans improve cholesterol, blood sugar and gut health?"
answer: "Adzuki beans may lower triglycerides and help maintain HDL, but the blood sugar and gut evidence is one diabetes trial and one mouse study."
actions:
  - "Eat a half-cup to one cup of cooked adzuki beans three to four times a week, keeping the polyphenol-rich seed coat on [6]."
  - "Soak dried beans overnight, discard the water, then cook 45–60 minutes; soaking cuts phytic acid by 30–50%."
  - "Choose plain cooked beans or unsweetened paste (anko); sweetened red bean paste carries significant added sugar and is better as a treat."
cautions:
  - "Never eat raw or undercooked beans; lectins can cause digestive upset and phytic acid can reduce mineral absorption."
  - "In type 2 diabetes, use adzuki beans as a complement to standard care, not a replacement [4]."
confidence: 2
confidenceNote: "Two randomized trials (an 8-week extract study and a 4-week diabetes food study) and one juice study without placebo; gut findings come from mice."
evidenceSummary:
  rctCount: 2
  observationalCount: 1
  metaAnalysisCount: 0
  replicated: false
  newestStudyYear: 2023
references:
  - id: "1"
    pmid: "18648655"
    title: "Azuki Bean Juice Lowers Serum Triglyceride Concentrations in Healthy Young Women"
    authors: "Maruyama C, Araki R, Kawamura M, Kondo N, Kigawa M, Kawai Y, et al."
    year: 2008
    journal: "Journal of Clinical Biochemistry and Nutrition"
  - id: "2"
    pmid: "30782097"
    title: "Safety and efficacy of adzuki bean extract in subjects with moderate to high LDL-C: a randomized trial"
    authors: "Kitano-Okada T, Nagata R, Han KH, Mikami N, Satoh K, Nishihira J, et al."
    year: 2019
    journal: "Bioscience, Biotechnology, and Biochemistry"
  - id: "3"
    pmid: "37160631"
    title: "Cholesterol-Lowering Activity of Adzuki Bean (Vigna angularis) Polyphenols"
    authors: "Kuriya K, Goto S, Kobayashi E, Nishio M, Nakamura M, Umekawa H"
    year: 2023
    journal: "Molecular Biology Reports"
  - id: "4"
    pmid: "29785114"
    url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC5953312/"
    title: "Convenient food made of extruded adzuki bean attenuates inflammation and improves glycemic control in patients with type 2 diabetes: a randomized controlled trial"
    authors: "Liu Y, Wang Q, Li S, Yue Y, Ma Y, Ren G"
    year: 2018
    journal: "Therapeutics and Clinical Risk Management"
  - id: "5"
    pmid: "35782919"
    url: "https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.918696/full"
    title: "Cooked Adzuki Bean Reduces High-Fat Diet-Induced Body Weight Gain, Ameliorates Inflammation, and Modulates Intestinal Homeostasis in Mice"
    authors: "Zhao Q, Liu Z, Zhu Y, Wang H, Dai Z, Yang X, et al."
    year: 2022
    journal: "Frontiers in Nutrition"
  - id: "6"
    url: "https://www.tandfonline.com/doi/full/10.1080/1343943X.2023.2206576"
    title: "Variation in antioxidant capacity of the seven azuki bean (Vigna angularis) varieties with different seed coat color"
    authors: "Nagao N, Sakuma Y, Funakoshi T, Itani T"
    year: 2023
    journal: "Plant Production Science"
---

Adzuki beans are small, rust-red legumes that have been central to East Asian cuisine and traditional medicine for millennia — most familiar as the sweetened red bean paste inside Japanese mochi and Korean tteok. A half-cup cooked delivers around 8 g of protein, 8 g of fiber, and meaningful amounts of folate, potassium, magnesium, and iron, all for under 150 calories [1]. What makes adzuki beans stand out even among legumes is their seed coat, which is unusually rich in polyphenols — including two catechin glucosides that inhibited cholesterol micellar solubility and bound bile acids in laboratory experiments [3]. Clinical research suggests that adzuki bean juice significantly lowered serum triglycerides in healthy young women [1], a randomized trial found that adzuki bean extract raised HDL cholesterol more than placebo after 4 weeks in people with moderate to high LDL [2], and an RCT in type 2 diabetes patients found that an adzuki bean-based food lowered the inflammation marker TNF-α more than a traditional diabetic diet while controlling blood sugar about as well as that diet [4]. In mice on a high-fat diet, cooked adzuki bean limited weight gain, eased inflammation, and shifted the gut microbiota [5].

