If you’re an athlete or are in the business of losing body fat and leaning up, a healthy protein intake is a top priority. What you might not realize is that the amino acids in protein are what make it so nutritionally beneficial.
When you eat protein foods, whether it’s steak, fish, eggs, or black beans, your body breaks the protein apart into individual amino acids, reorders them, refolds, them, and turns them into whatever it needs at the time. This makes sufficient intake of amino acids not just critical for a fast recovery from exercise, but necessary for all of the following:
Deep, restful sleep
Enjoyment & relaxation
Ability to cope with stress
Strong Immune system
Metabolic rate and fat burning
Most people just worry about reaching their daily protein intake goal and don’t give much thought to the individual amino acids. Assuming you eat a well-rounded diet, this approach works just fine; however, if your diet is restricted in any way, it’s a good chance you’re not getting all the amino acids you need. For example, avoiding meat or dairy, relying on protein powders, or simply having a limited diet due to a busy lifestyle could mean you’re missing out on certain nutrients your brain and body needs.
This article will provide a brief rundown on the amino acids, with a spotlight on eight amino acids that have special relevance for well being and body composition. Specific food sources of each amino acid are included. It should be noted that in general, you can get the amino acids you need from food; however, in certain cases supplementation is worth the investment.
What Are Amino Acids?
For human nutrition, there are 20 amino acids:
- 9 are considered essential (you must get them from food)
- 4 that are non-essential (if you have a balanced diet, your body should be able to produce them)
- 7 are conditionally essential (your body can normally produce them except in times of illness or stress in which case they need to be consumed in food).
Things can get a little confusing because in addition to the 20 protein-based amino acids we usually talk about, there are many other non-protein amino acids. There are also amino acid composites like creatine or carnitine (made from two amino acids), and compounds synthesized from amino acids, such as GABA or serotonin.
Finally, there are compounds like taurine, which technically is not an amino acid but is often called one. Along with tyrosine, arginine, and cysteine, it is considered “semi-essential” in children because the metabolic pathways that synthesize them are not fully developed.
Essential Amino Acids:
Histidine Isoleucine Leucine
Lysine Methionine Phenylalanine
Threonine Tryptophan Valine
Non-Essential Amino Acids:
Alanine Arginine Aspartic Acid
Cysteine Glutamic Acid Glutamine
Glycine Proline Serine
Examples of Non-Protein Amino Acids:
Ornithine Citruline Homocysteine
Examples of Amino Acid Compounds
Creatine Carnitine GABA
Benefits of Certain Amino Acids
#1: BCAAs: Leucine, Isoleucine & Valine
The BCAAs are actually three essential amino acids. They have a branched side chain that simplifies the job of converting each amino acid into energy during intense exertion. They can improve how long you can go before exhaustion for a couple of reasons.
First, BCAAs change the way your body uses glycogen (a fuel source for muscle). When subjects did a sprint workout designed to fully deplete glycogen, BCAA supplementation led to a 17 percent greater time to exhaustion due to the BCAA’s ability to switch the body into burning more fat for fuel.
BCAAs can also reduce the sensation of fatigue. When BCAA levels in the blood drop, more tryptophan reaches the brain. Tryptophan turns into serotonin in the brain and leads to feelings of tiredness and mental fatigue during exercise. BCAAs prevent this.
The most important amino acid of all is a BCAA known as leucine that regulates mTOR, which is the primary pathway involved in muscle building. Some people have suggested just taking leucine instead of all three BCAAs as a package. However, this can lead to an imbalance in blood amino acid levels, reducing the tissue repair response.
Therefore, you want to get your BCAAs from a food source like meat or fish, whey protein, or a leucine-enriched supplement that provides leucine in a ratio of about 4-to-1 to isoleucine and valine.
Where To Get It: Whey protein is the best supplemental protein source because in addition to containing the BCAAs in the right quantities, it has a large array of other amino acids, which play a role in sustaining protein synthesis. Milk, eggs, grass-fed beef, and salmon are other BCAA-rich foods, followed by poultry and other animal products.
Unfortunately, plant foods are low in BCAAs, with seeds, soy, and some vegetables like watercress being highest in leucine. Yellow peas, lentils, and other beans are more vegetarian foods with a moderate amino acid profile.
Tyrosine activates energizing pathways in the brain. It can also reduce your desire to eat. Specifically, it can improve dopamine levels so that you have fewer cravings for foods high in sugar and fat.
Tyrosine is also beneficial during sleep deprivation. In one study, researchers gave a tyrosine supplement to subjects in the military who were sleep deprived and had them perform a series of active performance tasks with a cognitive component. Tyrosine was able to offset the decline in performance that was not seen in a placebo group.
For the general population, tyrosine supplementation may be useful when needing to perform well on an exam, job interview, or work project on little sleep. Being as most of us walk around sleep deprived with too many responsibilities, a diet rich in tyrosine is a top priority.
Where To Find It: Eggs, fish, poultry, wild game (bison, elk, etc.), beef, pork, and cheese. Leafy greens such as spinach and mustard greens are also packed with tyrosine. Tyrosine supplements are also available in stand alone form or in blends with other amino acids.
Tryptophan provides the raw material for the brain to manufacture serotonin, a neurotransmitter that boosts mood, calms the central nervous system, and conveys a feeling of contentment. It is important for achieving satisfaction during a meal so that appetite is better managed and you don’t go bingeing on everything in your kitchen.
