- Complete proteins contain all nine essential amino acids, whereas incomplete proteins are missing one or more.
- It can be hard to know if you’re getting good quality protein in your diet.
- INSIDER found out what the differences are between complete and incomplete proteins .
When it comes to a healthy diet, a lot of emphasis is placed on the quantity of protein in food, but not so much on the quality. The terms “complete” and “incomplete” protein refer to the quality of protein in a food and the types of amino acids it includes.
INSIDER corresponded with Perri Halperin, MS, RD, a dietitian at Mount Sinai Hospital in New York, about what these terms mean, and how they should play into your own nutrition.
Proteins are made up of amino acids.
Amino acids are the units that make up all proteins, and the human body can produce several of them on its own. The rest have to come from diet.
“Of the approximately 20 known amino acids, nine of them-histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine-cannot be made or modified by the body and must come from food,” Halperin said.
These nine are called essential amino acids. The rest are called “nonessential” not because they lack importance, Halperin explained, but because the body can produce them or synthesise them from other compounds independently.
Animal products tend to be complete proteins.
Animal products, such as chicken, eggs, dairy, and seafood, tend to be complete proteins made up of all nine essential amino acids, but there are a number of complete proteins that are plant-based as well, including quinoa, buckwheat, and soy.
Incomplete proteins tend to be plant-based.
Incomplete proteins tend to be plant-based and are either low, or lacking, in one or more of these amino acids, making the protein imbalanced.
Examples of incomplete protein are rice and vegetables.
Getting the right kind of protein in a vegan diet is easier than you may think.
If you don’t eat animal products then don’t worry – your protein sources aren’t necessarily all incomplete. In fact, the Academy of Nutrition and Dietetics states that vegetarian and vegan diets can be “healthful” and “nutritionally adequate,” and even have some advantages over omnivorous diets like lower risk of heart disease and type 2 diabetes.
A number of common plant-based foods are complete proteins already, including quinoa, buckwheat, and soy. Eating a variety of nutritious foods helps ensure that you’re getting a significant amount and quality of protein. “Legumes such as lentils, beans, edamame/soybeans as well as nuts, seeds and whole grains are good vegetarian sources of protein,” Halperin said.
Eating a balanced diet is important.
Keep in mind that there are far more nutritional properties to food than just protein. Incomplete proteins can be combined within a day or a single meal to ensure that all essential amino acids are included in one’s diet.
Protein combining is something we tend to do already anyway in a balanced meal so you probably don’t need to worry too much about which amino acids you’re getting. If you have a plant-based diet, you can combine your protein intake to ensure you are getting a complete balance of the amino acids that your body needs.
“A diet of incomplete protein can eventually lead to malnutrition,” Halperin said, “however as long as you are eating a varied diet, little concern needs to be paid to pairing complementary proteins when meal planning.”
The average person doesn’t need to worry too much about the details of protein quality.
The metric known as PDCAAS, Protein Digestibility-Corrected Amino Acid Score, that measures the value of protein in foods. While governing bodies like the World Health Organisation have used for this quantification, Halperin cautioned that it’s not an all-encompassing measurement and isn’t likely to be highly useful for the purpose of evaluating an individual’s nutrition.
“The average person should focus on incorporating a variety of protein sources into their diet, as opposed to the specifics on the PDCAAS,” Halperin said. There’s really no need for most people to get too granular about how much of each amino acid they’re eating – that time and energy is better spent elsewhere, like learning how to prepare new protein-rich foods.
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