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## What makes adzuki beans distinctive

Adzuki beans (Vigna angularis) are not simply interchangeable with other legumes. Several properties set them apart nutritionally.

**Seed coat polyphenols** — The deep reddish-brown color of adzuki beans comes from a concentrated layer of polyphenols in the outer seed coat. Two catechin glucosides abundant in adzuki beans — (+)-catechin 7-O-β-D-glucopyranoside (C7G) and (+)-epicatechin 7-O-β-D-glucopyranoside (E7G) — were evaluated for cholesterol-lowering potential in laboratory experiments [3]. They inhibited the micellar solubility of cholesterol, bound bile acids, and reduced the amount of cholesterol taken up by Caco-2 cells, an intestinal cell model. The antioxidant capacity of adzuki beans is much higher in deep-colored varieties than in light-colored ones and is localized at the seed coat [6].

**Fiber and resistant starch composition** — Adzuki beans contain both soluble and insoluble fiber, plus a notable fraction of resistant starch. Resistant starch escapes small intestine digestion and travels intact to the colon, where it serves as a prebiotic substrate for bacteria that produce butyrate and other short-chain fatty acids. In mice fed a high-fat diet that included 15% whole cooked adzuki bean, the gut microbiota composition changed [5]; that study tested the whole bean, not its fiber on its own.

**Pancreatic lipase inhibition** — One of the more unusual properties of adzuki bean polyphenols is their ability to inhibit pancreatic lipase, the enzyme that breaks down dietary triglycerides in the small intestine so they can be absorbed. In laboratory and clinical research, adzuki bean juice inhibited pancreatic lipase activity by 29–57% depending on concentration — a mechanism similar to orlistat (a prescription weight-loss drug), but operating at a much lower magnitude through a food source [1].

**Nutritional profile** — Per half-cup cooked: approximately 8 g protein, 8 g dietary fiber, 150 calories, 35 mcg folate (10% DV), 612 mg potassium (13% DV), 60 mg magnesium (14% DV), 2.3 mg iron (13% DV). The protein quality is reasonable as plant proteins go, with a good amino acid profile for a legume, though not a complete protein — combining with rice or other grains provides all essential amino acids, as reflected in traditional adzuki bean and rice dishes across Asia.

## Blood sugar and metabolic effects

The glycemic index of adzuki beans is low (around 26–34), but the more clinically relevant evidence is their effect in people with established blood sugar dysregulation. In a randomized controlled trial, 120 patients with type 2 diabetes were assigned to eat an extruded adzuki bean food daily or to follow a traditional diabetic low glycemic index diet for 4 weeks [4]. Glycemic control improved in both groups compared with baseline, but the difference was not statistically significant, and the authors report that the adzuki bean food had a similar hypoglycemic effect as the low glycemic index diet [4]. The adzuki bean group did have a significantly lower level of the inflammation marker TNF-α than the control group, although its interleukin-6 (IL-6) level rose slightly [4].

Several mechanisms could contribute to the blood sugar effects of adzuki beans. Resistant starch bypasses the small intestine entirely, reducing the carbohydrate load available for glucose conversion. Soluble fiber forms a viscous gel that slows gastric emptying and delays glucose absorption. Polyphenols inhibit alpha-glucosidase and alpha-amylase — enzymes that break complex starches into absorbable glucose in the intestine. The authors of the diabetes trial note that further clinical studies are needed to explore the underlying mechanism [4].

