Essential amino acids are organic compounds that your body needs to function. You can get them from certain foods.
Amino acids, often referred to as the building blocks of proteins, are compounds that play many critical roles in your body.
You need them for vital processes such as building proteins, hormones, and neurotransmitters.
Amino acids are concentrated in protein-rich foods such as meat, fish, and soybeans.
Some people also take certain amino acids in supplement form as a natural way to boost athletic performance or Boost mood.
They’re categorized as essential, conditionally essential, or nonessential depending on several factors.
In this article you’ll find all the basics about essential amino acids, including how they function, food sources rich in essential amino acids, and the potential benefits of taking a supplement.
Amino acids are organic compounds composed mainly of nitrogen, carbon, hydrogen, and oxygen.
Your body needs 20 different amino acids to grow and function properly. While all 20 of these are important for your health, only 9 are classified as essential (1).
These are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Although your body can make nonessential amino acids, it cannot make essential amino acids, so you have to get them from your diet.
The best sources of essential amino acids are animal proteins such as meat, eggs, and poultry. However, some plant foods, such as the soy products edamame and tofu, contain all nine essential amino acids. This means they are “complete” protein sources (2, 3).
After you eat protein, your body breaks it down into amino acids and then uses them for various processes, such as building muscle and regulating immune function (1).
Several nonessential amino acids are classified as conditionally essential.
These are essential only under specific circumstances, such as during illness, pregnancy, infancy, or trauma.
For example, arginine is considered nonessential, but your body can’t make as much as you need when you’re healing from a serious injury or fighting certain diseases, such as cancer (4).
That’s why, in certain situations, people may take arginine supplements to meet their bodies’ needs.
Additionally, certain amino acids, including glycine and arginine, are considered conditionally essential during pregnancy because a pregnant person needs more of these amino acids to support their own health and the health of the fetus (5, 6).
Summary
Your body can’t produce the nine essential amino acids, so you need to get them from your diet. Conditionally essential amino acids are nonessential amino acids that become essential in certain circumstances, such as illness or pregnancy.
There are nine essential amino acids, each of which performs a number of important jobs in your body:
As you can see, essential amino acids are at the core of many vital processes.
Although amino acids are most recognized for their role in muscle development and repair, your body depends on them for so much more.
That’s why essential amino acid deficiencies can negatively affect your entire body, including your nervous, reproductive, immune, and digestive systems.
People can have different amino acid needs based on stage of life, chronic illness, and acute health issues such as an infection or a surgery.
However, most people get all the amino acids they need through their diet.
Summary
All nine essential amino acids perform important roles in your body. They’re involved in many processes, including tissue growth, energy production, immune function, and nutrient absorption.
While essential amino acids can be found in a wide array of foods, taking concentrated doses in supplement form has been linked to several health benefits.
Tryptophan is necessary for the production of serotonin, a chemical that acts as a neurotransmitter in your body.
Serotonin is an essential regulator of mood, sleep, and behaviors.
While low serotonin levels have been linked to depressed mood and sleep disturbances, several studies have shown that taking tryptophan supplements may help reduce symptoms of depression and boost mood (16, 17, 18, 19).
A review that included 11 high quality studies found that taking 0.14–3 grams (g) of tryptophan per day could help decrease anxiety and increase positive mood in generally healthy people (18).
Many people take valine, leucine, and isoleucine, the three essential BCAAs, to alleviate fatigue, Boost athletic performance, and stimulate muscle recovery after exercise.
In a small 2017 study, resistance-trained athletes took BCAAs at a dose of 0.039 g per pound (lb) — 0.087 g per kilogram (kg) — of body weight, with a 2:1:1 ratio of leucine, isoleucine, and valine.
Those who took the BCAAs showed improved performance and muscle recovery and decreased muscle soreness compared with those who took a placebo (20).
A review of eight studies found that taking BCAAs was superior to rest for promoting muscle recovery and reducing soreness after exhaustive exercise (21).
What’s more, another review that included nine studies found that taking BCAAs helped reduce muscle damage and soreness after resistance exercise in active men (22).
Taking BCAAs has also been shown to reduce the rating of perceived exertion — how intensely a person feels they are working during exercise — in people performing high intensity exercise (23).
Taking amino acid supplements may be helpful for people who are healing after surgery (24, 25).
A study in 243 people with pelvis or long bone fractures found that those who took conditionally essential amino acids for 2 weeks after surgery had lower rates of death and medical complications than those who received standard nutrition (25).
