Free Amino Acids: They Help Build Muscle & Absorption Is The Key

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Along with providing information on whether amino acid supplements might be right for you, this article also links to Fullscript where you can buy amino acid supplements. Order online through Fullscript’s secure healthcare formulary to get the best prices and free shipping on professional-grade supplements.

What Are Amino Acids?

Amino acids are the building blocks of proteins, which are needed for essentially everything including supporting growth and repair of tissues, synthesizing hormones and enzymes, maintaining immune function, and serving as precursors to neurotransmitters.

There are 20 different amino acids that can be combined in various ways to form proteins. Out of these, nine are considered essential amino acids because the body cannot synthesize them, meaning they must be obtained through the diet. The other 11 can be made from other amino acids so we don’t need to get them through the diet.

Amino acids have various functions, including assisting in the creation and repair of tissues, forming enzymes that facilitate chemical reactions, and playing a role in immune function. They are found in various food sources, particularly in proteins like meat, fish, eggs, and legumes, and can also be taken as dietary supplements.

What Are The Different Types of Amino Acids?

Amino AcidDescription
HistidineEssential, important for growth and repair
IsoleucineEssential, Branched-Chain, involved in muscle metabolism
LeucineEssential, Branched-Chain, helps in muscle repair and energy production
LysineEssential, involved in growth and immune function
MethionineEssential, provides sulfur and is a building block
PhenylalanineSemi-essential, important for the immune system and cell division
ThreonineEssential, vital for protein balance in the body
TryptophanEssential, a precursor to neurotransmitters
ValineEssential, Branched-Chain, stimulates muscle growth and regeneration
ArginineSemi-essential, aids in the structure of proteins
CysteineNon-essential, part of the structure of collagen, a precursor to Glutathione
TyrosineSemi-essential, precursor to hormones and neurotransmitters
AlanineNon-essential, used in protein synthesis
AsparagineNon-essential, involved in metabolic control
Aspartic AcidNon-essential, involved in energy production
Glutamic AcidNon-essential, involved in immune response
GlutamineNon-essential, aids in gastrointestinal health, a precursor to Glutathione
GlycineNon-essential, part of the structure of collagen, precursor to Glutathione
ProlineNon-essential, essential for collagen formation
SerineNon-essential, involved in metabolism and immune system

How Amino Acid Intake Relates To Protein Intake

Proteins are long chains made up of many amino acids. So a gram (about a postage stamp) of protein will break down to about a gram of amino acids. When you eat foods rich in protein, your body breaks down the protein into individual amino acids during digestion. These amino acids are then absorbed and used by the body.

Complete Proteins: Animal sources of protein such as meat and dairy contain all the essential amino amino acid. Essential amino acids cannot be produced by the body and must be obtained from the diet. Foods that contain all essential amino acids are considered complete proteins and include many animal products, quinoa, and soy.

Incomplete Proteins: Incomplete proteins, on the other hand, lack one or more essential amino acids. Vegetarians get all of the essential amino acids by combining protein sources. In short, your protein intake directly affects how many amino acids your muscles have available to build muscle and support bodily functions.

Exercise, Protein & Amino Acid Intake, and Muscle Building

When a person does resistance training, it causes microscopic damage to muscle tissues. Following this exercise, the body needs to repair and build new proteins to repair, recover and increase muscle mass.

When amino acids (especially branched-chain amino acids, or BCAAs) become available in the bloodstream, such as after consuming a protein-rich meal or supplement, cells in the muscle can sense this increase. The mTOR pathway is then activated, sending signals to the protein-building machinery inside the cell to increase in protein synthesis.

This is why protein intake (providing amino acids) around the time of resistance exercise can support muscle recovery and growth. It’s part of the broader science that leads to nutritional strategies for athletes.

