What are complementary proteins and what are specific food examples?

What Are Complete Proteins?

First off, amino acids (AAs) are the building blocks of protein. There are nine essential and 11 non-essential amino acids; essential AAs must be obtained from food sources while non-essential AAs can be made in the body. So when it comes to complete proteins, the food source contains all nine of the essential amino acids. Complete proteins are mostly found in animal sources and their byproducts, including meat, poultry, eggs, milk, cheese, and yogurt, though can also be found in a few plant-based sources. Incomplete proteins, on the other hand, do not contain all nine essential amino acids. However, pairing certain plants with limiting amino acids with another plant with different limiting AA can equate to a complete protein. Recognized as complementary proteins, a combination of nuts and seeds, legumes, grains, or some veggies together can produce a complete protein.

Complete Protein Foods

1. Soy

Soy is perhaps one of the most notorious plant-based foods filling the diets of vegetarians and vegans. Despite the nutritional differences between tofu and tempeh, each are esteemed contenders in the plant-based protein game. Edamame is also considered a complete protein, delivering nine grams of protein per half cup. Enjoy edamame as snack, mixed into Asian-inspired cuisine, or in this bistroMD’s edamole recipe. And for those with a dairy allergy or lactose intolerance, soymilk is a notable alternative to traditional cow’s milk.

2. Quinoa

Supplying eight grams of protein per one cup serving, quinoa is not only considered a complete protein, but is also full of fiber, iron, and magnesium. Though quinoa is mostly used as a rice substitute, it also complements a number of flavorful recipes.

3. Buckwheat

While buckwheat may not contain the same volume of protein as quinoa, it still is a valued complete protein. But contrary to its name, buckwheat is not kin to wheat or even a grain at all, and is actually a type of seed. Buckwheat can be enjoyed for breakfast, lunch, and dinner, including in these eight recipe ideas. 

4. Pumpkin Seeds

Along with supplying nine grams of protein per ¼ cup, fall’s favorite seed is considered a complete protein. Aside from the protein of pumpkin seeds, they are rich in healthy fats and supply advantageous fiber for digestive and heart health. Find the health benefits pumpkin seeds are shown to provide and nutritious recipe ideas here.

5. Rice and Beans

Rice and beans may just be one of the the most budget-friendly complete protein duos. Along with packing protein, the combo is also a significant source of fiber. And considering the wide varieties and versatility of each, the flavor pairings are endless, including this vegetarian taco bowl. 

6. Peanut Butter Sandwich

Considering peanuts are a legume, smearing natural peanut butter on top of whole-grain bread produces complete protein. But aside from that childhood classic, top whole grain toast with PB and banana chunks, apple slices, fresh blueberries, cinnamon, and other favorite naturally-sweetened garnishes for a quick breakfast or snack!

7. Noodle Stir-Fry with Peanuts

Though the childhood classic is sometimes hard to bargain with, peanut butter is not confined to bread… As it enriches the flavor of noodles in this spicy Thai recipe! But in addition to the enticing essence of the dish, the pairing of noodles and peanut butter equals a complete protein.

8. Hummus and Whole Grain Pitas

Hummus is a noteworthy protein source thanks to its use of chickpeas, also known as garbanzo beans. Though chickpeas offer plant protein, they are considered incomplete and need the assistance of a whole grain, which can be “completed” by pairing hummus and whole grain pita slices. 

9. Fried Rice with Peas

Though they tend to be overlooked, peas are a high protein vegetable offering seven grams of protein per one ounce. The podded veggie is rich in B vitamins as well as vitamins A and C, thiamin, and iron. Along with throwing peas in soups and casseroles, their inclusion in fried rice produces a complete protein.

10. Barley and Lentil Soup

Lentils are a part of the legume family and come in three main varieties, including brown, green, and red. Along with supplying nine grams of protein per ½ cup, lentils are an excellent source of fiber, folate, and iron. Like peas, lentils can complement grains and meals to create a complete protein, and comprises this barley lentil soup recipe.

While consuming the combos together is beneficial and boosts the volume of the meal plate, nutrition experts suggest consuming complementary proteins at the same time is not required. What matters most is embracing a well-balanced diet, as protein needs can be met by consuming varied sources throughout the day.

I am currently training for my second marathon in my adult life, and while the aches and pains feel the same as last year, and as the mileage starts to creep up it feels like deja vu- one minor detail has changed: this year I am running the marathon as a vegetarian.

Vegetarian endurance athletes have become quite a trend in the last couple of years. Some noteworthy endurance athletes include Brendon Brazier (vegan ironman), Rich Roll (vegan ultra ironman), Robert Cheeke (vegan body builder), and Michael Arnstein (fruitarian ultra runner); just to name a few.

Giving up meat during this marathon training means I will be missing out on complete proteins and key amino acids from my diet. These amino acids are also called limiting amino acids and they are: lysine, threonine, methionine, and tryptophan. Limiting amino acids are found in the shortest supply from incomplete proteins. Incomplete proteins are those found in plant food sources and geletin.

