Power of Legumes: Health Benefits and Nutritional Value

Nourishing Hearts, Preventing Cancer, and Sustaining the Planet: Legumes’ Triple Impact on Health, as We Unearth the Secrets of this Versatile Plant-Based Wonder.

The Fabaceae or Leguminosae family, also called legumes, peas, or beans, is the third most extensive group of blossoming plants, with a staggering 20,000 plus species. These legumes are widely consumed in various diets globally due to their high nutritional value. They are a cost-effective source of protein, vitamins, complex carbohydrates, and fiber.

The terms “legumes,” “pulses,” and “beans” are commonly used interchangeably, but they each have specific and distinct definitions. A legume encompasses all plants from the Fabaceae family, including their leaves, stems, and pods. On the other hand, a pulse is an edible seed found within a legume plant. This category includes beans, lentils, and peas. For example, while a pea pod is considered a legume, the actual pea inside the pod is the pulse. While the entire legume plant is commonly used in farming practices such as cover crops, livestock feed, and fertilizers, the seeds or pulses are typically consumed on our plates. Beans, in various forms such as kidney, black, pinto, navy, and chickpeas, are just one type of pulse.

According to the U.S. Dietary Guidelines, legumes should be a prominent part of one’s diet, with a recommended intake of approximately 3 cups per week. The DASH Eating Plan, created by the National Heart, Lung, and Blood Institute, also emphasizes legumes, suggesting 4-5 half-cup servings per week. In 2016, the United Nations Food and Agriculture Organization (FAO) designated the International Year of Pulses, highlighting the vital role that pulses play in promoting food production and providing nutritional diversity to combat hunger and malnutrition.

The Harvard School of Public Health identifies the following as crucial nutrients for maintaining a healthy diet:

• Protein
• Folate
• Fiber
• Iron
• Phosphorus
• Polyunsaturated and monounsaturated fatty acids

The Impact of Legumes on Health

Cardiovascular disease

cardiovascular disease encompasses a range of conditions that impact the heart and the blood vessels. Legumes contain elements such as fiber, folate, and phytochemicals that can positively impact heart health. Legumes have low saturated fat and sodium in their natural, unprocessed state. The fiber in legumes can specifically aid in reducing blood cholesterol levels without the need for weight loss.

Legumes possess numerous elements that, when consumed as a component of a well-rounded diet rich in plants, can potentially aid in the prevention of multiple chronic illnesses:

It also has the potential to reduce abrupt increases in blood sugar levels, both of which pose risks for cardiovascular disease.  A study analyzing various observational studies revealed that consuming legumes approximately four times a week was linked to a 14% decrease in the risk of coronary artery disease. Similarly, another study of 11 clinical trials found that the intake of legumes reduced fasting total cholesterol and LDL cholesterol by 7% and 6%, respectively, while also increasing HDL cholesterol by 2.6%. The authors suggested that this effect could be attributed to soluble fiber, oligosaccharides, and phytochemicals in legumes.

Additionally, a cohort study examining the relationship between legume consumption and heart health found that individuals who consumed legumes at least four times a week were associated with a 22% reduced risk of heart disease and an 11% reduced risk of cardiovascular diseases (such as stroke and heart attack) compared to those who consumed legumes less than once a week. Moreover, a meta-analysis of 36 randomized controlled trials involving 1,803 participants revealed that substituting red meat with plant-based proteins like legumes can reduce risk factors for cardiovascular disease, such as blood cholesterol, triglycerides, and blood pressure.

Cancer

Studies on animals and cells suggest that legumes, with their high fiber, phytochemical, and mineral content, may possess properties that can help prevent cancer. For instance, certain nutrients found in legumes, like zinc, have been linked to a more robust immune system and reduced oxidative stress on cells. Additionally, selenium and phytic acid have been shown to hinder tumor growth in mice. However, the evidence from human studies on the connection between legumes and cancer prevention is not as definitive.

