Keeping track of all of the important nutritional information and advice can be challenging, particularly if you don’t have a background in health and nutrition.
It can be hard enough to remember all of the important nutrients you should be getting, let alone try to keep straight how much of each nutrient you need and how many calories you should be eating.
Even most people who don’t have much background or education in terms of nutrition have a general understanding that protein is an important macronutrient to be getting in your diet, but the world of protein can be downright confusing.
You listen to your health, nutrition, and fitness expert speak about the importance of getting “complete“ proteins in your diet, but what is a complete protein? What are incomplete proteins? What are some complete protein examples?
In this article, we will answer your question, what is a complete protein, and discuss everything you need to know about them, including the benefits and examples of complete protein foods.
We will cover:
- What Is a Complete Protein?
- Complete Protein Examples
Let’s get started!
What Is a Complete Protein?
Before we can really explain what a complete protein is, it’s helpful to have a quick primer on proteins in general.
Protein is one of the three macronutrients, alongside carbohydrates and fats.
Protein is formed by molecules known as amino acids, which are linked together into different configurations using peptide bonds to form all different types of proteins.
There are 20 different amino acids used by the body, and every single food that you eat that contains protein contains some or all of these same 20 amino acids in varying amounts.
Much like the 26 letters of the alphabet, the 20 different amino acids can be strung together in different patterns and in different quantities and arrangements to form the many thousands of different biological proteins.
For example, whether you eat beef, eggs, chicken, yogurt, or soybeans, you’ll be getting protein, and all of these protein-containing foods will be broken down in the body during the digestive process into their constituent amino acids.
Even though the sources of all of these proteins are different, they all contain some or all of the same 20 amino acids; there are no novel amino acids in random foods that are different from the normal 20.
Of the 20 amino acids, nine are considered essential amino acids, which means that the body requires these amino acids but cannot produce them endogenously.
They must be consumed in the diet. The other 11 amino acids are typically considered nonessential amino acids because the body can manufacture them by reassembling other amino acids and molecules as necessary.
According to the Cleveland Clinic, the essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Note that some amino acids are considered “conditional amino acids “ in that under certain conditions, such as pregnancy, certain disease states, and stress, the body cannot manufacture these amino acids in sufficient quantities, so they become essential in that you have to consume more of them in your diet to supplement what your body is unable to make on its own.
Although different sources cite slightly different lists, conditional amino acids typically include arginine, cysteine, glutamine, tyrosine, glycine, proline, and serine.
However, in the discussion of complete proteins, the nine essential amino acids that are always considered essential are the ones that come into play.
Transitioning our discussion now to complete proteins, a complete protein is one that contains all nine essential amino acids. It may contain any or all of the remaining nonessential amino acids as well, but in order to be considered a complete protein, it must contain all of the essential amino acids.
This is what differentiates a complete vs. an incomplete protein.
Whereas complete protein foods provide all nine essential amino acids, incomplete protein foods are lacking in at least one of the nine essential amino acids.
An incomplete protein food may provide eight of the essential amino acids and all of the other non-essential amino acids, but as long as at least one essential amino acid is absent from the food in a sufficient quantity, the food is considered an incomplete protein food.
Complete Protein Examples
Most animal-based proteins are complete protein foods. This makes sense logically because when we eat meat, poultry, or fish, we are consuming animal flesh, or more specifically, muscle tissue.
Like the human body, the bodies of animals require the same proteins to form the structural components of the very muscle tissues and connective tissues that we are consuming.
In order for the organism’s body to make that tissue, all of the amino acids were necessary. Thus there is a complete protein with all of the essential amino acid building blocks (and usually all of the nonessential ones, too).
Examples of complete protein sources include the following:
- Meat: Beef, pork, bison,
- Poultry: Turkey, chicken, duck, quail
- Fish and seafood
- Dairy: Milk, cheese, yogurt, cottage cheese
- Whole soy: Soybeans, tofu, edamame, tempeh
- Quinoa and buckwheat
- Hemp seeds
- Nutritional yeast
Unfortunately, most plant-based protein sources are incomplete proteins, lacking at least one of the essential amino acids.
Soy is a notable exception, which makes soy foods such as tofu, tempeh, edamame, and soybeans particularly beneficial for vegans, vegetarians, and those following a plant-based diet.
Examples of incomplete protein foods include legumes such as beans, peas, lentils, chickpeas, nuts, seeds, vegetables, and most whole grains.
Notable exceptions when it comes to complete protein foods that are whole grains are buckwheat and quinoa.
Quinoa is technically a seed, although it is consumed like a cereal grain. It is considered a complete protein source, and although it certainly contains much more protein than most whole grains, it should be noted that you won’t get as much protein in a serving of quinoa as you would with a serving of any type of meat, dairy, eggs, or soy.
The good news is that you can combine incomplete protein sources to form complete protein meals.
In other words, by using what is referred to as a complementary pairing, you can eat two or more different sources of incomplete protein to provide your body with a resultant complete protein food, which would include all of the nine essential amino acids.
The important thing to keep in mind when combining incomplete proteins to form complete proteins is that you have to choose foods that provide a different array of essential amino acids so that you indeed are consuming some of all of the nine essential amino acids.
In other words, most legumes provide a similar amino acid profile.
If you were to eat two different legumes in the same meal, such as green peas and lentils, without consuming any other protein source, you will still not be getting a complete protein food.
This is because both the peas and lentils will be lacking the same amino acids, so you’ll just be getting more of the ones already found in the foods rather than making up for the ones that are missing.
Instead, you can pair your legumes with a whole grain, such as brown rice, barley, whole wheat couscous, freekeh, or amaranth, or add vegetables like spinach, broccoli, or kale. You could also add pine nuts, flax seeds, walnuts, or some other type of nuts or seeds to round out your amino acid profile.
We used to think that the timing mattered when eating complete proteins and that you had to pair your incomplete proteins to form a complete protein meal in one sitting rather than spread out throughout the course of the day.
However, according to the National Institute of Health, the temporal component is more long-term, and as long as you are getting all of the essential amino acids over the course of the 24-hour day, the body treats the resource pool of amino acids as a complete protein.
Therefore, if you eat whole grains with nut butter for breakfast, and hummus for lunch, even though these may not be complete proteins foods on their own, and they are not eaten at the same time, the body will still have all of the resources it needs and will treat the resultant outcome like a complete protein.
Overall, it’s important to eat complete protein foods or form complete proteins with complementary incomplete proteins in order to provide your body with all of the amino acids it needs for muscle repair and growth, and everyday functions.
Animal-based foods, such as meat, poultry, dairy, and eggs, are the best sources of complete protein, but there are also a few complete proteins for vegans, including soy, nutritional yeast, spirulina, and quinoa.
If you are looking to get more protein into your diet, we have some great high-protein lunches for you to try.