A review of 20 studies looking at the effects of taking BCAAs in people with cancer undergoing surgery found that those who took BCAAs around the time of surgery had reduced postoperative complications from infections and fluid accumulation in the abdomen (26).
What’s more, according to results from one study, taking essential amino acid supplements may help reduce loss of muscle volume in older adults recovering from knee replacement surgery (27).
Summary
Taking certain essential amino acids in supplement form may help Boost mood, support exercise performance and recovery, and help Boost health outcomes after surgery.
Because your body cannot produce essential amino acids, it’s important to get them through your diet.
Many foods are rich in essential amino acids, making it easy to meet your daily needs (28).
Here are the daily required intakes for the essential amino acids, according to the World Health Organization. These are for adults per 2.2 lb (1 kg) of body weight (29):
To find out how much you should consume per day, you can multiply the numbers given above by your weight in kilograms. For example, a person who weighs 60 kg (132 lb) should consume 1,200 mg (1.2 g) of isoleucine per day.
Meeting these requirements is very easy with most diets, so there’s usually no need to track your intake of individual amino acids.
For example, one 174-g piece of braised chicken breast provides 55.9 g of complete protein, easily meeting or exceeding the needs listed above (30).
Foods that contain all nine essential amino acids are referred to as complete proteins.
The following foods are complete protein sources:
Soy and pea protein are plant-based complete protein sources (2, 3, 31).
Other plant-based sources of protein, such as beans, nuts, and certain grains, are considered incomplete proteins because they lack one or more of the essential amino acids.
However, if you’re following a plant-based diet, you can still ensure proper intake of all nine essential amino acids by eating a variety of plant proteins each day.
For example, choosing a variety of plant-based proteins, such as beans, nuts, seeds, whole grains, and vegetables, can ensure that you meet your essential amino acid needs, even if you choose to exclude animal products from your diet.
Summary
Many animal and plant foods, such as meat, eggs, quinoa, and soy, contain all nine essential amino acids and are considered complete proteins.
Most people get enough essential amino acids through their diet.
However, there are some benefits to taking essential amino acid supplements. For example, athletes often take them to enhance exercise performance and recovery.
One review that included 10 high quality studies found that doses of BCAAs of up to 115.6 mg per lb (255 mg per kg) per day could help reduce delayed onset muscle soreness in trained individuals after exercise (32).
Additionally, people may choose to take individual amino acids, rather than blends, to support certain aspects of health, such as mood.
A review that included 11 high quality studies found that taking 0.14–3 g of tryptophan per day could help Boost mood in healthy people (18).
As you can see, dosing varies depending on the type of amino acid you’re taking and what your goal is.
Amino acid supplements are considered safe for most people. However, they’re usually not necessary if you’re getting enough protein in your diet.
Nonetheless, amino acid supplements may offer certain benefits for specific groups of people.
If you’re interested in taking essential amino acid supplements, speak with a healthcare professional who is knowledgeable about dietary supplements, such as your doctor or a registered dietitian.
They can recommend specific dosing and tell you how best to take your supplement, depending on your health goals. Additionally, they can help you choose a supplement from a reputable brand that offers products tested by third-party organizations.
Summary
Dosing of amino acid supplements depends on the specific amino acid and your reason for using it. If you’re interested in taking essential amino acid supplements, consult a qualified healthcare professional.
There are nine essential amino acids, which you must get through your diet — histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
They’re vital for functions throughout your body, including protein synthesis, tissue repair, and nutrient absorption.
Some may also help prevent muscle loss, support recovery after surgery, and Boost mood, sleep, and athletic performance.
These vital compounds are found in many animal- and plant-based foods, so most people can meet their daily needs by eating a healthy, balanced diet. You can also take essential amino acid supplements if needed.
This article addresses some of the questions relating to how hepatitis δ virus (HDV), an agent so far unique in the animal world, might have arisen. HDV was discovered in patients infected with hepatitis B virus (HBV). It generally makes HBV infections more damaging to the liver. It is a subviral satellite agent that depends upon HBV envelope proteins for its assembly and ability to infect new cells. In other aspects of replication, HDV is both independent of and very different from HBV. In addition, the small single-stranded circular RNA genome of HDV, and its mechanism of replication, demonstrate an increasing number of similarities to the viroids – a large family of helper-independent subviral agents that cause pathogenesis in plants.
