Evidence: High Possible Benefits: Very High Safety: Reasonable
TABLE OF CONTENTS
What is EAA?
EAA stands for essential amino acids. These amino acids are required for survival but the body cannot synthesize them, so we need to obtain them from food or supplements to survive. Essential amino acids include lysine, histidine, threonine, methionine, tryptophan, phenylalanine, leucine, isoleucine, and valine. Because there are 9 EAAs, an EAA supplement can have a wide variety of effects. This article is about the main benefits of an EAA supplement, its potential side effects, the best time to take it, and more.
What does EAA do for the body?
EAA contains 9 essential amino acids. Each of them has its unique effect on the body. Since there are at least 9 “ingredients” in most EAA supplements, they do have a wide variety of pleasant and unpleasant effects.
Leucine is the main activator of protein synthesis. It also helps activate the SIRT1 gene. This effect may be associated with slowing down aging but more research is needed to prove this.
Isoleucine has strong anti-catabolic effects, which means it slows down the breakdown of muscle mass, amongst other things in the body.
Valine shares similar properties to those of isoleucine and leucine but to a lesser extent. Its effects are not as pronounced as those of leucine and isoleucine.
Phenylalanine mainly plays a role in adrenergic and dopaminergic neurotransmission. The body converts L-phenylalanine into L-Tyrosine, which is then converted into L-DOPA. Decarboxylation of L-DOPA results in the synthesis of dopamine. Dopamine can then convert into adrenaline and noradrenaline through the dopamine-beta-hydroxylase enzyme.
Tryptophan can be converted into 5-HTP, which acts as a precursor to serotonin. Serotonin can then convert into melatonin, which is why people often take tryptophan to enhance sleep quality. The body can also make NAD+ molecules from tryptophan through a series of biological reactions. This pathway is most active in the morning when as much as 95% of tryptophan consumed is used directly for this purpose.
Lysine serves as a building block for many proteins in the body. This amino acid interacts with arginine in many ways and should be kept in balance unless you have a strong reason to off-balance them (such as herpes simplex). Taking too much of one can override the functions of the other. For example, high doses of lysine could hinder the ability of arginine to produce nitric oxide.
Histidine helps regulate and metabolize trace minerals, such as copper, zinc, iron, manganese, and more. This amino acid is used by the body to make specific hormones and metabolites that impact kidney function, the transmission of nerves, stomach secretions, and the immune system.
Threonine acts as a precursor to glycine. Among other roles, glycine works in the brain to reduce unwanted muscle contraction. This is why people sometimes take threonine to prevent muscle weakness or muscle spasms. Unfortunately, the amino acid doesn’t seem effective in this regard.
Methionine is a “methyl donor” and plays an important part in the methylation process. Because of this, it can speed up or help maintain many chemical reactions in the body. This amino acid acts as an antioxidant and helps protect damaged tissues.
Possible benefits
It is important to note that all of the potential benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.
Major benefits
Correcting a deficiency – Since essential amino acids are essential, the body needs at least some amount of them to survive and function properly. Not getting enough of them can lead to multiple health problems, some of which can be serious. Fortunately, a deficiency in these amino acids is relatively rare and shouldn’t happen unless you consume very low amounts of protein.
Minor benefits
Reduced fatigue – Leucine, isoleucine, and leucine supplements can reduce both mental and physical fatigue after a workout when taken at doses of 10+ grams (combined in a BCAA supplement). This benefit directly leads to other proven benefits, such as improved processing accuracy and reaction time.
Increased fat oxidation and weight loss – When combined with aerobic exercise (such as running, swimming, or riding a bike), the BCAA trio can aid the fat-burning effect by preserving glucose and helping the body utilize fat as a fuel source.
Improved aerobic exercise – This effect mainly applies to untrained or lightly trained individuals. Whether or not EAA can increase cardio and time to exhaustion in athletes is not yet clear.
Improved carbohydrate absorption – BCAAs promote insulin secretion from the pancreas and help the body utilize carbohydrates. Taking these amino acids before a carbohydrate-rich meal lowers the blood glucose spike from it.
Reduced symptoms of herpes simplex – Lysine supplements can override and block the absorption of arginine. Arginine is considered a nutrient for HSV and promotes replication while lysine prevents replication. If you suffer from herpes, try supplementing with 2 or more grams of L-lysine.
