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What Is Complete Protein? (Examples & Definition)

Michael Garrico
Published by Michael Garrico
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: March 16, 2022

People trying to gain lean body mass often excessively consume animal-sourced proteins as they are known for having a complete amino acid profile.

However, my years as an athletic trainer taught me that consuming too much protein from supplements and animal products can compromise one's health.

So I have spent hours researching and analyzing the data to figure out if a complete protein meal plan can also come from plant-based sources.

This article will explain what a complete protein is, the best sources of complete proteins, and how to reach complete protein requirements for optimal muscle growth.

Let's begin.

Quick Summary

  • Complete proteins are food sources with all nine essential amino acids needed for muscle tissue development and repair.
  • Complete proteins are found in meat and animal products such as eggs, fish, beef, pork, and poultry.
  • Most plant foods are incomplete proteins, but a few, such as whole soy, quinoa, spinach, and amaranth, are complete proteins.

The Difference Between Complete Proteins And Incomplete Proteins

bowl of powder

The primary distinction between complete and incomplete proteins is their respective essential amino acid content.

Essential amino acids are nine of the twenty building blocks of protein that our body needs to build muscles, repair tissues, and support metabolism [1].

These essential amino acids include: 

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

In summary, foods that include all the essential amino acids our bodies require are called "complete proteins." In contrast, those lacking in one or more of these essential amino acids are considered incomplete protein sources.

Are There Benefits To Getting The Nine Essential Amino Acids From Diet?

Getting the essential amino acids from diet completes the twenty building blocks of protein our bodies need to sustain optimal health.

Twenty amino acids are required by our bodies to support normal biological processes and functions, such as:

  • Proper food digestion
  • Nutrient absorption
  • Muscular tissue regeneration
  • Effective energy generation
  • Lean muscle mass retention
  • Concentration and mood enhancement
  • Improvement in physical performance

However, because our bodies can only produce eleven of the amino acids we require, we must obtain the remaining nine from food [2].

When we eat foods high in protein, they are metabolized by our digestive system into amino acids. However, not all foods contain these organic compounds in sufficient quantities to meet the body's protein requirements [3] [4].

That is why it is vital to develop a varied, high-protein meal plan to ensure enough intake of the essential amino acids required for normal protein synthesis and muscle health maintenance.

What Are The Best Complete Protein Sources?

different protein food sources

The best sources of complete proteins are a variety of animal and plant-based foods.

Animal-Based Foods

According to research, animal-based foods are the best sources of complete proteins for non-vegans, as all essential amino acids are typically found in animal products [5].

Here are a few examples of complete animal proteins:

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Dairy (Milk and cheese)

However, while animal protein is one of the best sources, you don't have to eat it to get the full health benefits of complete protein intake.

"For someone who wants the most muscle and to maximally build structures in their body, I would try to combine proteins in each meal." - Marie Spano, RD, CSCS, the Atlanta-based lead author of Nutrition for Sport, Exercise, and Health

In people with a high risk of chronic diseases, the source of protein is more important than the amount of protein. So, experts recommend eating foods from a variety of organic animal and plant-based sources throughout the day [6].

A great resource of complete proteins are whey protein powders.

Plant-Based Foods

soy beans

Most plant-based foods that are high in protein, including corn, lentils, peanuts, broccoli, and mushrooms, are deficient in one or more essential amino acids [7].

However, there are a few plant-based complete proteins that contain the essential amino acids required by the body for the formation and repair of muscle tissues, including:

  • Soy
  • Hemp seeds and Chia seeds
  • Nuts (Roasted American Pistachios)
  • Cereals and whole grains (quinoa, amaranth, buckwheat)
  • Leafy greens (Spinach)

It's critical to remember that you don't have to eat animal protein at every meal to maintain an amino acid-rich diet, as some meat products may contain excessive amounts of saturated fat, sugar, and sodium [8].

Nutritionists recommend that you obtain most of your protein from various vitamin and mineral-dense plant foods.

How Much Protein Do I Need?

woman holding tray of eggs while thinking

The daily protein recommendation is 0.8 grams per kilogram of body weight, according to the American Society of Nutrition (ASN)  [9].

However, adults wanting to build muscle should increase their protein consumption to 1.8 to 2 grams per kilogram of body weight (0.8 to 0.9 grams per pound of body weight), as this is the recommended amount for tissue growth [10].

Some people regularly consume large amounts of meat and animal products to receive essential amino acids and meet their protein requirements.

However, those who abstain from meat and animal products get the complete proteins they need by combining various plant-based incomplete protein sources in the same meal.

The best part about a varied plant-based diet is that it can improve overall health and longevity because protein-dense plants are also high in fiber, vitamins, minerals, and antioxidants.

Is It Necessary To Eat Complete Protein Foods To Get Enough Protein?

It is not necessary to eat complete proteins from animal sources to get enough of this macronutrient if a wide variety of plant foods are consumed throughout the day.

Research suggests that eating sufficient calories from a nutritious, varied plant protein diet should provide an adequate supply of the essential amino acids your body needs [11].

To summarize, both animal and plant-based sources can provide a full amino acid profile, but eating complete proteins alone will not result in the development of lean body mass.

Consuming this essential nutrient in conjunction with natural dietary supplements and regular exercise will allow you to get the most out of it.

If some of these plant foods are not available in your country, you can always fill in the gaps with some protein powders:


References

  1. https://www.ncbi.nlm.nih.gov/books/NBK557845/
  2. https://www.medicalnewstoday.com/articles/324229
  3. https://www.healthline.com/health/protein-digestion
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872778/
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3905294/
  6. https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/
  7. https://www.medicalnewstoday.com/articles/322827
  8. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/saturated-fats
  9. https://pubmed.ncbi.nlm.nih.gov/28298271/
  10. https://pubmed.ncbi.nlm.nih.gov/22150425/
  11. https://www.medicalnewstoday.com/articles/196279

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