A University of Otago meta-analysis of 24 randomized controlled trials found that eating about half a cup of legumes each day was associated with modest reductions in total cholesterol, LDL cholesterol and fasting blood sugar among nearly 2,000 adults.
By yourNEWS Media Newsroom
Adding a modest serving of beans, lentils or other legumes to the daily diet may improve several important markers of metabolic and cardiovascular health, according to a large review of randomized controlled trials.
Researchers at the University of Otago pooled results from 24 trials involving 1,938 adults and found that participants consuming approximately 86 grams of legumes per day — roughly half a cup cooked — experienced measurable reductions in total cholesterol, LDL cholesterol and fasting blood glucose compared with people following control diets without the added legumes.
Across the studies, total cholesterol fell by an average of 0.23 mmol/L, while LDL cholesterol declined by 0.16 mmol/L. Fasting blood sugar decreased by 0.18 mmol/L.
The researchers characterized the changes as modest but potentially meaningful when considered across large populations.
“The LDL reduction is modest, but at a population level it could translate into fewer cardiovascular events,” the review’s lead author said.
The analysis received a moderate-certainty rating under the GRADE system, indicating researchers believe the overall conclusions are reasonably reliable and unlikely to be substantially reversed by additional studies.
That assessment applied to the pooled findings involving cholesterol and fasting blood glucose.
Reductions in LDL cholesterol generally emerged within six to 12 weeks of increasing legume consumption, according to the report.
Researchers noted that the time frame resembles the period in which cholesterol changes can become detectable during clinical trials of statin medications, although the review did not suggest legumes produce an effect equivalent to statin therapy.
Earlier randomized-trial meta-analyses have similarly found that consumption of non-soy legumes can reduce cholesterol levels, according to research cited in How Not to Diet [1].
The new analysis adds considerably to that evidence by combining data from nearly 2,000 participants.
Legumes include foods such as black beans, kidney beans, chickpeas, lentils, split peas and mung beans. Although researchers documented improvements in laboratory measurements, they could not determine that any single nutrient was responsible.
Instead, the benefits may result from the nutritional combination found naturally within whole legumes.
A half-cup serving of cooked beans or lentils typically supplies about six to eight grams of dietary fiber, according to nutrition reference information [2].
Fiber has long been associated with digestive health and regularity [3], but it may also influence cholesterol metabolism and the rate at which carbohydrates are absorbed.
Meal composition and the type of carbohydrate consumed can affect post-meal blood glucose responses, according to dietary guidance cited in research examining carbohydrate sources [4].
Legumes also provide plant protein and minerals, including magnesium.
Magnesium performs numerous essential functions in the human body, while inadequate dietary intake remains relatively common, according to reports examining magnesium-rich foods [5].
Traditional legumes such as mung beans have also been described as nutrient-dense foods because they combine plant protein, fiber, vitamins and minerals [6].
The authors cautioned against attributing the observed cholesterol and glucose changes solely to fiber, magnesium or any other individual nutrient.
Because the trials tested legumes as whole foods, the effects could reflect interactions among multiple components, including fiber, minerals, plant proteins and other naturally occurring compounds.
The findings also suggest that substantial dietary changes may not be necessary to incorporate legumes into a person’s routine.
Researchers proposed replacing common refined carbohydrate side dishes, such as white rice or dinner rolls, with approximately half a cup of black beans, lentils or chickpeas several evenings each week.
Using legumes as substitutions rather than simply adding them on top of an existing meal can increase their intake without necessarily increasing the total amount of food consumed.
Researchers suggested making that substitution at least four nights per week as one practical way of approaching the intake levels used in the trials.
People who do not regularly eat legumes may want to introduce them gradually because rapidly increasing fiber intake can cause temporary gas or digestive discomfort.
The report suggested soaking dried beans overnight before cooking. It also proposed adding a small amount of apple cider vinegar to the soaking water as a method that may shorten cooking time and reduce gastrointestinal discomfort, although individual responses can vary.
Lentils and split peas offer a faster alternative because they generally require less preparation and cooking time than larger dried beans.
Separate research has examined the effects of soaking and cooking on the nutritional characteristics of legumes [7].
Variety may also be useful.
Rotating among lentils, chickpeas, black beans, mung beans, split peas and other legumes can provide somewhat different combinations of nutrients while making the dietary pattern easier to sustain.
The report suggested combining legumes with foods such as leafy green vegetables, olive oil and walnuts as part of a broader heart-conscious eating pattern.
Research on vegetarian nutrition has found that replacing animal-derived fats with plant-derived fats can lower LDL cholesterol [8].
Other foods, including avocados and pumpkin seeds, can contribute additional magnesium, potassium and unsaturated fats alongside legume-based meals.
The researchers emphasized several limitations.
The trials measured changes in cholesterol and blood glucose but did not directly evaluate liver fat.
Although abnormal cholesterol and blood sugar frequently occur alongside metabolic conditions involving the liver, the study could not determine whether the improvements observed in blood tests were accompanied by reductions in liver fat.
The research also does not establish legumes as replacements for cholesterol-lowering, diabetes or other prescribed medications.
“These findings support dietary change as an adjunct, not an alternative, to medication,” a dietitian who was not involved in the research said.
People receiving treatment for diabetes, cardiovascular disease or other chronic conditions were advised to discuss significant dietary changes with their clinicians.
The findings arrive amid growing interest in “food as medicine,” an approach increasingly being incorporated into prevention and treatment programs at medical institutions [9].
Rather than positioning food as a replacement for conventional medical care, the approach examines how dietary patterns can work alongside other treatments to improve health outcomes and reduce chronic-disease risk.
For legumes, the amount associated with improvement in the new review was relatively small: approximately half a cup per day.
Across the 24 randomized trials, that daily serving was associated with lower LDL and total cholesterol as well as lower fasting blood sugar, suggesting that an inexpensive dietary staple may provide measurable metabolic benefits when consumed consistently.
Explainer Infographic
Comments