Key Takeaways
- Prediabetes is now the norm, not the exception. 43.5% of U.S. adults have it, including 48.6% of adults 45 to 64 and 52.1% of adults 65 and older.
- A new 12-week trial of 72 adults with prediabetes found that one cup of chickpeas a day lowered total cholesterol by about 15 points. One cup of black beans a day lowered a key inflammation marker, IL-6.
- These results were presented at a scientific meeting and have not yet been published in a peer-reviewed journal, so treat them as preliminary.
- Four earlier trials point the same way. Beans and lentils lowered LDL and total cholesterol in adults with high cholesterol, men in a controlled feeding study, adults with larger waists, and adults with prediabetes.
- Blood sugar results are mixed. The new trial saw no change in glucose. Other trials saw better after-meal glucose or HbA1c, and one paired beans with calorie restriction.
- You don’t need a fancy plan. A cup of beans a day, canned or cooked at home, is cheap and easy to start. Ramp up slowly to avoid gas.
Beans are getting more attention from researchers, and it’s overdue. They cost less than a dollar a serving, they have fed people for thousands of years, and yet many Americans skip them for expensive supplements and trendy superfoods.
A 2025 study presented at the annual meeting of the American Society for Nutrition found that eating one cup of beans a day lowered cholesterol or inflammation in adults with prediabetes. The findings are simple, affordable, and actionable. Here’s what the research shows and why it matters.
Why This Matters: Blood Sugar Problems Are Common
We have a metabolic health problem as a nation. According to the CDC’s U.S. Diabetes Surveillance System, 43.5% of U.S. adults had prediabetes in 2021–2023. That is an estimated 115.2 million people. It gets more common with age. Among adults 45 to 64, 48.6% have prediabetes. Among adults 65 and older, it’s 52.1%.
Full diabetes follows the same pattern. Diabetes, including both diagnosed and undiagnosed people, affects 20.6% of adults 45 to 64 and 28.8% of adults 65 and older. And only about 1 in 5 adults with prediabetes (21.4%) know they have it.
Prediabetes is an earlier stage of the same disease process as type 2 diabetes. It just hasn’t reached the point of an official diagnosis yet. Diabetes is just further down the same road.
Diabetes and prediabetes are not really blood sugar problems. Blood sugar is the symptom. Underneath, it is a fat problem: too much fat in the liver and the pancreas. That impairs liver function, drives insulin resistance, keeps the body in a state of low-grade inflammation, and raises the risk of heart disease and full-blown type 2 diabetes.
Blood sugar is also a late warning sign. Insulin tends to rise first, and the body can keep blood glucose normal for years by producing more insulin. In my own analysis of the CDC’s NHANES 2021–2023 data, about 1 in 4 U.S. adults with normal blood sugar already has elevated insulin resistance (HOMA-IR of 2.5 or higher).*
To fix poor metabolic health, we need to change what we eat. Beans are a great place to start.
The New Study: Black Beans, Chickpeas, and Prediabetes
The trial referred to above was led by researchers at the Illinois Institute of Technology and presented at NUTRITION 2025 in June 2025. It enrolled 72 adults with prediabetes. Participants were randomly assigned to eat 1 cup of black beans, chickpeas, or rice (the comparison food) every day for 12 weeks. They ate at home as they normally would, rather than in a controlled feeding setting. Blood samples were taken at baseline, 6 weeks, and 12 weeks. The team measured cholesterol, inflammation markers, and blood sugar, and ran glucose tolerance tests at the beginning and end.
Since this is a conference presentation, it has not been thoroughly peer-reviewed. So take the findings as being preliminary until the full study is published.
Chickpeas and cholesterol
In the chickpea group, total cholesterol dropped significantly, from an average of 200.4 mg/dL to 185.8 mg/dL after 12 weeks. That is a drop of nearly 15 points in three months from one dietary addition.
Black beans and inflammation
In the black bean group, the inflammation marker interleukin-6 (IL-6) fell significantly, from an average of 2.57 pg/mL at the start to 1.88 pg/mL at 12 weeks.
