The main finding of this study was that replacing red and processed meat with legumes reduced LDL and total cholesterol levels in the blood. There are a few likely explanations for why this occurred.

Legumes are a nutritious group of foods. They are a good source of fiber, several B vitamins, potassium, magnesium, zinc, and phytochemicals.^[3]^[4] Legumes also have a healthy fatty acid profile, meaning that they contain a low amount of saturated fat, and of the modest amount of fat they contain, much of it is polyunsaturated fat.^[5]

As a result, the participants in the legume group consumed more fiber (34 vs. 27 grams/day), less saturated fat (11% vs. 13% of calories), less cholesterol (256 vs. 338 mg/day), and more polyunsaturated fat (8.4% vs. 7% of calories) than the participants in the meat group.

Although each of these differences isn’t large, in combination they can lead to a meaningful difference in blood cholesterol levels. Higher intakes of saturated fat are known to increase blood cholesterol levels, and decreasing saturated fat intake can decrease blood cholesterol levels, especially if it’s replaced with polyunsaturated fat.^[6]^[7]

Increasing dietary cholesterol intake doesn’t meaningfully increase blood cholesterol levels, on average, although the effect is highly individual.^[8]^[9]^[10] Moreover, it’s apparent that increasing dietary cholesterol more strongly increases blood cholesterol levels in the context of diets that are relatively high in saturated fat and low in polyunsaturated fat.

Increasing fiber intake can also improve blood lipids,^[11] particularly if it’s soluble fiber,^[12]^[13] which legumes contain.^[14] Soluble fiber decreases cholesterol absorption in the body and increases the excretion of bile acids, which are synthesized from cholesterol.^[15]^[4]^[12] Fiber may also contribute to reductions in blood cholesterol by increasing the production of short-chain fatty acids.^[15]^[4]^[12] The phytosterols in legumes is another component that has blood cholesterol-lowering properties.^[16]^[17]

Mechanisms by which increasing legume intake could reduce cardiovascular disease risk

Adapted from McRae, 2017, J Chiropr Med.

In accordance, evidence from meta-analyses of randomized controlled trials has indicated that consuming legumes reduces blood cholesterol levels. A meta-analysis of 12 randomized controlled trials published in 2023 reported that daily legume consumption (at least 120 grams, typically) reduced total cholesterol by 8.5 mg/dL and reduced LDL-C by 7.4 mg/dL.^[1]

A limitation of this evidence is the presence of high heterogeneity in the analyses, which is related to differences between studies in the legume intervention, as well as what legumes were compared to. For example, in some studies, the participants in the control group ate whole-grain wheat-based products (e.g., bread, breakfast cereals), whereas in other studies they ate spaghetti, white rice, or carrots, or simply followed their usual diet.

When evaluating the health effects of a particular food, it’s important to consider what it’s compared to. Foods are rarely added to the diet in isolation. Typically some other food is subtracted from the diet to make room, and not all substitutions are similar in terms of their health effects. For example, as mentioned above, although decreasing saturated fat intake can decrease blood cholesterol levels, the greatest decrease occurs when it is replaced with polyunsaturated fat.

With respect to studies that had the participants reduce their meat intake and increase their legume intake, reductions in blood cholesterol have been reported,^[18]^[19]^[20] but unlike in the summarized study, 2 of these studies had the participants consume soy products, and the other one had the participants increase their consumption of other plant foods besides legumes.

In an 8-week crossover trial that was similar to the summarized study, participants with type 2 diabetes consumed a heart healthy diet, and replacing 2 servings of red meat with nonsoy legumes (lentils, chickpeas, peas, or beans) on 3 days per week resulted in greater decreases in LDL-C (−16 vs. −9 mg/dL).^[21]

The evidence pertaining to the effect of legumes on blood cholesterol levels aligns with evidence from observational studies on the relationship between legume consumption and cardiovascular disease risk. In meta-analyses comparing the participants with a higher legume intake to the participants with a lower legume intake, the risk of cardiovascular disease was 6% lower and the risk of coronary artery disease was 10% lower in the participants with the highest intake.^[22] Furthermore, dose-response analysis suggested that the greater the weekly legume intake, the greater the risk reduction.

Associations between legume consumption and cardiovascular disease risk

Adapted from Mendes, et al., 2023, Nutr Metab Cardiovasc Dis.

Similarly, evidence from prospective cohort studies estimates that replacing 50 grams of processed meat per day with 50 grams of legumes per day is associated with a 23% lower risk of cardiovascular disease (moderate certainty evidence), whereas replacing minimally processed red meat with legumes is associated with a 6% lower risk of cardiovascular disease (low certainty evidence).^[2]

The effects of replacing red and processed meat with legumes on cardiovascular risk factors Original paper