Raw red kidney beans can make you ill. In 2018, 200 of 1,700 people who ate lunch at a French military base developed stomach illness, and investigators pointed to a chili con carne made with undercooked kidney beans. The raw beans measured 66,667 hemagglutinating units per gram of a lectin called phytohemagglutinin, and the chili itself held more than the potentially toxic dose of 400 units per gram. The FDA says that as few as four or five raw beans can trigger symptoms.
Kidney beans are one of many kinds of common bean, Phaseolus vulgaris, the same species as black, pinto and navy beans. The species was domesticated twice, independently, in Mesoamerica and in the Andes. White kidney beans, sold as cannellini, carry about a third of the toxin of red ones but still need proper cooking.
Cooked, a cup (177 g) has 15.3 g of protein, 11.3 g of fiber and 58% of the daily folate for 225 calories, and their glycemic index is 24. Much of the research below pools all pulses, or uses concentrated white kidney bean extract supplements, so it does not show what a bowl of red kidney beans does on its own.
Health benefits of kidney beans
The top findings from 17 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 →- ★★Slightly lower weight with white kidney bean extractAcross 8 trials, white kidney bean extract capsules lowered body weight by 1.62 kg more than placebo in adults with overweight or obesity. These are supplements, not cooked beans; a separate 12-week trial in 81 people also found more weight and fat loss than placebo.
- ★★Lower LDL with a daily serving of pulsesEating about a serving a day (130 g) of beans, chickpeas, lentils or peas lowered LDL a little (by 0.17 mmol/L) across 26 trials. This covers pulses as a group, not kidney beans alone.
- ★Possibly lower heart disease risk in bean studiesIn 23 pooled studies of whole beans or bean extracts, the authors report 11% lower cardiovascular disease risk and 22% lower coronary heart disease risk. The studies were mixed, so treat the figures as rough.
- ★Mixed blood sugar results after kidney bean mealsIn 17 adults with type 2 diabetes, red kidney beans with rice lowered blood sugar at 90 to 150 minutes, though not the total rise. In 6 young men, a red kidney bean breakfast gave blood sugar and insulin responses similar to bran cereal or white bread.
- ★Lower blood pressure 2 hours after kidney beansIn 8 healthy adults, three-quarters of a cup of red kidney beans lowered blood pressure and artery stiffness 2 hours later, compared with white rice. It was a small pilot that measured short-term blood vessel responses, not long-term heart disease.
All 17 studies, strongest evidence first
Capsules of white kidney bean extract lowered body weight by 1.62 kg more than placebo in adults with overweight or obesity
This is a supplement, not cooked beans. Meta-analysis of 8 randomized trials (543 people) of oral white kidney bean extract, which blocks an enzyme that digests starch. Waist size fell 1.58 cm and fat mass 1.17 kg, while fasting blood sugar, triglycerides and insulin did not change. No serious side effects were linked to the extract, and the authors call for larger, longer trials.
Eating about a serving a day of pulses (beans, chickpeas, lentils and peas) lowered LDL cholesterol by 0.17 mmol/L
Pooled pulses, not kidney beans alone. Meta-analysis of 26 randomized trials (1,037 people) lasting at least 3 weeks, in which a median of 130 g a day (about 1 serving) replaced other foods. Apolipoprotein B and non-HDL cholesterol did not change, and the authors call for longer, higher-quality trials.
A breakfast tortilla with red kidney beans raised fullness and lowered hunger about as much as one with beef in older adults
Randomized crossover trial in 35 adults averaging 72 years old, who ate tortilla breakfasts with 135 g of red kidney beans, 135 g of black beans or 80 g of beef. Appetite ratings, food eaten at a pizza lunch and 24-hour energy intake did not differ between the three meals.
Three-quarters of a cup of red kidney beans lowered blood pressure and arterial stiffness 2 hours later compared with white rice
Pilot crossover trial in 8 healthy adults who ate black, navy, pinto or red kidney beans or white rice on separate days. The wave reflected back along the arteries was lower after red kidney and black beans than after rice, navy or pinto beans. It measured short-term blood vessel responses, not long-term heart disease.
Red kidney beans with rice lowered blood sugar at 90 to 150 minutes compared with rice alone in type 2 diabetes, but the total rise did not differ
Randomized crossover trial in 17 adults with type 2 diabetes, 14 of them taking metformin. They ate rice alone or rice with pinto, black or red kidney beans, each matched to 50 g of available carbohydrate, and blood sugar was tracked for 180 minutes. The overall rise (area under the curve) was lower for the pinto and black bean meals but not for the kidney bean meal.
