Red beans: a cholesterol food that must be boiled properly

By a meta-analysis of 23 trials in adults eating common beans for 4 to 8 weeks, beans lowered LDL cholesterol by 19 percent. The pooled beans were red, navy, pinto and others, some trials were not randomized and some used bean extract, so the figure belongs to beans as a family. The rule red kidney beans add is about cooking. According to the FDA, as few as four or five raw red kidney beans can bring on nausea and vomiting within 1 to 3 hours, a toxic dose drawn from outbreak descriptions, mostly in the UK between 1976 and 1989. Fully cooked beans hold 200 to 400 units of the lectin against 20,000 to 70,000 in raw ones. The FDA advises at least 30 minutes of boiling and says slow cookers do not get hot enough, since the ones it cites reached only 75 C.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Dried raw red kidney beans in UK data carry 266 calories, 22.1 g protein, 6.4 mg iron and 1370 mg potassium per 3.5 oz (100 g). — CoFID 2021 Beans, red kidney, dried, raw (13-109) (n = 1 record) Evidence E source
  266 calories, protein 22.1 g, iron 6.40 mg, magnesium 150 mg, potassium 1370 mg, copper 0.68 mg, folate 130 ug, sodium 18 mg per 3.5 oz (100 g)
• Boiled red kidney beans in UK data carry 100 calories, 8.6 g protein, 11.1 g fiber and 2.26 mg iron per 3.5 oz (100 g), because they take up water. — CoFID 2021 Beans, red kidney, dried, boiled in unsalted water (13-659) (n = 1 record) Evidence E source
  100 calories, protein 8.6 g, AOAC fiber 11.1 g, iron 2.26 mg, potassium 366 mg, folate 45 ug, sodium trace per 3.5 oz (100 g)

What a real portion looks like

• In the US survey database, 1 cup of kidney beans weighs 6.5 oz (185 g) and an unspecified serving is taken as 92 g. — USDA FNDDS Kidney beans, NFS (41105990) (n = 2 measures) Evidence E source
  1 cup 185 g, quantity not specified 92 g

What your body absorbs

• In stable isotope trials in young women, only 2.5 percent of the iron in whole red bean porridge was absorbed, and bean polyphenols cut absorption by up to 45 percent. — Young women, 16 or 17 per study, six isotope absorption studies (n = 16-17 per study) Evidence B source
  Iron absorption 2.5% from whole red bean porridge; -14% with 50 mg polyphenols, -45% with 200 mg; removing polyphenols and phytate raised absorption 2.6-fold
• In a crossover trial in 22 Rwandese women with low iron status, phytic acid strongly reduced iron absorption from iron-biofortified bean meals (406 ug absorbed as eaten, 746 ug with over 95 percent removed in the laboratory). — 22 Rwandese women with low iron status eating composite bean meals with potatoes or rice (n = 22) Evidence B source
  Iron absorbed from biofortified bean meals 406 ug native, 599 ug at ~50% and 746 ug at >95% dephytinization
• In 29 young Brazilian adults, iron absorption from a single 3.5 oz (100 g) meal of cooked common beans was about 0.4 percent, whether or not the variety was bred for more iron. — 29 young adult volunteers eating 3.5 oz (100 g) of cooked labeled common beans (n = 29) Evidence B source
  0.409% (SD 0.040%) versus 0.407% (SD 0.038%), no difference
• In 10 healthy adults eating a Jamaican red kidney bean meal, about 79 percent of the essential amino acids were digested, with a protein quality score (DIAAS) of 0.63. — 10 healthy adults (5 men, 5 women) eating a typical Jamaican meal with red kidney beans (n = 10) Evidence C source
  Mean indispensable amino acid digestibility 79.4% (range 69.0% threonine to 85.7% lysine), DIAAS 0.63 limited by methionine