Improved mood and well-being – Supplemental phenylalanine can improve well-being mainly for people with depression but also for non-depressed individuals. L-lysine supports emotional processing and healthy functional connectivity between the default mode network and emotion-related brain regions. This results in a calmer mood, improved well-being, and greater life satisfaction.
Improved social cognition – L-tryptophan has been shown by multiple studies to support prosocial interactions and increase people’s motivation to socialize. Those who take the supplements also tend to be more empathetic, charitable, and altruistic.
Reduced appetite – L-tryptophan is fairly effective at suppressing appetite and reducing food cravings. Those who tend to overeat as a coping mechanism tend to eat less when they take tryptophan.
Weight loss – Histidine has a very mild but beneficial effect on weight loss in obese women with metabolic syndrome. It is somewhat effective at lowering insulin resistance and fat mass. L-tryptophan can also aid fat loss but the benefit is secondary to the reduction of appetite. If you take EAA or isolated tryptophan but eat the same amount of calories, it will not have a notable impact on your weight.
Improved sleep quality – 5-HTP, a byproduct of tryptophan, helps synthesize serotonin, which can turn into melatonin at night. Those who take the supplement often have deeper and more restorative sleep. One study has also found that taking L-tryptophan reduces sleep terrors. If you take the supplement to improve sleep quality, take it 30-60 minutes before bedtime.
Improved exercise performance – Multiple studies support that L-tryptophan is at least mildly effective at increasing power output and delaying time to exertion during exercise sessions.
Reduced symptoms of depression – This effect is mostly due to phenylalanine and the main reason is an increase in dopamine levels. About 80% of those who take the supplement notice an improvement in their well-being. It is important to note that this improvement happens in the short term and likely won’t last once you stop taking the supplement.
Reduced stress – L-phenylalanine is somewhat effective at reducing acute stress when taken at low doses. Higher doses may actually increase stress response because of elevated adrenaline levels.
Treatment of vitiligo – Several studies show that L-phenylalanine may be helpful for people with vitiligo when paired with ultraviolet A light.
Reduced pain – D-Phenylalanine (DPA) slows the action of the enzymes carboxypeptidase A or endorphinase and enkephalinase, which can directly reduce pain. The research on this effect is rather limited.
Reduced symptoms of ADHD – People with ADHD have a general deficit in amino acid transport, absorption, or both. This often leads to significantly lower levels of phenylalanine and tyrosine in the body.
Reduced birth defects – Eating more methionine during pregnancy can lower the risk of neural tube birth defects.
Improved working memory – L-phenylalanine is a precursor to L-tyrosine, which has been shown to preserve working memory during acute stressors. These two amino acids do not seem to have a memory-boosting effect outside stressful situations.
Reduced muscle contractions in people with spinal spasticity – Taking 2 grams of L-threonine 3 times a day has been shown to reduce muscle contractions in people with spinal spasticity caused by spinal cord injury. Unfortunately, the benefit is only modest and there is not much evidence to support it.
Possible side effects
These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.
Drowsiness
Stomach pain
Nausea
Vomiting
Diarrhea
Blurry vision
Amino acid imbalance – All essential and non-essential amino acids need to be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects without enough of another amino acid. That is most notably the case for glycine and methionine, but the principle applies to other amino acids, such as lysine and arginine, and the BCAA trio. Using a single amino acid supplement may lead to a negative nitrogen balance, which can lessen how well your metabolism works. A protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.
Increased levels of homocysteine – Even low doses of methionine can elevate homocysteine levels in the blood. This is especially the case for people with impaired methylation.
Worsened symptoms of ALS – Supplemental L-threonine may worsen lung function in those suffering from ALS. This was observed when people took 2-4 grams daily for up to 12 months.
FIGLU – If you are deficient in vitamin B9 (folate), too much histidine can cause an unwanted chemical called formiminoglutamic acid (FIGLU) to build up in the body. People with a vitamin B9 deficiency should avoid the supplement.
Serotonin syndrome – This potential side effect can happen to those who take high doses of tryptophan. Fortunately, it is uncommon and shouldn’t happen unless you take over 100 mg of tryptophan per kg of body weight or if you combine the supplement with SSRIs or SNRIs.