A red kidney bean breakfast gave blood sugar and insulin responses similar to bran cereal or white bread in young men
Small trial in 6 healthy young men who ate breakfasts built around red kidney beans, bran cereal or white bread, matched for digestible carbohydrate, protein and fat. Responses to a standard whole-wheat bread lunch 4 hours later were also similar. This is a null result in a very small, old study.
The essential amino acids in red kidney beans were about 79% digestible in people
Nonrandomized trial in 10 healthy adults who ate a Jamaican meal made with isotope-labeled beans. Digestibility of individual essential amino acids ranged from 69.0% (threonine) to 85.7% (lysine). A protein quality score of 0.63 (the digestible indispensable amino acid score) was estimated from published amino acid data, lowest for methionine.
A white kidney bean extract supplement taken before meals for 12 weeks cut body weight and fat mass more than placebo on a calorie-restricted diet
This is a supplement, not cooked beans. In a double-blind trial, 81 people with overweight or moderate obesity took 700 mg or 1000 mg of a proprietary extract, or placebo, three times a day, and the effect grew with the dose. Two authors are consultants to the extract’s manufacturer.
A baked common bean snack (32 g a day) for 4 weeks lowered apolipoprotein B-100 but no other blood fat or blood sugar marker
Randomized crossover trial in 20 people with overweight and a blood lipid problem, comparing the snack with no snack. The drop was linked to the extra fiber eaten. The snack was made from common beans, the species that includes kidney beans, not from kidney beans alone.
Across studies of common beans (the species that includes kidney beans), the authors report an 11% lower risk of cardiovascular disease and a 22% lower risk of coronary heart disease
Review and meta-analysis of 23 studies of whole beans or bean extracts, picked from 340 found. It mixes trial designs and supplements, and the blood sugar results were not significant with very high heterogeneity (I2 = 98%). The authors call for standardized trials, so treat the figures as rough.
Higher legume intake went with a 6% lower risk of dying from any cause
Pooled legumes (beans, lentils, peas and soy), not kidney beans alone. Meta-analysis of 32 cohorts with 1,141,793 people. Stroke deaths were 9% lower, but there was no clear link with deaths from cardiovascular disease, heart disease or cancer. The authors rate the certainty of evidence as low to moderate.
Eating legumes 4 or more times a week went with a 22% lower risk of coronary heart disease than eating them less than once a week
Pooled legumes. US cohort of 9,632 men and women followed for an average of 19 years, with legume intake from a food frequency questionnaire. The risk of cardiovascular disease was 11% lower. Cohorts show a link, not proof of cause.
People who raised their dry bean intake the most were about two thirds less likely to have an advanced bowel polyp come back
Dry beans overall, not kidney beans alone. Analysis of the Polyp Prevention Trial, which followed people who had had polyps removed. The group with the biggest rise in dry bean intake (a median 370% above baseline) had an odds ratio of 0.35 (95% CI 0.18 to 0.69) for advanced adenoma recurrence. It is an observational analysis inside a trial.
Across 27 cohorts, eating more pulses showed no link with type 2 diabetes, and total legumes showed a weak rise in risk
Pooled legumes (pulses and soy). Federated meta-analysis of 27 cohorts with up to 42,473 new cases among 807,785 adults. Total legumes had a weak positive link (rate ratio 1.02 per 20 g a day), driven by Europe (Germany, the UK and Sweden), with high heterogeneity (I2 = 74%).
Mice fed cooked dark red or white kidney bean flour had milder colitis after a chemical triggered gut inflammation
Lab study in mice fed a diet with 20% kidney bean flour for 3 weeks, then given dextran sodium sulfate for 7 days. The bean diets raised short-chain fatty acids and gut barrier markers and lowered inflammatory signals. Mouse results may not carry over to people.
In mice on a high-fat diet, roasted red kidney beans prevented high cholesterol while boiled ones improved glucose tolerance
Mice ate 10% roasted or boiled red kidney bean for 12 weeks. Roasted beans held 24.5% resistant starch against 3.1% in boiled beans, and both kinds lowered markers of liver injury. This is a mouse study of how processing changes the effect.