So, in the simplest of terms, cells continuously sense the levels of amino acids and other nutrients in the system. When an abundance of amino acids is suddenly available in the aftermath of resistance training, mTOR is turned on, resulting in protein synthesis. It is worth noting that the actual biological process is incredibly complex and involves many other factors and signaling pathways. [PMC8201612]

Who Might Need An Amino Acid Supplement

In the following sections, we’ll dive deeper into problems with digestive health and medication interactions that might be affecting a person’s ability to break down and absorb the amino acids provided by the protein in foods. But first, let’s outline who might be able to benefit from amino acid intake. Here’s an overview:

  • Protein Malnutrition: In cases of protein malnutrition, where dietary intake is inadequate to meet protein needs, amino acid supplements can help fill the gap.
  • Vegetarian and Vegan Diets: Specific amino acid supplements might be useful if dietary choices are limited. Consult with a Registered Dietitian to assess your specific needs.
  • Athletic Performance: Muscle Synthesis:
    • Essential Amino Acids: Essential amino acid (EAA) supplements, particularly effective at stimulating muscle protein synthesis even at low doses, play a crucial role in enhancing skeletal muscle maintenance and performance, with benefits observable both with and without exercise. [PMC10561576]
  • Elderly Populations: Poor stomach acid production, GERD medications and other factors may reduce the breakdown of protein and absorption of amino acids as a person gets older. If this is the case, older adults might benefit from amino acid supplementation to meet their protein needs.
  • Wound Healing: In cases of severe wounds, burns, or surgery, amino acid supplementation may be used to support the healing process by aiding in protein synthesis.
  • Canker Sores and Herpes Outbreaks: Doses of Lysine greater than 3 grams per day were found to improve canker sores. [PMC6419779]
  • Mental Health Disorders: Certain amino acids might be useful in the management of mental health disorders. Here’s how specific amino acids and neurotransmitters relate:
    • Glutamate: Glutamate is a major excitatory neurotransmitter in the nervous system.
    • GABA (Gamma-Aminobutyric Acid): GABA is a major inhibitory neurotransmitter in the brain.
    • Tyrosine: Tyrosine is a precursor for the neurotransmitters Dopamine, Norepinephrine, and Epinephrine.
    • Tryptophan: Tryptophan can be converted into the neurotransmitter Serotonin.
    • Glycine: Glycine serves as an inhibitory neurotransmitter in the spinal cord and brainstem.
    • Histidine: Histidine can be converted into the neurotransmitter Histamine.
    • Serine: Serine acts as a co-activator at the NMDA receptor.
    • Aspartate: Aspartate can act as a neurotransmitter in certain parts of the nervous system.
    • Arginine: Arginine is a precursor for Nitric oxide (NO), a signaling molecule that can act as a neurotransmitter.
  • Chronic Liver Disease: Certain amino acid supplements have been used to support liver function and may help with the management of liver diseases. Consult a Registered Dietitian for your specific situation.
  • Metabolic Disorders: People with genetic disorders may not be able to metabolize certain amino acids. These may require a specific amino acid formulation based on the disorder. Contact a Registered Dietitian.
  • Critical Illness or Severe Stress: During times of extreme physiological stress, such as critical illness or severe injury, amino acid supplementation may be used as part of medical care.

Are You Absorbing Amino Acids From The Foods You Eat?

The digestion and absorption of amino acids when protein is consumed is a complex process influenced by several factors:

