Black beans against other beans: the differences are smaller than the sample spread

Black beans are sold as the better bean, on account of the dark coat. The measured differences are small. USDA reference samples, measured dry, put black and pinto beans within a gram of protein and a tenth of a milligram of iron of each other. Iron inside black beans alone runs from 3.2 to 9.1 mg per 100 g dry between samples, and that spread within one class is far wider than the gap between classes. Where black beans have been fed side by side with other beans, they mostly tie. In a breakfast tortilla, 135 g of black beans, 135 g of red kidney beans or 80 g of beef left 35 older adults equally full, and what they ate over the rest of the day did not differ. In 17 adults with type 2 diabetes, black and pinto beans eaten with rice both cut the three-hour glucose rise against rice alone, and red kidney beans did not reach significance. The one result that favours black beans specifically comes from 8 healthy people measured six hours after a single 0.75-cup serving, whose arteries were more relaxed than after pinto or navy beans. That is a pilot, and the authors did not measure the seed-coat pigments in the blood. The headline figures you may have seen, LDL down 19 percent and cardiovascular risk down 11 percent, come from a review of 23 trials. That review pooled bean extracts sold as supplements with whole beans, and trials with observational reports, and in its glucose analysis heterogeneity reached 98 percent. Those two numbers describe bean pills and bean plates mixed together, which makes them a number for neither.

How much is actually in it

• On a dry-matter basis USDA reference samples put black and pinto beans within a gram of protein and a tenth of a milligram of iron of each other. The spread inside each class, iron 3.2 to 9.1 mg per 100 g of dry matter in black beans, is far wider than the gap between classes. — USDA Foundation Foods, Beans, Dry, Black (0% moisture), 126 samples; Beans, Dry, Pinto (0% moisture), 250 to 252 samples (n = 126 and 252 samples) Evidence E source
  Black: protein 24.4 g (21.4 to 26.8), iron 5.34 mg (3.22 to 9.11), magnesium 180 mg (153 to 228); pinto: protein 23.7 g (18.8 to 30.8), iron 5.4 mg (3.4 to 7.67), per 100 g dry matter

What a real portion looks like

• 135 g of black beans, 135 g of red kidney beans or 80 g of beef in a breakfast tortilla left 35 older adults equally full, and their lunch intake and 24-hour energy intake did not differ between the three. — 35 older adults, mean age 72, BMI 25, randomised crossover, ad libitum pizza lunch and weighed 24-h food records (n = 35) Evidence B source
  Fullness and satisfaction up, hunger and desire to eat down after all three meals; appetite AUCs, lunch intake and 24-h energy intake not different between black beans, red kidney beans and beef
• 120 g a day of mixed black, great northern, navy and pinto beans for 6 weeks lowered LDL by 0.21 mmol/L against rice in adults with mild hypercholesterolaemia, and the same amount of peas did not. — 180 Canadian adults with mild hypercholesterolaemia, 60 per arm, single-blind parallel trial, 6 weeks (n = 180) Evidence B source
  LDL -0.21 mmol/L (-0.39 to -0.03) beans vs rice; peas -0.11 (-0.29 to 0.07); non-HDL -0.20 and total cholesterol -0.28 lower with beans; no change in TG, glucose, insulin or BP
• One cup (180 g) a day of canned beans rotating black, navy, pinto, dark red kidney and white kidney for 4 weeks lowered LDL by 8.1 percent against rice in adults with raised LDL, while half a cup did not reach significance. — 73 adults with elevated LDL cholesterol, multicentre randomised crossover, 4-week periods; 66 completed the 1-cup and 68 the half-cup treatment (n = 73) Evidence B source
  Total cholesterol -5.46% (1 cup, P = 0.04) vs -0.65% rice; LDL -8.08% (1 cup, P = 0.002) vs +0.49% rice; half cup -2.74% and -3.84%, not significant

