Amino Acids: Food Sources & Essential Functions

Amino acids are the building blocks of life. They are essential for muscle growth, tissue repair, immune function, and hormone production. While the body can make non-essential amino acids, essential amino acids must be obtained directly from our food.

In this guide, we’ll explore the vital roles of amino acids, their sources (including detailed amino acid food lists), their benefits, and practical tips to ensure you’re getting enough through your diet. Discover how a balanced intake of amino acids can enhance your nutrition and support your body’s needs.

What Are Amino Acids?

Amino acids are organic compounds that combine to form proteins. They play a crucial role in the body’s functioning and are vital for growth and development.

There are 20 different amino acids that can form proteins in the human body. Nine amino acids are essential, meaning we must get them from our food. Understanding the sources of essential amino acids is crucial for maintaining a balanced diet.

Often referred to as the “alphabet of life,” they combine in various sequences to form the vast array of proteins that play crucial roles in our bodies.  

Each amino acid is composed of a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a unique side chain.

Amino acids’ functions range from supporting metabolism, repairing body tissues, and aiding in the production of neurotransmitters to serving as precursors for enzymes and hormones.  In essence, amino acids are indispensable for the proper functioning and maintenance of life.

Types of Amino Acids

Amino acids, the building blocks of proteins, are classified into essential and non-essential.  Meanwhile, some of the non-essential amino acids become conditionally essential in times of stress or sickness when we cannot make enough of them from the essential amino acids.

Essential Amino Acids

The essential amino acids that your body cannot produce from other substrates are:

1. histidine,
2. isoleucine,
3. leucine,
4. lysine,
5. methionine,
6. phenylalanine,
7. threonine,
8. tryptophan and
9. valine.

Branched-chain amino Acids (BCAAs) (i.e., leucine, isoleucine, and valine) are critical for muscle growth and recovery. They are in protein-rich foods like meat, eggs, and dairy products.

Non-Essential Amino Acids 

While your body can make non-essential amino acids, they still play crucial roles in health and metabolism. For example, cysteine is vital for protein synthesis, detoxification, and various metabolic processes.

The following non-essential amino acids are still valuable in the diet, especially during periods of growth or stress: 

1. alanine,
2. arginine,
3. asparagine,
4. aspartic acid,
5. cysteine,
6. glutamic acid,
7. glutamine,
8. glycine,
9. proline,
10. serine, and
11. tyrosine.  

Conditionally Essential Amino Acids

Finally, conditional amino acids are a subset of the non-essential amino acids that become essential under certain conditions, such as illness, injury, or stress, where our bodies cannot make enough of them from the essential amino acids alone. 

The conditionally essential amino acids are:

1. arginine,
2. cysteine,
3. glutamine,
4. glycine,
5. taurine,
6. proline and
7. tyrosine. 

Do I Need to Manage My Amino Acid Intake?

Whole foods generally contain amino acids in the forms and ratios our bodies require.  So, if you’re following a diverse omnivorous diet from whole foods with plenty of protein, there’s no need to worry too much about your intake of individual amino acids.

However, people getting most of their protein from plant-based sources must ensure they get enough of each amino acid.  Plant-based foods tend to contain more of some amino acids and less of others, like tryptophan, methionine, and tyrosine.  People following a plant-based diet also require more amino acids to compensate for reduced bioavailability.  

Benefits of Eating Foods High in Amino Acids

Consuming foods rich in amino acids offers a multitude of health benefits, given their central role in nearly every biological process:

• Protein Synthesis: Protein synthesis is a fundamental muscle growth and cell repair process. Consuming adequate amino acids from diverse food sources supports efficient protein synthesis. This process helps build and repair tissues, making it essential for athletes and individuals recovering from injuries.
• Muscle Growth: Amino acids play a critical role in muscle growth. Ensuring a diet rich in essential amino acids is key for athletes and individuals undergoing recovery.
• Cell Repair: Amino acids are vital for cell repair and maintaining healthy tissues and organs.
• Muscle Growth and Repair: Amino acids, especially branched-chain amino acids (BCAAs), support the synthesis of muscle proteins, aiding in muscle growth and recovery after physical activity.
• Hormone Production: Amino acids are precursors to hormones like insulin and growth hormone, which regulate metabolism and growth.
• Enzyme Formation: Many enzymes, which facilitate biochemical reactions in our body, are proteins made from amino acids.
• Neurotransmitter Function: Amino acids synthesize compounds like serotonin and dopamine, which regulate mood, sleep, and cognition.
• Immune System Support: Amino acids like glutamine and arginine play a vital role in maintaining a healthy immune response, promoting the production of immune cells.
• Energy Production: Protein is a poor energy source, but if we consume minimal energy from carbohydrates and fat, amino acids can be broken down to provide an energy source for bodily functions.
• Tissue Repair: Amino acids are essential for the repair of tissues, especially skin, hair, and nails.
• Digestive Health: Certain amino acids aid in the production of digestive enzymes and help maintain the health of the digestive tract lining.
• Immune function: Amino acids also play a crucial role in supporting the immune system.

Incorporating various foods high in amino acids ensures our body has the tools to perform these vital functions optimally.

How Much Protein Do I Need?

Protein is an essential macronutrient for building and repairing tissues, producing enzymes and hormones, and supporting overall growth and development.  

The amount of protein you require depends on several factors, including age, gender, physical activity level, and unique health goals. However, prioritising protein while reducing energy from carbs and fat can improve satiety and reduce hunger, which helps with fat loss.

Our satiety analysis has shown the proportion of energy coming from protein in your diet (i.e. protein %) is the dominant factor in the satiety equation.  The chart below shows the satiety response to protein % in your food, created from our analysis of more than a million days of data from free-living people just like you. 

The chart below shows the distribution of protein intake from our dataset, showing that we naturally gravitate to the ‘bliss point’ protein intake that aligns with eating the most.  Intriguingly, this bliss point of 12.5% protein is just about the lower limit of the official Acceptable Macronutrient Distribution Range for protein of 10%.  So, if you’re treating the official minimum intake as a target, you’re likely setting yourself up for overeating. 

People who consume a very low protein diet (e.g., fruitarian or therapeutic keto) may eat less overall.  However, this may not be ideal due to the potential loss of lean muscle mass and lower nutrient density. 

The chart above shows an Optimal Nutrient Intake of 40% protein that we use as a stretch target in our Macros Masterclass.  Moving from 12.5% to 40% protein aligns with a 34% reduction in energy intake. 

How Much of Each of the Amino Acids Do You Need? 

As detailed below, each amino acid has its unique function(s), similar to vitamins and minerals.  Thus, we require minimum absolute intakes to ensure our bodies have the raw ingredients they need to function. 

Establishing minimum amino acid requirements has been challenging. The official targets have been revised considerably over the past two decades.  The table below shows the minimum intake of each amino acid established by the WHO and the Dietary Guidelines for Americans, which are set by the US Department of Agriculture (USDA) and Health and Human Services (HHS).  Both are set in milligrams per kilogram of body weight per day (mg/kg/day). 

Amino Acid	WHO (mg/kg/day)	USA (mg/kg/day)
Histidine	10	14
Isoleucine	20	19
Leucine	39	42
Lysine	30	38
Methionine+Cysteine	10.4 + 4.1 (14.5 total)	19 total
Phenylalanine+Tyrosine	25 total	33 total
Threonine	15	20
Tryptophan	4	5
Valine	26	24

It’s important to note that these recommended daily intakes are the minimum amounts we need to prevent deficiency-related diseases.  As you’ll see below, these minimum amino acid targets typically align with the maximum energy intake. 

Optimal Amino Acid Intake

When we dive deeper, our analysis shows that getting more of each amino acid per calorie aligns with eating less.   The chart below shows the satiety response curves for each amino acid.