## Cardiovascular effects

A controlled study in healthy young women found that consuming azuki bean juice daily for one full menstrual cycle (approximately 28 days) decreased serum triglycerides by 15.4% compared to control — and a more concentrated azuki juice form reduced triglycerides by 17.9% — relative to no intervention [1]. The proposed mechanism was pancreatic lipase inhibition: by reducing lipase activity by 29–57%, adzuki bean polyphenols reduce how much dietary fat is absorbed, which translates to lower postprandial and fasting triglycerides.

For cholesterol specifically, an 8-week randomized, double-blind, placebo-controlled trial in people with moderate to high LDL cholesterol found that adzuki bean extract produced a significantly greater change in HDL cholesterol than placebo after 4 weeks, with no adverse effects [2]. By week 8 the extract group's HDL change had returned to baseline while the placebo group's had fallen below it; the authors describe the study as a short-term first step in establishing the plausibility of HDL-maintaining effects [2].

At the molecular level, two adzuki bean polyphenols, C7G and E7G, inhibited cholesterol micellar solubility, bound bile acids and reduced cholesterol uptake in a Caco-2 intestinal cell model in laboratory experiments [3].

## Gut health and inflammation

In a mouse model of diet-induced obesity, adding 15% cooked adzuki bean to a high-fat diet for 12 weeks significantly inhibited weight gain and hepatic steatosis, lowered serum triacylglycerol and the liver enzymes ALT and AST, and alleviated systemic inflammation and metabolic endotoxemia [5]. Gut microbiota analysis showed that cooked adzuki bean regulated the microbiota composition: it decreased the abundance of lipopolysaccharide (LPS)-producing bacteria (Desulfovibrionaceae, Helicobacter and Bilophila) and enriched Muribaculaceae, Anaeroplasma and Lachnospiraceae [5].

Short-chain fatty acids produced from adzuki bean fiber fermentation include acetate, propionate, and butyrate. Butyrate serves as the primary fuel for colonocytes and plays a key role in maintaining gut barrier integrity, regulating gene expression in colon cells, and suppressing inflammatory signaling. Propionate is transported to the liver and influences lipid metabolism. Acetate circulates systemically and has effects on energy substrate utilization. Together, these fermentation products link adzuki bean consumption in the upper gut to systemic metabolic effects downstream.

## Practical guidance

**Portion:** A half-cup of cooked adzuki beans (about 115 g) provides meaningful amounts of the fiber and polyphenols studied. Increasing to one cup per serving, or including adzuki beans three to four times per week, is consistent with the research context.

**Forms:** Dried adzuki beans require soaking (8+ hours) and cooking (45–60 minutes). Canned adzuki beans are available in Asian grocery stores and retain their nutritional profile well — rinse to reduce sodium. Unsweetened adzuki bean paste (anko) is a traditional preparation that concentrates fiber and protein. Sweetened versions contain significant added sugar and are better regarded as a treat than a health food.

**Antinutrient management:** Like most legumes, adzuki beans contain phytic acid and lectins that can reduce mineral absorption and cause digestive discomfort in sensitive individuals. Soaking overnight and discarding soaking water reduces phytic acid by 30–50%. Thorough cooking inactivates lectins — raw or undercooked beans should not be eaten. Sprouting adzuki beans (2–3 days) is another approach that increases available minerals and reduces antinutrient load while creating a crunchy, versatile ingredient.

**Pairing with rice:** Adzuki beans paired with short-grain rice is a classical preparation (sekihan in Japanese cuisine, patbap in Korean) that traditional medicine systems long considered health-supporting. The combination provides all essential amino acids and a meaningful improvement in the glycemic profile of white rice, validated by research on legume-rice pairings generally.

See our [lentils page](/lentils/protein-fiber-and-longevity) and [black beans page](/black-beans/anthocyanins-blood-sugar-and-gut-health) for comparisons with other nutritionally similar legumes, and our [resistant starch page](/resistant-starch/gut-health-and-metabolism) for more on how fermentable fiber shapes gut health and metabolism.