What your body absorbs

• In 17 adults with type 2 diabetes, black beans and pinto beans eaten with rice cut the 3-hour glucose area under the curve compared with rice alone, while red kidney beans did not reach significance. — 17 men and women aged 35 to 70 with type 2 diabetes controlled by metformin or lifestyle, 4 x 4 crossover, breakfast meals matched for 50 g available carbohydrate (n = 17) Evidence B source
  Net glucose lower for all three bean/rice meals at 90, 120 and 150 min; incremental AUC significantly lower for pinto and black bean meals, not for kidney beans
• Cutting phytate by 90 percent raised iron absorption from beans by 60 to 130 percent in 20 women, and the bean's polyphenol level, high or low, made no difference to how much iron was absorbed. — 20 women, paired double-meal crossover, stable iron isotopes, four bean lines: two low-phytate and their two normal-phytate parents, each high or low in polyphenols (n = 20) Evidence B source
  Fractional iron absorption 6.1% from low-phytate high-polyphenol bean vs parents (60% and 130% higher); 4% from low-phytate low-polyphenol line, 50% higher than its parent; no difference by polyphenol level
• In 9 middle-aged women, muscle protein synthesis after meals with 23 g of protein from navy or black beans plus whole wheat bread was not measurably different from lean beef, and nor was it after black beans or bread alone at one meal. — 9 healthy women aged about 56, randomised crossover, isonitrogenous 23 g protein meals; 8 further women as a non-randomised 5 g protein control (n = 9) Evidence B source
  Fractional synthetic rate not different between complete, complementary and incomplete protein meals after breakfast (P = 0.90) or over 24 h (P = 0.38)

What it does to your health

• Six hours after a 0.75-cup serving, black beans left arteries more relaxed than pinto or navy beans in 8 healthy adults, with lower pulse wave velocity than pinto and lower LDL than rice. — 8 healthy adults, single-blind randomised crossover, 0.75 cup of black, navy, pinto or red kidney beans or white rice, measurements at 1, 2 and 6 h (n = 8) Evidence B source
  6 h: PWV lower after black bean vs pinto; augmentation pressure lower after black bean vs rice and pinto; wave reflection lower after red kidney and black bean vs rice, navy and pinto; LDL lower 6 h after black bean vs rice (p < 0.05)

What people believe that the data does not support

• A meta-analysis pooling 23 trials of bean extracts and whole beans reported 19 percent lower LDL and 11 percent lower cardiovascular risk, but its post-meal glucose difference was not significant, and heterogeneity in that glucose analysis reached 98 percent. — 23 peer-reviewed clinical and randomised trials of common bean extract or whole bean, from 340 screened articles (n = 23 studies) Evidence C source
  LDL -19%; CVD risk -11%; CHD -22%; 60-min postprandial glucose mean difference -2.01 (-4.6 to -0.63) but not significant between arms, I2 = 98%; weight gain higher in controls, MD 1.62 (0.37 to 2.86)

Who this works differently for

• In 9 adults with arterial stiffness, systolic pressure did not rise in the 2 hours after 0.75 cup of black beans, where it rose 4 percent after white rice, and only whole wheat, not beans, lowered the augmentation index from 26 to 16 percent. — 9 adults aged 50 to 64 with established arterial stiffness, single-blind randomised crossover, 0.75 cup black beans vs wheat berries vs white rice (n = 9) Evidence B source
  Systolic BP +4% after rice, unchanged after beans or wheat; augmentation index 26.1 to 16.2% after wheat only; heart rate slightly lower after all foods

The bottom line

If you are choosing between black beans and another common bean, choose by price and by what you like. In the trials that fed several classes side by side, black beans tied with red kidney beans on fullness, tied with pinto on glucose, and won once, in eight people, on arterial tone. The two longer trials agree that beans as a group lower LDL in adults with raised cholesterol when you eat enough of them, and enough has been measured twice. One cup a day, 180 g of canned beans rotating black, navy, pinto and two kinds of kidney bean, lowered LDL by 8.1 percent against rice over four weeks in 73 adults with raised LDL. Half a cup did not reach significance. Over six weeks, 120 g a day of a black, great northern, navy and pinto mix lowered LDL by 0.21 mmol/L in 180 adults with mildly raised cholesterol, and the same amount of peas did not. Glucose, insulin, triglycerides and blood pressure did not move in that trial. Canned beans were what the people in the four-week trial ate, and neither trial can say whether the black beans in the mix did more or less than the rest. For protein, 23 g from navy or black beans plus whole wheat bread left muscle protein synthesis in 9 middle-aged women no different from lean beef, and black beans alone at one meal were no different either over 24 hours. Nine women cannot show that two foods are equal, only fail to tell them apart. Iron is the weak point, and phytate rather than colour is what limits it. In 20 women, cutting phytate by 90 percent raised iron absorption from beans by 60 to 130 percent, while the polyphenol level of the bean, high or low, changed nothing. Those were experimental lines bred for low phytate, not a bean you can buy. The vascular findings need care in the reading. Eight healthy adults had more relaxed arteries six hours after black beans than after pinto beans. In 9 people aged 50 to 64 with stiff arteries, systolic pressure did not rise after a 0.75-cup serving of black beans, where it rose 4 percent after white rice. In that second trial only whole wheat brought the augmentation index down, from 26 to 16 percent, and beans did not. Eight people in one trial, nine in the other, one meal each, and windows of two to six hours. This is a hypothesis, and nobody has run the trial that would settle whether darker beans do anything the lighter ones do not. Two gaps to be honest about. Our corpus holds no meta-analysis that compares bean market classes at all, and no human trial of the black bean pigments on their own. And there is nothing on this page about who should go carefully, because no card came back for safety: no upper limit, no drug interaction, no group for whom these trials would be a bad idea. If you take regular medication, that question goes to the person who prescribes it, because this page has nothing to answer it with.