The table below shows each essential amino acid’s bliss point and the Optimal Nutrient Intake (in grams per 2000 calories).  We’ve also shown the reduction in energy intake (i.e. satiety response) that occurs when we move from the bliss point to the ONI. The bliss point is the concentration of each amino acid that aligns with maximum energy intake. In contrast, the optimal nutrient intake is a stretch target that aligns with eating less.

Amino acid	Bliss Point	ONI	Satiety Response
tryptophan	0.75	2.2	21%
cystine	0.90	2.1	23%
methionine	1.45	4.1	27%
histidine	1.9	4.7	24%
phenylalanine	2.6	6.9	26%
tyrosine	2.1	5.7	25%
threonine	2.6	7.0	25%
valine	3.1	8.0	27%
isoleucine	3.1	7.7	25%
lysine	4.6	13.2	24%
leucine	4.7	13.2	24%

Cysteine

Cysteine is a sulphurous amino acid required to produce insulin, skin, hair, biotin, glutathione, taurine, and sulphate.  It’s critical for detoxifying chemicals, buffering oxidative stress, and mediating insulin resistance.

N-acetylcysteine (NAC) is a form of the amino acid cysteine that supports detoxification and liver health. Although it’s considered non-essential, lack of cysteine is associated with poor immune function, aging, cancer, decreased ability to metabolise drugs and toxic chemicals, and poor wound healing. 

Satiety Response to Cysteine

People who hit the ONI target for cysteine (2.1 g/2000 calories) consume 23% less energy than those who consume the bliss point intake (0.9 g/2000 calories).

Cysteine-Rich Foods

Popular cysteine-rich foods include :

• egg white,
• liver,
• cod,
• shrimp,
• ground pork,
• whole egg,
• salmon,
• caviar,
• asparagus,
• duck eggs,
• liver,
• roast beef,
• pork ribs, and
• oysters.

Histidine

Histidine is an essential amino acid that your body uses to regulate the utilisation of minerals like iron, copper, molybdenum, zinc, and manganese.  Low histidine is associated with allergies, poor hearing, heavy metal toxicity, schizophrenia, hypertension, Parkinson’s Disease, poor memory, rheumatoid arthritis, and thyroid issues.

While too little can contribute to the adverse outcomes mentioned above, too much can also exacerbate symptoms. 

Excess histidine relative to other amino acids converts readily to the dreaded neurotransmitter histamine, which has also been linked to allergies, gastrointestinal symptoms, metabolic dysfunction, and memory disorders.  Thus, it’s critical to get your amino acids from fresh, complete protein sources with a balanced amino acid profile is essential.

Satiety Response to Histidine

People who hit the ONI target for histidine (4.7 g/2000 calories) consume 24% less energy than those who consume the bliss point intake (1.9 g/2000 calories).

Histidine-Rich Foods

Popular histidine rich foods include:

• sirloin steak,
• ground pork,
• cod,
• tuna,
• beef broth,
• nori,
• egg white,
• roast beef,
• chicken breast,
• mackerel and
• pork.

Isoleucine

Isoleucine is another essential amino acid required for healing muscle tissue, supporting energy production, regulating the immune system, and recovering from strenuous physical activity. 

Isoleucine is also an essential cofactor for macronutrient metabolism, haemoglobin synthesis, glucose transport, and mediating a healthy stress response.

Isoleucine deficiency can result in muscle wasting, muscle tremors, and low energy levels.

Satiety Response to Isoleucine

People who hit the ONI target for isoleucine (8.8 g/2000 calories) consume 25% less energy than those who consume the bliss point intake (3.2 g/2000 calories).

Isoleucine-Rich Foods

Popular foods containing more isoleucine per calorie include:

• egg white,
• cod,
• tuna,
• nori,
• chicken breast,
• sirloin steak,
• shrimp,
• mackerel,
• watercress,
• salmon,
• ground pork,
• chard,
• liver,
• beef broth,
• filet mignon and
• roast beef.

Leucine

Leucine is an essential amino acid that’s considered to be a branched-chain amino acid (BCAA).  Like isoleucine and valine—the other BCAAs—these amino acids get a lot of attention because they’re most important for muscle protein synthesis. 

