“Are beans a good source of protein?” is a question I get a lot in bean classes and outreach events, and many people have asked me to write a post about protein in beans. So, here we go! I hope this is helpful, and I’m happy to take further questions.
My professor Henry Thompson and I recently wrote an article about what makes beans and other pulses (e.g., chickpeas, cowpeas like black-eyed peas, dry peas, and lentils) so incredible nutritionally.1 I’ve touched on this before, especially on the Bean Nutrition post I wrote, but I want to do more of a deep dive on protein here so that we can look into some common questions:
- How much protein is in beans?
- I’ve heard beans are an incomplete protein. What does that mean, and is it true?
- Do I need to eat beans and rice (or another grain) at the same time to get enough healthy protein?
- Are beans only an important source of protein for vegetarians?
Check out this video that my incredible husband helped me make, where I dive into bean protein.
How Much Protein Is in Beans?
Let’s start by establishing this: beans are rich in protein. Depending on factors such as the variety and growing conditions, pulses are about 16 to 30% protein.2,3 Some pulses, like lupin, are even higher in protein, estimated at up to 44% protein.4
A half-cup of cooked beans (or other pulses) is considered a serving size and contains slightly over 100 calories. In that amount, you’re getting about 7 grams of protein, although it can vary from a range of 5-9 grams, depending on the type of pulse.
To make some comparisons across beans and other foods – like grains and animal proteins – that are not biased by calories, let’s look at the nutrition breakdown in terms of 100-calorie portions. This way, we’re looking at how much nutrition is packed into the same amount of calories, giving us a sense of how nutrient-dense these foods are. We’ll start by comparing beans to grains, which are also an important source of protein around the globe, partially because of the sheer volume of grains that we consume. In fact, cereal grains are the main dietary source of plant proteins worldwide5 because, well, we eat a lot of grains. Although, it is notable that as globalization and economic growth are occurring, many are switching more towards animal proteins, with associated challenges for human and environmental health.5
The Protein Content of Beans Versus Cereal Grains
As you can see in the tables below, beans offer more protein than grains. The amount of course depends on the type of pulse and grain, but generally speaking, the protein content of pulses is at least double that of grains.1 Even compared to quinoa, which many of us think of as a good source of protein, beans are packing a lot more protein. You can see that in the protein row highlighted in blue in the table. I know, I also highlighted fiber (in green), but I couldn’t resist – the fact that pulses are about 2-3 times higher in fiber than even whole grains1 is simply too impressive to not point out!
This high protein content, being rich in micronutrients (i.e., vitamins and minerals) like folate, iron, and potassium, and the fact they are one of the best natural sources of dietary fiber, make beans and other pulses a very nutrient-dense food.
A few notes about the tables: the FDC ID number corresponds to the ID in FoodData Central,6 which is a great place to find nutrition information. MV means missing value (as in, there was no value in FoodData Central). Table modified from the information provided in our paper.1
Alright, you say, so beans have more protein than other grains. I already expected that. What about beans compared to other sources of protein, including animal proteins? Great question. Let’s check that out, also looking at 100-calorie portions to avoid biasing things by calories.
The Protein Content of Beans Versus Other Proteins
You can see below that boneless, skinless chicken breast cooked in no oil is higher in protein (let’s be real, though, how many people eat chicken like that and actually enjoy it?). But if you look overall, pulses are holding their own in terms of protein content, even when matched up against animal proteins. Plus, pulses contain very little fat – which is not always the case for these other protein foods – and they are packed with a lot of dietary fiber, which is critical to our health. And here’s the thing – in many developed countries, protein consumption is not a problem and we eat way more protein than we need, but we seriously under-consume fiber.1,7 So, thinking beyond only protein and also focusing on the other nutrition and dietary components in a food is something we should actively take into consideration.