A lectin purified from white kidney beans slowed the growth of nasopharyngeal and liver cancer cells in a dish
Cell study with an isolated 60-kDa lectin, not beans as eaten. Half of the cell growth was blocked at 18.8 µM in nasopharyngeal (HONE1) cells and 19.7 µM in liver (HepG2) cells, against more than 80 µM in WRL68 liver cells. It says nothing about eating beans.
Who should be careful with kidney beans
Most people can eat kidney beans freely once they are cooked. Take a little care if one of these applies:
- Raw or undercooked dried beans. The lectin phytohemagglutinin causes nausea, vomiting and diarrhea within 1 to 3 hours, and in a UK analysis 50 suspected incidents were reported between 1976 and 1989. Soak dried beans for at least 5 hours, pour off the water, and boil them hard in fresh water for at least 30 minutes. Do not cook raw kidney beans in a slow cooker, because it may not destroy the toxin, and canned beans are already cooked.
- Irritable bowel syndrome or a gassy gut. Beans are naturally high in galacto-oligosaccharides, which can trouble people on a low FODMAP diet. Monash University says canned beans, or beans that are boiled and drained, tend to be lower in FODMAPs.
How to choose, store and eat kidney beans
- Dried: after soaking, dark red kidney beans take about 1½ to 2 hours to cook. In one test, boiling for 10 minutes at 100°C destroyed the toxin, and the FDA advises at least 30 minutes to be safe.
- Canned: already cooked and safe to eat straight from the can. Monash says draining and rinsing lowers FODMAPs, and in its tests cooking red kidney beans for more than 30 minutes cut FODMAPs by 32%.
- In meals: trials used three-quarters of a cup of red kidney beans, and 135 g in a breakfast tortilla. In diabetes, rice with kidney beans lowered blood sugar at 90 to 150 minutes compared with rice alone.
Sort dried beans before cooking to remove stones, dirt, and damaged or shriveled seeds, and keep them in a cool, dry place in a tightly covered container for up to a year. Cooked beans keep for 3 to 4 days in a covered container in the fridge, or up to 6 months in the freezer.
Sources
- Phytohaemagglutinin (kidney bean lectin). Bad Bug Book, second edition. US Food and Drug Administration. 2012.
- Home food fact checker. UK Food Standards Agency.
- Rodhouse JC, Haugh CA, Roberts D, Gilbert RJ. Red kidney bean poisoning in the UK: an analysis of 50 suspected incidents between 1976 and 1989. Epidemiol Infect. 1990.
- Watier-Grillot S, Larréché S, Mazuet C, et al. From foodborne disease outbreak (FBDO) to investigation: the plant toxin trap, Brittany, France, 2018. Toxins (Basel). 2023.
- Including legumes on a low FODMAP diet. Monash FODMAP blog.
- New research: FODMAP content of common plant-based foods and processed foods suitable for vegetarian and vegan eating patterns, part 2. Monash FODMAP blog.
- How to store and cook dried beans. University of Maine Cooperative Extension. 2021.
- EFSA Panel on Nutrition, Novel Foods and Food Allergens. GlycoLite and helps to reduce body weight: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006. EFSA J. 2019.
History of kidney beans
Kidney beans belong to the common bean, Phaseolus vulgaris, which was domesticated twice from wild plants in two separate places. Genome studies of wild plants and landraces confirm one domestication in Mesoamerica and one in the Andes, from gene pools that had split before people arrived. Less than 10% of the 74 Mb of DNA tied to domestication was shared by the two events.
Common beans reached Europe after 1492. A 2023 genome study found that the first beans to take hold there were of Andean origin, after Francisco Pizarro’s expedition to northern Peru in 1529. Later, Andean and Mesoamerican types interbred: in a study of 307 European landraces, 67% were of Andean origin and about 44% of the bean germplasm came from hybrids between the two pools.
The name refers to the bean’s resemblance to a human kidney. Besides the red kind there are light speckled and red speckled types, and the white kidney bean is known as cannellini in Italy, the UK, Australia and the US. In India the red type is called rajma, in Jamaica they are called red peas, in La Rioja, Spain, small ones are called caparrones, and in the Netherlands and Indonesia they go into a soup called brenebon.