What cooking and storage change

• According to the FDA, cooking cuts kidney bean lectin from 20,000 to 70,000 units in raw beans to 200 to 400 in fully cooked beans, and slow cookers are not hot enough. — Home cooking of dried red kidney beans Evidence E source
  Raw 20,000-70,000 hau, fully cooked 200-400 hau; boiling 10 min at 100 C destroyed the toxin, FDA advises at least 30 min

What it does to your health

• By a meta-analysis of 23 trials, some not randomized and some using bean extract, common beans (red, navy, pinto and others) lowered LDL cholesterol by 19 percent. — Adults in clinical and randomized trials of whole beans or bean extract, 4 to 8 weeks (n = 23 trials) Evidence B source
  LDL cholesterol -19%, CVD risk -11%, CHD risk -22%
• In a pilot crossover trial in 8 healthy adults, 3/4 cup of red kidney beans lowered blood pressure and pulse wave velocity at 2 hours compared with rice. — 8 healthy adults, single meals of 3/4 cup beans or rice at least 6 days apart (n = 8) Evidence B source
  Lower blood pressure and pulse wave velocity at 2 h versus rice (p < 0.05), effect size not given in abstract
• In 19 healthy young men, a white bun filled with red bean paste had a medium glycemic index of 58. — 19 healthy men (9 Chinese, 10 Indian), mean age 24.7 years, in Singapore (n = 19) Evidence B source
  GI 58 (SEM 4), same as plain steamed white bun at 58

Safety, limits and interactions

• According to the FDA, as few as four or five raw red kidney beans can trigger lectin poisoning, with nausea and vomiting within 1 to 3 hours. — All people who eat raw or undercooked kidney beans Evidence E source
  Onset 1 to 3 hours, recovery usually within 3 to 4 hours
• Laboratory and animal data suggest that Phaseolus vulgaris lectins act as anti-nutrients that can cause intestinal disorders unless destroyed by heat. — Review of Phaseolus vulgaris lectin research, mostly laboratory and animal studies Evidence D source
  Direction only, no pooled estimate
• A case report describes anaphylaxis to cooked Phaseolus vulgaris beans driven by a 10 kDa protein that survives cooking. — One 20-year-old woman in Spain (n = 1) Evidence C source
  IgE recognized 25-75 kDa proteins in raw beans and one ~10 kDa protein in cooked beans

What people believe that the data does not support

• By a meta-analysis of 6 randomized trials, bean extract pills did not produce significant weight loss versus placebo (mean difference -3.9 lb (-1.77 kg)). — Adults taking Phaseolus vulgaris extract supplements versus placebo (n = 6 trials) Evidence A source
  Weight MD -3.9 lb (95% CI -7.3 to 0.73; metric: -1.77 kg, -3.33 to 0.33), body fat MD -4.1 lb (95% CI -7.5 to -0.71; metric: -1.86 kg, -3.39 to -0.32)
• The EU did not authorize the claim that a white kidney bean extract helps to reduce body weight. — EU health claim application for a standardized aqueous white kidney bean extract Evidence E source
  Non-authorized

Who this works differently for

• In a crossover trial in 35 older adults, a breakfast tortilla with 4.8 oz (135 g) of red kidney beans was as filling as one with 2.8 oz (80 g) of beef. — 35 older adults, mean age 72.4 years, three breakfast test meals (n = 35) Evidence B source
  Appetite AUCs, ad libitum lunch intake and 24 h energy intake did not differ between beans and beef
• In an Italian clinic series of 55 children allergic to legumes including common bean, 74.5 percent reacted to more than one legume. — 55 children under 18 with IgE-mediated allergy to pea, lentil, chickpea, common bean or soy, Italy 2022-2024 (n = 55) Evidence C source
  Multi-legume allergy 74.5%, anaphylaxis at onset 12.7%, median age at first reaction 18 months

