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Nutrition

From Soybeans to Chickpeas to Lentils: Understanding the Terminology of Legumes and Pulses

July 28, 2023

by Alison M. Duncan, PhD, RD, FDC

From Soybeans to Chickpeas to Lentils: Understanding the Terminology of Legumes and Pulses

Most people are aware that plant foods like soybeans, kidney beans, chickpeas and lentils are nutritious and contribute to a healthy diet. What is less understood is the categorization of these plant foods as legumes and/or pulses. It can be confusing that a soybean is a legume but not a pulse, but this confusion is easily avoided by understanding what legumes and pulses are.

Legumes are the broadest category at the top of the organizational chart of legumes and pulses (Figure 1). Legumes are part of the Fabaceae or Leguminosae botanical family and have the unique feature that their seeds grow in pods.1 This feature is easily recognizable when you consider that legumes include soybeans, peanuts, fresh green beans, fresh green peas, dry beans, chickpeas, lentils, and dry peas. The seeds of these plants grow in pods and all of them are legumes. Legumes are also distinct in their ability to convert nitrogen from the air into a form of nitrogen that they can use for their own growth. This is because the roots of the legumes interact with a bacteria called rhizobia that convert nitrogen from the air into ammonia which then is converted into other nitrogen compounds (nitrates and nitrites) that the legumes can use to support their growth.2 It is notable that since legumes can use nitrogen from the air to support their own growth, they do not need as much synthetic nitrogen fertilizers. Another benefit is that legumes can provide that nitrogen to the soil which improves the health of the soil. In short, this process of nitrogen fixation means that legumes contribute to sustainable agriculture.3 Legumes are organized into 3 major categories: oilseed legumes, fresh legumes, and pulses.4

  1. Oilseed legumes are a type of legume that have oil in their seeds and include soybeans and peanuts.4 Oil can be efficiently extracted from oilseed legumes which is why we see soybean oil and peanut oil used in our food system.
  • Soybeans are an oilseed legume that have been widely studied for their health benefits. Soybeans are sometimes called soy or soya or even soya beans.
  1. Fresh legumes are a type of legume that we eat in their fresh form.4 They include fresh green beans and fresh green peas. These both grow in pods and that means they are legumes.
  1. Pulses are the largest category of legumes and include dry beans, chickpeas, lentils and dry peas (4). Pulses are a distinct type of legume because they have dry seeds which means that there is very little oil in their seeds. This explains why we don’t see oils made from dry beans, chickpeas, lentils, or dry peas. There are many varieties of each pulse; for example, dry beans (or just beans) can be navy, red kidney, white kidney, pinto, adzuki, or cranberry beans, among many others.4 Pulses, like other legumes, have garnered a lot of attention for their nutrient content, health benefits, and culinary versatility.

These multiple legume categorizations can cause confusion, but better understanding the key differences can bring clarity. Remember, soybeans and pulses are all legumes, their seeds grow in pods, and they can fixate nitrogen. There are three types of legumes; legumes that have a lot of oil in their seeds (oilseed legumes), legumes that are fresh (fresh legumes), and legumes that do not have a lot of oil in their seeds (pulses). In the end, you can’t go wrong by including any and all legumes into your diet.

Figure 1

References

  1. Hughes J, Pearson E, Grafenauer S. Legumes – A comprehensive exploration of global food-based dietary guidelines and consumption. Nutrients. 2022;14:3080.
  2. Stagnari F, Maggio A, Galieni A, Pisante M. Multiple benefits of legumes for agriculture sustainability: an overview. Chem Biol Technol Agric. 2017;4:2.
  3. Lindström K, Mousavi. SA. Effectiveness of nitrogen fixation in rhizobia. Review Microb Biotechnol. 2020;13:1314-35.
  4. Pulse Canada. What is a pulse? https://pulsecanada.com/pulse/what-is-a-pulse. Accessed June 26, 2023.

This blog is sponsored by SNI Global and U.S. Soy.