Black beans and red beans: nearly the same bean on the plate

In a four-week crossover trial in 73 adults with raised LDL cholesterol, a daily cup (180 g) of canned beans lowered LDL by 8.1 percent, while white rice moved it up 0.5 percent. The beans rotated daily between black, dark red kidney and three other kinds, so that trial cannot tell black from red. Half a cup lowered LDL by 3.8 percent, which did not reach significance. A second trial, 60 adults per group with mildly high cholesterol over six weeks, found that 120 g a day of a bean mix with black beans and no red kidney beans lowered LDL by 8.1 mg/dL (0.21 mmol/L) against rice (95% CI -0.39 to -0.03). On the plate the two beans are close. Boiled without salt, 100 g gives 132 calories for black beans and 127 calories for red kidney beans, with 8.7 to 8.9 g protein in both, going by one USDA record per bean. Black beans carry more fiber (8.7 against 7.4 g) and magnesium (70 against 45 mg). Red kidney beans carry more iron (2.94 against 2.1 mg) and potassium (403 against 355 mg). The British table, built from different samples, puts boiled red kidney beans at 100 calories, so the tables disagree by about a fifth.

How much is actually in it

• Boiled without salt, 3.5 oz (100 g) of black beans and red kidney beans are close: 132 vs 127 calories and about 8.7 to 8.9 g protein, with black beans higher in fiber and magnesium and red beans higher in iron and potassium. — USDA SR Legacy: Beans, black, mature seeds, cooked, boiled, without salt (FDC 173735); Beans, kidney, red, mature seeds, cooked, boiled, without salt (FDC 175194) Evidence E source
  Per 100 g black vs red kidney: energy 132 vs 127 calories; protein 8.86 vs 8.67 g; fiber 8.7 vs 7.4 g; iron 2.1 vs 2.94 mg; potassium 355 vs 403 mg; magnesium 70 vs 45 mg
• The UK table puts boiled red kidney beans at 100 calories and 8.6 g protein per 3.5 oz (100 g), lower in energy than the US figure of 127 calories, so tables disagree by about a fifth. — CoFID 2021 code 13-659 Beans, red kidney, dried, boiled in unsalted water vs USDA SR Legacy FDC 175194 Evidence E source
  CoFID per 3.5 oz (100 g): 100 calories, protein 8.6 g, AOAC fiber 11.1 g, iron 2.26 mg, potassium 366 mg, folate 45 ug; USDA: 127 calories, protein 8.67 g, fiber 7.4 g, iron 2.94 mg

What a real portion looks like

• In US survey data a cup of cooked black beans weighs 6.3 oz (180 g), about 238 calories, and 1 oz of dry beans yields 70 g cooked. — USDA FNDDS 41102020 Black beans, from dried, no added fat (FDC 2707361) and 41102080 from canned (FDC 2707363) Evidence E source
  1 cup 180 g; 1 oz dry yields 70 g cooked; canned quantity not specified 90 g; 180 g x 132 calories/100 g = 238 calories (arithmetic)

What your body absorbs

• In stable-isotope studies in young women, only 2.5% of iron was absorbed from red bean porridge, and removing polyphenols and phytic acid raised absorption 2.6-fold. — young women, 16 or 17 per study, 6 iron isotope absorption studies (n = 16-17 per study) Evidence B source
  Iron absorption from whole bean porridge 2.5%; 200 mg bean polyphenols cut absorption 45%; removing polyphenols and phytic acid raised it 2.6-fold
• In two crossover RCTs in 30 young and 25 older adults, two ounce-equivalents of black beans delivered 3.02 g essential amino acids against 7.36 g from pork, with lower availability in the blood at any age. — 30 young (mean 26 y) and 25 older (mean 64 y) adults, single standardized meals (n = 55) Evidence B source
  EAA content per 2 oz-eq: pork 7.36 g, eggs 5.38 g, black beans 3.02 g; pork and eggs gave greater EAA bioavailability than black beans (p < 0.0001); age made no difference
• In a crossover RCT in 10 young and 10 older adults, uptake of lysine and threonine from black beans did not differ significantly between ages, while for sorghum it was 19% lower in older people. — 10 young (21.8 y) and 10 older (72.8 y) adults, 20 g labeled protein from milk, sorghum or black beans (n = 20) Evidence B source
  Black beans: no age difference (P = 0.849); sorghum 19% lower in older adults (P = 0.041)

