Does Every Protein Have All 20 Amino Acids? Understanding Your Nutrition Diet

October 29, 2025 •

2 min read

Despite a common misconception, not every protein contains all 20 amino acids. The key to understanding your nutrition diet lies in distinguishing between complete and incomplete proteins, which answers the question, 'Does every protein have all 20 amino acids?'

Quick Summary

Not all protein sources are created equal. The distinction between complete and incomplete proteins, based on their essential amino acid content, is key. A balanced and varied intake of different protein sources throughout the day can easily ensure you meet all your body's needs.

Key Points

Not all proteins are created equal: The answer to 'Does every protein have all 20 amino acids?' is no; proteins are categorized as 'complete' or 'incomplete' based on their essential amino acid profile.
Essential amino acids must be consumed: Your body cannot produce the nine essential amino acids, so they must be obtained through your diet.
Combining incomplete proteins is effective: Combining different plant protein sources, like grains and legumes, throughout the day ensures you get all essential amino acids.
Forget meal-by-meal combining: The human body maintains an amino acid pool, so there is no need to combine complementary proteins in the same meal.
Variety is paramount: A varied diet rich in whole foods, rather than a focus on one food source's completeness, is the best strategy for obtaining all necessary amino acids.
Plant-based complete proteins exist: Some plant foods like soy, quinoa, and buckwheat are considered complete proteins, containing all nine essential amino acids.

What are Amino Acids and Why are they Important?

Proteins, vital for functions like tissue repair and hormone production, are made of 20 amino acids. These are categorized into essential, which your body can't make, and non-essential, which it can. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

The Complete vs. Incomplete Protein Distinction

Understanding if a protein is complete or incomplete answers whether does every protein have all 20 amino acids. Complete proteins contain all nine essential amino acids. Animal products are typically complete proteins, while some plant foods like soy, quinoa, and buckwheat also qualify. Incomplete proteins lack one or more essential amino acids and include most plant-based foods such as legumes, nuts, seeds, and grains. Combining incomplete proteins throughout the day is a simple way to get all essential amino acids.

How to Achieve a Complete Protein Profile

For those on a plant-based diet, getting all essential amino acids is straightforward. The body maintains an "amino acid pool" from foods eaten throughout the day, eliminating the need to combine specific proteins in every meal. Pairing grains with legumes, or nuts/seeds with legumes, are classic ways to create complete protein profiles.

Complete vs. Incomplete Protein Sources: A Comparison


Feature	Complete Proteins	Incomplete Proteins
Source	Animal-based (meat, eggs, dairy) and certain plant-based foods (soy, quinoa)	Most plant-based foods (legumes, nuts, seeds, grains)
Essential Amino Acids	All nine essential amino acids present in sufficient amounts	Deficient in one or more essential amino acids
Dietary Planning	Easier to ensure all essential amino acids are consumed from a single source	Requires combining different sources throughout the day to acquire all essential amino acids
Nutrient Density	Often comes with saturated fats and other components that require moderation	Rich in fiber, complex carbohydrates, vitamins, and minerals

Beyond the Label: Why Variety is Paramount

Focusing on complete vs. incomplete labels shouldn't overshadow the importance of a varied diet. A diverse intake of whole foods naturally provides all necessary amino acids and other vital nutrients, regardless of dietary choices.

Conclusion

In summary, not every protein source contains all 20 amino acids. The key is understanding complete and incomplete proteins based on essential amino acid content. A varied and balanced nutrition diet incorporating different protein sources throughout the day easily ensures all amino acid requirements are met.

For more information on protein quality and dietary requirements, a reliable source is Harvard's The Nutrition Source.

Frequently Asked Questions

Complete proteins contain all nine essential amino acids. Incomplete proteins lack one or more of these essential amino acids, which are the ones your body cannot produce on its own.

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Most plant proteins are incomplete, but notable exceptions like soy, quinoa, and buckwheat contain all nine essential amino acids and are considered complete proteins.

No, it is a common misconception. The human body uses an amino acid pool and can combine essential amino acids from different foods consumed throughout the day.

Popular pairings include rice and beans, hummus and whole-grain pita, or a peanut butter sandwich on whole-wheat toast.

While animal proteins are generally more easily absorbed and are complete, a varied and balanced plant-based diet can provide all necessary amino acids and offer additional health benefits like fiber and antioxidants.

Focus on a varied and balanced diet that includes a wide range of protein sources. This ensures you get all the essential amino acids and other crucial nutrients for overall health.