When looking at a nutrition label, it might appear that protein is just protein, since that’s the only way it’s listed. But there is a difference between incomplete proteins and complete proteins.
Proteins are made up of amino acids, each of which can appear in food in varying amounts, or not at all. That can make it hard to know if you’re really getting the protein you need.
One way to simplify eating is to consume complete protein sources, which contain the essential amino acids in the necessary amounts.
Read more to learn the differences between complete and incomplete proteins, as well as a list of complete protein foods.
What is a complete protein?
There are a total of 20 amino acids that make up the body’s proteins, but only nine of them are considered essential. An essential amino acid is one that the body cannot produce on its own and therefore must be obtained from food.
A complete protein is one that has all nine essential amino acids in the necessary amounts. They include phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.
The easiest way to consume a complete protein is to choose animal sources such as meat, poultry, fish, eggs, and dairy.
These foods contain what is called high biological value protein, which refers to how efficiently the body can use a protein. Those that contain the most essential amino acids score the highest.
That doesn’t mean you can’t get all your amino acids on a vegetarian or vegan diet. For example, soy is a complete protein, and there are ways to combine other vegan foods to get everything you need.
By eating a variety of plant foods throughout the day, you can get all the essential amino acids.
complete protein foods
Below is a quick review of the quality and quantity of protein found in the different food groups.
animal proteins
Meat, poultry and seafood: These have the highest amounts of complete protein per serving of any whole food. This protein is well absorbed and used by the body.
- Beef (22g per 3oz. serviceground, 85 percent lean, roasted)
- Chicken (24g per 3oz. servicegrilled chicken breast)
- Turkey (26g per 3oz. servicegrilled chicken breast)
- Pig (23g per 3oz. serviceroast loin)
- Duck (23g per 3oz. servicegrilled chicken breast)
- Salmon (22g per 3oz. serviceCooked)
- Tilapia (23g per 3oz. filletCooked)
- Swordfish (20g per 3oz. serviceCooked)
- trout (23g per 3oz. serviceCooked)
- Shrimp (20g per 3oz. serviceCooked)
- Crab (16g per 3oz. servicesteamed)
- scallops (17g per 3oz. servicesteamed)
- tuna (22g per 3oz. serviceCanned)
- sardines (21g per 3oz. serviceCanned)
Eggs (6 grams each): While they don’t contain as much protein per serving as meat, poultry, or fish, eggs are among the highest in biological value.
milk proteins
Dairy: Cow’s milk has one of the highest amounts of protein per serving compared to other milks, and it is a complete protein with a high biological value.
Soy milk is comparable in amount of protein with 7-8g per cup and it is also a complete protein, but it has a lower biological value than cow’s milk.
Greek yogurt (17g per 6oz. service): Also a dairy source, Greek yogurt is so concentrated (compared to other yogurts) that it’s an excellent source of protein, perfect for breakfast or after a workout.
vegetable proteins
soy (22 g per cup, cooked): Soy is the only food in the plant kingdom that is considered a complete protein.
incomplete vegetable proteins
With the exception of soybeans, foods from the plant kingdom are considered incomplete sources of protein, as they are typically limited in one essential amino acid or another.
That’s where food matching is vital to ensure you’re getting all the essentials! Below is a list of some plant foods with their limiting content of essential amino acids and proteins.
Legumes: Legumes include beans, peas, and lentils. They have a high lysine content but a limited methionine content.
Seeds: Although they are rich in other amino acids, many seeds are limited in lysine.
Grain: Whole grains provide protein, carbohydrates, and fiber, but like seeds (and nuts), most are high in methionine and tend to be lower in lysine.
How to Combine Complementary Proteins
Conventional wisdom once held that complementary proteins should be combined at each meal.
But we now know that our bodies are smart enough to do it on their own as long as we eat complementary protein sources throughout the day (or even for 2-3 days!).
The classic vegan combination most of us are familiar with is rice and beans.
While neither is complete on its own, together they provide all nine essential amino acids. at the levels necessary to be considered complete, and more often than not tons of heart-healthy fiber.
But there are many other delicious and creative combinations that you can try.
A good rule of thumb to keep in mind is to try mixing legumes with grains, such as hummus and pita, or adding quinoa and beans to your salad.