  • Type of Protein: Different proteins are broken down at various rates. Animal proteins tend to be digested more easily than plant proteins. Proteins in raw foods may be less digestible than those in cooked foods.
  • Enzyme Activity: Proteases and peptidases are enzymes that break down proteins into amino acids. Variations in these enzymes can influence digestion.
  • Gastric Acidity: The acidic environment in the stomach helps in denaturing proteins, making them more accessible for enzymatic digestion.
  • Presence of Other Nutrients: Fats and fiber, for example, can slow down gastric emptying and may influence protein digestion and absorption.
  • Health of the Digestive Tract: Conditions like Crohn’s disease, celiac disease, or food intolerances can affect protein absorption.
  • Age and Individual Needs: Aging might slow down digestion, and individual needs (such as those for athletes or pregnant women) can affect how proteins are processed.
  • Preparation of the Food: Proteins in well-cooked and well-chewed food are typically digested more efficiently.
  • Protein Quality: Proteins containing a full set of essential amino acids are typically better utilized by the body.
  • Hormones: Various hormones like gastrin, secretin, and cholecystokinin play a role in the digestion process, affecting the speed and efficiency of protein digestion.
  • Microbiome: Gut flora can have some influence on amino acid absorption, particularly in the case of non-digestible proteins.
  • Competition with Other Amino Acids: Different amino acids may compete for absorption, and an excess of one might inhibit the absorption of another.
  • Drug Interactions: Certain medications might affect digestion and absorption of proteins.
  • Physical State of the Protein Source: Liquids or blended protein foods might be digested and absorbed faster than solid ones.
  • Hydration and Electrolyte Balance: Adequate water and electrolyte balance are essential for optimal enzyme function and nutrient absorption.

Understanding these factors is vital, particularly for individuals with specific dietary needs or health conditions, as they can have a direct impact on how proteins are utilized by the body. A healthcare provider or dietitian can offer personalized guidance based on individual health, lifestyle, and dietary patterns.

Acid Blockers And Protein Digestion: Not Good

Stomach acid, mainly hydrochloric acid, is absolutely required for the process of protein digestion. A very low pH ranging from 1.5 to 3.5 activates pepsin-the main protein breakdown enzyme and helps other proteolytic enzymes to function. The acidic gastric environment also has other functions, such as denaturing proteins (unfolding them to expose peptide bonds), killing or inhibiting pathogens, and signaling other digestive processes. It’s an essential part of the overall digestive process, particularly in the initial stages of protein digestion. If this acidic environment is altered (as might happen with long-term use of certain antacids or other medical conditions), it can lead to reduced efficiency in protein digestion.

However, the importance of stomach acid in digestion also raises concerns about the long-term use of acid-reducing medications, such as proton pump inhibitors (PPIs) and H2 receptor blockers. These medications are commonly prescribed for conditions like gastroesophageal reflux disease (GERD) and peptic ulcers to reduce stomach acid production. Typically, they are approved for short-term use, ranging from a few weeks to a few months, depending on the specific condition and medication. Long-term use of these medications might lead to a reduction in the stomach’s ability to digest proteins efficiently due to decreased acid levels, potentially resulting in malabsorption and nutritional deficiencies.

Also, prolonged suppression of stomach acid might affect the absorption of other essential nutrients like calcium, magnesium, and vitamin B12. Therefore, the duration of acid-reducing medication use must be carefully monitored by healthcare providers. This begs the question of how they might what effects these medicines are having on protein and essential nutrient absorption without extensive and expensive tests.

Other Medicines That Affect Protein Digestion

Acid blocking medicines are the most common medications to derail protein digestion and absorption, but they are not alone. Here are some other examples that should be considered.

  • Antibiotics: Some antibiotics can disrupt the gut microbiome, leading to changes in the digestion and absorption of proteins. The imbalance in gut bacteria can affect the enzymes and transporters involved in protein absorption.
  • NSAIDs (Nonsteroidal Anti-Inflammatory Drugs): Chronic use of NSAIDs may lead to gastrointestinal issues like ulcers or inflammation, reducing protein digestion and absorption.
  • Orlistat (a weight-loss drug): This drug inhibits the activity of lipase, an enzyme responsible for fat digestion. Since dietary fats are needed for the absorption of some proteins, Orlistat might indirectly affect protein absorption.
  • Chemotherapy Drugs: These medications may cause nausea, vomiting, and changes in appetite, leading to reduced protein intake. They may also cause mucositis, which can affect protein digestion and absorption.
  • Corticosteroids: Long-term use of corticosteroids can lead to changes in protein metabolism, affecting how the body uses amino acids.
  • Laxatives and Anti-Diarrheal Medications: These can alter gastrointestinal transit time, potentially affecting protein digestion and absorption.
  • Anticonvulsants: Some antiepileptic drugs may interfere with vitamin D metabolism, which can affect protein metabolism indirectly.
  • Thyroid Medications: These can affect overall metabolism, including protein metabolism.
  • Diuretics: By affecting the electrolyte balance, diuretics may influence protein metabolism indirectly.
  • HIV Medications: Some antiretroviral drugs may affect protein absorption and utilization.

