Amino acids are the building blocks of protein and are vital for a variety of bodily functions. Without protein, the human body would not be able to function as it does. Every biochemical process that occurs to sustain life is powered by protein!
Not only is the human body able to use amino acids for various purposes, but it’s also able to recycle them. The body is very efficient in breaking down old proteins into amino acids so they can be reused to make new proteins. Most of the amino acid pool is used for making protein and other nitrogen-containing compounds like DNA bases, neurotransmitters, hormones, etc. Under certain metabolic situations, amino acids can also be used as a source of energy by the body. It is important to clarify that the body does not store amino acids! If the amino acids aren’t used for biological processes, they are broken down and the nitrogen is excreted in the urine as urea.
Of the 20 amino acids found in your body’s protein, nine are considered “essential” amino acids. They are considered essential because the human body is unable to produce them, so it’s up to us to obtain them through our diet! As a result, eating a well-balanced diet is crucial for overall health. Let’s take a deeper look at the essential amino acids and how you can get them through food.
Essential Amino Acids
Phenylalanine: Phenylalanine is an amino acid that helps produce neurotransmitters like dopamine, tyrosine, adrenaline, and noradrenaline. Due to its effect on specific neurotransmitters, phenylalanine is used in modern medicines as an antidepressant. It is also involved in the structure of various proteins and enzymes, helping to produce other amino acids within the body. It is found in plant and animal sources like pumpkin seeds, soy, eggs, and seafood.
Valine: Valine is a branched-chain essential amino acid alongside leucine and isoleucine. Branched-chain amino acids are used in your body to help make energy. A research study published in a 2018 edition of Bioscience, Biotechnology, and Biochemistry specifically looked at the effects of valine on animal subjects during exercise. The results of the study demonstrate that acute supplementation of valine, but not leucine or isoleucine (the other BCAAs), is “effective for maintaining liver glycogen and blood glucose and increasing spontaneous activity after exercise, which could contribute to the reduction of fatigue during exercise.”
Valine and the other BCAAs can be supplemented for building muscle, healing tissue and bones, increasing energy, alleviating liver and gallbladder disease, or supporting the body during severe protein deficiency. Natural sources include dairy products, meat, soy, beans, whole grains, nuts, and vegetables.
Tryptophan: This amino acid is important in the regulation of nitrogen within the body and acts as a precursor to the neurotransmitter serotonin, which regulates sleep, mood, and appetite. This makes it one of the most important amino acids for depression and mood treatments! The body uses tryptophan to help make melatonin as well (hello, post-Thanksgiving dinner nap…), which helps regulate the sleep-wake cycle.
The liver can also use tryptophan to produce niacin (vitamin B3), which is needed for energy metabolism and DNA production. In order for tryptophan to be changed into niacin, the body needs enough iron, riboflavin, and vitamin B6. Tryptophan can be found in sources like poultry, fish, cheese, eggs, milk, seeds, and more.
Threonine: This amino acid is needed by the thymus gland to make T-cells or T lymphocytes, that work to fight off infections inside the body. Essentially, it helps boost our immune system! It also helps regulate fat metabolism. Threonine deficiency can lead to fatty liver and even liver failure. Threonine allows for proper elastin function. Elastin is a protein that’s found in connective tissue and lets the skin, tendons, and ligaments resume shape after stretching or contracting. Increasing threonine may help speed the healing of wounds, burns, and other forms of trauma as it is needed for the improper production of collagen.
It may also relieve anxiety and depression. Threonine is a precursor to glycine, which helps calm nerves and support cognitive health. Glycine is known for its ability to help improve sleep, mental performance, mood, and memory. Natural sources include fish, cheese, poultry, and lentils.
Isoleucine: Another of the commonly-supplemented BCAAs (remember, those are the branched-chain amino acids) is isoleucine. A research study published in The Journal of Nutrition found that oral administration of isoleucine resulted in a significant decline in plasma glucose levels. Isoleucine helps lower blood glucose!
