The Benefits of Pulses

By Paul E. Lemanski, MD, MS, FACP

Medicines are a mainstay of American life and the healthcare system not only because they are perceived to work by the individuals taking them, but also because their benefit may be shown by the objective assessment of scientific study. Clinical research trials have shown that some of the medicines of Western science may reduce the risk of heart attacks, strokes and cardiovascular death while others may reduce certain types of cancer.

In the first 87 installments of the Non-Medicated Life, certain dietary practices and a healthy lifestyle have been shown to accomplish naturally for the majority of individuals most of the benefits of medications in the treatment of chronic medical conditions such as hypertension, high cholesterol, pre-diabetes, diabetes and heart disease. As a medical intervention, certain dietary practices and a healthy lifestyle may accomplish such benefits with fewer side effects, may reduce the number and amount of medication – and may allow actual discontinuation of medication. 

This is true for the dietary practice of consuming more pulses – the edible seeds of plants in the legume family. Pulses include all dry beans, peas, chickpeas and lentils. Moreover, pulses encourage sustainable agriculture by improving soil health and requiring less water than other crops. 

Most people have heard the old adage, “Beans, beans are good for your heart.” But why might that be? Heart disease is contributed to by multiple factors including high LDL cholesterol, high blood pressure, and metabolic derangements such as pre-diabetes and diabetes. It appears that the consumption of pulses may have a beneficial effect on each of these. 

Pulses such as chickpeas and lentils have been shown to lower blood levels of LDL or “the bad’ cholesterol. This is the type of cholesterol which when in excess gains access to the arterial wall to form a cholesterol plaque. A cholesterol plaque is a necessary first step in the process of atherosclerosis, or hardening of the arteries, that sets an individual up for a heart attack with involvement of the heart arteries – and a stroke with involvement of the brain and neck arteries. 

Daily legume consumption may lower the LDL by up to 20%, most likely on the basis of their soluble fiber content. Moreover, within cholesterol plaques it is not just the presence of LDL that increases risk, but also the oxidation of that LDL. Of all pulses, lentils have been shown to decrease LDL oxidation the most, with chickpeas a close runner-up.

Pulses may also help lower blood pressure, another major risk factor in the development of heart disease. Pulses are low in saturated fat and contain both fiber – soluble and insoluble – and plant protein, both of which have been associated with lower blood pressure. Indeed, legume consumption has been shown to lower blood pressure in individuals with hypertension, but also will slightly lower blood pressure in normal individuals – but never in a range to cause problems.

Pulses have also been shown to reduce blood sugar in those with pre-diabetes and diabetes and combat hyperinsulinism, the condition of excess insulin production that results from insulin resistance. Insulin resistance generally occurs in individuals with a genetic predisposition (a family history of diabetes) who are overweight or obese. 

For reasons that are not clear, such individuals require higher amounts of insulin to pump glucose from the bloodstream into body cells, thereby maintaining normal blood levels of glucose. Over time, however, the cells that produce insulin begin to burn out from the excess production. As a consequence, fasting blood glucose slowly rises. By the time a diagnosis of diabetes (fasting blood glucose greater than 126 mg/dl) is made, 50 to 70% of the cells that produce insulin have been lost to burn out, and cannot be replaced. The composition of pulses can be shown to help prevent this loss.

The composition of pulses includes plant protein, carbohydrate, fat and fiber. Although you might think that the carbohydrate of pulses would contribute to insulin resistance by increasing blood glucose, the soluble fiber of pulses actually slows the absorption of carbohydrate. 

This slowing of absorption is important, because it has been observed that the highest risk for the development of pre-diabetes and diabetes occurs in those with rapid rising of blood sugar, and a concomitant spike in insulin production. While a serving of most beans has about four grams of fiber, a serving of lentils has nine grams of fiber. For purposes of preventing insulin resistance, it is generally best to keep the ratio of total carbohydrate to fiber greater than five, and the consumption of pulses certainly helps in this regard.

As part of plant-based diet, pulses may also slow gastric emptying, and thus contribute to sustained sense of fullness or satiety after a meal. A study done with lentils confirmed a slowing of gastric emptying, which also slowed the absorption of carbohydrate during the following meal. In addition to effects on satiety, this slowed the rise of blood sugar, and helped combat insulin resistance. 

Indeed, individuals with type-2 diabetes on insulin placed on a plant-based diet (including pulses) showed a reduction in body weight and blood sugar with insulin requirements cut 60% – allowing about 50% of those in the study to get off insulin. It is important that any individual with diabetes not institute such a plant-based diet without discussion with their primary care provider, their endocrinologist, and in my opinion, help from a registered dietitian.

In summary, consumption of the edible seeds of plants in the legume family, collectively called pulses, obtain significant health benefits. Pulses help to lower LDL cholesterol and reduce its oxidation, reduce blood pressure, and improve cardio-metabolic risk by reducing insulin resistance. They reduce multiple cardiovascular risk factors and through this mechanism reduce the risk for heart attack and stroke. As such, the consumption of pulses presents another powerful tool for those interested in pursuing the non-medicated life.

Paul E. Lemanski, MD, MS, FACP (plemanski3@gmail.com) is a board-certified internist practicing internal medicine and lifestyle medicine in Albany. Paul has a master’s degree in human nutrition, he’s an assistant clinical professor of medicine at Albany Medical College, and a fellow of the American College of Physicians.