Of course, these interactions between drugs and protein absorption are complex and they depending on individual health, the specific drug, the dosage, and the length of time they are used.

Other Factors That Affect Protein Digestion

Inadequate stomach acid and enzyme production can significantly affect the digestion of proteins and have broader implications for overall health. Here’s how these factors play a role:

  • Reduced Activation of Pepsin: Stomach acid (hydrochloric acid) is essential for activating pepsinogen into pepsin, the main enzyme that breaks down proteins in the stomach. Without sufficient acidity, the conversion of pepsinogen to pepsin is less efficient, leading to reduced breakdown of proteins into smaller peptides. The pH of 1.5 to 3.5 is ideal for this process, and a higher pH may hamper the activation of pepsin.
  • Inefficient Protein Denaturation: Acid helps to denature or unfold proteins, exposing the peptide bonds that link amino acids and making them more accessible to digestive enzymes. Inadequate stomach acid may hinder this denaturation process, making proteins more resistant to enzymatic digestion.
  • Impaired Function of Other Proteolytic Enzymes: Besides pepsin, other proteolytic enzymes also function optimally in the acidic environment of the stomach. A lack of stomach acid might decrease the efficiency of these enzymes, further inhibiting protein digestion.
  • Potential Nutritional Deficiencies: Inadequate protein digestion can lead to malabsorption of amino acids, the building blocks of proteins. Over time, this may result in deficiencies in essential amino acids, impacting various physiological functions, from tissue repair to immune system function.
  • Increased Risk of Infection: Stomach acid has antimicrobial properties, killing or inhibiting potential pathogens in ingested food. A reduction in stomach acid might decrease this protective effect, increasing the risk of gastrointestinal infections.
  • Potential Underlying Causes: The inadequate production of stomach acid and enzymes could be a symptom of underlying health conditions, such as atrophic gastritis, certain autoimmune disorders, or chronic use of acid-reducing medications like proton pump inhibitors (PPIs). Addressing the root causes is essential for long-term management.
  • Therapeutic Considerations: For individuals diagnosed with inadequate stomach acid and enzyme production, supplemental digestive enzymes, dietary modifications, and other therapeutic interventions might be necessary. Working with healthcare providers to create a personalized treatment plan is crucial.

In summary, the adequate production of stomach acid and enzymes is vital for efficient protein digestion. Any inadequacy in these factors can lead to a cascade of digestive and nutritional issues. Understanding the underlying causes, monitoring the symptoms, and taking appropriate therapeutic measures are essential in managing these challenges and maintaining overall digestive health.

Low Stomach Acid, IgG Food Sensitivities, and Leaky Gut

IgG food sensitivities and leaky gut (aka increased intestinal permeability) are complicated conditions that can be affected by many factors. While there isn’t enough scientific evidence directly linking low stomach acid to IgG food sensitivities in people with leaky gut, it is plausible to consider how low stomach acid might indirectly contribute to these issues.

  • Inadequate Protein Digestion: As previously discussed, low stomach acid can lead to inefficient protein digestion. If proteins are not broken down properly, larger protein fragments might enter the intestines. In some people, these undigested proteins may trigger an immune response, resulting in the production of IgG antibodies against specific foods.
  • Intestinal Permeability (Leaky Gut): Low stomach acid may also affect other aspects of digestion, such as bile production and the balance of gut bacteria. These disturbances can contribute to a leaky gut, where the tight junctions between intestinal cells become more permeable. This increased permeability might allow undigested food particles, including those triggering IgG sensitivities, to pass into the bloodstream, exacerbating immune reactions.
  • Gut Microbiome Imbalance: Stomach acid plays a role in controlling the growth of bacteria in the gut (SIBO). Low stomach acid might lead to an imbalance in gut flora, which has been linked to increased intestinal permeability and possibly food sensitivities. A disrupted gut microbiome can further influence the immune system and its responses to food antigens.
  • Complex Interactions: Both IgG food sensitivities and leaky gut have many interacting factors that drive their presence. Each can be influenced by diet, stress, medications, infections, and genetic factors. Low stomach acid might be just one element in a complex web of interactions leading to these conditions.

