You probably know beans sit on every nutritionist's good-for-you list. Most of us never put them on the actual shopping list anyway. Researchers are now trying to pin down what they do when you eat them every single day.
In a 12-week trial presented at the annual meeting of the American Society for Nutrition, 72 adults with prediabetes ate a cup a day of either black beans, chickpeas or white rice.
A team at Illinois Institute of Technology checked their blood at the start, at six weeks and at 12.
The two bean groups came out ahead on different markers. Chickpeas moved cholesterol. Black beans moved inflammation.
Also read: How coffee affects your heart and blood pressure if you drink it every day
What the trial found in people's blood
In the chickpea group, total cholesterol fell from an average of 200.4 to 185.8 mg/dL over the 12 weeks.
In the black bean group, a marker of long-running inflammation called interleukin-6, or IL-6, fell from 2.57 to 1.88 picograms per milliliter. IL-6 is a signal the immune system releases when the body is under low-grade stress.
Blood sugar did not change in either group. The researchers describe the finding as an early signal, not a final verdict.
Lead author Morganne Smith, a doctoral candidate at Illinois Institute of Technology, summed up the result.
Also read: 7 foods research links to better lung function and lower disease risk
"Our study found that bean consumption helped significantly lower cholesterol and reduce inflammation in people with prediabetes, although glucose levels were not changed," she said.
Why beans may act on the heart
Beans carry three things the typical American plate is often short on. The first is soluble fiber, which binds cholesterol in the gut and carries some of it out of the body.
The second is resistant starch, a type of carbohydrate that feeds friendly gut bacteria. The third is polyphenols, plant compounds with anti-inflammatory effects.
A half cup of cooked black beans delivers about 7.5 grams of fiber and roughly 7.6 grams of plant protein. That single serving covers close to a third of most adults' daily fiber target.
Also read: Your next prescription may be a group walk in the park, Lancet trial suggests
What the mouse evidence adds
An earlier animal study from the US Department of Agriculture's Agricultural Research Service, highlighted by UCLA Health, fed the same half-cup dose to mice on a high-fat diet.
LDL cholesterol fell 28 percent in those mice. Triglycerides fell 37 percent. The researchers caution that findings in mice do not automatically carry over to people.
What a serving looks like
Chickpeas and lentils sit in the same neighborhood as black beans on fiber and protein. All three are cheap and keep for months canned or dried.
Longer trials in larger groups of people are still needed before the heart effects can be called settled.
Also read: After decades of research, this is what creatine actually does to your body
The trial served a cup of beans a day. Smith suggested blending them into soups, scattering them on a salad, or pairing them with grains like rice or quinoa. Canned beans work; drain and rinse them to cut salt.
Also read: Could a handful of pistachios help you sleep? Here is what the research actually shows
This article is made and published by Jesper Bengtson, who may have used AI in the preparation.