Allergic reactions – Supplemental phenylalanine can trigger allergic reactions that can cause itching, tingling in the mouth, swelling of the face or hands, and trouble breathing.
Toxicity – While acute toxicity from any essential amino acid is rare, taking high amounts of EAA could lead to chronic toxicity and cause multiple health problems, some of which are serious. For example, doses of leucine over 500 mg/kg/d have caused increases in serum ammonia and very high doses of isoleucine can increase levels of urea in the body. To prevent chronic toxicity, it is best to stay below 40 grams of supplemental EAA a day unless you have a great reason to take more.
Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.
Who should not take EAA?
You should probably avoid taking the supplement if you:
eat high amounts of protein from food (most whole foods contain at least some amount of each essential amino acid)
experience a severe adverse reaction after taking the supplement
are deficient in folate (vitamin B9); L-histidine in EAA can cause FIGLU in this case
take SSRIs or SNRIs (the combination of these and L-tryptophan can lead to serotonin syndrome)
have high blood pressure and-or take drugs for high blood pressure
are deficient in arginine
eat high amounts of muscle meat
suffer from schizophrenia (the phenylalanine in EAA can lead to a movement disorder called tardive dyskinesia in schizophrenics)
are inactive
Who will benefit the most?
You should consider taking the supplement if you:
consume very little protein (less than 0.3 grams/pound of body weight)
are on a plant-based diet but don’t eat legumes
are muscular and work out a lot
wish to reduce appetite and food cravings
suffer from depression or generalized anxiety disorder
often experience uncontrolled muscle contractions
are an older person (older people need up to 2 times more EAAs than young adults for similar activations of muscle protein synthesis and to reduce age-related catabolic effects)
How much EAA should you take?
Each essential amino acid has an RDA (recommended daily allowance). The RDAs for all adult men and most adult women are: 14 mg/kg/day of histidine 19 mg/kg/day of isoleucine 42 mg/kg/day of leucine 38 mg/kg/day of lysine 19 mg/kg/day of methionine + cysteine 33 mg/kg/day of phenylalanine + tyrosine 20 mg/kg/day of threonine 5 mg/kg/day of tryptophan 24 mg/kg/day of valine
The RDAs for pregnant women are: 18 mg/kg/day of histidine 25 mg/kg/day of isoleucine 56 mg/kg/day of leucine 51 mg/kg/day of lysine 25 mg/kg/day of methionine + cysteine 44 mg/kg/day of phenylalanine + tyrosine 26 mg/kg/day of threonine 7 mg/kg/day of tryptophan 31 mg/kg/day of valine
The RDAs for lactating women are: 19 mg/kg/day of histidine 30 mg/kg/day of isoleucine 62 mg/kg/day of leucine 52 mg/kg/day of lysine 26 mg/kg/day of methionine + cysteine 51 mg/kg/day of phenylalanine + tyrosine 30 mg/kg/day of threonine 9 mg/kg/day of tryptophan 35 mg/kg/day of valine
Since these amino acids are found in almost every food, you probably already get sufficient amounts from food alone. About 0.36 grams of protein/pound of body weight should be enough to prevent a deficiency.
The optimal protein intake is highly individual and can range anywhere from 0.36-1 gram of protein/pound of body weight, depending on your age, gender, activity levels, goals, genes, and more.
If you plan to take EAA as a supplement, 20 grams appears to be the best daily target for most people. This amount should provide most of the benefits without meaningful side effects.
Some people may benefit from doses higher than 20 grams. These include older people, bodybuilders, very physically active individuals, and those on a low-protein diet.
Each essential amino acid has a safety limit, whether it is well-established or not. To stay on the safe side, don’t take more than 50 grams of supplemental EAA daily unless you have a great reason to do so.
Food sources of EAAs
All EAA are found in all whole foods that contain dietary protein.
The amount of EAA per gram of protein varies from food to food but a general rule of thumb is that the more protein you eat, the more EAAs you are getting from food.
The easiest way to find out exactly how much essential amino acids you are getting from food is with Cronometer.com. This free app allows you to track all vitamins, minerals, and more.