It’s important to note that the relationships between low stomach acid, IgG food sensitivities, and leaky gut are not well-established in scientific literature. While there are plausible connections, more research is needed to definitively prove these links. Treatment for these conditions should be personalized and guided by healthcare providers familiar with the individual’s specific symptoms and medical history. It would likely involve a combination of dietary modifications, supplementation, stress management, and possibly medication to address the underlying causes and symptoms.

Are Amino Acid Supplements Safe?

Most people can safely take amino acid supplements within recommended dosages. Because our bodies naturally find amino acids in food and use them for essential functions, they usually tolerate amino acid supplementation well. Overall, if you need to supplement your protein needs, amino acid supplements can be a valuable addition. Consult a Registered Dietitian to understand your specific protein needs.

Medication Interactions With Amino Acid Supplements

The interactions between medications and amino acid supplements is complex, and it depends on the specific amino acid or supplement in question. Here’s a general list of some medications that might interact with amino acid supplements:

  • Levodopa: Protein intake affects the effectiveness of levodopa and this would also be true for amino acids.
  • Chemotherapy Drugs: Interactions might occur with certain amino acid supplements, potentially affecting the efficacy of cancer treatments.
  • Blood Pressure Medications: Arginine affects nitric oxide which might improve blood pressure
  • Thyroid Hormones: All foods interfere with thyroid medication absorption, so take this medicine on an empty stomach.

Supplement Interactions with Amino Acids

  • Vitamin B6 (Pyridoxine): This vitamin is critical for the metabolism of amino acids. It helps in the conversion of amino acids into other forms that your body can use. If you’re taking an amino acid supplement, you may also need to take a B6 supplement to ensure the amino acids are properly utilized by your body.
  • Magnesium: Magnesium helps to transport amino acids across cell membranes. Without adequate magnesium, your body might not utilize amino acids properly.
  • Vitamin B9 (Folic Acid): This vitamin is important for the metabolism of certain amino acids. In particular, it plays a role in the breakdown of the amino acid homocysteine. A deficiency in folic acid could result in high levels of homocysteine, which is linked to heart disease.
  • Vitamin C (Ascorbic Acid): Vitamin C helps to enhance the absorption of amino acids, especially the amino acid L-Carnitine, which is essential for fat metabolism.
  • Zinc: Zinc is involved in the metabolism of amino acids, carbohydrates, and lipids. It also enhances the action of amino acids in protein synthesis.
  • Iron: Iron is essential for the synthesis of amino acids, collagen, neurotransmitters, and hormones. Iron deficiency can affect amino acid metabolism, so it’s important to maintain adequate iron levels when taking amino acid supplements.

Testing Your Amino Acid Status

Specialized Testing For Amino Acids:

Plus Information on Vitamins, Minerals, Heavy Metals, and Methylation

Whenever there is a question about actual digestion and absorption of nutrients, it is impossible to know which nutrients are at an adequate level, and which are not without testing. The NutrEval provides insight into each of these critical areas. The Report is comprehensive.

Insurance companies generally don’t cover the cost of specialized testing so you will not usually hear them mentioned by your doctor. And, while these tests are not cheap, they are easily available here.

Food First!

Although this article discusses supplements in detail, don’t forget that we are absolutely committed to the “Food First” approach to nutrition. When it comes to your health, the totality of your eating habits far surpasses the impact of individual nutrients or any single supplement you consume. Even though this article doesn’t delve into the broader picture of your overall diet, it’s crucial to keep this element at the forefront of our minds. Your food needs to provide all the vitamins, minerals, fiber, and phytochemicals to nourish your body systems down to the cellular level.