What cooking and storage change

• Home-boiled beans without salt carry 1 to 2 mg sodium per 3.5 oz (100 g), while canned red kidney beans carry 231 mg drained and 208 mg after rinsing, and low-sodium canned black beans 138 mg. — USDA SR Legacy: red kidney boiled without salt (FDC 175194), canned drained (174285), canned drained rinsed (175243); black boiled without salt (173735), boiled with salt (175237), canned low sodium (175238) Evidence E source
  Sodium per 3.5 oz (100 g): red kidney boiled 2 mg, canned drained 231 mg, rinsed 208 mg (about 10% less); black boiled 1 mg, boiled with salt 237 mg, canned low sodium 138 mg

What it does to your health

• In a crossover RCT in 17 adults with type 2 diabetes, black beans with rice lowered the glucose response against rice alone, while red kidney beans with rice lowered glucose at 90 to 150 minutes but not the total response. — 17 men and women with type 2 diabetes, aged 35-70, test breakfasts with 50 g available carbohydrate (n = 17) Evidence B source
  Net glucose lower for all bean meals at 90, 120 and 150 min; iAUC lower for pinto and black bean meals but not kidney bean meal vs rice
• In a pilot crossover RCT in 8 healthy adults, 3/4 cup of black or red kidney beans lowered wave reflection, a measure of vascular tone, more over 6 hours than rice, navy or pinto beans. — 8 healthy adults, single 3/4 cup servings, measured up to 6 h (n = 8) Evidence B source
  Lower wave reflection after red kidney and black bean vs rice, navy, pinto (p < 0.05); LDL-C lower 6 h after black bean vs rice
• In a 4-week crossover RCT in 73 adults with high LDL, a daily cup (180 g) of canned beans including black and dark red kidney lowered LDL cholesterol by 8.1% against rice. — 73 adults with fasting LDL 116-193 mg/dL (3.0-5.0 mmol/L), 4-week periods, daily rotation of black, navy, pinto, dark red kidney, white kidney beans (n = 73) Evidence B source
  LDL -8.08% with 1 cup beans vs +0.49% with rice (P = 0.002); 1/2 cup -3.84% (not significant)
• In a 6-week RCT with 60 adults per group, 120 g a day of mixed beans including black beans lowered LDL cholesterol by 8.1 mg/dL (0.21 mmol/L) against rice, while peas did not. — adults with mild hypercholesterolemia, 60 per group, 6 weeks, beans (black, great northern, navy, pinto) vs peas vs rice (n = 180) Evidence B source
  LDL -8.1 mg/dL (95% CI -15 to -1.2; metric: -0.21 mmol/L, -0.39 to -0.03) beans vs rice; peas -0.11 (-0.29 to 0.07)

Safety, limits and interactions

• The FDA says as few as four or five raw kidney beans can trigger symptoms, raw beans carry 20,000 to 70,000 toxin units against 200 to 400 when fully cooked, and consumers should boil them for at least 30 minutes. — all people; red kidney beans highest, white kidney about one third Evidence E source
  Toxic dose 4-5 raw beans; raw 20,000-70,000 hau vs cooked 200-400 hau; FDA advice: boil for at least 30 minutes

Who this works differently for

• In a crossover RCT in 35 older adults, a 4.8 oz (135 g) serving of black or red kidney beans in a breakfast tortilla was as filling as 2.8 oz (80 g) of beef. — 35 older adults, mean age 72.4 y, single breakfast test meals (n = 35) Evidence B source
  Appetite AUCs, ad libitum lunch intake and 24-h energy intake did not differ between black beans, red kidney beans and beef
• In a 10-week RCT in 110 mildly anemic Guatemalan toddlers, five cans of refried black beans a week raised hemoglobin by 7.3 to 11.4 g/L in all groups, with no extra gain from added iron overall. — 110 children aged 12-36 months with Hb 100-115 g/L, five 5.5 oz (156 g) cans per week for 10 weeks (n = 110) Evidence B source
  Hb increase 7.3-11.4 g/L across groups without significant difference by treatment