Isoleucine has diverse physiological functions, such as assisting wound healing, detoxification of nitrogenous wastes, stimulating immune function, and promoting the secretion of several hormones. Necessary for hemoglobin (a protein that carries oxygen from respiratory organs to the rest of the body) formation and regulating energy levels, isoleucine is concentrated in muscle tissues in humans. Sources include eggs, seaweed, meat, fish, and cheese.
Methionine: Methionine is a unique amino acid. It contains sulfur and can produce other sulfur-containing molecules in the body such as glutathione, taurine, SAM, and creatine. it is also involved in starting protein production in your cells. It helps the body absorb minerals like zinc and selenium, which are important for your body’s overall health and function. It is involved in the growth of tissues, metabolism, and detoxification. Foods with higher levels of methionine include eggs, some meat, and fish.
Histidine: Histidine, when used with zinc, can help protect against colds and reduce their duration. Histidine supplementation may also reduce the duration of viral or bacterial infections. Because it plays a role in regulating immune system response and the production of histamines, histidine may help decrease the severity of allergic reactions and inflammatory processes.
In aminal studies, supplementation with histidine has been shown to defend against diabetic complications in multiple ways, such as reducing triglyceride and cholesterol levels and decreasing lipid (fat) oxidation in the kidneys and liver. Studies have also found that higher dietary histidine intake is associated with reduced obesity, BMI, waist circumference, and blood pressure. Food sources include meat, fish, nuts, and seeds.
Leucine: The third of the BCAAs is critically-involved in muscle growth and repair, sometimes referred to as the primary or main BCAA due to its properties. As well, it helps regulate blood sugar and encourages the healing process! Food sources include meat, dairy, and fish.
Lysine: Lysine is involved in hormonal and enzymatic regulation. In addition to helping you absorb calcium more efficiently, L-lysine behaves like a serotonin receptor antagonist. That’s a wordy phrase – it means that it partially binds to serotonin receptors in order to help prevent anxiety responses.
Lysine also helps support healthy gut function. An extremely common problem that millions of people have is leaky gut syndrome (many don’t even know they have it!). This condition is when larger-than-intended particles make their way out of your digestive system and into the rest of your body. This may cause allergic reactions, low energy, joint pain, autoimmune disease, and thyroid disease.
A form of L-lysine known as poly-L-lysine was very recently found to have anti-inflammatory effects on the lining of the gut. Hopefully, we’ll be seeing more research on this topic! Food sources of lysine include fish, eggs, dairy products, and meat.
From the Dietitian
Each one of these nine essential amino acids must be present in your diet to ensure your body can properly perform at its best. As mentioned, there are hundreds of bodily functions and processes that require amino acids from dietary proteins.
A lack of any amino acid brings about serious complications. These include, but are not limited to:
- Depression
- Anxiety
- Insomnia
- Fatigue
- Muscle weakness
- Physical stunting
I want to highlight the bolded symptoms above that can result from a lack of amino acids. Depression, insomnia, and fatigue are all symptoms that many people live with on a regular basis. Through research, I have found that food is so powerful that it can change the way we think, how we feel, and how we move. While many folks turn to medication to help, you’d be surprised by what we can find in our own diets. But please – speak with a medical professional before making any major changes to your diet or medications.
To ensure you’re getting all of the essential amino acids that you need, start with assessing your fridge, pantry, and freezer. Do you have meat, poultry, eggs, or dairy? What about spinach, broccoli, red/sweet potatoes, black beans, or legumes? If you do not have a variety of these dietary protein sources at home, I would recommend making an action plan to buy and stock up on one or two of these food groups. This is only the first step in real behavioral change! Once the food makes it to your home, you still have to prepare it. Planning time and ingredients or meals to prep is necessary to some degree to take full advantage of all of their powerful nutrients.
What food science teaches me is that if we want to feel good, move well, and live well, we need to invest in our nutrition on a daily basis. Living well takes intentionality!
If you’re interested in adjusting your diet, the YMCA Nutrition Counseling Program helps adults find a healthier way of eating that’s right for them with the help of our Registered Dietitian. Learn more »
—Mattie Lefever, LDN, RDN
