What is thiamine?
Thiamine, or vitamin B1, is a water soluble vitamin found naturally in some foods and added to others. All of the B vitamins are essential for energy production because they help convert carbohydrates to glucose, the body’s primary fuel source. Thiamine is important for nutrient metabolism, a healthy liver, skin, hair, eye and nervous system functions. Thiamine is sometimes called the “anti-stress” vitamin because it strengthens the immune system and thus increases the body’s tolerance to stress.1
Recommended dietary allowance for thiamine (Vitamin B1)
The RDA for thiamine is as follows:
Newborns, 6 months: 0.2 mg (adequate intake)
Infants, 7 months to 1 year: 0.3 mg (adequate intake)
Children, 1 to 3 years: 0.5 mg (RDA)
Children, 4 to 8 years: 0.6 mg (RDA)
Children, 9 to 13 years: 0.9 mg (RDA)
Men, 14 to 18 years: 1.2 mg (RDA)
Women, 14 to 18 years: 1 mg (RDA)
Men, 19 years and older: 1.2 mg (RDA)
Women, 19 years and older: 1.1 mg (RDA)
Pregnant or breastfeeding women: 1.4 mg (RDA)
Food sources of vitamin B1
Most thiamine in the Standard American Diet comes from fortified foods like cereals and grains. Other rich sources of thiamine include:
- Meat, especially pork and organ meats
- Whole grains
- Wheat germ
- Blackstrap molasses
Do be aware that some organic processed foods like crackers, etc. are not fortified with thiamine. This may mean that children who are excessively picky eaters and are eating primarily organic processed foods may be at increased risk of thiamine deficiency compared to children eating conventional food products.
Thiamine deficiency is quite rare in the United States since it’s in so many fortified foods. However, low intakes can result in a deficiency after several weeks. Other causes include malabsorption as a result of various gastrointestinal concerns, increased urinary losses, and excess glucose, making diabetics more prone. Alcoholics are at the greatest risk of beriberi due to the increased need coupled with the increased urinary losses.
A deficiency profoundly impacts energy production. The symptoms are often vague at first, beginning with fatigue, weight loss, muscle weakness and vomiting. A more severe deficiency can lead to beriberi, resulting in peripheral neuropathy, muscle weakness, and cramping. There are three forms of beriberi; wet, dry, and acute. In wet beriberi, the heart is more severely impacted than in dry, resulting in cardiomegaly, tachycardia, right sided heart failure, and edema. Dry beriberi primarily affects the muscles and edema is not present. Acute beriberi is most common in infants who were breastfed by thiamine deficient mothers. Symptoms in the child include nausea, vomiting, anorexia, tachycardia, cardiomegaly, and lactic acidosis. Thiamine deficiency seizures have been reported.
Treatment for thiamine deficiency depends on the severity and type, but typically supplementation can reverse the effects.
Toxicity of thiamine
It is unlikely that thiamine will reach a toxic level from food sources alone. The body compensates for excess thiamine, absorbing less of the nutrient and excreting more through the urine. A Tolerable Upper Intake Level has not been established for thiamine and oral intakes of up to 500 mg a day have no known side effects. Intravenous or intramuscular doses are associated with skin irritation, headache, cardiac arrhythmia, and in some cases, anaphylactic shock.
Thiamine supplementation in clinical and naturopathic medicine
The most important use of thiamine is to treat beriberi, although it’s typically only an issue in developing countries and in alcoholics. Very rare cases have been reported in extremely picky eaters, see below. Children who have diabetes may be at a greater risk of developing beriberi due to elevated blood sugar causing increased thiamine excretion by the kidneys.1
Essential tremors are a condition of the nervous system that causes involuntary and rhythmic shaking. The exact cause of ET is unknown, but it’s hypothesized that the area of the brain responsible for controlling muscle movements is impaired. ET can affect children. In one study, intramuscular thiamine led to rapid and persistent improvements in the symptoms of two patients with essential tremor.2 High doses of intramuscular thiamine are relatively affordable, effective, and considered safe for prolonged treatment.2 Although the research on thiamine and ET is relatively limited and conducted on small populations, the results are remarkably effective, safe, and long lasting.
Since thiamine is a cofactor involved in brain function and neurotransmitter synthesis, it has been studied in relation to epilepsy. Several studies have found thiamine deficiency in the central nervous system to reduce seizure thresholds. In one animal study, thiamine treatment increased the clonic and tonic seizure threshold in mice and significantly enhanced the anticonvulsant effect of medications at ineffective dose.3 This means thiamine administration with antiepileptic medication may improve efficacy, resulting in a decrease in the necessary dose.3
Another study found that 50 mg/day of oral thiamine improved the neuropsychological functions in chronic epileptics taking anticonvulsant medications.4 Thiamine improved functions such as visuo-spatial analysis, visuo-motor speed and verbal abstracting ability.4 Some anti-epileptic medications result in B vitamin depletions and supplementing with thiamine can reduce this risk.
