ARI Publication 40 – 2013 Version

Amino Acids

Rationale: Protein is made of long strands of individual amino acids. When protein is digested
properly, digestive enzymes split the long protein molecule into small peptides and individual amino
acids, which the body can absorb. Those amino acids can then be reassembled to make a wide
array of critical substances, such as neurotransmitters, hormones, enzymes, antibodies,
immunoglobulins, glutathione, and many other substances. Amino acids are the “building blocks” of

Some children with autism have self-limited diets that are low in protein, and some have digestive
problems that limit their ability to digest protein into individual amino acids. Either of these
problems can lead to insufficient amino acids.


  1. Ensure diet contains sufficient protein (two 4-oz servings/day).
  2. Consider digestive enzymes (with proteases and peptidases) to more completely digest the
    protein into individual amino acids
  3. Give “free-form” amino acids; “free-form” means that the amino acids exist as individual
    molecules, rather than part of a large protein molecule that needs to be digested. General
    amino acid supplements are available, and they can also be customized by a compounding

Amino acids can be tested either from blood (when fasting for 10 hours) or from a urine sample (24
hour is best). Fasting blood plasma reveals circulating levels of amino acids related more to
metabolism than to diet/digestion. 24-hour urine amino acid analysis shows what’s in excess or not
usable and what’s deficient, if kidney transport is normal. Urine has to be interpreted carefully, as
high levels in the urine can indicate “wasting” or excessive excretion, resulting in a low body level.
Amino acid levels very greatly with age. so it is important to use a lab that has age-specific reference ranges. or the results will be incorrect and misleading.

It may also be useful to measure levels of neurotransmitters in platelets (blood), as low levels of
neurotransmitters can be treated by supplementing with amino acids and vitamins/minerals,
allowing the body to build their own.

One study of 56 children with autism and 45 neurotypical controls of similar age and gender found
that the autism group had significantly lower levels of several amino acids, including tryptophan
(needed to make serotonin) and phenylalanine and tyrosine (needed to make dopamine). The
children with autism also had higher levels of glutamate, an excitatory neurotransmitter, which may
relate to seizures, stimming, and other problems in children with autism. There was a lot of
variation within the autism group, so individual testing of amino acids is recommended.

Adams JB et al, Nutritional and Metabolic Status ofChildren with Autism vs. Neurotypical Children, and
the Association with Autism Severity, Nutr. Metab {Lond) 2011 Jun 8:8(1):34.

Several other studies of amino acids in children with autism have been conducted, but they have
generally been flawed due to small sample size, lack of an overnight fast, and lack of controls of
similar age (plasma amino acid levels vary substantially with age).