Sources

1. bbb-c1-10 · reference dataset
   USDA Foundation Foods Beans, Dry, Black (0% moisture) — Protein 24.4 G, range 21.4–26.8 (median 24.5), 126 samples · Iron, Fe 5.34 MG, range 3.22–9.11 (median 4.84), 126 samples · Magnesium, Mg 180.0 MG, range 153.0–228.0 (median 179.0), 126 samples · Beans, Dry, Pinto (0% moisture) — Protein 23.7 G, range 18.8–30.8 (median 23.8), 252 samples · Iron, Fe 5.4 MG, range 3.4–7.67 (median 5.23), 250 samples
   USDA FoodData Central, Foundation Foods, release 2026-04-30 · checked 2026-09-23
2. bbb-c1-03 · randomised crossover trial
   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 2026-09-23
3. bbb-c1-06 · randomised controlled single-blind parallel trial
   Participants (n = 60 per group) were randomly assigned to 6 wk of regular consumption of foods containing either 120 g (∼0.75 cups) of beans (mixture of black, great northern, navy, and pinto) or 120 g (∼0.75 cups) peas (mixture of yellow and green), or identical foods containing white, parboiled rice (control foods). ... 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 2026-09-23
4. bbb-c1-09 · multicentre randomised crossover trial
   canned beans (daily rotation of black, navy, pinto, dark red kidney, white kidney) ... Total cholesterol on study day 29 was lower for 1CB (P = 0.04) but not ½CB (P = 0.77) compared with WR (–5.46%, –2.74%, –0.65% changes from study day 1, respectively) ... 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)
   J Nutr, 2021 · checked 2026-09-23
5. bbb-c1-01 · randomised crossover trial
   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. The white long grain rice control, pinto beans/rice, black beans/rice, red kidney beans/rice test meals, matched for 50 grams of available carbohydrate, were consumed at breakfast after a 12 hour fast. ... 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 2026-09-23
6. bbb-c1-04 · randomised crossover isotope trial
   Fractional iron absorption from the lpa bean high in PPs was 6.1% (95% CI: 2.6, 14.7), which was 60 and 130% higher compared with the parent high in PPs (P < 0.001) and low in PPs (P < 0.001), respectively. ... There was no difference between the lpa beans high or low in PPs or between the parents high or low in PPs. A 90% reduction in PA leads to an increase in bioavailable iron from beans, independent of the PP concentration.
   J Nutr, 2013 · checked 2026-09-23
7. bbb-c1-05 · randomised crossover trial with a non-randomised control arm
   isonitrogenous meals containing 23 g protein/meal from 1) complete protein (lean beef), 2) 2 incomplete, but complementary protein sources (navy/black beans and whole wheat bread), and 3) single incomplete protein sources (black beans or whole wheat bread at 1 meal), but providing a complete amino acid profile over 24 h. ... Meals containing complete, complementary, or incomplete proteins did not differentially influence FSR responses after breakfast (P = 0.90) or 24 h (P = 0.38).
   J Nutr, 2024 · checked 2026-09-23
8. bbb-c1-02 · pilot randomised crossover trial
   There was greater vasorelaxation 6 h following consumption of darker-coloured beans, as shown by decreased vascular tone: PWV was lower after consuming black bean compared to pinto bean, augmentation pressure was lower after consuming black bean compared to rice and pinto bean, 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 2026-09-23
9. bbb-c1-08 · systematic review and meta-analysis mixing clinical trials and observational reports on bean extracts and whole beans
   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. ... However, diabetes studies indicated that the postprandial glucose level at the peak of 60 min for common bean consumers was low (mean difference = -2.01; 95% CI [-4.6, -0.63]), but the difference between the treated and control was not significant, and there was a high level of heterogeneity among studies (I2 = 98%).
   Nutrients, 2021 · checked 2026-09-23
10. bbb-c1-07 · randomised crossover pilot trial
    Peripheral and central systolic blood pressure was increased (4%) after eating white rice but not after the consumption of wheat or beans. A marked decline in augmentation index at 75 bpm (arterial stiffness) from 26.1 ± 3.6% to 16.2 ± 2.0% was observed 2 h after eating whole wheat but not beans or white rice.
    Nutrients, 2025 · checked 2026-09-23