Cooked beans are cheap and well studied, and the lectin scare applies to raw ones

Key takeaways

• A 2014 review of 26 randomized trials found that about one serving a day of beans, lentils, chickpeas or peas lowered LDL cholesterol by about 5% over a median of six weeks³.
• Raw or undercooked red kidney beans carry a lectin that can cause severe vomiting from as few as four or five beans, so the FDA advises soaking at least five hours and boiling at least 30 minutes⁴⁵.
• In three feeding trials, fewer than half of people eating a half cup of pinto or baked beans a day reported more gas in the first week, and only 19% did with black-eyed peas⁹.
• The American Institute for Cancer Research says population studies show no added risk for breast cancer survivors who eat soy foods, and it counts one to two servings a day as moderate¹¹.
• In USDA’s 2023 price data, a cup of pinto beans cooked from dry cost about 24 cents, roughly a third of the canned price, and Harvard’s Nutrition Source says rinsing canned chickpeas removes about 40% of their sodium¹⁴¹⁵.

In the late 1980s, researchers began following 785 people aged 70 and older in five groups: Japanese, Swedes, Greeks in Greece, and Greek and Anglo-Celtic Australians¹. They wanted to know which foods went with a longer life.

One food group stood out. For every extra 20 grams of legumes a day, less than a quarter cup, the risk of dying during up to seven years of follow-up fell by about 8%¹. Vegetables, fruit, grains, dairy and meat showed no clear link in the same analysis¹.

The 2004 paper was titled “Legumes: the most important dietary predictor of survival in older people of different ethnicities.” Yet it was a small study with 169 deaths, and it can’t show that beans caused anything¹.

That tension runs through the legume story. Beans, lentils, chickpeas and peas are cheap, filling and central to cuisines from Mexico to India. The best evidence for them is real but quieter than the headlines. And the scariest claim, that lectins make beans toxic, fits one mistake: eating them raw or undercooked.

Beans lower LDL a little, but the heart links are real but uncertain

The strongest evidence comes from randomized trials, where people are assigned by chance to one diet or another. A 2014 review in the Canadian Medical Association Journal pooled 26 such trials with 1,037 people³.

The median amount was 130 grams of pulses a day, which the authors describe as about one serving³. Using USDA serving weights, that’s roughly two-thirds of a cup of cooked lentils or three-quarters of a cup of black beans¹³.

Over a median of six weeks, LDL cholesterol, the “bad” kind, fell by about 5%³. That’s modest, and results varied a lot from trial to trial³. The trials were short, so they can’t say whether the drop lasts or prevents heart attacks.

Funding deserves the scrutiny you’d give a drug study. Thirteen trials were publicly funded, seven mixed public and industry money, and four were funded by industry alone³. Several review authors disclosed support from Pulse Canada and Saskatchewan Pulse Growers, groups that promote the crops³. That doesn’t make the results wrong, but you should know it.

The long-term picture comes from cohort studies, which follow what people eat over years without assigning diets. A 2019 umbrella review in Advances in Nutrition, which updated six earlier reviews to cover 28 cohort studies, compared people who ate the most legumes with those who ate the least².

The top eaters had an 8% lower risk of developing cardiovascular disease and a 10% lower risk of coronary heart disease, plus lower rates of high blood pressure and obesity². But the review found no link with dying of heart disease, or with stroke or diabetes².

The reviewers rated their certainty as low for cardiovascular disease and very low for every other outcome, coronary heart disease included². Bean eaters may differ in ways a questionnaire can’t capture. The 2004 survival study has similar limits: its groups recorded diets in different ways, and the paper doesn’t discuss its weaknesses¹. Our article on the Blue Zones explains why claims about long-lived hot spots are disputed.

Your legume cooking chart

Nutrition figures per cooked cup come from USDA FoodData Central’s SR Legacy records for legumes boiled without salt¹³. Cooking guidance comes from the American Institute for Cancer Research (AICR), Harvard’s Nutrition Source and the FDA⁴¹²¹⁵.