We require leucine for cell signalling, muscle protein synthesis, stimulating the release of anabolic hormones regulating blood sugar, promoting growth and recovery of muscle and bone tissues, and growth hormone production.  Hence, leucine is critical for development or injury, and intake may increase in these scenarios.

Falling short of your leucine intake for prolonged periods can result in decreased appetite, trouble feeding, lethargy, stunted growth, weight loss, skin rashes, hair loss, and unexplained skin peeling, known as desquamation.

Work by Professor Don Layman highlights that older adults require at least three to four grams of leucine, which corresponds to 30 to 40 g of protein per meal, to initiate muscle protein synthesis.

Interestingly, this target aligns with the bliss point for leucine, or 4.7 grams/2000 calories, which seems to be the point at which our bodies seem to get more from our diet. 

Satiety Response to Leucine 

People who hit the ONI target for leucine (13.2 g/2000 calories) consume 27% less energy than those who consume the bliss point intake (4.7 g/2000 calories).

Leucine-Rich Foods

Some of the most leucine-rich foods include:

• egg whites
• chicken breast
• sirloin steak
• Greek yogurt (non-fat)
• shrimp/prawns
• liver
• cottage cheese (low-fat)
• salmon  
• mackerel
• filet mignon
• chicken thigh
• ground beef  
• chicken drumstick  

For more details, see Visualising 30 Grams of Protein in Everyday Foods.

Lysine

Lysine is a necessary component of the majority of proteins within your body. 

We require lysine for muscle growth, calcium absorption, and carnitine synthesis.  Carnitine shuttles fatty acids into the mitochondria to make energy.  Hence, it makes sense that lysine deficiency manifests as anaemia, fatigue, poor concentration, loss of bone mass, tiredness, and infertility. 

We find lysine in limited quantities in plant foods like corn, nuts, and seeds, which are incomplete proteins.  If you don’t get enough lysine from other foods, you can’t fully utilise the protein you eat. 

Satiety Response to Lysine

People who hit the ONI target for lysine (13.2 g/2000 calories) consume 24% less energy than those who consume the bliss point intake (4.6 g/2000 calories).

Lysine-Rich Foods

Some popular lysine-rich foods include:

• cod,
• tuna,
• sirloin steak,
• shrimp,
• mackerel,
• salmon,
• egg white,
• chicken breast,
• ground pork,
• roast beef, and
• filet mignon.

Methionine

Methionine is a sulphurous essential amino acid used to produce other sulphur-containing compounds within the body.  We require sulphur for detoxification, cardiovascular health, synthesising hair, skin, and nails, protecting your body from oxidative stress, and building and fixing DNA.

Methionine contains a methyl group (CH3), which drives processes like methylation.  Unfortunately, plant-based foods—especially beans and vegetables—tend to have less methionine, meaning someone following a strictly plant-based vegan diet should pay attention to how much they’re getting.

A methionine deficiency can impair detoxification and induce depression, fatigue, anxiety, disorders related to faulty methylation, connective tissue dysfunction, and nails and hair that break easily.  However, you cannot fully utilise other amino acids if your methionine intake is inadequate because amino acids work synergistically.  Thus, methionine inadequacy can also contribute to the deficiency of other amino acids.

Satiety Response to Methionine 

People who hit the ONI target for methionine (4.3 g/2000 calories) consume 27% less energy than those who consume the bliss point intake for methionine (1.45 g/2000 calories).

The satiety response to methionine is greater than all other amino acids. This is likely because methionine is the limiting amino acid in processed foods. Hence, we need to consume more protein and energy to get enough methionine to build complete proteins in our bodies.

Methionine-Rich Foods

Popular methionine-rich foods include:

• egg white,
• cod,
• tuna,
• shrimp,
• mackerel,
• salmon,
• sirloin steak,
• chicken,
• nori,
• ground pork and
• scallops.