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## Evidence Review

### Triglyceride Reduction in Healthy Women — Maruyama et al. (2008) — PMID 18648655

This controlled study from Tokai University enrolled healthy young women assigned to consume 150 g/day of azuki bean juice (approximately 18 g dried azuki beans) or a more concentrated azuki bean juice preparation over one full menstrual cycle, compared to no intervention. Serum lipids were measured before and after the intervention period.

**Key findings:** The standard azuki bean juice group showed a statistically significant 15.4% decrease in serum triglycerides (p < 0.05) compared to baseline and control. The concentrated azuki bean juice group showed a 17.9% reduction that approached significance (p = 0.055). No significant changes were observed in LDL or HDL cholesterol in this study. In parallel in vitro experiments, azuki bean juice inhibited pancreatic lipase activity by 29.2%, and concentrated azuki bean juice inhibited it by 56.9% — a dose-dependent effect that mechanistically explains the triglyceride-lowering action.

**Significance:** This is the most methodologically direct human evidence that azuki bean consumption specifically reduces triglycerides through pancreatic lipase inhibition — a mechanism distinct from the fiber-mediated effects seen with most other legumes. The magnitude of effect (15–18% triglyceride reduction) is clinically meaningful. Limitations include the all-female, young, apparently healthy sample, modest sample sizes in each group, and the lack of a rigorous placebo control. The study does not speak to effects in people with dyslipidemia or in men.

### Adzuki Bean Extract and HDL Cholesterol — Kitano-Okada et al. (2019) — PMID 30782097

This 8-week, randomized, double-blind, placebo-controlled, parallel-group trial evaluated the safety and efficacy of a polyphenol-containing adzuki bean extract on lipid metabolism in people with moderate to high LDL cholesterol (LDL-C).

**Key findings:** After 4 weeks, the change in HDL cholesterol (ΔHDL-C) was significantly greater in the adzuki bean group than in the placebo group (3.76 ± 7.79 mg/dL versus −0.08 ± 6.03 mg/dL). By week 8, ΔHDL-C had fallen in both groups: the adzuki bean extract group returned to baseline levels (0.36 ± 5.36 mg/dL), while the placebo group dropped below baseline (−3.17 ± 7.79 mg/dL). No adverse effects were observed in the participants receiving the extract.

**Significance:** The authors describe this as a short-term study and a first step in establishing the practicality, safety, and plausibility of HDL-C-maintaining effects of adzuki bean extract in people. Because the extract group's HDL change was back at baseline by week 8 while the placebo group's had fallen below it, the result is better read as maintaining HDL than as a lasting rise. Whether the effect holds in longer trials is not yet known; it would be a different benefit from the triglyceride effect observed in the Maruyama study.

### Adzuki Bean Polyphenols and Cholesterol Absorption — Kuriya et al. (2023) — PMID 37160631

This mechanistic study evaluated the cholesterol-lowering potential of two polyphenols identified as abundant in adzuki beans: (+)-catechin 7-O-β-D-glucopyranoside (C7G) and (+)-epicatechin 7-O-β-D-glucopyranoside (E7G). It was carried out in vitro, using cholesterol micelles, bile acids, and Caco-2 cells as an intestinal model.

**Key findings:** Both C7G and E7G inhibited cholesterol micellar solubility in a dose-dependent manner — meaning they reduce how much cholesterol stays dissolved in the micelles that carry it toward absorption — and their inhibitory activity was as strong as that of (+)-catechin (IC50 values of 0.23, 0.22 and 0.26 mg/ml for C7G, E7G and (+)-catechin, respectively). The polyphenols also showed binding activity toward bile acids and changed them into an insoluble form. When Caco-2 cells were treated with C7G or E7G, the amount of cholesterol they took up was significantly lower than in vehicle-treated control cells, with no cytotoxicity under the conditions used, while the mRNA level of the cholesterol transporter NPC1L1 remained unchanged.

**Significance:** This study offers a laboratory picture of how adzuki bean polyphenols may suppress cholesterol absorption, and the authors suggest that C7G and E7G are the main active compounds in adzuki beans. As a mechanistic study rather than a clinical trial, it does not establish clinical efficacy directly, but it supports the biological plausibility of the cardiovascular effects seen in human research.