In their report titled “Food, Nutrition, and Cancer Prevention: A Global View,” the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research advocate for including pulses in most meals as a key public health objective. This is to help achieve their recommended daily intake of at least 30 grams of dietary fiber, as a diet high in fiber has been linked to a lower risk of certain cancers, including colorectal cancer. The WCRF specifically states that foods rich in dietary fiber can reduce the likelihood of developing colorectal cancer, indicating that other elements in high-fiber foods could impact cancer development. One element worth noting is the generation of butyrate, a short-chain fatty acid that promotes digestive well-being.

Gastrointestinal wellness

Legumes are a rich source of fiber, resistant starches and non-digestible carbohydrates such as oligosaccharides. Resistant Starch, also known as slowly digestible starch, is not broken down in the digestive system and instead travels to the colon, where it functions similarly to fiber. It helps to promote the production of bulky stool and acts as a prebiotic for good bacteria, such as Bifidobacteria. As these bacteria ferment-resistant starches and oligosaccharides, they produce gas, leading to bloating and abdominal cramping in some individuals.

To alleviate this side effect, it is recommended to soak dried beans for at least three hours before cooking. However, in the long term, these beneficial bacteria aid in maintaining regular bowel function and may even lower the risk of cancer by reducing the presence of harmful compounds. During the fermentation process, the bacteria also produce a short-chain fatty acid called butyrate, which has been linked to the prevention of colorectal cancer.

Diabetes

Legumes are known for their low glycemic index, high fiber content, and inclusion of slow-digesting resistant starch, all of which have potential benefits in preventing diabetes. However, there is no clear answer yet on whether legumes can effectively prevent type 2 diabetes or lower blood glucose levels. The findings from various research studies have been inconsistent and inconclusive, with limited small-scale trials and large cohort studies failing to provide consistent evidence of their effectiveness.

A study following 35,988 older women in the U.S. who did not have diabetes initially found no significant correlation between the amount of beans consumed and the risk of developing diabetes after 6 years. Similarly, a different study of 64,277 middle-aged women in China without diabetes at the beginning discovered that those who consumed the most legumes (approximately 1/3 cup daily) had a 38% lower risk of type 2 diabetes after 4.5 years compared to those who consumed the least amount. It should be noted that the Chinese study included soybeans and peanuts in their definition of legumes, while the previous U.S. study did not.

Promoting Health for Both You and the Environment

Food production places a significant strain on our environment due to the impact of agriculture on climate change, deforestation, extinction of species, and reduction of freshwater resources. However, the effect on human health and the environment varies depending on the type of food. Generally, plant-based foods have lower greenhouse gas emissions and require less land and water than animal-based foods. As we strive towards healthy diets and sustainable food systems, legumes are expected to play a crucial role, particularly with a projected global population of 10 billion by 2050. The 2019 EAT-Lancet report, which proposes a “planetary health diet,” suggests including 50 grams of legumes (equivalent to ¼ cup) in the daily food intake.

Legumes possess various qualities that contribute to their sustainability as a crop. For instance, they emit significantly less greenhouse gases per area than other crops and can sequester carbon in the soil. Additionally, they have the ability to utilize nitrogen from the atmosphere, reducing the need for nitrogen fertilizers. This results in nitrogen-rich residues remaining in the soil after harvest, which benefits the subsequent crop. According to the FAO, legumes that are resistant to drought can be particularly advantageous in arid regions, where ensuring food security is often a challenge. Furthermore, they can aid in reducing food waste since pulses can be dried and stored for extended periods without compromising their nutritional value.

Summary

Legumes, despite their wide range of types, possess many shared advantages. They are affordable, environmentally friendly, and considered a low glycemic index food. Furthermore, they are a good source of protein and fiber, making them satisfying. Their texture is often described as “meaty”, allowing them to substitute for animal-based proteins in various dishes. Moreover, their mild taste makes them adaptable to complement other ingredients and can be easily paired with various seasonings.

Source:

Harvard T.Chen School of Public Health. Legumes and Pulses