Blood sugar
There were no significant changes in blood sugar markers. That may be because of what else people were eating. Moving blood sugar usually takes a bigger overall change, such as a whole-foods plant-based diet or meaningful weight loss. Fasting insulin may have changed, as that is more sensitive and an earlier marker of improvement, but it wasn’t measured.
Study presenter Morganne Smith, a doctoral candidate at the Illinois Institute of Technology, said the results could be used to inform dietary guidelines and public health programs aimed at preventing heart disease and diabetes, according to the American Society for Nutrition’s release.
Earlier Studies Point the Same Way
Trials that use a real serving of beans each day tend to agree with the new study. A tiny portion doesn’t count. Many reviews of bean research pool studies where people ate only small amounts, even in the “high” groups. In those studies, no one is eating enough beans to make a “hill of beans” of difference. So it’s more useful to look at trials with realistic daily servings.
Beans lower LDL and total cholesterol
A 2024 randomized trial in the Journal of Nutrition tested 120 grams of beans a day, about three-quarters of a cup, against a rice-based control. It ran 6 weeks in 60 adults per group with mild high cholesterol. The bean group had significantly lower LDL, non-HDL, and total cholesterol than the rice group.
The dried pea group did not get the same LDL benefit. The researchers also found that fiber intake did not track with the LDL drop in the bean group. They suggest other compounds in beans may be giving some of the benefits.
A 2010 crossover feeding trial at Penn State, published in Lipids, enrolled 64 middle-aged men. Each man ate a high-legume diet (about 1.5 servings per 1,000 calories) and a “healthy American” diet for 4 weeks apiece, in random order. Both diets were controlled for macronutrients, including saturated fat. The legume diet lowered total and LDL cholesterol more than the healthy American diet. Insulin-sensitive men saw the biggest improvements, and insulin-resistant men saw smaller benefits for some lipid markers.
Lentils help cholesterol, inflammation, and after-meal glucose
A 2024 trial in Nutrients followed 38 adults with larger waists for 12 weeks. They ate either 980 grams of cooked green lentils a week (about 140 grams a day) in prepared midday meals or meat-based meals with no lentils. The lentil group had lower LDL and total cholesterol and a smaller blood sugar rise after meals. Two inflammatory markers, interleukin-1β and interleukin-17, also decreased.
Legumes and the gut microbiome
A 2025 trial in Nature Communications tested a calorie-restricted, legume-enriched diet against a calorie-restricted control diet. It enrolled 127 adults with prediabetes in Singapore and lasted 16 weeks. Both groups lost weight, but the legume group had bigger drops in LDL cholesterol, total cholesterol, and HbA1c. Their gut bacteria also shifted toward fiber-digesting species. This was a multi-part diet, not beans alone, so the results can’t be credited to legumes by themselves.
Why Beans Work
Beans help through several overlapping routes.
Soluble fiber. Beans are rich in soluble fiber, which binds cholesterol in the gut so less of it gets absorbed. Fiber is probably part of the story, though the 2024 Journal of Nutrition trial suggests it isn’t the whole story.
Prebiotic activity. The fiber in beans feeds beneficial gut bacteria, which produce short-chain fatty acids, especially butyrate, that help calm inflammation. The gut microbiome appears to matter for metabolic health, too.
Low glycemic index. Beans are a slow carb. They digest slowly and don’t send a rush of sugar into the bloodstream, unlike refined carbohydrates.
Plant protein. When beans replace animal protein at a meal, saturated fat intake drops, and that indirectly lowers LDL cholesterol.
Phytochemicals. Beans contain saponins and polyphenols that may lower cholesterol through additional pathways.
Nutrient density. Beans supply folate, magnesium, and potassium, nutrients many Americans fall short on. They are also a good plant source of iron and zinc.
Practical Tips: How to Eat a Cup of Beans Every Day
- Top your salads. Chickpeas, black beans, or pinto beans all work.