Hepatitis δ virus (HDV) was first detected 33 years ago in patients with a more severe form of hepatitis B virus (HBV) infection.[1] It was identified in both liver biopsies and the serum from such patients via a novel antigen, designated the δAg. Later, HDV was found to be an infectious agent separable from HBV. However, it is dependent upon HBV for the provision of envelope proteins so as to achieve particle assembly, and for new rounds of infection. For both viruses, the only susceptible cells are liver hepatocytes.[2] Thus, a complete and natural cycle of HDV infection and the emergence of new virus particles demand that both HBV and HDV infect the same hepatocyte. HDV, similarly to HBV, is a blood-borne infection, and may be transmitted by parenteral routes. For example, both are readily transmitted by contamination on needles shared in intravenous drug use. Unlike HBV, HDV is not typically a sexually transmitted disease, although such transmission may sometimes occur.[3]
Hepatitis δ virus infections have now been detected in many parts of the world, always in association with HBV.[4,5] Lookback studies of patient sera reveal that even prior to 1977 there were significant life-threatening HDV infections in the Amazon basin of South America.[6] Currently, many nucleotide sequences have been obtained for HDV isolates from around the world, and are available in the Subviral RNA Database.[101] They differ by no more than 30 nucleotides in length but as much as 30% in sequence.[5] They have been divided into eight clades, based partly on nucleotide sequence and partly on geographic associations, although such geographic associations can sometimes be blurred, for example by population movements.
As mentioned previously, HDV is dependent upon HBV infection for its propagation. HBV is a member of a family of viruses known as Hepadnaviridae, which replicate via reverse transcription. Most retroviruses package an RNA genome and after infection use reverse transcription to make a DNA provirus. By contrast, the hepadnaviruses package an RNA 'pregenome', which is partially reverse transcribed before being released as particles from the infected cell. Thus, the genome of the hepadnavirus is a partially dsDNA species with a relaxed circular conformation. During infection this genome is completed as a covalently closed dsDNA that acts in the nucleus as a template for the transcription by the host RNA polymerase II (RNAP II).[7]
Hepatitis B virus infections can progress from an acute phase to a chronic phase (defined as one lasting at least 6 months). HDV infections can arise as a 'coinfection' with HBV or as a 'super-infection' in a patient already chronically infected with HBV. Approximately 2 billion individuals worldwide have come into contact with HBV and potentially 400 million of these have progressed to a chronic infection. Such chronic HBV infections can cause significant liver damage, and over a period of 10–30 years have a 25–40% risk of progressing to cirrhosis and hepatocellular carcinoma. Co- and super-infections with HDV greatly increase the risk of fulminant hepatitis during the acute phase. If the HBV infection becomes chronic, so does the HDV, and this can greatly increase the liver damage relative to HBV alone, leading to a life-threatening loss of liver function or more rapid progression to liver cancer.[3]
As indicated in Figure 1, the HDV genome is a small ssRNA of approximately 1700 nucleotides in length that is circular in conformation.[8] This RNA can fold using approximately 74% base pairing to form an unbranched rod-like structure. The genome sequence shows no homology to the 3300-nucleotide genome of a hepadnavirus. Furthermore, the mode of replication of the HDV genome is fundamentally different.
Figure 1.
Comparison of hepatitis δ virus RNAs with those of a viroid. There are three stable HDV RNAs that accumulate during replication. The genome, which is the RNA assembled into new virus particles, and its exact complement, the antigenome, are approximately 1700 nucleotides in length, with a circular conformation and the ability, based on approximately 74% intramolecular base pairing, to fold into an unbranched rod-like structure. Both genome and antigenome contain their own ribozyme domain, of approximately 85 nucleotides (yellow box). The antigenome contains the open practicing frame for the δ antigen (blue box), but this protein is actually translated from a third RNA, the mRNA, which is linear, less than full length, 5′-capped and 3′-polyadenylated. Also indicated are the RNAs of a plant viroid, ASBVd. This approximately 250-nucleotide long RNA and its exact complement are indicated as plus and minus, even though there is no coding capacity. As with HDV, RNAs can be circular and have the ability to fold intramolecularly. While the RNAs of ASBVd may be almost rod-like, the RNAs of other viroids can have more complicated folding. For viroids such as potato spindle tuber viroid, the circular conformation is only found for the plus RNA.
ASBVd: Avocado sunblotch viroid; HDV: Hepatitis δ virus.
