Protein is everyone's favorite macronutrient right now. But focusing on the grams you get in a day isn't enough, dietitians say. You should also make sure to vary your protein sources so that you get complete protein throughout your day.
"A complete protein will contain all nine essential amino acids," Theresa Gentile, registered dietitian and spokesperson for the Academy of Nutrition and Dietetics, tells TODAY.com.
Those nine amino acids are called "essential" because our bodies can't make them, says Natalie Rizzo, registered dietitian and nutrition editor at TODAY. Instead, we have to get those essential amino acids from the food we eat.
Complete proteins, which include meat and dairy products, make that a little easier because you'll get all nine essential amino acids in one food. But, the experts say, with just a bit of planning, it's just as easy to get all those amino acids without eating animal products.
What is a complete protein?
A complete protein contains sufficient amounts of all nine essential amino acids, the dietitians explain.
There are 20 amino acids, which act as the building blocks for protein, Rizzo explains. Of those 20, nine are considered "essential," meaning we need to get them through our diets because our bodies aren't able to make them.
Your body uses amino acids to build and repair muscle, maintain hair and nail health, repair body tissues, break down food and make hormones, the Cleveland Clinic says.
The nine essential amino acids are:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
Anything that has protein in it has at least some of these amino acids, Rizzo says, but not all protein sources are considered "complete." That's because not all foods contain all nine of these amino acids in high enough amounts.
But that doesn't mean you need to go out of your way to only eat complete protein sources, the experts stress. As long as you get your protein from a variety of foods, you shouldn't have trouble getting all the amino acids your body needs.
Where to find complete proteins
Generally, animal sources of protein will contain good amounts of all nine essential amino acids. That means you can find complete protein in foods like:
- Poultry
- Beef
- Eggs
- Dairy
- Fish
Sometimes, people may refer to complete protein sources as "high quality" proteins, Rizzo says.
If you don't eat meat or you tend to favor plant-based foods, you can still get all the complete protein you need.
For one thing, soy is a complete protein, Rizzo says. So any soy-based protein — like tofu, edamame and tempeh — will provide all the essential amino acids.
And many plant-based foods contain at least some of the nine essential amino acids. So, if you think ahead and emphasize getting variety in your diet, it's very possible to get all the complete protein you need in your day — even if you don't eat animal products.
Previously, plant foods were considered "incomplete" proteins, Rizzo says. So vegans and vegetarians were encouraged to pair complementary amino acid-containing foods together in a meal or at least within two hours of each other, Gentile notes. (The classic example is beans and rice, for instance.)
These days, however, our thinking has evolved. For starters, "We call them 'limited proteins' now," Rizzo explains, "meaning that plant proteins still have these nine essential amino acids, but some (plant proteins) won't have all of them in large amounts."
That also means there's no need for plant-based folks to worry about stuffing all the amino acids in every single meal. By eating a variety of plant-based protein sources throughout your day, you'll naturally eat enough of the nine essential amino acids for your body to get the complete protein it needs, the experts say.
You can still eat your favorite plant-based protein combos if you want, of course, but you don't need to stress about it.
"If we can consume various incomplete proteins within the same day, our body will form them into complete proteins," Gentile explains, "so that way we can utilize them best in the body."
Look for these plant-based protein foods:
- Beans
- Lentils
- Whole grains
- Nuts
- Seeds
- Seitan (wheat gluten)
Along with soy, some other plant-based protein sources also contain a good amount of all nine essential amino acids, including quinoa, chia seeds, hemp seeds, buckwheat and pumpkin seeds. Still, depending on who you ask, these may or may not be considered "complete" proteins.
The bottom line is that most people — whether they eat meat or prefer plant-based foods — likely get enough different protein sources in their day that they don't need to go out of their way to look for complete proteins, Rizzo says.
But if you're on a very limited diet, you could be missing out on some essential amino acids, Rizzo explains. For instance, if you're only eating one plant-based protein source (like beans) or if you lean heavily on plant-based imitation meats (like those from Beyond Meat or Impossible), you may not be getting enough variety to round out your diet.