The bottom line

Blood sugar has been tested with single meals. In 17 adults with type 2 diabetes, black beans with rice lowered the total glucose response against rice alone. Red kidney beans with rice lowered glucose at 90 to 150 minutes, and the total response was not significantly lower. A pilot in 8 healthy adults found lower wave reflection, a measure of arterial tone, over six hours after 3/4 cup of black or red kidney beans than after rice, navy or pinto beans. Eight people eating one meal each is a signal to repeat on a larger group. Measured by portion, black beans deliver less usable protein than meat. In two crossover trials in 30 young and 25 older adults, two ounce-equivalents of black beans, a portion rule that does not equalize protein, held 3.02 g essential amino acids against 7.36 g in pork, and less of it reached the blood at either age. In a small trial of 10 young and 10 older adults, the uptake of lysine and threonine from black beans did not differ significantly between the two ages. For fullness they matched meat. In 35 adults with a mean age of 72, a 4.8 oz (135 g) serving of black or red kidney beans in a breakfast tortilla left people as full as 2.8 oz (80 g) of beef, with no difference in lunch or 24-hour intake. Iron is the weak spot. In isotope studies in young women, only 2.5 percent of the iron in a whole bean porridge was absorbed, and stripping out polyphenols and phytic acid in the laboratory raised that 2.6-fold, a step a home kitchen cannot copy. In 110 mildly anemic Guatemalan toddlers eating five 5.5 oz (156 g) cans of refried black beans a week for 10 weeks, hemoglobin rose 7.3 to 11.4 g/L in every group and added iron made no significant difference. Every group ate the beans, so the trial cannot say how much of that rise the beans caused. A cup of cooked black beans weighs 6.3 oz (180 g) in US survey data, about 238 calories by arithmetic from the USDA record, and 1 oz of dry beans gives 70 g cooked. Salt is the kitchen choice that matters. Beans boiled at home without salt carry 1 to 2 mg sodium per 3.5 oz (100 g). Canned red kidney beans carry 231 mg drained, and rinsing brought that only to 208 mg in one USDA record, with brands varying. Low-sodium canned black beans came in at 138 mg. The real caution is raw or undercooked kidney beans. The FDA says as few as four or five raw beans can trigger symptoms. Raw kidney beans hold 20,000 to 70,000 hemagglutinating units of the bean lectin and fully cooked ones 200 to 400, figures the FDA handbook gives for kidney beans with no separate number for black beans. The agency tells consumers to boil them for at least 30 minutes. We have no card on beans and medicines, pregnancy or allergy.