Hepatitis δ virus is considered to replicate through a symmetrical rolling-circle mechanism[9] that involves only RNA intermediates.[8] Replication of the HDV genome involves accumulation of new genomes and complementary RNA species known as antigenomes. As many as 300,000 molecules of genome accumulate per infected cell, along with approximately 100,000 copies of the antigenome.[10] It is thought that the genomic and antigenomic RNA circles act as templates for the generation of the multimeric strands of both polarities, which are greater than the 1700-nucleotide unit length. These are processed to a unit length since both the genome and antigenome contain a sequence of approximately 85 nucleotides that can act as a site-specific ribozyme.[11] After such ribozyme cleavage, the unit-length RNAs are ligated, possibly via a host ligase,[12] to form new circular RNA species. Since HDV does not encode its own replicase and can replicate autonomously in its host, one or more host RNAP is redirected for its replication.[8]
A third RNA species that is only approximately 900 nucleotides long and of antigenomic polarity is also produced at approximately 500 copies per cell.[13] As indicated in Figure 1, this mRNA is processed with a 5′-cap structure and is polyadenylated at its 3′-end because, similar to host mRNA precursors, it contains essential features, such as a polyadenylation site AAUAAA and an appropriately placed CA sequence, which acts as a polyadenylation cleavage and acceptor site.[14] The open practicing frame encodes a protein that is 195 amino acids long and is referred to as the small δAg. This protein is an RNA-binding protein essential for the accumulation of HDV genomic and antigenomic RNA,[15] although it is still controversial as to whether it is required for the transcription process.[8] During replication, an adenosine deaminase that acts on dsRNA (ADAR) converts an adenosine located in the termination codon of the small δAg on antigenomic RNA to an inosine.[16] Such action leads to the generation of an mRNA where the termination codon now encodes tryptophan, and thus to the production of a second viral protein species that is 19 amino acids longer at the C-terminus, referred to as the large δAg.[16] The large δAg is unable to support HDV RNA accumulation; however, in terms of the HDV lifecycle it plays an essential role in that it not only binds the HDV RNA, but then makes an interaction with the envelope proteins of HBV, leading to the assembly and release of new infectious HDV.[15,17] The unique 19 amino acid extension of large δAg contains a cysteine that undergoes farnesylation, and this is a necessary step in the functioning to achieve virion assembly.[18]
Before the COVID-19 pandemic, my role in the world of marketing technology drove me to think a lot about the balance between the efficiency of automated customer interactions and the trust built by human conversations.
Now, the human side of that equation has never felt more important — in spite of, or perhaps because of, the fact that most in-person interactions have become impossible. In many cases, finding the right mix of personal and machine contact has gone from a question of conversion rate and brand loyalty to one of physical, emotional and financial well-being for both businesses and consumers. Some companies are taking this very much to heart; Zappos, for example, has offered its live agents for any kind of conversation around the clock, purchase-related or not, as a general resource for human connection.
As companies are forced to reorganize, shift priorities and rethink fundamental business practices, they may perceive a need to automate as much as possible to allocate resources most effectively. But even in the best of times, that human conversation plays a key role in a number of points on the customer journey. Now, when consumers' lives are largely defined by upheaval, anxiety and financial insecurity, it's never been more important for buying experiences to deliver clear information, answers and the reassurance that sometimes only a personal interaction can give.
Customers typically escalate from digital interactions to a human conversation when they can't resolve an issue or get the info they need online. In our company's work with brands in high-touch industries like financial services, telecommunications, healthcare and insurance, we're seeing significant changes in call volume and the nimble application of data to route calls more effectively. For example, financial services businesses on our platform saw a 45% percent increase in call volume the week of March 15, around the same time that 3 million people lost their jobs and the Dow Jones lost 23% of its value. Consumers want to talk to a real person when faced with refinancing their mortgage or changing their retirement plans — or when they need reassurance that they're making the right decisions with their money.
Some contact centers are adapting quickly to a remote model, and businesses that relied heavily on face-to-face meetings are getting creative with virtual and digital experiences that allow for remote personal interactions. But live help options at other companies are suffering from the crippling volume, at times leaving customers with only an email abyss in which to toss a message and cross their fingers.
Even digital-first companies need to maintain opportunities for live human conversation in some form or risk alienating their customers. Consumers want to be able to communicate easily and immediately, especially in times of high stress. Research we conducted with Harris Poll found that when a brand doesn't offer the option for human interaction, more than half of consumers (52%) feel frustrated, and nearly one in five (18%) feel angry. Meanwhile, just 16% say they enjoy it.