Food choices, rather than supplements, are the most critical factors for a healthy gut microbiome. These trillions of tiny inhabitants in your gut affect your brain waves; they orchestrate your immune system. They possess the power to create molecules that can switch genes on or off and are even capable of synthesizing neurotransmitters. Opting for organic foods and steering clear of plastic packaging (including those labeled BPA-free) is a smart move to limit toxin exposure. The sum of all these parts leads to a powerful conclusion: the ultimate key to your health lies in the quality and balance of the food you consume. Supplements are secondary.

When you purchase linked products presented on this page, Supplement Sciences, LLC receives affiliate fees so that our dietitians can continue to create great content.

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Amino Replete (Pure Encapsulations)

This product contains all of the essential amino acids plus some other non-essential amino acids that have important functions. They include branched-chain amino acids.

Take 1 serving daily, mixed with 8 oz of water or juice, between meals, or as directed by a health professional.

Amount Per 1 Scoop (~ 9 g) Serving
Calories … 30
Total fat … 0g
Carbohydrate … 0g
Sugars … 5g
L-histidine … 80mg (from l-histidine)
L-isoleucine … 200mg (free-form)
L-leucine … 345mg(free-form)
L-lysine … 250mg(from l-lysine HCl)
L-methionine … 200mg (free-form)
L-phenylalanine … 175mg (free-form)
L-threonine … 161mg (free-form)
L-valine … 300mg (free-form)
L-alanine … 185mg (free-form)
L-arginine … 250mg (from l-arginine HCl)
L-glutamine … 439mg (free-form)
Glycine … 102mg (free-form)
L-serine … 88mg (free-form)
L-tyrosine … 169mg (free-form)
L-tryptophan … 42mg (free-form)
Pyridoxal 5’ phosphate … 3mg

Amino Complex Lemon NSF by Thorne

Because athletes need to know their supplements are trustworthy and compliant, every batch of an NSF Certified for Sport® product is tested for compliance with label claims and to ensure the absence of more than 200 substances banned by many major athletic organizations. Suggested Use: Mix 1 scoop with at least 8 ounces of water one to two times daily or as recommended by your health professional.

Amount Per 1 Scoop Serving
L-Cystine
 … 150mg
L-Histidine … 150mg
L-Isoleucine… 625mg
L-Leucine … 1.25g
L-Lysine … 650mg (Chloride)
L-Methionine … 50mg
L-Phenylalanine … 100mg
L-Threonine … 350mg
L-Tryptophan … 20mg
L-Tyrosine … 30mg
L-Valine … 625mg

To Sum It Up

While most people get plenty of amino acids from the protein in their foods, there are situations where supplements and testing are important. For example, atheletes use amino acid supplements to increase muscle mass and provide other benefits. They can also be a vital tool for meeting the nutritional needs of people at risk for poor absorption or with high protein needs. These situations would include wounds, digestive issues such as low stomach acid, and others who may have unique nutritional needs. Using tools like NutrEval testing, people are able to easily rule out suspected nutritional issues or work with their healthcare providers to figure our precise amino acid and micronutrient needs. Testing is the ideal way to tailor a precise supplementation regimen.


This Article is Not a Substitute for Medical Advice

Dietary supplements are not designed to diagnose, treat, cure, or prevent any disease. The Supplement Sciences website seeks to provide comprehensive access to the most relevant supplement information along with convenient online ordering. We do not provide medical advice and cannot guarantee that every product suggested is completely without risk. Since each person is unique in their health history and medication use, it is important to discuss supplements with your personal physician. Specifically, pregnant women and individuals being treated for cancer or liver or kidney problems must consult their physician about every nutritional supplement they plan to take. People taking medications for the treatment of HIV or with a history of organ transplant must not take supplements without consulting with their physician.


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