Best time to take EAA
All essential amino acids are at least somewhat water-soluble, so you don’t have to take them with food to absorb them well. Taking EAA with food is better if it causes stomach upset when you take it on an empty stomach.
To maximize the benefits, take EAA before or after a workout.
Whether you take the supplement in the morning or the evening doesn’t matter much. It should not interrupt your sleep in a significant way.
If you practice time-restricted eating, take EAA during your eating window to guarantee it won’t break your fast.
Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.
Interactions
Other amino acids All essential and non-essential amino acids need to be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects without enough of another amino acid. That is most notably the case for glycine and methionine, but the principle applies to other amino acids, such as lysine and arginine, and the BCAA trio. Using a single amino acid supplement may lead to a negative nitrogen balance, which can lessen how well your metabolism works. A protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.
Carbohydrates BCAAs promote insulin secretion from the pancreas and help the body utilize glucose. Taking this amino acid before a carbohydrate-rich meal lowers the blood glucose spike from it and increases muscle protein synthesis.
L-arginine The combination of arginine and lysine is highly effective for reducing many types of anxiety, state and trait anxiety in particular. Combining these two amino acids may and may not be effective for generalized anxiety disorder (GAD). To maximize this benefit, it is best to take L-arginine and L-lysine together and take 2.5 grams of each daily. Beware that taking these two together may negate the benefits of L-lysine related to the treatment of herpes simplex.
Resveratrol Both resveratrol and leucine can activate the SIRT1 gene and act synergistically in doing so when taken together. Whether or not this effect is of practical significance is not yet clear.
Vitamin B9 If you are deficient in vitamin B9 (folate), too much histidine can cause an unwanted chemical called formiminoglutamic acid (FIGLU) to build up in the body. People with a vitamin B9 deficiency should avoid the supplement.
Glycine For every gram of methionine, you need to consume at least half a gram of glycine if you wish to prevent side effects related to too much methionine. For optimal health, try to get about 1 gram of glycine for every gram of methionine.
TMG Trimethylglycine (TMG) can greatly mitigate the side effects associated with methionine supplementation. For example, TMG is the most effective supplement we know of for lowering homocysteine levels.
Sedatives Phenylalanine and tryptophan from EAA supplements may increase the effects and side effects of sedatives.
SSRIs Taking SSRIs together with L-tryptophan may lead to serotonin syndrome. The same applies to some other groups of anti-depressants, such as SNRIs and tricyclic antidepressants (TCAs).
Where to buy EAA
Amazon is the best option for ordering EAA supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.
Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.
FAQ
You can take the supplement daily and do not need to cycle it. However, it is certainly not a problem if you don’t take it daily. Not taking the supplement every once in a while could lead to better absorption. That is yet to be proven or disproven.
All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.
Yes. Most EAAs absorb and digest well if you take them before falling asleep. The supplement should not impact sleep quality in any significant way.
EAA should not become harmful once it exceeds the expiration date but can lose potency over time.
Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months or even years.
While toxicity is rare, too much EAA in the system can cause some health problems, often related to causing an imbalance in other amino acids. It is best to stay below 50 grams a day to prevent these side effects.
You may need more of this amino acid if you: – eat very little protein (less than 0.3 grams/pound of body weight) – are on a plant-based diet and avoid legumes – suffer from depression or anxiety – are muscular and work out a lot – are an older person (older people need up to 2 times more EAA than young adults for similar activations of muscle protein synthesis and the anti-catabolic effects)
Most essential amino acids get metabolized within a day after you consume them.
If you take the supplement before a workout, you may notice a mild increase in power output. Another short-term effect you may notice almost immediately is an increase in well-being, mainly due to L-tryptophan and phenylalanine. In the long term, you need to take EAA for a few weeks to begin noticing the benefits.
Amino acid supplements often come from animal products, but they do not have to be since all whole plant foods contain all essential amino acids. You can easily find vegan-friendly EAA pills and powders but always check the label to be sure. If you buy EAA in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.
All essential amino acids are at least somewhat water-soluble, so you don’t have to them with food to absorb them well.
While low doses may not break a fast, higher doses certainly can. If you practice time-restricted eating, take EAA during your eating window so it doesn’t break your fast.
References
Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.