The bottom line

The iron in beans is poorly absorbed. In stable isotope trials in young women, 16 or 17 per study, only 2.5 percent of the iron in a whole red bean porridge was absorbed from single meals, and 200 mg of bean polyphenols cut absorption by 45 percent. In 29 young Brazilian adults, one 3.5 oz (100 g) meal of cooked common beans gave about 0.4 percent absorption, whether or not the variety was bred for more iron. In 22 Rwandese women with low iron status, removing over 95 percent of the phytic acid raised iron absorbed from biofortified bean meals from 406 ug to 746 ug, and that removal was done in a laboratory. Protein does better. In 10 healthy adults eating a Jamaican red kidney bean meal, 79.4 percent of the essential amino acids were digested, and the protein quality score (DIAAS) came out at 0.63, limited by methionine, in a small nonrandomised study. Boiled red kidney beans carry 100 calories, 8.6 g protein and 11.1 g fiber per 3.5 oz (100 g) in UK tables, against 266 calories and 22.1 g protein for the dried beans, and the difference is mostly water taken up in the pot. In the US survey database a cup weighs 6.5 oz (185 g). In 35 older adults, mean age 72, a breakfast tortilla with 4.8 oz (135 g) of red kidney beans was as filling as one with 2.8 oz (80 g) of beef, over single test breakfasts. In a pilot of 8 healthy adults, 3/4 cup of red kidney beans lowered blood pressure and pulse wave velocity at 2 hours compared with rice, and the abstract gives no effect size. A white bun filled with sweet red bean paste had a glycemic index of 58 in 19 young men, the same as a plain steamed bun, so the number describes the bun. Bean extract pills for weight loss are a separate product. By a meta-analysis of 6 randomized trials, all with serious methodological flaws and mostly of white bean extract, weight loss against placebo did not reach significance (mean difference -3.9 lb (95% CI -7.3 to 0.73; metric: -1.77 kg, -3.33 to 0.33)). The EU did not authorize a weight loss claim for a white kidney bean extract. One case report describes anaphylaxis to cooked Phaseolus vulgaris beans in a 20-year-old woman in Spain, driven by a 10 kDa protein that cooking left intact. In an Italian clinic series of 55 children allergic to legumes, 74.5 percent reacted to more than one legume and 12.7 percent had anaphylaxis at onset, and the abstract does not say how many reacted to beans. Laboratory and animal data suggest that bean lectins cause intestinal disorders unless heat destroys them. We found no card on pregnancy or on interactions with medicines.