Disclaimer: I am not in any way out to attack grains (especially whole grains, which are amazing) or other sources of protein! But you wanted to see a comparison of protein, so I’m showing that. I’m also just providing some food for thought – yes, protein is important, but so is considering the overall nutrition in a food, which extends far beyond a hyper-focus on protein that seems to be perpetuated in the media these days.
Are Beans an Incomplete Protein?
Honestly, I think this is the wrong question to be asking, but it’s still important to address because there is a lot of misinformation out there about the protein quality of beans. So let’s unpack this.
First of all, what does it mean to be a complete or incomplete protein? Proteins are made of amino acids [ringing any high school biology class bells? 😉]. There are 20 amino acids, of which 9 are considered “essential” or ‘indispensable.” Basically, this means that we have to get these 9 essential amino acids from food because our body cannot make them. The remaining amino acids can be made by our body, for instance by using the essential amino acids as building blocks, and are called “non essential amino acids.” Mind you, we still need them despite the name non esstential! It’s just that technically our body can make them, so we don’t have to get them from food. A complete protein provides adequate amounts of all 9 of the essential amino acids.
So, are beans a complete protein? No, technically they are not. They are relatively low in the sulfur-containing amino acids, methionine (which is an essential amino acid) and cysteine (which our body can make from methionine), and also sometimes tryptophan.7 If you have heard the term “limiting amino acids” before, that’s what this is referring to – the amino acids that are low in a food and prevent it from being considered a complete protein.
However, beans DO contain all 20 amino acids, they are simply relatively low in some amino acids, particularly methionine.8 Animal proteins are considered complete proteins because they are high in all of the essential amino acids. Again though, it’s important to consider more than just the amino acid profile of a food, and also think about things like: fiber, fat content, other vitamins and minerals, and is it a healthy, sustainable food?
On the other hand, beans are rich in another essential amino acid, lysine. Grains – like rice, millet, and others – however, are relatively low in lysine, but high in methionine, which is the main amino acid considered to be low in beans.4,9 So, eating beans and rice, wheat, or other grains together helps make sure we get all the amino acids we need, even if we do not eat animal proteins. This is the idea of protein complementation, which brings us to an important question and common point of misunderstanding:
Do I need to eat beans and rice (or another grain) at the same time to get enough healthy protein?
And the answer is… no. Eat a balanced, healthy diet throughout the day, and things will be fine.7,10,11 You do not have to eat beans and rice – or wheat, millet, or whatever other grain you are eating – in the same bite, or even the same meal. The idea is to make sure our bodies are getting the nutrition they need – whether that is amino acids or other nutrition – throughout the day, week, and ultimately our whole lives. You don’t have to eat beans and grains in the same meal to achieve this, just aim for overall balance.
Are Beans Only an Important Source of Protein for Vegetarians and Vegans?
No, definitely not. Beans and other pulses provide an important protein source for – I would argue – all of us! Beans are very nutrient-dense, helping ensure we get all the nutrition we need without over-consuming calories. They are also associated with a wide variety of human health benefits, including promoting gut health and helping prevent chronic diseases such as type 2 diabetes, heart disease, and cancer like colorectal cancer.12 Not to mention the myriad of environmental benefits they can provide, such as helping conserve water and land and reduce greenhouse gas emissions.13
Is protein important? Yes, of course. But a hyper-focus on protein (to the point we consume way more than we need), is short-sighted. It’s time we think beyond just numbers and amino acid profiles of one food at a time to consider the bigger picture:
- Are we enjoying a healthy, overall balanced diet that promotes human and public health?
- How does our diet impact environmental health and sustainability?
And can beans and other pulses help us do that? 100 percent.
References for Are Beans a Good Source of Protein?
