THIAMINE (ALSO KNOWN AS VITAMIN B1)

Thiamine, also known as vitamin B1, is one of the eight B-complex vitamins. Thiamine cannot be manufactured by humans and is thus a true vitamin, obtained exclusively from the diet.

Thiamine is an enzyme cofactor, which means that it is a necessary component for enzyme function. Thiamine is a cofactor in the pyruvate dehydrogenase enzyme complex that converts pyruvate to acetyl coenzyme A (CoA), which is a rate-limiting step critical to carbohydrate metabolism. Thiamine also has a role in branched-chain amino acid metabolism, and is an antioxidant.

Thiamine deficiency is generally found in individuals with poor nutrition, especially in alcoholics. Symptoms are generally that of brain and nerve dysfunction, including memory loss, confusion, depression, and peripheral neuropathy, as well as muscle pain and weakness, high-output heart failure, gastrointestinal dysfunction, and fatigue.

The role of thiamine in the treatment of autism is not well studied. Children with ASD often have diets that are relatively deficient in many nutrients, including thiamine (https://www.ncbi.nlm.nih.gov/pubmed/28078576). Poor gut absorption, manifested as chronic diarrhea, can intensify vitamin deficiency from a poor diet. Thiamine is sometimes recommended in ASD also for its mitochondrial-targeting effects to promote energy metabolism, and being an antioxidant. Also see:
https://www.ncbi.nlm.nih.gov/pubmed/25553376
https://www.ncbi.nlm.nih.gov/pubmed/27330305
https://www.ncbi.nlm.nih.gov/pubmed/12195231

Thiamine is particular required for nerve function, including the proper development of myelin sheaths around nerves, and deficiency may result in the nerve degeneration. Thiamine is thus often recommended for neurological conditions including Alzheimer, multiple sclerosis and Bell palsy. Some sources indicate that thiamine can improve memory and concentration, improve appetite, and to promote a “healthy mental attitude”. By increasing acetyl CoA production, thiamine helps in the production of the neurotransmitter acetylcholine, of which deficiency can lead to confusion, skeletal and heart muscle weakness, and dysautonomia. Additional uses include cataract prevention, and as a powerful antioxidant.

Thiamine is water-soluble vitamin and thus considered to be generally non-toxic. Side effects are rare at usual doses used in supplementation.

Laboratory testing can reveal the presence of a deficiency of this nutrient, but is generally not likely to have clinically utility.