Viewing a nutrition label, it might appear that protein is simply protein, since that’s the only way it’s ever listed. But not all proteins are created equal.
Proteins consist of amino acids, each of which can appear in food in varying quantities — or not at all. That can make it hard to know if you’re really getting the protein you need.
One way to make eating simpler is to consume complete protein sources, which contain amino acids in the required quantities. Read further for the differences between complete and incomplete proteins, as well as a list of complete proteins.
What Is a Complete Protein?
There are 20 total amino acids that comprise protein in the body, but only nine of these are considered essential. An essential amino acid is one that the body can’t make on its own, and therefore must get from food.
A complete protein is one that has all nine essential amino acids. They include phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.
The simplest way to consume a complete protein is to choose animal sources like meat, poultry, fish, eggs, and dairy. These foods contain what is called high biological value protein, which refers to how efficiently a protein can be utilized by the body. Those containing the greatest supplies of essential amino acids score highest.
That doesn’t mean you can’t get all of 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 of your essential amino acids.
Complete Protein Foods
Below is a quick review of the quality and quantity of protein found in different food groups.
Meat, poultry, and seafood: These have the highest amounts of complete protein per serving of any whole food. This protein is well absorbed and utilized by the body.
- Beef (22 g per 3-oz. serving, ground, 85 percent lean, broiled)
- Chicken (24 g per 3-oz. serving, breast, roasted)
- Turkey (26 g per 3-oz. serving, breast, roasted)
- Pork (23 g per 3-oz. serving, loin, broiled)
- Duck (23 g per 3-oz. serving, breast, broiled)
- Salmon (22 g per 3-oz. serving, cooked)
- Tilapia (23 g per 3-oz. filet, cooked)
- Swordfish (20 g per 3-oz. serving, cooked)
- Trout (23 g per 3-oz. serving, cooked)
- Shrimp (20 g per 3-oz. serving, cooked)
- Crab (16 g per 3-oz. serving, steamed)
- Scallops (17 g per 3-oz. serving, steamed)
- Tuna (22 g per 3-oz. serving, canned)
- Sardines (21 g per 3-oz. serving, canned)
Dairy: Cow’s milk has among the highest amounts of protein per serving compared to other milks, and is a complete protein with a high biological value. Soy milk is comparable in protein quantity with 7–8 g per cup, and is also a complete protein, but has a lower biological value than cow’s milk.
- Milk (8 g per cup)
- Yogurt (9 g per 6-oz. container, low-fat, plain)
- Cheese made from cow milk, goat milk, sheep milk (6–8 g per ounce)
Greek yogurt (17 g per 6-oz. serving): Also a dairy source, Greek yogurt is so concentrated (compared to other yogurts), it’s an excellent source of protein — perfect for breakfast or after a workout.
Soybeans (33 g per cup): Soy is the only legume that’s considered a complete protein. Other legumes are high in lysine but limited in methionine. That’s where combining foods is vital, to ensure you get all the essentials!
Seeds: While high in other amino acids, many seeds are limited in lysine. Exceptions include the following, which are especially valuable for those following vegan diets.
- Pumpkin seeds (9 g per ounce)
- Sunflower seeds (5.5 g per ounce)
- Chia seeds (5 g per ounce)
- Hemp seeds (9 g per ounce)
- Buckwheat (4 g per ounce)
Grains: Whole grains provide protein, carbs, 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 must be combined at each meal. But now we know that our bodies are smart enough to do this on their own as long as we eat complementary protein sources throughout the day (or even over 2–3 days!).
The classic vegan combo that 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 and tons of heart-healthy fiber. But there are plenty of other delicious and creative combinations you can try.
One good rule of thumb to keep in mind is to try and mix legumes with grains, such as hummus and pita, or to add quinoa and beans to your salad.