Amino Acids for Teen Athletes: Essential, Non-Essential, and Complete Proteins

Amino acids are the building blocks of protein. The body combines them in different sequences to create thousands of proteins that support metabolism, muscle growth, tissue repair, energy production, and many other functions [1,3].

This guide explains the main categories of amino acids, the role of branched-chain amino acids, and the difference between complete and incomplete proteins.

What Are Amino Acids?

There are 20 common amino acids used to build proteins in the human body. These amino acids fall into three main categories: essential, non-essential, and conditional.

Essential Amino Acids

The body cannot produce essential amino acids in sufficient amounts, so they need to come from food. There are nine essential amino acids [1,3].

·       Histidine supports histamine production, which plays a role in immunity, digestion, sleep, and sexual function.

·       Isoleucine supports muscle metabolism and immune function.

·       Leucine plays a major role in protein synthesis, muscle growth, and growth hormone production.

·       Lysine supports hormone production and energy metabolism.

·       Methionine supports tissue growth, metabolism, and detoxification processes.

·       Phenylalanine is used to produce neurotransmitters including dopamine, epinephrine, and norepinephrine.

·       Threonine helps build structural proteins such as collagen and elastin.

·       Tryptophan is needed for serotonin production and nitrogen balance.

·       Valine supports muscle growth, tissue repair, and energy production.

Non-Essential Amino Acids

The body can normally produce non-essential amino acids in sufficient amounts. The 11 non-essential amino acids are [1,3]:

·       Alanine

·       Arginine

·       Asparagine

·       Aspartic acid

·       Cysteine

·       Glutamic acid

·       Glutamine

·       Glycine

·       Proline

·       Serine

·       Tyrosine

Conditional Amino Acids

Some amino acids that are usually produced by the body may become conditionally essential during illness, physical stress, or rapid growth. This category includes cysteine, glutamine, arginine, glycine, proline, serine, and tyrosine [1,3].

The overlap between the non-essential and conditional lists is expected. These amino acids are usually made by the body, but needs may rise in certain situations.

Other Amino Acid Classifications

Functional Amino Acids

Functional amino acids can come from both the essential and non-essential groups. They are studied for roles in cellular signaling, gene expression, growth, homeostasis, reproduction, antioxidant defense, neurological function, and immunity [1].

The seven functional amino acids listed in the source material are arginine, glutamine, leucine, tryptophan, cysteine, glutamate, and proline.

Branched-Chain Amino Acids

Branched-chain amino acids, often called BCAAs, include leucine, isoleucine, and valine. These three essential amino acids are involved in muscle building and repair [2]. Leucine plays a key role in signaling protein synthesis [1].

A balanced diet that includes enough high-quality protein can provide BCAAs without a separate supplement.

Complete and Incomplete Proteins

Complete Proteins

Complete proteins contain all nine essential amino acids. They are commonly found in animal-based foods, although some plant foods also qualify [4]. Examples include:

·       Fish

·       Poultry

·       Eggs

·       Beef

·       Pork

·       Dairy

·       Whole soy foods such as tofu, edamame, and miso

Incomplete Proteins

Incomplete proteins contain lower amounts of one or more essential amino acids. They are still valuable foods and can be paired with other sources to provide a full range of essential amino acids [4].

Common complementary pairings include:

·       Grains with legumes or vegetables.

·       Nuts or seeds with legumes or vegetables.

Examples of incomplete protein sources include legumes, nuts, seeds, whole grains, and vegetables.

The Main Takeaway

A balanced diet is usually enough to meet amino acid needs. Active teens can focus on eating enough total protein and including a variety of complete proteins or complementary plant proteins. Separate amino acid supplements are generally unnecessary when the overall diet provides adequate energy and protein.

Disclaimer

All content provided on this blog is for informational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment. Always consult your physician or qualified healthcare provider with any questions you may have regarding a medical condition or nutritional needs. While all posts are reviewed for accuracy by VUUR's medical advisor, a board-certified pediatric gastroenterologist, VUUR is not responsible for any health issues that may arise from the use or misuse of the information presented. Use this content at your own discretion.

Citations

1. Biagioli B. Sport Nutrition Specialist. National Council on Strength & Fitness; 2020.

2. Cleveland Clinic. 10 Foods High in Leucine and Its Benefits. Published June 10, 2025. Accessed October 3, 2025. https://health.clevelandclinic.org/foods-high-in-leucine

3. Cleveland Clinic. Amino Acids. Last reviewed August 23, 2023. Accessed October 3, 2025. https://my.clevelandclinic.org/health/articles/22243-amino-acids

4. Cleveland Clinic. Complete vs. Incomplete Proteins and Examples. Published December 6, 2022. Accessed October 3, 2025. https://health.clevelandclinic.org/do-i-need-to-worry-about-eating-complete-proteins