Legumes as human food
The legume plant family supplies a major fraction of the world’s human food, second only to members of the grass family, such as wheat, corn, and oats. Pulses include legumes that humans eat as dried seeds, including beans, peas, and lentils. Unfortunately, over the last 100 years, pulse consumption has declined from being a staple food to being a marginal aspect of many human diets.
Legumes and coronary heart disease
Legumes contain relative large amounts of protein, soluble fiber, and folate, which may reduce blood fats and reduce the risk of coronary heart disease. Researchers used data from 9,632 participants with an average age of 50 years in the National Health and Nutrition Examination Survey test this idea. Legume intake was grouped in four categories of increasing daily consumption. Compared to participants who ate legumes less than once per week, participants who ate legumes four or more times per week had significant 21 and 9 percent lower risks of developing coronary heart disease and cardiovascular disease during 19 years of follow-up. These results accounted for confounding factors such as age, systolic blood pressure, and body-mass index. Thus, more frequent legume intake predicted lower risk of coronary heart disease and cardiovascular disease independent of cardiovascular disease risk factors. Eat more beans to reduce your risk of heart disease.
Legumes and risk of mortality
A team of researchers investigated links between risk of mortality and categories of food consumption in five cohorts of different ethnicities (Japan, Sweden, Greece, Australia). Food categories included vegetables, legumes, fruits and nuts, cereals, daily products, meat and meat products, fish and shellfish, alcohol, and the ratio of monounsaturated to saturated fat. Participants included 785 men and women of age 70 or greater at baseline and followed for up to 7 years. Of the food groups, legume consumption showed the greatest effect in predicting the risk of death during follow-up. Each 20-gram (about 2/3 of an ounce) increase in legume intake per day predicted a significant 8 percent decrease in risk of mortality during follow-up. To put this result in context, one serving (1/2 cup of dry beans) of pinto beans comprises 35 grams. Thus, cohort members who ate one serving of pinto beans would reduce their risk of mortality by 14 percent. Eat more beans and live longer
What are pulses?
According to the World Health Organization, pulses include the subset of legumes that humans consume as dry beans, peas, and lentils and not fresh counterparts. Pulses have many positive attributes related to healthy nutrition, including high levels of fiber, protein, micronutrients (folate, selenium, iron, zinc), and vitamins (niacin, thiamin, riboflavin). While pulses are relatively high in carbohydrate, their glycemic index values are relatively low, especially for cooked, dried beans compared to canned beans. Because pulse plants fix nitrogen from the atmosphere and don’t need nitrogen fertilization, their ecological footprint is lower than many other food crops. Pulses are rich in the amino acid, leucine, which is relative low in cereal grains. Thus, combining pulses and whole cereal grains in the same meal (such as black beans and brown rice) provides a more complete source of high-quality protein. Randomized controlled trials and meta-analyses suggest that pulses may confer protective effects for cancer, cardiovascular disease, type 2 diabetes, and weight management. The USDA recommends that adults eat 2.5-3.5 cups of pulses daily as part of a healthy diet, yet most Americans fall short of this goal.
Legumes and cardiometabolic health
A recent systematic review and meta-analysis of studies related to legume consumption and metabolic health produced mixed results. Overall, little or no evidence suggests that legume consumption, whether soy products or not, leads to negative results. Mixed results may have arisen in part due to different methodologies. However, this review identified the strongest evidence for positive health effects of eating legumes, including significant and clinically meaningful reductions in blood LDL-cholesterol concentrations. In addition, higher intake to legumes predicted significant 14 percent lower risk of cardiovascular disease and 9 percent lower risk of coronary heart disease during follow-up. Higher intakes of non-soy legumes predicted lower risk of type 2 diabetes. Consistent with the last finding, higher consumption of pulses predicted better markers of blood sugar metabolism, including lower blood glucose, insulin, and HbA1c. Overall, evidence supports eating more legumes as part of a healthy diet with reduced risks of major chronic diseases
Legumes have a smaller environmental footprint
A recent review showed that increased legume consumption by humans (as opposed to livestock) might also help mitigate the potentially disastrous effects of climate change. First, unlike corn, wheat, and other cereal grains, legume can fix atmospheric nitrogen into biologically available forms. Aside from that which is harvested, the nitrogen fixed by a crop of legumes stays in the soil, reducing the need for nitrogen fertilization for a subsequent crop of, say, corn. About 30-50 percent of nitrogen added as fertilizer ends up running off a farmer’s field and polluting streams or polluting groundwater. Second, the wider cultivation of drought-tolerant legumes by low-income farmers could help sustain them and reduce their incentive to move to a city to find food and work. The rub these days seems to be insufficient effort on the part of universities, private industry, and non-governmental organizations to develop and promote more productive varieties of legumes that can be grown just as profitably as cereal grains. A recent perspective noted that, “increased public perception of the health and well-being advantages of a grain legume-rich diet may be an important driver of cultural change in considering grain legumes as key to food security.”
Legumes and blood sugar
A recent narrative review of 18 studies used data from participants with or without diabetes. Of five studies that included participants with diabetes, three studies reported significantly reduced levels of fasting blood sugar in response to legume dietary supplementation. However, the quality of the evidence was very low. Legume supplementation did not produce significant reductions in diabetes-related metabolic factors for participants without diabetes. This review provides mild support for persons with diabetes eating legumes to help manage their blood sugar.
Legumes and high blood pressure
Legumes contain compounds, including fiber, bioactive peptides, and flavonoid polyphenols, that are linked to lower levels of blood pressure. Researchers used data for 7,522 participants in the UK with an average age of 58 years in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk Cohort to test the idea that higher intake of legumes might reduce risk of developing hypertension (high blood pressure). Hypertension was defined as systolic and/or diastolic blood pressure over 140 or 80 mm Hg. After adjusting for confounding factors, participants who ate 56-70 grams per day of cooked legumes per day had a significant 43 percent lower risk of developing hypertension over an average follow-up of 3.7 years. In addition, men and women with a very low levels of legume intake (3.2 and 2.8 grams per day of cooked legumes, respectively) had significant 37 and 58 percent higher risks, respectively, of developing hypertension. Thus, women responded more to low and high intakes of legumes than men, perhaps because men on average ate 29 percent more legumes than women. The average UK resident consumes about 27 grams of legumes per day. Thus, doubling legume intake would bring the average UK resident’s legume consumption close to the level found to be most protective against developing hypertension.
Given the multiple health and environmental benefits of eating more legumes, why not eat more of them? You can grow beans in your garden, make tasty lentil soup, and enjoy pinto or black beans in burritos. Why not start now?