Compared with other foods

Sources

1. rdbn-daily-r6-16 · food composition dataset
   Beans, red kidney, dried, raw (13-109): Energy 266 kcal | Protein 22.1 g | Iron 6.40 mg | Magnesium 150 mg | Potassium 1370 mg | Copper 0.68 mg | Folate 130 ug | Sodium 18 mg
   CoFID 2021 (Public Health England, OGL v3.0), code 13-109 Beans, red kidney, dried, raw · checked 2026-09-29
2. rdbn-daily-r6-17 · food composition dataset
   Beans, red kidney, dried, boiled in unsalted water (13-659): AOAC fibre 11.1 g | Energy 100 kcal | Protein 8.6 g | Iron 2.26 mg | Potassium 366 mg | Folate 45 ug | Sodium Tr
   CoFID 2021 (Public Health England, OGL v3.0), code 13-659 Beans, red kidney, dried, boiled in unsalted water · checked 2026-09-29
3. rdbn-daily-r6-18 · food composition dataset
   Kidney beans, NFS, FNDDS 41105990, fdc_id 2707379: 1 cup 185 g | Quantity not specified 92 g
   USDA FNDDS (FoodData Central survey 2024-10-31), Kidney beans, NFS, food code 41105990, fdc_id 2707379 · checked 2026-09-29
4. rdbn-daily-r6-03 · randomized crossover trial
   Iron absorption was lowered by 14% with 50 mg PP (P < 0.05) and by 45% with 200 mg PP (P < 0.001). The mean iron absorption from whole bean porridge was 2.5%.
   J Nutr, 2010 · checked 2026-09-29
5. rdbn-daily-r6-04 · randomized crossover trial
   PA strongly decreases iron bioavailability from iron-biofortified beans, and a high PA concentration is an important impediment to the optimal effectiveness of bean iron biofortification.
   J Nutr, 2014 · checked 2026-09-29
6. rdbn-daily-r6-05 · randomized trial
   Mean iron absorption from the meal with common beans was 0.409% (±0.040%) and mean iron incorporation from the meal with target beans for biofortification 0.407% (±0.038%) and did not differ between the groups.
   Clin Nutr ESPEN, 2018 · checked 2026-09-29
7. rdbn-daily-r6-06 · nonrandomized human trial
   Mean RKB-IAA digestibility (%) was 79.4 ± 0.5, ranging from 69.0 ± 1.2 (threonine) to 85.7 ± 1.7 (lysine).
   J Nutr, 2023 · checked 2026-09-29
8. rdbn-daily-r6-11 · agency guidance
   Raw kidney beans contain from 20,000 to 70,000 hau, while fully cooked beans contain from 200 to 400 hau.
   FDA Bad Bug Book, 2nd edition (2012), Phytohaemagglutinin (kidney bean lectin) · checked 2026-09-29
9. rdbn-daily-r6-01 · meta-analysis
   Findings indicated that common beans reduced LDL cholesterol by 19 percent, risk of cardiovascular disease (CVD) by 11 percent, and coronary heart disease (CHD) by 22 percent.
   Nutrients, 2021 · checked 2026-09-29
10. rdbn-daily-r6-07 · randomized crossover trial
    Blood pressure and pulse wave velocity (PWV) were lower at 2 h following red kidney bean and pinto bean consumption compared to rice and navy bean, respectively (p < 0.05).
    Nutr Metab Cardiovasc Dis, 2021 · checked 2026-09-29
11. rdbn-daily-r6-09 · randomized crossover trial
    Asian breakfast foods were of medium (white bun filled with red bean paste=58 (sem 4); Chinese steamed white bun=58 (sem 3)) to high GI
    Br J Nutr, 2018 · checked 2026-09-29
12. rdbn-daily-r6-10 · agency guidance
    Toxic dose: As few as four or five raw beans can trigger symptoms.
    FDA Bad Bug Book, 2nd edition (2012), Phytohaemagglutinin (kidney bean lectin) · checked 2026-09-29
13. rdbn-daily-r6-12 · systematic review
    Studies have shown that lectins are anti-nutritional factors that can cause intestinal disorders.
    Crit Rev Food Sci Nutr, 2018 · checked 2026-09-29
14. rdbn-daily-r6-13 · case report
    Only one protein with a molecular weight of approximately 10 kDa was recognized in cooked beans.
    Allergol Immunopathol (Madr), 2025 · checked 2026-09-29
15. rdbn-daily-r6-02 · meta-analysis
    A meta-analysis revealed a statistically non-significant difference in weight loss between P. vulgaris and placebo groups (mean difference (MD) − 1.77 kg, 95 % CI − 3.33, 0.33).
    Br J Nutr, 2011 · checked 2026-09-29
16. rdbn-daily-r6-15 · regulatory decision
    POL-HC-8466 Standardised aqueous extract from white kidney bean (Phaseolus vulgaris L.) Helps to reduce body weight -/- Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-8466, snapshot 2026-09-21 · checked 2026-09-29
17. rdbn-daily-r6-08 · randomized crossover trial
    Appetite sensation AUCs, ad libitum pizza intake, and 24-h energy intake did not significantly differ between the test meals.
    J Nutr, 2025 · checked 2026-09-29
18. rdbn-daily-r6-14 · retrospective cohort
    Multi-legume allergy predominated (74.5%), with frequent co-allergy among pea, lentil, and chickpea (56-86%).
    Nutrients, 2026 · checked 2026-09-29