### RCT in Type 2 Diabetes — Liu et al. (2018) — PMID 29785114

In this randomized controlled trial, 120 patients with type 2 diabetes were randomly assigned either to a control diet (the traditional diabetic low glycemic index diet) or to daily consumption of an extruded adzuki bean convenient food (EABCF). Diet information and blood samples were collected at baseline and after a 4-week intervention, and 106 patients completed the trial. The aim was to investigate the effects of the food on glycemic control and inflammation.

**Key findings:** Glycemic control improved in both groups compared with baseline, but the difference was not statistically significant (p > 0.05). The adzuki bean group showed decreased inflammation, with a significantly lower tumor necrosis factor alpha (TNF-α) level than the control group (adjusted p < 0.01), along with a slight increase in the interleukin-6 (IL-6) level (adjusted p = 0.004). After excluding exogenous insulin users, a subgroup analysis of 89 participants, based on baseline fasting insulin, found that after 4 weeks the adzuki bean diet increased insulin secretion to normal levels in the group with hypoinsulinism (baseline fasting insulin below 5.2 mU/L), although that difference only showed a trend toward statistical significance (p = 0.079).

**Significance:** The authors conclude that the adzuki bean food had a similar hypoglycemic effect as the traditional diabetic low glycemic index diet and a greater inhibitory effect on inflammation, and that further clinical studies are needed to explore the underlying mechanism. It is the only diabetes trial among the studies cited here, it lasted 4 weeks, and its inflammation results were mixed: lower TNF-α, but slightly higher IL-6.

### Gut Microbiota and Inflammation in High-Fat Diet Model — Zhao et al. (2022) — PMID 35782919

This controlled animal study fed mice either a low-fat diet or a high-fat diet, with or without 15% cooked adzuki bean, for 12 weeks. Outcomes included weight gain, liver fat (hepatic steatosis), serum triacylglycerol and liver enzymes, systemic inflammation, metabolic endotoxemia, and the composition of the gut microbiota.

**Key findings:** In mice fed the high-fat diet, cooked adzuki bean significantly inhibited weight gain and hepatic steatosis, reduced high levels of serum triacylglycerol (TG), alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and alleviated systemic inflammation and metabolic endotoxemia. It also regulated the gut microbiota: it decreased the abundance of lipopolysaccharide (LPS)-producing bacteria (Desulfovibrionaceae, Helicobacter and Bilophila) and of several high-fat-diet-dependent taxa, and enriched Muribaculaceae, Anaeroplasma, Lachnospiraceae and related groups.

**Significance:** The authors present these results as new evidence for understanding the anti-obesity effect of whole cooked adzuki bean, and they link the alleviation of inflammation and metabolic disorders to the changes in gut microbiota composition. Limitations are that this is an animal study, which does not directly establish human clinical outcomes, and that the effects were seen in mice fed a diet containing 15% cooked adzuki bean.

### Antioxidant Capacity Across Varieties — Nagao et al. (2023)

This comparative laboratory study evaluated the total antioxidant capacity and the phenolic profiles of seven adzuki bean varieties in relation to their seed coat color, which was measured with a color-difference meter. Antioxidant capacity was assessed as DPPH radical-scavenging activity.

**Key findings:** Antioxidant capacity was found in the seed coat, not the cotyledons, of all the varieties except the white one. In extracts of whole, unground seeds it ranged widely, from 36.2 to 2.8 μmol Trolox equivalents per gram dry weight, and it correlated positively with total phenolics content and negatively with color lightness (L*). The deep-colored varieties had much higher antioxidant capacity than the light-colored ones. Anthocyanin was present in only three of the darker varieties; Tamba-dainagon, the most popular red-colored variety, and three others contained none, yet the varieties without anthocyanin, except for one white variety, clearly showed antioxidant capacity.

**Significance:** The authors conclude that the adzuki seed coat is an effective potential source of natural antioxidants. This is a laboratory measurement of antioxidant capacity, not a trial of health outcomes in people. Because the capacity was localized at the seed coat, whole beans with the seed coat left on are the form most relevant to this finding.