Legume	Soak first?	Stovetop cooking	Per cooked cup
Lentils	No	About 30 to 40 minutes	230 calories, 17.9 g protein, 15.6 g fiber
Split peas	No	About 30 to 40 minutes	231 calories, 16.3 g protein, 16.3 g fiber
Chickpeas	Yes, 3 hours to overnight	Simmer 60 to 90 minutes	269 calories, 14.5 g protein, 12.5 g fiber
Black beans	Yes, overnight cold or 1 to 4 hours hot	Simmer until soft	227 calories, 15.2 g protein, 15.0 g fiber
Pinto beans	Yes, overnight cold or 1 to 4 hours hot	Simmer until soft	245 calories, 15.4 g protein, 15.4 g fiber
Red kidney beans	Yes, at least 5 hours; drain	Boil hard in fresh water at least 30 minutes, then until soft	225 calories, 15.3 g protein, 13.1 g fiber
Great northern beans	Yes, overnight cold or 1 to 4 hours hot	Simmer until soft	209 calories, 14.7 g protein, 12.4 g fiber
Soybeans (mature)	Yes, overnight cold or 1 to 4 hours hot	Simmer until soft	296 calories, 31.3 g protein, 10.3 g fiber

Yield and shortcuts. One cup of dry beans or peas makes about 2½ to 3 cups cooked, and a 15-ounce can gives about 1½ cups drained¹². A pressure cooker can finish presoaked beans in about 15 minutes¹².

Lentils are the beginner’s legume: no soaking, quick cooking and about 6.6 milligrams of iron per cup¹³. Soybeans are the outlier, with roughly twice the protein of other beans¹³. Our protein and fiber articles cover daily targets.

The lectin warning is real for one bean cooked the wrong way

Lectins are proteins that bind to carbohydrates. All plants make them, and raw legumes and whole grains have the most⁶.

The lectin that matters most is phytohaemagglutinin, found in raw and undercooked beans⁴. At high levels it can cause nausea, severe vomiting and diarrhea, according to the FDA⁴.

Red kidney beans are the classic culprit. A Kansas State University food-safety explainer puts raw red kidney beans at 20,000 to 70,000 hemagglutinating units, a lab measure of lectin activity⁵. Thorough cooking brings that down to a few hundred⁵. Cannellini, the white kidney bean, start with roughly a third of the red bean’s load, and fava beans with a tenth or less⁵.

The dose that sickens people is tiny. Citing the FDA’s “Bad Bug Book,” the same explainer says four or five raw or half-cooked red kidney beans can bring on hard vomiting in a few hours, and diarrhea often follows⁵. The good news: symptoms usually clear three to four hours after they start⁵.

Ten minutes at a full 212°F boil destroys the toxin, and specialists recommend a half hour so the beans heat all the way through⁵. A slow cooker probably never reaches that temperature, which is why it’s the wrong tool for raw kidney beans⁵. Harvard’s Nutrition Source adds that low-heat slow cooking or undercooking of any raw beans may leave some lectins active⁶.

Canned beans are already cooked, and the FDA says their low lectin levels won’t affect you⁴.

What about lectin-free diets?

Lectin-free diet plans go much further, blaming lectins for obesity, chronic inflammation and autoimmune disease⁶. Those ideas have sold best-selling books and lectin-blocking enzyme pills, Harvard’s Nutrition Source observes. Yet few human studies have measured how much active lectin people eat, and the autoimmune link is still a theory⁶.

Meanwhile, population studies tie lectin-containing foods such as legumes, whole grains and nuts to lower rates of heart disease and type 2 diabetes⁶. Harvard’s reviewers judge that the payoff from eating these foods is much larger than any risk from their lectins⁶.

If you feel better avoiding a particular food, that’s your call. But there’s not enough evidence that lectins in properly cooked beans harm healthy people.

Phytates trade a little iron for other benefits, and soaking helps

Phytates, or phytic acid, are how seeds, legumes and whole grains store phosphorus⁷. In the gut, phytates bind iron, zinc and calcium eaten at the same meal, so you absorb less of them⁷.

That’s why phytates are called antinutrients. Yet they may also help blunt blood sugar spikes and keep kidney stones from forming, and lab and animal work hints at antioxidant effects⁷.

Kitchen traditions already handle the downside. Phytates break down when beans are soaked overnight, simmered, sprouted or fermented⁷.

Most people eating a varied Western diet get enough of these minerals⁷. The people who should pay more attention are those with an iron or zinc deficiency already, vegans, and anyone whose diet relies on beans or grains at every meal with little variety⁷.