Phenylalanine

Phenylalanine is another essential amino acid that’s a precursor of tyrosine.  We require tyrosine to make energy, thyroid hormones, and dopamine.

Phenylalanine is vital for producing dopamine, norepinephrine, and epinephrine neurotransmitters. It can be found in high-protein foods like eggs, cheese, and soy products.”

Dopamine production may play the most significant role in tyrosine production.  Dopamine is a neurotransmitter involved with satisfaction, concentration, and reward.  Thus, it can allow you to feel content with your life and how much you ate and enhance learning and memory. 

Low dopamine is associated with conditions like depression, anxiety, attention deficit disorder (ADD) and attention-deficit/hyperactivity disorder (ADHD), as well as neurodegenerative conditions like Parkinson’s, Alzheimer’s, and dementia.  Low phenylalanine—and thus tyrosine and dopamine—can also manifest as fatigue and addiction. 

A condition known as phenylketonuria (PKU) occurs when the enzyme that converts phenylalanine to tyrosine does not work correctly.  In this case, phenylalanine builds up to toxic levels and can contribute to cognitive dysfunction, brain damage, and even death.

Satiety Response to Phenylalanine

People who hit the ONI target for phenylalanine (5.6 g/2000 calories) consume 26% less energy than those who consume the bliss point intake for phenylalanine (2.6 g/2000 calories).

Phenylalanine Rich Foods

Popular phenylalanine foods, that provide more phenylalanine per calorie, include:

• egg white,
• watercress,
• nori,
• tuna,
• cod,
• shrimp,
• liver,
• sirloin steak,
• mackerel,
• ground pork,
• chicken breast and
• salmon.

Threonine

We require threonine for healthy-functioning cardiovascular, hepatic (liver), nervous, gastrointestinal, and immune systems. Threonine also helps form connective tissues like tooth enamel, collagen, and elastin, serving as a glycine precursor. Inadequate threonine is associated with confusion, digestive problems, agitation, fatty liver disease, and depression. 

Satiety Response to Threonine 

People who hit the ONI target for threonine (7.6 g/2000 calories) consume 25% less energy than those who consume the bliss point intake (2.6 g/2000 calories).

Threonine-Rich Foods

Popular threonine foods, supplying the most threonine per calorie, include:

• nori,
• watercress,
• tuna,
• cod,
• sirloin steak,
• egg white,
• mackerel,
• salmon,
• shrimp,
• chicken breast,
• ground pork,
• roast beef, and
• liver.

Tryptophan

If someone consumes a diet low in niacin (vitamin B3), the body can make it from tryptophan. 

Tryptophan also serves as a precursor to the feel-good neurotransmitter serotonin and the sleep-promoting neurotransmitter melatonin.  Because it serves as a serotonin precursor, tryptophan helps manage sweet cravings and appetite and makes you feel content and happy.

Tryptophan deficiency is associated with anaemia, anxiety, depression, decreased serotonin, fatty liver disease, insomnia, poor concentration, disordered eating habits, and suicidal thoughts. 

The tryptophan is limited if you consume a lot of corn (maize).  Thus, you must ensure you get adequate tryptophan from other sources. 

Satiety Response to Tryptophan

People who hit the ONI target for tryptophan (1.9 g/2000 calories) consume 21% less energy than those who consume the bliss point intake (0.75 g/2000 calories).

Tryptophan-Rich Foods

Popular tryptphan rich foods include:

• beef broth,
• watercress,
• tuna,
• cod,
• egg white,
• ground pork,
• shrimp,
• sirloin steak,
• salmon,
• mackerel,
• chicken,
• liver,
• mozzarella, and
• spinach.

Tyrosine

In a healthy person, tyrosine is considered non-essential, as we can make it from phenylalanine.  However, this amino acid becomes conditionally essential if someone has a condition like phenylketonuria (PKU). 

Because tyrosine is a dopamine precursor, it boosts cognition and working memory under stress.  It also improves exercise tolerance in heat and is a precursor to thyroid hormones.