The most frequently asked question I get asked when becoming a vegetarian involved getting enough protein. While I do not eat meat, fish, or dairy (except for yogurt) I get plenty of protein in my diet by using protein complementation.

Protein complementation is the most efficient way to get all 9 amino acids into a vegetarian’s diet. Protein complementation is when you combine two vegetable proteins (legumes and grains for an example) to get all 9 amino acids that are essential for your body. The breakdown of protein complementation goes like this:

By combining vegetarian protein sources you can ensure that you are getting all 9 amino acids. Protein complementation does not have to be done at the same meal. If you ate beans for lunch and then had some raw almonds for a snack later, you would be adding the methionine that you had missed out on during lunch.

A vegetarian diet, if planned correctly, can provide you with all of the vitamins, minerals, and amino acids the body needs.

And get access to immersive learning experiences, collaboration, and networking with the greatest minds in nutrition.

If you're a vegan, or strict vegetarian, you may want to pay closer attention to the types of protein sources you consume because most plant-based foods are incomplete proteins.

Being incomplete doesn't mean plant-based foods are low in protein. You can get plenty of protein from plants, but almost every plant-based food is low in one or more essential amino acids that your body needs to thrive. How much of a problem is this and what can a vegan do?

It may sound bad, but as long as you eat a variety of protein sources every day you'll be just fine. The combination of different protein sources will ultimately ensure you get an ample supply of all the amino acids every day.

Amino acids are the building blocks of protein. Your body needs them to make the protein structures that build and maintain the tissues in your body.

There are many different amino acids; they all have similar structures but are differentiated by their side chains. All proteins, no matter what food they come from, are made up of amino acids. But the number and order of the amino acids that make up a cow's rump or a navy bean are different from the ones that make up your body parts.

When you eat round steak or baked beans (or anything that contains any protein at all, even a tiny amount), your digestive system breaks it down into amino acids that are absorbed into your bloodstream. From there, the amino acids are used to build the proteins that make up your muscles, organs and lots of other tissues.

Not all amino acids are essential. Your body can make many amino acids from the leftover bits of old amino acids and a few other raw materials found in the body, but there are some amino acids that the human body can't manufacture. These amino acids are called the essential amino acids because you have to consume them.

These are the essential amino acids:

• Histidine
• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine

Animal proteins all contain every single one of these essential amino acids, so they're called complete proteins. If you're an ovo-lacto-vegetarian (you eat eggs and dairy products), you can get complete proteins from those foods.

Plant proteins are a little different. Each plant that you eat has a different amino acid profile. For example, grains and cereals are extremely low in lysine. So low that they can't even be considered a source of lysine. If you only eat grains and cereals, you won't get enough lysine, and that's bad.

However, legumes, such as peanuts, peas, dry beans, and lentils, contain a lot of lysine. On the flip side, legumes aren't good sources of tryptophan, methionine, and cystine, but those amino acids are found in grains and cereals. As long as you eat some grains and some legumes, you'll get some of each essential amino acid.

Grains and legumes are called complementary proteins because when you combine them, you get all of the essential amino acids. Nuts and seeds are also complementary to legumes because they contain tryptophan, methionine, and cystine.

You don't need to eat complementary proteins together at every meal. As long as you get a variety of proteins throughout the day, you'll get ample amounts of each amino acid. But if you're interested, here are some ways to combine your complementary proteins.

• Bean soup and crackers
• Black beans and rice
• Pasta and peas
• Whole wheat bread and peanut butter

• Hummus (chickpeas and tahini)
• Lentils and almonds
• Roasted nuts, seeds, and peanuts

Soy is one plant protein that contains all the essential amino acids. It's also a good source of healthy fats and phytochemicals (plant chemicals that may be good for you). It's usually served as tempeh or tofu, and soy milk is a popular replacement for milk. Edamame is another easy source of soy protein.

Amaranth, quinoa, hemp seed, and chia are also complete proteins, so adding any of these foods, along with combining your other protein sources, will help you get all your essential amino acids met every day.

Thanks for your feedback!

What are your concerns?

Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. Hoffman JR, Falvo MJ. Protein - which is best?. J Sports Sci Med. 2004;3(3):118-30.

2. Tessari P, Lante A, Mosca G. Essential amino acids: Master regulators of nutrition and environmental footprint?. Sci Rep. 2016;6:26074. doi:10.1038/srep26074

3. Marsh KA, Munn EA, Baines SK. Protein and vegetarian diets. Med J Aust. 2013;199(4 Suppl):S7-S10.

• Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Sixth Edition. Wadsworth Publishing Company, 2013.

• Smolin LA, Grosvenor, MB. Nutrition: Science and Applications. Third Edition. Wiley Publishing Company, 2013.