Bean gas is real, usually milder than feared, and tends to ease

Beans carry resistant starches and certain sugars, called oligosaccharides, that your small intestine can’t digest. Bacteria in your colon ferment them, and the byproduct is gas⁸. The federal National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists beans, peas and lentils among foods some people find gassy¹⁰.

How much gas, though? Two nutrition researchers tested it in three feeding studies, with people eating a half cup of beans a day for 8 to 12 weeks⁹.

In the first week, fewer than half reported more gas with pinto beans or baked beans⁹. With black-eyed peas, only 19% did⁹. Even on control diets with no beans, 3% to 11% reported more gas⁹. The authors concluded that worries about bean gas may be exaggerated⁹.

Symptoms also tend to ease. In the 2014 cholesterol review, 11 trials reported digestive symptoms, and most said those symptoms improved as the trial went on³. Only two trials lost even one or two people because of them³.

Some people try over-the-counter enzyme products for bean gas. NIDDK advises asking a doctor before taking supplements for gas¹⁰.

Soy and breast cancer: the old worry hasn’t held up

Soybeans contain isoflavones, compounds with a structure similar to human estrogen¹¹. Early mouse studies suggested they could feed some breast cancers. But rodents process isoflavones differently and reached blood levels far above what people get from soy foods¹¹.

AICR says population studies don’t link soy foods to a higher risk of any cancer¹¹. Its 2018 expert report graded the evidence on soy and breast cancer risk as “Limited, no conclusion,” because study results are mixed¹¹.

For survivors, AICR says the research consistently shows no increased risk from soy foods¹¹. Limited evidence even suggests lower death rates among women who eat soy a year or more after diagnosis¹¹. Population studies have not found harmful interactions with anti-estrogen medicines¹¹.

AICR counts one to two servings of whole soy foods a day as moderate. One serving is about ⅓ cup of tofu, 1 cup of soy milk or ½ cup of edamame¹¹. Up to three servings a day, eaten long-term in Asia, has not been linked to higher risk¹¹.

The caution is for pills and powders. AICR says the findings on foods don’t support isolated isoflavone or soy protein supplements, especially in amounts beyond a normal diet¹¹. If you’ve had breast cancer, talk with your oncology team about supplements.

Canned or dried: both count, and the price gap is big

AICR says canned and cooked dry beans have equivalent nutritional quality¹². The main difference is salt.

In USDA’s data, a cup of canned chickpeas, liquid included, carries about 670 milligrams of sodium¹³. Chickpeas boiled at home without salt have about 11 milligrams per cup¹³.

Draining and rinsing canned chickpeas removes about 40% of the sodium, according to Harvard’s Nutrition Source¹⁵. No-salt-added cans are another option¹².

Price is the other difference. In USDA Economic Research Service data from 2023, dried pinto beans cost about 24 cents per cup cooked, compared with about 72 cents for canned¹⁴. Dried black beans ran about 26 cents a cup, against 78 cents canned¹⁴.

One surprise in the same data: dried lima beans cost about 97 cents a cup, slightly more than canned limas at about 94 cents¹⁴. Check the math before assuming dried always wins.

A one-pound bag of dried pinto beans, at about $1.50 in 2023, makes roughly six cups of cooked beans¹⁴. Cook a big pot on the weekend and freeze it in 1½-cup portions, the size of a drained can.

What the evidence shows

Claim	Evidence rating	What it rests on
Eating legumes lowers LDL cholesterol a little	Strong evidence	26 randomized trials; about 5% lower, short trials3
Legume eaters get less heart disease	Promising but early	Consistent cohort links, low certainty, no link with heart deaths2
Legumes are the key to a longer life	Not enough evidence	One small study of 785 older adults1
Raw or undercooked kidney beans are safe to eat	Evidence says no, or unsafe	FDA documents vomiting and diarrhea from the lectin45
Lectins in properly cooked beans harm healthy people	Not enough evidence	Very little human research; theory only6
Most people get more gas when they start eating beans daily	Evidence says no, or unsafe	Fewer than half reported more gas in week one, and symptoms tended to fade39
Soy foods raise breast cancer risk or harm survivors	Evidence says no, or unsafe	Population studies show no added risk11

Tradition got the soaking pot right

Many readers know beans through family cooking: frijoles de la olla, hoppin’ John, ful medames, a pot of dal. Most of these recipes rely on a long simmer, and whole beans usually get a soak first.

Food science explains why that method works. The long boil destroys the kidney bean lectin⁵. Soaking and cooking cut phytates⁷, and pouring off the soak water may ease gas¹².

