Complete vs. Incomplete Protein Sources

Delving into the world of fitness and nutrition, it’s easy to be overwhelmed by talk of nutrients. The one you inevitably end up hearing about – a lot— is protein.

But what is it? You’ve probably heard or read about it as a big part of building muscle, but there are some other important and often-overlooked aspects of the different protein sources that you may not know.

Let’s start with the basics…

What Is Protein?

One of the three macronutrients your body needs to function properly (along with fats and carbohydrates), proteins are primarily important for tissue growth and repair, but also necessary for digestion, metabolism, and the production of antibodies to fight infection. Comprising 10% of your brain and 20% of your heart, liver, and skeletal muscles, protein is obviously key to maintaining a strong, healthy body. What you may not realize, however, is how important it is for a healthy mind.

When you digest protein, it’s broken down into its component amino acids, which are then reassembled into 50,000 different forms your body can use for things like hormones, enzymes, and neurotransmitters. Not only do these amino acids form the building blocks of your brain’s neural network and have significant impact on your mood and brain function, but are especially important in infants’ developing brains.¹ Specifically, the protein neurexin, is responsible for directing new nerve cells to their correct locations in the brain where they form their initial connections.

Complete vs Incomplete Protein Sources

Your body needs 22 different types of amino acids to function properly. Adults can synthesize 13 of those within the body (known as non-essential amino acids), but the other 9 must be obtained from food (known as essential amino acids). It’s these essential amino acids that derive the classification of protein as either complete or incomplete.²

Complete Protein Sources

Complete proteins are those that contain all essential amino acids in sufficient quantity – these are typically animal-based proteins, but a few plant sources are also considered complete. A few examples are (* indicates plant-based):

Incomplete Protein Sources

Incomplete proteins are those that don’t contain all 9 essential amino acids, or don’t have sufficient quantities of them to meet the body’s needs, and must be supplemented with other proteins. These include:

Just because they are incomplete doesn’t make them inferior, though, they just need to be combined to provide the right balance of essential aminos. Proteins that, in combination, make a complete amino acid profile are known as complementary proteins. Here are a few tasty examples:

Complementary proteins don’t necessarily need to be eaten together, but since your body doesn’t store amino acids for later use in protein combining, they should be eaten throughout a day’s meals.³

Plant vs. Animal Protein Sources

A bit of a controversy is brewing over whether animal or plant-based proteins ⁴ are better for you. Some nutritionists argue that humans are better suited to digesting animal proteins since they are closer to our own biological makeup and contain all the amino acids we need to survive. On the other side, many contend that plant-based proteins are healthier and animal-based proteins are not necessary if you have proper variety in your diet.⁵

While animal proteins have somewhat better absorption and availability to the body (See: The Protein Digestibility Corrected Amino Acid Score), what I’ve found is that most of the arguments for either side have less to do with the proteins themselves,⁶ and more to do with the foods in which they are found (i.e., meats being higher in fat and cholesterol vs. grains being high in carbohydrates) and the morality of eating animals. For most people, the body handles both types of protein equally well.

One potential problem with animal protein is that it tends to be higher in sulfur-containing amino acids, which causes increased acidity and could lead to calcium depletion as the body tries to balance out its pH level. This is typically not an issue when consumed in moderation with a well-balanced diet, however.

The only major knock on plant protein is its incompleteness, but that is, again, easily overcome with a well-balanced diet.

How Much Of Protein Sources Should You Eat?

The current Recommended Daily Allowance of protein for adults is 0.36 grams per pound of body weight. This translates to 64 grams of protein for a 180lb man. Research shows that protein intakes as high as 0.8 – 1.0 gram/lb can help those individuals looking to build muscle, or retain muscle while losing fat during a resistance training program. We will cover protein requirements and absorption in more depth in other articles.

A higher protein diet is often recommended during a fat loss program because of protein’s high thermic effect (up to 30% of calories from protein are burned off during digestion) and its ability to satisfy hunger.

For your reference:

So How Exactly Should You Eat Your Protein Sources?

As with so many things, the key to protein is balance. It is a vital and often-misunderstood part of our diets, but we need to remember that the quality and type of protein can be as important as how much we consume.

Making sure you have a good combination of high-quality proteins in your diet is a good step towards a healthy body and mind.

Are there any protein sources not mentioned in the article you like?