What is a Complete Protein Made Up Of?

January 11, 2026 •

2 min read

According to nutritional science, the human body can produce 11 of the 20 amino acids it needs to function, but must obtain the remaining nine from food. This is the central concept behind understanding what is a complete protein, which is a source of protein that contains all nine of these essential amino acids.

Quick Summary

A complete protein is any food source that provides all nine essential amino acids necessary for human health. These amino acids must be obtained through diet because the body cannot produce them internally. Complete proteins are vital for building and repairing tissues, regulating hormones, and other critical bodily functions. Both animal and several plant-based foods can be excellent sources.

Key Points

Essential Amino Acids: A complete protein contains all nine essential amino acids that the human body cannot produce internally.
Animal and Plant Sources: Complete proteins can be sourced from both animal products like meat, eggs, and dairy, as well as plant-based foods like soy, quinoa, and buckwheat.
Complementary Proteins: Vegetarians and vegans can combine different incomplete plant-based proteins (e.g., rice and beans) throughout the day to create a complete amino acid profile.
Vital for Body Functions: Complete proteins are crucial for building and repairing muscle, producing hormones and enzymes, and supporting immune health.
Dietary Variety is Key: Focusing on a varied diet with a mix of different protein sources ensures the body receives all the necessary essential amino acids over a 24-hour period.

The Building Blocks of Life: Amino Acids

Proteins are composed of basic organic compounds called amino acids. The human body uses 20 different amino acids, which are classified as either essential or non-essential. Essential amino acids, numbering nine, cannot be synthesized by the body and must come from food, including histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The 11 non-essential amino acids can be produced by the body internally. A complete protein source provides all nine essential amino acids in sufficient amounts. Foods lacking or low in one or more essential amino acids are considered incomplete proteins.

Complete Protein Sources: Animal vs. Plant-Based

Complete proteins are available from both animal and plant-based foods.

Animal-based complete protein sources:

Meat and Poultry
Fish and Seafood
Eggs
Dairy Products

Plant-based complete protein sources:

Soy Products (tofu, tempeh, edamame)
Quinoa
Buckwheat
Chia and Hemp Seeds
Spirulina

The Role of Complementary Proteins

Vegetarians and vegans can obtain all essential amino acids by consuming a variety of plant-based foods throughout the day, a practice known as protein complementation. The body can combine amino acids from different incomplete proteins eaten over a 24-hour period.

Common examples of complementary protein pairings:

Rice and beans
Peanut butter on whole-wheat bread
Hummus and pita bread
Lentil soup with whole-grain crackers

Complete vs. Incomplete Protein: A Comparative Look


Feature	Complete Protein	Incomplete Protein
Essential Amino Acids	Contains all nine essential amino acids in adequate amounts.	Lacks or is low in one or more of the nine essential amino acids.
Primary Sources	Animal-based foods (meat, dairy, eggs) and some specific plant-based foods (soy, quinoa).	Most plant-based foods, such as beans, nuts, seeds, and grains (when consumed individually).
Dietary Importance	Provides a single, convenient source for all essential amino acids, especially for individuals with high protein needs.	Requires strategic food combining throughout the day to ensure all essential amino acids are met.
Examples	Beef, fish, eggs, milk, quinoa, soy.	Legumes (beans, lentils), most grains, nuts, seeds, and vegetables.

Why Your Body Needs Complete Protein

A balanced intake of essential amino acids is vital for numerous bodily functions, including:

Muscle Growth and Repair
Hormone and Enzyme Production
Immune Function
Tissue Maintenance
Neurological Function

Conclusion: Prioritizing a Varied Diet

Complete proteins are dietary sources providing all nine essential amino acids that our bodies cannot make. These are found in animal products and certain plant foods like quinoa and soy, as well as through complementary plant protein combinations. A varied diet with diverse high-quality protein sources ensures the body receives all necessary amino acids over the day, supporting various functions from muscle to brain health. Consulting a healthcare provider or registered dietitian is recommended for personalized dietary advice.

Frequently Asked Questions

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. They are called 'essential' because the human body cannot produce them, so they must be obtained through diet.

Yes, most animal-based protein sources, including meat, poultry, fish, eggs, and dairy, are considered complete proteins because they contain all nine essential amino acids.

Absolutely. Vegans and vegetarians can get complete proteins by consuming specific plant-based foods like soy, quinoa, and buckwheat, or by combining various incomplete protein sources throughout the day, such as rice with beans or hummus with pita.

No, this is a common misconception. The body can store essential amino acids and will combine them from various food sources eaten throughout the day to form complete proteins.

Yes, soybeans and products derived from them, such as tofu, tempeh, and edamame, are recognized as excellent complete plant proteins.

Essential amino acids cannot be produced by the body and must be obtained from food. Non-essential amino acids can be synthesized by the body internally and therefore do not need to be specifically included in the diet.

Complete proteins are important because they provide all the necessary building blocks for crucial bodily functions, including muscle repair, immune system support, hormone production, and overall tissue maintenance.