Amino Acids
What are Amino Acids?
What are amino acids? Amino acids (AA) are the building blocks to proteins [1]. There are two categories: essential and non essential. Essential AAs are not made by the body and come from proteins that we eat, while nonessential AA are ones that our body produces on its own. There are 20 total.
What do they do? AAs are used by the body to grow, heal wounds, break down foods, produce energy, and more [1,2]. Each AA plays a specific role to help the body function optimally [2].
Many children on the autism spectrum are picky eaters and may have decreased protein intake, leading to amino acid deficiency. One research study highlighted that up to 60% of children on the autism spectrum may be deficient in at least one amino acid, most commonly valine, leucine, phenylalanine, and lysine. [6]
Consuming enough protein and B vitamins in the diet is important for sufficient amino acid levels. [6-7]
Food Sources of Amino Acids
The following foods contain all 9 essential amino acids and are called “complete proteins”
Note that the following foods also contain amino acids, but are not “complete proteins” and may be missing one or few essential amino acids:
List of Amino Acids
Essential Amino Acids - our bodies do not make these and we must get them from our diet
Phenylalanine: milk, eggs, cheese, nuts, soybeans, chicken, beef, pork, beans and fish
Valine: meats, fish, soy, and dairy
Threonine: lean beef, lamb, pork, collagen, gelatin, cheese
Tryptophan: chicken, turkey, red meat, pork, tofu, fish, beans, milk, nuts, seeds, oatmeal, and eggs
Methionine: turkey, beef, fish, pork, tofu, milk, cheese, nuts, beans, and quinoa
Leucine: salmon, chickpeas, brown rice, eggs, soybeans, nuts, beef
Isoleucine: meat, fish, poultry, eggs, cheese, lentils, nuts, and seeds
Lysine: red meat, pork, and poultry, parmesan, cod and sardines, eggs soybeans, tofu, isolated soy protein, spirulina, fenugreek seed
Histidine: pork, beef, lamb, chicken, turkey, fish, soy, beans, milk, cheese, nuts, seeds, whole grains, and eggs
Non-Essential Amino Acids - our bodies naturally make these and do not need to be obtained from the diet
Alanine
Arginine
Asparagine
Aspartic acid
Cysteine
Glutamic acid
Glutamine
Glycine
Proline
Serine
Tyrosine
Recommended Intake
A majority of individuals who consume sufficient protein are likely to get the amount of amino acids their bodies need. The recommended intake of protein will vary based on the age of your child. Visit the protein note to learn how much protein your child needs each day.
These recommendations are based on the Recommended Dietary Allowance (RDA), which is the average daily level of intake sufficient to meet the nutrient recommendations of nearly all (97-98%) of healthy individuals.
Deficiency
While uncommon in developed countries, protein deficiency can occur when one’s diet is imbalanced, extreme picky eating, or there are other health conditions that affect protein metabolism.
Symptoms of protein deficiency are as follows: edema (swollen/puffy skin), fat accumulation in the liver, problems on the hair, skin, and nails, muscle loss, stunted growth in children, high risk for bone fractures, worse infections, and a larger appetite [3]. You can also experience mood changes, weakness and fatigue, and slow healing wounds [4].
Who is at risk? The elderly, people who eat imbalanced diets, extreme picky eaters, those with kidney disease and protein-related diseases (like PKU and maple urine syndrome) hospitalized patients, vegetarians/vegans, and cancer patients [3, 4].
Toxicity
Protein toxicity is almost impossible to achieve through diet for healthy individuals. This is mostly likely to occur when excessively supplementing with AAs.
Protein toxicity is predominant in people with kidney disease who consume too much protein. The signs include constipation, increased fatigue, bad breath, weight gain, increased urge to urinate.
Protein toxicity differs from protein poisoning, which happens when people follow very high protein diets without carbohydrates and fiber to balance it (carnivore diet, strict paleo diet, etc.)
Supplements
AA supplements can be purchased either in blend or individual AAs. They are commonly used by athletes and bodybuilders and are generally not needed for healthy children, except in the case of deficiency. They can have side effects including GI distress, nausea, and vomiting [5], depending on the dose and the person’s tolerance.
Our favorite supplement for kids that contains a wide variety of amino acids and 10 grams of protein per scoop is collagen. Read more about supplementation and use of collagen in the Collagen note. Other examples of amino acid supplements include:
Note: All supplements are linked to Amazon for convenience, however, buying supplements on Amazon does not guarantee quality, as there are many “unverified resellers” selling nutrition supplements. To buy supplements that are verified to be sent directly to the consumer, you can create an account on the Autism Dietitian FullScript and search for the respective supplement under “Catalog”.