Increased serotonin can also improve sleep, which is why tryptophan is often used as a first line of defense to fight insomnia. Tryptophan also improves release of growth hormone, which is necessary for exercise recovery, has anti-aging effects, and encourages fat burning.
Where To Get It: Although tryptophan is available in many foods (bananas, beans, dairy, meat, nuts, and grains), eating foods containing tryptophan won’t affect brain levels of serotonin. Tryptophan competes for transport into the brain with the BCAAs. Tryptophan is the least abundant amino acid protein, meaning that the presence of BCAAs will inhibit tryptophan influx into the brain, lowering serotonin levels.
For this reason, diets high in BCAAs are associated with low mood and depression. The most well known (but incorrect) serotonin-producing trick is having milk before bed. Although it does contain tryptophan, milk is also packed with BCAAs, which compete for passage into the brain and reduce tryptophan influx. People who swear by milk for sleep are most likely getting a psychological placebo-like effect. A research review of the issue recommends supplementing with tryptophan at opportune times, such as before bed.
Threonine is important for the formation of tissue in the body and plays a key role in the production of collagen and elastin, giving it anti-aging benefits. Threonine also helps metabolize fat, preventing the buildup of fat in the liver. It can also be used by the liver to produce glucose, making it useful for stabilizing blood sugar.
Where To Get It: Animal products are packed with threonine—beef and lamb providing the greatest concentration. Seafood, soy, beans, nuts, and seeds also supply a healthy dose of threonine. Unless you completely avoid these foods, supplementation is unnecessary.
Glycine is a super important amino acid, having many therapeutic benefits in addition to supporting overall health. First, it has anti-aging effects, being used to form collagen for tissue repair. It’s also used in the synthesis of creatine—the energy source that powers maximal intensity exercise—and enhances blood sugar control.
Interestingly, glycine has circadian effects and may indirectly contribute to improving the occasional sleepiness and fatigue that come with sleep restriction. Finally, glycine is especially useful for wound healing as well as improving GI health because it helps rebuild the tissue that lines the digestive tract.
Where To Get It: Foods high in gelatin, including all animal products will provide a healthy dose of glycine. Plant-based sources include beans, spinach, kale, cauliflower, cabbage, pumpkin, banana, and kiwi. Most nuts and seeds are also good sources. During times of extreme training stress or if you are struggling with gut issues, supplementation with glycine in powder form may be beneficial.
Glutamine is the most abundant amino acid in the muscles and blood, providing fuel for rapidly dividing cells, enhancing muscle repair, and boosting the immune system.
Glutamine has antioxidant effects, being used by the body to synthesize glutathione, the body’s internally produced antioxidant. Intense training significantly depletes glutamine, and studies of elite athletes, especially endurance athletes, show that they are more likely to get sick after an event due to reduced glutamine levels.
Glutamine can also be used by the brain as an energy source, making it useful when you are trying to deal with cravings for high-carb foods. In fact, glutamine is used in the treatment of alcohol and drug withdrawal because of how it helps stabilize brain function and calm obsessive thoughts.
Where To Get It: Present in animal products, nuts, seafood, and seeds, most healthy people don’t need supplemental glutamine. It can be taken therapeutically during times of intense training loads or as a way to outsmart food cravings. Try 2 grams of powdered glutamine in water anytime you feel a craving coming on.
Carnitine is actually an amino acid composite made from lysine (important for tissue repair and immunity) and methionine (needed for absorption of nutrients and metabolism of fats). It can make such a powerful difference in energy levels and metabolic health that it’s worth highlighting here.
Carnitine is responsible for the transport of fats into the cells to be used for energy in the body. By raising the level of muscle carnitine, you support the fat burning process and increase energy levels. For example, one study found that 6 months of carnitine supplementation resulted in a 35 percent greater work output despite a lower rating of perceived exertion in competitive triathletes.
Health benefits of adequate carnitine include increased less inflammation, improved cognition and motivation, and better insulin sensitivity.
Where To Get It: Animal products like meat, fish, poultry, and milk are the best sources. In general, the redder the meat, the higher its carnitine content. Dairy products contain carnitine primarily in the whey fraction. If you choose to supplement, there are three commercially available forms:
L-Carnitine is typically used for athletic performance and metabolic benefits.
Acetyl-L-Carnitine is often used for treating Alzheimer’s and brain disorders.
Propionyl-L-Carnitine is used for treating heart disease and peripheral vascular disease.
Avoid D-carnitine supplements. They interfere with the natural form of L-carnitine and may produce unwanted side effects.
Best known for increasing nitric oxide, a compound that regulates blood vessel flexibility so that you have improved delivery of essential nutrients to cells, arginine is also important for stimulating release of growth hormone.
This combination makes arginine important as you age: Every year after age 30, GH levels naturally plummet and vascular health is impaired. People naturally dial back their high-quality protein intake as they get older, making arginine intake a key issue for anti-aging.
Studies show arginine supplementation can significantly lower blood pressure and beneficially affect carbohydrate metabolism. It also appears to have immune benefits in people recovering from illness or surgery.
Where To Get It: Animal products including eggs, dairy products, poultry, beef, seafood, seeds, and nuts. Chocolate, soy, and brewer’s yeast also contain a decent amount of arginine. Whey protein is a good supplemental source and most amino acid blends contain a healthy dose of arginine as well.