Similarly, a study published by Harvard Business Review found that stressed customers who used an automated technology like an online investing platform didn't trust the provider as much if it did not offer human service — but "merely having the option to access a person seemed to be all most people needed to feel supported." For businesses in the financial services and health care industries—where the risk and values are high, as is the potential for customer concern and uneasiness — this is particularly important.
While you want to make it as easy as possible for customers to talk to a representative, you don't want to flood the call center with service calls. One of the best ways to strike a balance is to make sure you are putting answers to common questions front and center. This is especially important during a crisis like the one we're facing now. Our health care customers have done a great job of this by putting information about COVID-19 on their home pages, adapting their search ads to direct people to landing pages with pertinent information and providing access to interactive online symptom checkers. By making the information that people are looking for online complete and easy to find, the call volume many of our health care customers are seeing has remained fairly flat.
As more businesses automate their points of customer contact, they need to assess what they're gaining and losing in the process. Automation helps brands deliver more convenient, lower friction customer experiences, but companies need to remember that AI isn't a complete replacement for dynamic human conversation, especially in a situation where every decision comes with higher stakes. If marketers do their jobs well, the lessons and empathy gained from those conversations will benefit their brands far into the future.
During my law enforcement career in Arizona, a father came to our department, worried. His teenage son, who was experiencing mental illness, had started making alarming comments and had bought an assault weapon, raising fears that he might soon resort to violence.
The father was undocumented and felt nervous to come forward. But his love for his son and his community prevailed, and the trusting relationships we had built fostered a mutual understanding that we would not only treat him fairly but also take care of his child.
Trust was the foundation for the father to come to us. As it was in this case, trust is essential to our being able to keep the public safe — a critical lesson I have learned during nearly four decades of work in law enforcement.
Trust is the lifeblood of community-oriented policing, and it is especially essential to reach marginalized groups — including undocumented immigrants — who might otherwise be afraid to come forward to law enforcement with information.
My experience and the existing evidence, including a new paper this month from researchers in California and elsewhere, overwhelmingly suggest that immigrants — including undocumented immigrants — pose no greater threat to public safety than anyone else. As a whole, immigrant communities embody core American values, they work hard, and care deeply about their faith, families and communities.
Law enforcement officers have to overcome many barriers to build trust with immigrant communities. Some are related to stereotypes and language barriers. But perhaps the greatest is fear among immigrant witnesses and victims that going to the police for help could inadvertently expose them or their loved ones to immigration consequences such as deportation. When law enforcement is able to overcome community members’ concerns through culturally sensitive outreach and trust-building, it can save lives.
The growing prominence of harmful rhetoric in the debate — references to immigrant “invasions” — has further undermined trust. I am concerned it will continue to unnecessarily divide our communities and pose a danger to all of us, while putting a target on the backs of people I’ve sworn to serve and protect.
Our federal immigration system, broken as it has been for decades now, doesn’t help. Immigrants who want to follow the law and come to the U.S. in search of safety and opportunity often find few if any lines to do so legally. People migrating today face a far more restrictive immigration landscape than did our ancestors who made us Americans, and for many of those who are already in the U.S. without authorization, there is no viable way to get right by the law.
Fortunately, the solution is clear — immigration reforms.Republicans and Democrats must come together with serious solutions, pairing border security with a pathway to lawful status for members of our communities who contribute to our social fabric and economy every day.
With legal status, they also could contribute even more to everyone’s safety, since they won’t be afraid to come forward with vital information. We are all safer when immigrants feel safe, welcomed and normalized.
Immigration reform that would provide security and certainty to longtime, law-abiding U.S. residents not only would help them and their families — it also would help me and other law enforcement professionals do our jobs and Boost public safety.
Ramon Batista is the chief of police of Santa Monica, California. This post drew from testimony he gave July 13 during a House Judiciary subcommittee hearing titled “The Consequences of Criminal Aliens on U.S. Communities.”
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John Taylor†
Fox Chase Cancer Center, PA 19111, USA Tel.: +1 215 728 2436 Fax: +1 215 728 2412 john.taylor@fccc.edu
Martin Pelchat
Department of Biochemistry, Microbiology & Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada Tel.: +1 613 562 5800 ext. 8846 Fax: +1 613 562 5452 mpelchat@uottawa.ca
†Author for correspondence
Fox Chase Cancer Center, PA 19111, USA Tel.: +1 215 728 2436 Fax: +1 215 728 2412 john.taylor@fccc.edu