DISCLAIMER: Before starting any supplement or medication, always consult with your healthcare provider to ensure it is a good fit for your child. Dosage can vary based on age, weight, gender, and current diet.
Amino Acids & Autism in the Research
Amino Acids and Vitamin Deficiencies
Nutritional deficiencies arise when one doesn’t eat a balanced diet. This is commonly seen in people with ASD, as they are typically picky eaters.
A study found that almost 60% of autistic children were deficient in at least one AA, particularly valine, leucine, phenylalanine, and lysine [6].
B vitamins are required for AA production. When supplemented, many typical ASD behaviors improved. A study showed that when children were supplemented with B12, their ASD symptoms improved [7]. Low B12 and high homocysteine levels correlated with increased hyperactivity and oppositionality symptoms [7].
Children with autism were studied and showed deficiencies in nutritional and metabolic status, including vitamin insufficiency, increased oxidative stress, and reduced energy. These biomarkers differed depending on the severity of ASD [8].
Amino Acids and Inflammation
A study found that between two groups, the autistic group tends to have increased glutamate levels while glutamine tends to be decreased [6]. Glutamate in the blood is linked with inflammation, especially in the brain [6].
Another study found the AAs helped protect the intestines from inflammation by strengthening the structure and inhibiting oxidative stress pathways, which are vital for inflammation. These pathways are cut off by strengthening the immune system, another function of AAs (tyranine, alanine, etc.) [9]
Amino Acids and Behavioral Changes
A study investigating the relationship between AA, Choline (affects sensory processing, cognitive function, memory, learning, and methionine production), and B vitamins found that mice with the MTHFR enzyme deficiency had improved anxiety and repetitive behaviors after two weeks of choline supplements [7]. With choline deficiencies, these symptoms can worsen.
Those with ASD tend to have decreased levels of serotonin and dopamine. Tyrosine and tryptophan help increase those “happy” hormones, which helps decrease hyperactivity and increase focus [7].
Children with ASD also tend to have abnormal lysine. Decreased lysine causes agitation, while increased lysine, causes intellectual disability or behavioral issues [7].
-
[1] Amino acids: Medlineplus medical encyclopedia. MedlinePlus. https://medlineplus.gov/ency/article/002222.htm. Accessed October 6, 2022.
[2]Kubala J. Essential amino acids: Definition, benefits and food sources. Healthline. https://www.healthline.com/nutrition/essential-amino-acids#how-many-are-there. Published February 3, 2022. Accessed October 6, 2022.
[3] BSc AA. 8 signs and symptoms of protein deficiency. Healthline. https://www.healthline.com/nutrition/protein-deficiency-symptoms#TOC_TITLE_HDR_11. Published October 31, 2017. Accessed October 6, 2022.
[4] Protein deficiency: 7 signs you're not getting enough protein. WebMD. https://www.webmd.com/diet/ss/slideshow-not-enough-protein-signs. Accessed October 6, 2022.
[5] Holeček M. Side effects of amino acid supplements. Physiol Res. 2022;71(1):29-45. doi:10.33549/physiolres.934790
[6] Ghanizadeh A. Increased glutamate and homocysteine and decreased glutamine levels in autism: a review and strategies for future studies of amino acids in autism. Dis Markers. 2013;35(5):281-286. doi:10.1155/2013/536521
[7]Jennings L, Basiri R. Amino Acids, B Vitamins, and Choline May Independently and Collaboratively Influence the Incidence and Core Symptoms of Autism Spectrum Disorder. Nutrients. 2022;14(14):2896. Published 2022 Jul 14. doi:10.3390/nu14142896
[8] Adams JB, Audhya T, McDonough-Means S, et al. Nutritional and metabolic status of children with autism vs. neurotypical children, and the association with autism severity. Nutr Metab (Lond). 2011;8(1):34. Published 2011 Jun 8. doi:10.1186/1743-7075-8-34
[9] He F, Wu C, Li P, et al. Functions and Signaling Pathways of Amino Acids in Intestinal Inflammation. Biomed Res Int. 2018;2018:9171905. Published 2018 Feb 26. doi:10.1155/2018/9171905
Authors
Brittyn Coleman, MS, RDN/LD, CLT
Miriam Stein, Nutrition Student