- Blend them into soup. White beans or lentils add creaminess without dairy. A little coconut cream helps.
- Make hummus. Chickpeas, tahini, lemon, and garlic make a filling snack.
- Swap your side. Serve beans or lentils instead of white rice or pasta.
- Start with canned beans. You don’t have to cook from dry. Rinse them, and watch for added salt or sugar.
- Use spices. Cumin, garlic, and onions are staples in our kitchen, with a little coriander. Smoked paprika is great for refried-style beans.
- Try an Instant Pot. Pressure cooking helps the spices soak in, and we find the flavor and color beat stovetop beans.
If you’re not used to beans, start with smaller amounts and build up over a week or two. Your gut bacteria will adjust, and digestive discomfort usually fades. In the 2024 Nutrients lentil trial, stomach symptoms were rated “none” or “mild” throughout, even at a large daily dose.
If you like these ideas, and you want a few more ways to improve your metabolic health, download the free guide, 10 Simple Ways to Support Healthy Metabolism. It doesn’t matter what your diet is now as these tips work with any dietary pattern.
Frequently Asked Questions
How many beans do I need to eat to see results? The trials used about 3/4 cup to 1 cup of cooked beans a day (120 grams in the Journal of Nutrition trial, 1 cup in the new prediabetes trial), for 6 to 12 weeks. Lentil intake in the Nutrients trial was about 140 grams a day.
Will beans lower my blood sugar? Not necessarily on their own. The new prediabetes trial found no change in glucose markers. The lentil trial found a smaller after-meal blood sugar rise, and the Singapore trial found lower HbA1c, but that diet also included calorie restriction and other changes. Beans work best as part of a bigger shift to whole plant foods.
Are chickpeas or black beans better? The trial did not compare them head to head. Chickpeas were tied to lower cholesterol and black beans to lower IL-6, so eating a mix makes sense.
Are canned beans okay? Yes. Canned beans are a fine way to start. Choose ones without added salt or sugar, and rinse them.
Will beans give me gas? They can at first. Begin with a half cup or less and increase over one to two weeks. The 2024 lentil trial reported only mild or no stomach symptoms.
Do peas work like beans? In the Journal of Nutrition trial, dried peas did not lower LDL the way beans did. Stick with beans and lentils for cholesterol.
Should I change my medication if I eat more beans? No. If you take medicine for diabetes or cholesterol, talk with your doctor before making major diet changes, since your needs may shift as your numbers improve.
Your Next Step
Have you had your beans yet today? Try adding one cup a day for the next 12 weeks, the same length as the new trial, and then ask your doctor to recheck your cholesterol. Better yet, come and get your baseline metabolic lab testing done at True Wealth Health Coaching, and then work with me to improve your health. I’ll coach you so that you get the best results with the least amount of frustration. If your HbA1c is in the diabetic range and doesn’t come down a full point within 90 days, I’ll work with you for free until it does.
*Note on method. This is the author’s own analysis of public-use data from the National Health and Nutrition Examination Survey (NHANES), August 2021–August 2023 (files DEMO_L, DIQ_L, GLU_L, INS_L, GHB_L), from the CDC’s National Center for Health Statistics. The analysis included non-pregnant adults 18 and older in the fasting subsample (8 to under 24 hours) who had not been told by a doctor that they have diabetes. “Normal blood sugar” meant fasting glucose under 100 mg/dL (26.6% had HOMA-IR of 2.5 or higher; 95% CI 22.7–30.5; n = 1,263) or, more strictly, fasting glucose under 100 mg/dL and A1C under 5.7% (24.8%; 95% CI 20.4–29.2; n = 1,051). HOMA-IR was calculated as fasting insulin (µU/mL) × fasting glucose (mg/dL) ÷ 405. Estimates use the NHANES fasting sample weights, and confidence intervals account for the survey design. The 2.5 cutoff is widely used but not an official standard, and insulin assays are not standardized across laboratories.