- Didinger, Chelsea, and Henry J. Thompson. “Defining nutritional and functional niches of legumes: A call for clarity to distinguish a future role for pulses in the dietary guidelines for Americans.” Nutrients 13.4 (2021): 1100. (https://www.mdpi.com/2072-6643/13/4/1100)
- Azarpazhooh, Elham, and Jasim Ahmed. “Composition of Raw and Processed Dry Beans and Other Pulses.” Dry Beans and Pulses: Production, Processing, and Nutrition (2022): 129-157. (https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119776802.ch6)
- Messina, Virginia. “Nutritional and health benefits of dried beans.” The American journal of clinical nutrition 100.suppl_1 (2014): 437S-442S. (https://academic.oup.com/ajcn/article/100/suppl_1/437S/4576589)
- Lucas, M. Mercedes, et al. “The future of lupin as a protein crop in Europe.” Frontiers in plant science 6 (2015): 705. (https://www.frontiersin.org/articles/10.3389/fpls.2015.00705/full)
- Poutanen, Kaisa S., et al. “Grains–a major source of sustainable protein for health.” Nutrition reviews 80.6 (2022): 1648-1663. (https://academic.oup.com/nutritionreviews/article/80/6/1648/6422500)
- FoodData Central: https://fdc.nal.usda.gov/
- Katz, David L., et al. “Perspective: The public health case for modernizing the definition of protein quality.” Advances in Nutrition 10.5 (2019): 755-764. (https://www.sciencedirect.com/science/article/pii/S2161831322004276)
- Nosworthy, Matthew G., et al. “Impact of processing on the protein quality of pinto bean (Phaseolus vulgaris) and buckwheat (Fagopyrum esculentum Moench) flours and blends, as determined by in vitro and in vivo methodologies.” Journal of Agricultural and Food Chemistry 65.19 (2017): 3919-3925. (https://pubs.acs.org/doi/full/10.1021/acs.jafc.7b00697)
- Anitha, Seetha, Mahalingam Govindaraj, and Joanna Kane‐Potaka. “Balanced amino acid and higher micronutrients in millets complements legumes for improved human dietary nutrition.” Cereal Chemistry 97.1 (2020): 74-84. (https://onlinelibrary.wiley.com/doi/full/10.1002/cche.10227)
- Mariotti, François. “Plant protein, animal protein, and protein quality.” Vegetarian and plant-based diets in health and disease prevention. Academic Press, 2017. 621-642. (https://www.sciencedirect.com/science/article/pii/B9780128039687000356)
- Marinangeli, Christopher PF, et al. “Enhancing nutrition with pulses: defining a recommended serving size for adults.” Nutrition reviews 75.12 (2017): 990-1006. (https://academic.oup.com/nutritionreviews/article/75/12/990/4675268)
- Didinger, Chelsea, et al. “Nutrition and human health benefits of dry beans and other pulses.” Dry Beans and pulses: Production, processing, and Nutrition (2022): 481-504. (https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119776802.ch19)
- Foyer et al. 2016: Foyer, Christine H., et al. “Neglecting legumes has compromised human health and sustainable food production.” Nature plants 2.8 (2016): 1-10. (https://www.nature.com/articles/nplants2016112)
Very interesting article.
Thank you for commenting! Glad you found it interesting. I plan to create more posts like this is people find them helpful.
What a great article! Last week I was just talking about this and got confused about the incomplete part of bean protein. I ve got it all straightened out now. For seniors, protein is important to retain muscle mass. The doctors, dieticians and AARP emphasize the importance of protein for seniors. And fiber too, come to think of it. Beans are a healthy addition to our diets and I’m doing my best to encourage my friends to eat more beans! Your articles and recipes inspire me.
Thank you very much for the kind words, Jackie! I’m so glad you found this helpful and that I can provide some recipe inspiration as well. I love that you’re encouraging your friends to eat more beans – I do that, too. Go beans! 🙂
It’s great to see clarification from someone like you who is both educated and passionate about educating others in the benefits of beans. I’m vegetarian and this is very helpful. Ironically I love beans and rice together which is why I love Mexican cuisine so much 🙂
Glad you found this helpful! It was fun to write, and I think it’s an important message to share. And cheers to loving Mexican cuisine! I love Costa Rican gallo pinto, too.