Sources

1. bbrb-r5-01 · USDA SR Legacy composition, dataset
   Per 100 g, SR Legacy: Beans, black, mature seeds, cooked, boiled, without salt (NDB 16015, FDC 173735) energy 132 kcal, protein 8.86 g, fiber 8.7 g, iron 2.1 mg, potassium 355 mg, magnesium 70 mg; Beans, kidney, red, mature seeds, cooked, boiled, without salt (NDB 16033, FDC 175194) energy 127 kcal, protein 8.67 g, fiber 7.4 g, iron 2.94 mg, potassium 403 mg, magnesium 45 mg
   USDA SR Legacy 2019, FDC 173735 and 175194 · checked 2026-09-30
2. bbrb-r5-02 · CoFID composition, dataset
   Beans, red kidney, dried, boiled in unsalted water (CoFID 13-659), per 100 g: Energy 100 kcal; Protein 8.6 g; AOAC fibre 11.1 g; Iron 2.26 mg; Potassium 366 mg; Sodium Tr; Folate 45 ug
   CoFID 2021 (Public Health England, OGL v3.0), code 13-659 · checked 2026-09-30
3. bbrb-r5-04 · USDA FNDDS portion weights, dataset
   Black beans, from dried, no added fat (FNDDS 41102020, FDC 2707361): 1 cup 180 g; 1 oz dry, yield after cooking 70 g. Black beans, from canned, no added fat (FNDDS 41102080, FDC 2707363): 1 cup 180 g; Quantity not specified 90 g
   USDA FNDDS 2021-2023, food codes 41102020 and 41102080 · checked 2026-09-30
4. bbrb-r5-09 · RCT (absorption)
   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%. PP and PA removal increased absorption 2.6-fold (P < 0.001) and removal of PP from dephytinized porridge doubled absorption (P < 0.001).
   J Nutr, 2010 · checked 2026-09-30
5. bbrb-r5-10 · RCT (crossover)
   We conducted two investigator-blinded, randomized crossover trials in young (n = 30; mean age ± SD: 26.0 ± 4.9 y) and older adults (n = 25; mean age ± SD: 64.2 ± 6.6 y). ... Two oz-eq portions of pork (7.36 g EAA) and eggs (5.38 g EAA) resulted in greater EAA bioavailability than black beans (3.02 g EAA) and almonds (1.85 g EAA) in young and older adults, separately or combined (p < 0.0001 for all).
   Nutrients, 2023 · checked 2026-09-30
6. bbrb-r5-12 · RCT (crossover)
   The isotope plasma-to-meal ratio for lysine and threonine was 19% lower in older adults compared with young adults for sorghum (P = 0.041), whereas it was not significantly different for milk (P = 0.277) and black beans (P = 0.849).
   Am J Clin Nutr, 2026 · checked 2026-09-30
7. bbrb-r5-03 · USDA SR Legacy composition, dataset
   Sodium per 100 g, SR Legacy: kidney, red, boiled, without salt (FDC 175194) 2 mg; kidney, red, canned, drained solids (FDC 174285) 231 mg; kidney, red, canned, drained solids, rinsed in tap water (FDC 175243) 208 mg; black, boiled, without salt (FDC 173735) 1 mg; black, boiled, with salt (FDC 175237) 237 mg; black, canned, low sodium (FDC 175238) 138 mg
   USDA SR Legacy 2019, FDC 175194, 174285, 175243, 173735, 175237, 175238 · checked 2026-09-30
8. bbrb-r5-05 · RCT (crossover)
   Seventeen men and women with type 2 diabetes controlled by metformin (n = 14) or diet/exercise (n = 3) aged 35-70 years participated in the randomized 4 × 4 crossover trial. ... Postprandial net glucose values were significantly lower for the three bean/rice treatments in contrast to the rice control at 90, 120 and 150 minutes. Incremental area under the curve values were significantly lower for the pinto and black bean/rice meals compared to rice alone, but not for kidney beans.
   Nutr J, 2012 · checked 2026-09-30
9. bbrb-r5-06 · RCT (crossover, pilot)
   Vascular tone (primary endpoint), haemodynamics and serum biochemistry (secondary endpoints) were measured in 8 healthy adults before and at 1, 2, and 6 h after eating ¾ cup of beans or rice. ... and wave reflection magnitude was lower after consuming red kidney bean and black bean compared to rice, navy bean, and pinto bean (p < 0.05). LDL-cholesterol concentrations were lower 6 h after black bean consumption compared to rice (p < 0.05).
   Nutr Metab Cardiovasc Dis, 2021 · checked 2026-09-30
10. bbrb-r5-07 · RCT (crossover)
    LDL cholesterol on study day 29 was also lower for 1CB (P = 0.002) but not ½CB (P = 0.30) compared with WR (-8.08%, -3.84%, +0.49% changes from study day 1, respectively) and did not differ between 1CB and ½CB (P = 0.11).
    J Nutr, 2021 · checked 2026-09-30
11. bbrb-r5-08 · RCT
    Mean LDL-cholesterol was lower in the bean group (-0.21; 95% CI: -0.39, -0.03) but not the pea group (-0.11; 95% CI: -0.29, 0.07) relative to rice after 6 wk.
    J Nutr, 2024 · checked 2026-09-30
12. bbrb-r5-14 · agency position
    Toxic dose: As few as four or five raw beans can trigger symptoms. ... Raw kidney beans contain from 20,000 to 70,000 hau, while fully cooked beans contain from 200 to 400 hau. ... Consumers should boil the beans for at least 30 minutes to ensure that the product reaches sufficient temperature, for a sufficient amount of time, to completely destroy the toxin.
    US FDA, Bad Bug Book, 2nd edition, 2012, Phytohaemagglutinin chapter · checked 2026-09-30
13. bbrb-r5-11 · RCT (crossover)
    Older adults [n = 35, age 72.4 ± 6.66 y, BMI (in kg/m2) 25.1 ± 3.25] consumed 3 breakfast tortilla test meals containing 1 serving of black beans (135 g), red kidney beans (135 g), or beef (80 g) in a randomized, crossover design. ... Appetite sensation AUCs, ad libitum pizza intake, and 24-h energy intake did not significantly differ between the test meals.
    J Nutr, 2025 · checked 2026-09-30
14. bbrb-r5-13 · RCT
    In a masked, stratified-randomised intervention trial, children received five 156-g cans of refried black beans per week for 10 consecutive weeks. ... Hb concentrations increased by the order of 7.3-11.4 g l(-1) during the intervention, but without significant differences across treatments.
    Public Health Nutr, 2005 · checked 2026-09-30