Beans also serve a value many natural-health readers prize: self-reliance. A bag of dried beans keeps a year or longer in the pantry¹², costs little and needs no processing beyond drying.

Questions readers ask

The bottom line

Beans, lentils, chickpeas and peas are among the cheapest whole foods you can buy, and trials show they nudge LDL cholesterol down. The long-term heart links are encouraging but uncertain, and claims that beans alone explain long lives go beyond the data.

Cook them the traditional way: soak whole beans, boil red kidney beans hard, and skip the slow cooker for raw ones. Start small if gas worries you, rinse canned beans, and enjoy soy foods in normal amounts.

Related reading

• Who needs the new protein goal of up to twice the RDA
• Most Americans fall far short on fiber, and one swap a week closes the gap
• A daily handful of nuts holds up in research, but go easy on Brazil nuts
• Purpose tracks with a longer life, while the Blue Zones story is less certain
• The healthiest natural habits cost little, and these are the places money still matters

Sources

1. Darmadi-Blackberry I, Wahlqvist ML, Kouris-Blazos A, Steen B, Lukito W, Horie Y, Horie K. “Legumes: The Most Important Dietary Predictor of Survival in Older People of Different Ethnicities.” Asia Pacific Journal of Clinical Nutrition, 2004;13(2):217-220. apjcn.qdu.edu.cn
2. Viguiliouk E, Glenn AJ, Nishi SK, et al., Sievenpiper JL. “Associations Between Dietary Pulses Alone or With Other Legumes and Cardiometabolic Disease Outcomes: An Umbrella Review and Updated Systematic Review and Meta-analysis of Prospective Cohort Studies.” Advances in Nutrition, 2019. University of Insubria repository record. irinsubria.uninsubria.it
3. Ha V, Sievenpiper JL, de Souza RJ, et al. “Effect of Dietary Pulse Intake on Established Therapeutic Lipid Targets for Cardiovascular Risk Reduction: A Systematic Review and Meta-analysis of Randomized Controlled Trials.” CMAJ, 2014;186(8):E252-E262. pubmed.ncbi.nlm.nih.gov
4. U.S. Food and Drug Administration. “Natural Toxins in Food.” Content current as of September 26, 2024. fda.gov
5. Blakeslee K. “Cooking Dry Beans Safely” (citing the FDA Bad Bug Book). Kansas State University, October 13, 2017. k-state.edu
6. Harvard T.H. Chan School of Public Health, The Nutrition Source. “Lectins.” Last reviewed January 2022. nutritionsource.hsph.harvard.edu
7. Harvard T.H. Chan School of Public Health, The Nutrition Source. “Are Anti-Nutrients Harmful?” Last reviewed January 2022. nutritionsource.hsph.harvard.edu
8. Harvard T.H. Chan School of Public Health, The Nutrition Source. “Legumes and Pulses.” Updated November 15, 2024. nutritionsource.hsph.harvard.edu
9. Winham DM, Hutchins AM. “Perceptions of Flatulence From Bean Consumption Among Adults in 3 Feeding Studies.” Nutrition Journal, 2011;10:128. DOAJ record. pubmed.ncbi.nlm.nih.gov
10. National Institute of Diabetes and Digestive and Kidney Diseases. “Treatment for Gas in the Digestive Tract.” Last reviewed June 2021. niddk.nih.gov
11. American Institute for Cancer Research. “Soy: Intake Does Not Increase Risk for Breast Cancer Survivors.” Last updated April 8, 2021. aicr.org
12. American Institute for Cancer Research. “Beans & Lentils Food Facts.” Last updated April 7, 2021. aicr.org
13. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy records 172421 (lentils), 172429 (split peas), 173757 (chickpeas), 173735 (black beans), 175200 (pinto), 175194 (red kidney), 175191 (great northern), 174271 (soybeans), 175195 (canned kidney beans) and 175206 (canned chickpeas). Accessed October 2026. fdc.nal.usda.gov
14. USDA Economic Research Service. “Fruit and Vegetable Prices” (2023 data, all vegetables table). Updated December 9, 2025. ers.usda.gov
15. Harvard T.H. Chan School of Public Health, The Nutrition Source. “Chickpeas (Garbanzo Beans).” Updated November 15, 2024. nutritionsource.hsph.harvard.edu