The Pros and Cons of Legumes as a Protein Source

Legumes are an excellent protein source

Whether for health, ethical, or environmental reasons, more people are eating more plant-based protein sources. One reason you might want to do this is for health and longevity. Is there evidence to support this? A study discussed on found consuming larger quantities of plant-based protein reduced the risk of death by 16%. Plants may contain substantial amounts of protein, although not all sources contain a full array of the essential amino acids your body needs but can’t make. However, if you eat a variety of plant-based protein sources, you’ll get the full array of essential amino acids.

One source of plant-based protein that many vegetarians and vegans depend on is legumes, examples of which include beans, lentils, peas, peanuts, alfalfa, clover, and soybeans. Legumes have become more popular these days due to the popularity of plant-based foods. Who doesn’t enjoy lentil soup, black beans, or hummus, a spread made from pureed chickpeas?

First, let’s look at some of the upsides of legumes as a source of protein. Then, we’ll see if there are any downsides.

The Upsides of Legumes as a Protein Source

One of the biggest pros of eating more legumes for protein is they’re a nutritional powerhouse. Along with protein, you get B-vitamins and minerals such as iron, calcium, potassium, zinc, and phosphorus. Unlike meat and dairy protein sources, legumes are rich in fiber. The combination of protein and fiber is a powerful duo for curbing hunger too. In fact, a cup of cooked beans contains almost half the day’s recommended daily intake of fiber. Research shows most people don’t get enough dietary fiber for optimal health.

Numerous studies also link diets rich in legumes with a lower risk of cardiovascular disease. A 2017  analysis of six studies involving over 21,000 subjects found those who consumed more legumes had a lower risk of dying of all causes. Plus, eating a diet rich in legumes can lower LDL-cholesterol due to their high fiber content.

Also, legumes are blood-sugar friendly due to their high fiber content. A study carried out by researchers at the University of Toronto showed that a diet rich in beans, lentils, and chickpeas, improve blood sugar control, triglycerides and lower blood pressure in type 2 diabetics. These benefits may help people with diabetes lower their risk for the number one cause of death in people with diabetes, cardiovascular disease.

As if you need another reason to eat beans and lentils, the fiber in legumes is also beneficial for your gut microbiome. The trillions of friendly bacteria that live in your gut and help keep it in balance thrive on soluble fiber in beans and lentils. Plus, many legumes are a rich source of antioxidants. For example, red beans, kidney beans, black beans, and pinto beans contain more antioxidants than many fruits and vegetables.

If you’ve ever struggled to lose weight, you know it’s not always easy. Adding more legumes to your diet may give you an edge. The combination of protein and fiber boosts satiety and makes it easier to shed extra pounds of body fat. A meta-analysis of 21 studies looking at the effect legumes have on bodyweight shows consuming these foods modestly boosts weight loss even in the absence of calorie restriction.

Cons of Legumes as a Protein Source

There are a few downsides to legumes as a sole protein source. As mentioned, legumes are deficient in one of the essential amino acids called methionine. However, whole grains are an abundant source of this amino acid. As long as you’re getting methionine from other sources, such as whole grains, you don’t need to get them from legumes. However, eating legumes alone wouldn’t supply a complete source of all the essential amino acids.

The protein in legumes is also a bit less digestible than the protein in meat and dairy. About 80% of the protein you get from legumes your body absorbs while you absorb 90% from meat and dairy. However, you absorb enough protein from legumes to make it a viable source of protein, especially for people who eat a plant-based diet.

Legumes also contain phytic acid, an antioxidant that reduces the absorption of some minerals, including calcium, zinc, and iron. This is less of a problem for people who include non-plant-based sources of these minerals in their diet. If legumes are your main source of protein, you do have to worry about the potential of mineral deficiencies. That’s why it’s a good idea to eat a varied diet.

Some people also experience gas and bloating when they eat a diet rich in legumes. These symptoms are most pronounced when you first add these foods to your diet or when you consume too much too soon. It takes time for your gut to adapt to a diet high in fiber. When you cook dried beans or lentils, let them soak overnight and discard the water before cooking. Doing this will reduce the amount of indigestible carbohydrates responsible for the gas and bloating. Lentils are easier to digest than beans and black beans are usually the easiest bean to digest.

The Bottom Line

Legumes are nutritious and a good source of protein, although they lack the essential amino acid methionine. That shouldn’t be a problem if you’re eating a varied diet. For example, whole grains are a good source of methionine. However, you don’t absorb the protein from legumes as efficiently as from animal-based foods but there are still upsides to getting some of your protein from beans and lentils. The bonus is you get fiber and antioxidants when you add more legumes to your diet. That’s something most of us can use more of. Plus, beans and lentils are inexpensive and versatile. Enjoy adding them to your diet.



  • org. “Consumption of Plant-Based Proteins Could Add Years to Your Life”
  • gov. “Healthy food trends – beans and legumes”
  • Arch Intern Med. 2001 Nov 26;161(21):2573-8. doi: 10.1001/archinte.161.21.2573.
  • Biomed Res Int. 2017; 2017: 8450618.Published online 2017 Nov 2. doi: 10.1155/2017/8450618.
  • com. “Beans May Improve Blood Glucose Control”
  • Arch Intern Med. 2012;172(21):1653-1660. doi:10.1001/2013.jamainternmed.70
  • com. “Antioxidant Superstars: Vegetables and Beans”
  • org. “Legumes May Aid Glycemic Control, Cut Lipids”
  • Am J Clin Nutr, 103 (5) (2016), pp. 1213-1223.
  • com. “Legumes: Good or Bad?”


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The Wonderful (And Healthy) World of Beans and Legumes

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A New Reason to Add Beans and Lentils to Your Diet

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Nine Amazing Health Benefits of Kidney Beans

Get Fuller & Curb Those Cravings with Plant-Based Protein

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