The beans are also behind Louisiana’s red beans and rice, traditionally served on Mondays, and Mexican-style chili con carne. Their toxin is best documented in the UK, where the FDA counts seven outbreaks between 1976 and 1979 and a 1980 report in the British Medical Journal described poisoning from raw red kidney beans. A 1995 South African study noted that importing dry red kidney beans for planting or eating was prohibited there because of their potential toxicity.
Sources
- Schmutz J, McClean PE, Mamidi S, et al. A reference genome for common bean and genome-wide analysis of dual domestications. Nat Genet. 2014.
- Bellucci E, Benazzo A, Xu C, et al. Selection and adaptive introgression guided the complex evolutionary history of the European common bean. Nat Commun. 2023.
- Angioi SA, Rau D, Attene G, et al. Beans in Europe: origin and structure of the European landraces of Phaseolus vulgaris L. Theor Appl Genet. 2010.
- Kidney bean. Wikipedia.
- Noah ND, Bender AE, Reaidi GB, Gilbert RJ. Food poisoning from raw red kidney beans. Br Med J. 1980.
- Phytohaemagglutinin (kidney bean lectin). Bad Bug Book, second edition. US Food and Drug Administration. 2012.
- Venter FS, Thiel PG. Red kidney beans: to eat or not to eat? S Afr Med J. 1995.
Frequently asked questions about kidney beans
Are kidney beans good for you?
For most people, yes, if they are cooked properly. Cooked kidney beans have 8.67 g of protein and 6.4 g of fiber per 100 g, and a cup (177 g) gives 58% of the daily folate. In a trial of 35 older adults, a kidney bean breakfast raised fullness about as much as beef did, and trials of pulses as a group lowered LDL cholesterol by 0.17 mmol/L. Few trials tested kidney beans alone, and none here reaches strong evidence.
Are raw kidney beans poisonous?
Yes. As few as four or five raw red kidney beans can cause nausea and vomiting within 1 to 3 hours, according to the FDA, because of the lectin phytohemagglutinin. Raw beans hold 20,000 to 70,000 hemagglutinating units against 200 to 400 once fully cooked. Soak dried beans for at least 5 hours, pour off the water, and boil them in fresh water for at least 30 minutes, and do not use a slow cooker.
Are canned kidney beans safe to eat straight from the can?
Yes. The UK Food Standards Agency says canned beans from the supermarket are safe because they have been pre-soaked and boiled to kill toxins. Draining and rinsing them also lowers FODMAPs, according to Monash University, which helps if beans upset your gut. Dried beans cooked at home still need the soak and hard boil.
Do kidney beans cause gas?
They can in some people, and no trial here measured gas directly. Monash University notes that legumes are naturally high in galacto-oligosaccharides and fructans, which can be troublesome on a low FODMAP diet. In its tests, cooking red kidney beans for more than 30 minutes cut FODMAPs by 32%, against 13% for lentils. Canned beans that are drained and rinsed tend to be lower still.
Are kidney beans high in protein?
Fairly high for a plant food. Cooked kidney beans have 8.67 g of protein per 100 g, or 15.3 g in a cup (177 g), and protein supplies about 29% of their calories. The protein is not perfectly balanced: the live nutrition data score it 90 out of 100, limited by methionine and cysteine, and in 10 adults about 79% of the essential amino acids were digested.
Are kidney beans good for weight loss?
No study here tested weight loss with whole kidney beans. White kidney bean extract supplements lowered weight by 1.62 kg more than placebo in a meta-analysis of 8 trials, but the EFSA panel judged the evidence insufficient for one extract’s weight claim in 2019. Cooked beans have 127 calories and 6.4 g of fiber per 100 g, so they fill a plate cheaply, which is a swap effect and not a proven effect of the beans.
Are kidney beans good for people with diabetes?
They can fit, but the evidence is small. Cooked kidney beans have a glycemic index of 24, which is low. In 17 adults with type 2 diabetes, rice with red kidney beans lowered blood sugar at 90 to 150 minutes compared with rice alone, though the total rise did not differ significantly, and in 6 healthy men a kidney bean breakfast gave blood sugar and insulin responses similar to bran cereal or white bread. Check portions and choices with your care team.
What is the difference between red and white kidney beans?
They are the same species, Phaseolus vulgaris, and differ mainly in color and toxin level. White kidney beans, sold as cannellini, hold about a third of the phytohemagglutinin of red ones, but they still need proper cooking. Most food trials here used red kidney beans, while the extract supplements and the lectin study used white ones.