Low tyrosine intake is associated with low blood pressure, decreased body temperature, restless leg syndrome (RLS), stress, exhaustion, poor memory, inadequate concentration, reduced thyroid function, and apathy.

Satiety Response to Tyrosine

People who hit the ONI target for tyrosine (5.7 g/2000 calories) consume 25% less energy than those who consume the bliss point intake (2.1 g/2000 calories).

Tyrosine-Rich Foods

Some popular tyrosine rich foods, that contain more tyrosine per calorie, include:

• egg white,
• nori,
• salmon,
• cod,
• tuna,
• ground pork,
• shrimp,
• sirloin steak,
• mackerel,
• chicken breast,
• liver, and
• watercress.

Valine

Our final essential amino acid, valine, is required for emotional regulation, immune function, muscle regeneration, coordination, and growth.  

Low valine consumption may result in poor muscle tone, vomiting, lethargy, excessive dehydration, and seizures.

Satiety Response to Valine

People who hit the ONI target for valine (8.5 g/2000 calories) consume 27% less energy than those who consume the bliss point intake for valine (3.1 g/2000 calories).

Valine-Rich Foods

Popular valine-rich foods that supply more valine per calorie include:

• nori,
• egg white,
• watercress,
• cod,
• tuna,
• mackerel,
• sirloin steak,
• salmon,
• liver,
• shrimp,
• chicken breast,
• ground pork and
• liver.

Glycine

Glycine is an important amino acid found in collagen and gelatin from the connective tissue of aminals. Glycine-rich foods like bone broth and poultry can support various bodily functions.

While we don’t have intake data on glycine from our Optimisers, this conditionally essential amino acid is worth mentioning for its role in synthesising the master antioxidant glutathione and connective tissue. 

It is also critical for balancing methionine intake, as too much methionine in proportion to glycine can result in high homocysteine levels.

Aside from these rules, glycine has many other benefits, like sounder sleep, improved liver function, and healthier skin.  It has a sweet taste, which makes it an excellent zero-carb sugar replacement in drinks and smoothies.  However, if you begin supplementing glycine, glutamine intake must be considered, too.

Inadequate glycine levels or insufficient intake of its precursor threonine can contribute to low energy levels, slowed wound healing, impaired detoxification, premature ageing, and connective tissue dysfunction.

Glycine-Rich Foods

Glycine rich foods, that provide more glycine per calorie include:

• bone broth,
• collagenous cuts of meat (i.e., bones and joints),
• shrimp,
• cod,
• watercress,
• ground pork,
• beef liver,
• salmon,
• egg white,
• chicken liver,
• lamb liver,
• roast beef,
• pork ribs,
• chives, and
• oyster.

Action Steps

Understanding amino acids’ role can revolutionise your health journey. Adequate protein intake for those on a whole-food diet should suffice.  Incorporating a variety of amino acids into your diet is crucial for overall health. Whether you’re looking to enhance muscle growth, support immune function, or improve your skin’s health, understanding the functions and sources of amino acids can help you make informed dietary choices.

Increase Your Protein Intake

Our high-protein food lists can assist if you struggle to get adequate protein (e.g. less than 12.5%).

Increase Your Protein %

But if you’re ready to dial up your satiety to crush your craving with fewer calories, check out our protein-rich food lists.

Need Some Extra Help? 

Finally, our Macros Masterclass is here to help you adjust your diet to meet your protein needs without excess energy.  When you’re ready to elevate your dietary standards and reach for the Optimal Nutrient Intakes for all the essential nutrients, our Micros Masterclass awaits.

More

• A Guide to Leucine-Rich Foods for Optimal Protein Synthesis
• Best Vitamins for Weight Loss (According to the Data)
• Mineral Mastery: Satiating Hunger and Elevating Satiety
• What Are Macros (and How to Optimise Them for Weight Loss)
• Ultra-Processed Foods and the Hedonic Factor
• Optimal Amino Acid Intakes for Satiety and Weight Loss
• NutriBooster Recipe Books
• Macros Masterclass
• Micros Masterclass