In a small pilot study, researchers administered thiamine to children with autism spectrum disorder (ASD) twice a day for two months. Eight of the ten children showed improvements in ASD symptoms scores.5 Another study conducted on 141 children with ASD found positive results after three weeks of thiamine supplementation.6 Although these studies are promising, the effect of thiamine supplementation in children with ASD may be explained by the selective eating behaviors of children with ASD and their increased risk of nutrient deficiencies. It’s difficult to determine whether thiamine supplementation improves ASD symptoms or if it simply restores deficiencies that result in improvements. Either way, increasing foods rich in thiamine is a safe and effective way to avoid nutrient deficiencies in children with ASD.
Infantile thiamine deficiency
Infantial thiamine deficiency (ITD) usually appears after two to three weeks of thiamine deprivation. Early symptoms are mild and include anorexia, vomiting and irritability, followed by a quick decline with high infant mortality rates. Although this disorder is rare in developed countries and can be treated with supplementation, babies born to thiamine deficient mothers or fed thiamine-deficient formula are at a greater risk.
Thiamine supplementation has been used as a palliative treatment in mothers struggling with postpartum depression (PPD).7 PPD is associated with an increased risk of learning disabilities, ADHD and anxiety in toddlers. Thiamine supplementation has been shown to have some promising therapeutic effects in PPD that ultimately improve the cognitive development of the child.7 Although the findings are limited, they do suggest a promising role of thiamine in PPD in the mother and potentially the development of the offspring. Clinically I do find that B complex supplementation may be helpful for some, but not all women with postpartum depression. B complex supplements should be used carefully in nursing mothers, as some infants can become agitated with high doses.
Notes about thiamine deficiencies in children with extreme picky eating behaviors
As listed above, children with autism spectrum disorder are at increased risk for global vitamin and nutrient deficiencies due to their extreme picky eating behaviors. I strongly recommend reading the review article: Relationship between Vitamin Deficiencies and Co-Occurring Symptoms in Autism Spectrum Disorder. In clinical practice I have seen significant improvements in some, but not all ASD patients with B vitamin supplementation (typically in B-complex form). Discussions of methylfolate and methylB12 in autism spectrum disorder are best reserved for another article. Several case studies also report extremely serious cases of severe nutrient deficiencies in patients with picky eating behaviors, including Beriberi.
Note that while not all ASD patients improve with B complex patients, I do see a general trend toward improvements in picky eaters who supplement with a B complex and zinc. In fact, many patients have their picky eating behaviors improve with liquid B complex and zinc lozenge supplementation. For more information about zinc supplementation in picky eaters see our article When should a child supplement with zinc
Thiamine is generally a safe supplement, but adding any medication or supplement should be considered under the supervision of your primary care provider or a qualified nutrition professional. Chronic overconsumption of any one of the B vitamins can result in an imbalance in the others. A B-complex may be a better alternative to a specific B vitamin supplement.
If you are looking for a good B complex supplement, speak with your primary care provider or naturopathic doctor near you. Or check out the Naturopathic Pediatrics Fullscript shop for recommendations on favorite brands. Remember we cannot give dosing or supplement recommendations online, please speak with your child’s doctor to determine their correct dose.
Thiamine, or vitamin B1, is a water soluble vitamin essential for energy production, nutrient metabolism, and nervous system function. Most thiamine is consumed through fortified foods like grains and cereals, but it can also be found in whole food sources like meat, legumes, nuts and seeds. A deficiency of thiamine is known as beriberi, and although it’s quite rare, it can be dangerous. Children with diabetes and those born to thiamine deficient mothers are at a greater risk of deficiency. Thiamine is most often used to treat beriberi in alcoholics and children in developing countries. It also has positive effects in epilepsy, essential tremors, autism, and postpartum depression. Thiamine supplements are generally quite safe but too much of one B vitamin can result in an imbalance of the others. The safest way to boost thiamine intake is to eat a wide range of whole food sources.
- Mount Sinai. Vitamin B1. 2023.
- Costantini A. High-dose thiamine and essential tremor. BMJ Case Rep. 2018;2018:bcr2017223945. Published 2018 Mar 30. doi:10.1136/bcr-2017-223945
- Mesdaghinia A, Alinejad M, Abed A, Heydari A, Banafshe HR. Anticonvulsant effects of thiamine on pentylenetetrazole-induced seizure in mice. Nutr Neurosci. 2019;22(3):165-173. doi:10.1080/1028415X.2017.1357919
- Botez M et al. Thiamine and folate treatment of chronic epileptic patients: a controlled study with the Wechsler IQ scale. Epilepsy Research. 1993;16:2.
- Lonsdale D, Shamberger RJ, Audhya T. Treatment of autism spectrum children with thiamine tetrahydrofurfuryl disulfide: a pilot study. Neuro Endocrinol Lett. 2002;23(4):303-308.
- Robea MA, Luca AC, Ciobica A. Relationship between Vitamin Deficiencies and Co-Occurring Symptoms in Autism Spectrum Disorder. Medicina (Kaunas). 2020;56(5):245. Published 2020 May 20. doi:10.3390/medicina56050245
- Dhir S, Tarasenko M, Napoli E, Giulivi C. Neurological, Psychiatric, and Biochemical Aspects of Thiamine Deficiency in Children and Adults. Front Psychiatry. 2019;10:207. Published 2019 Apr 4. doi:10.3389/fpsyt.2019.00207
- Robea MA, Luca AC, Ciobica A. Relationship between Vitamin Deficiencies and Co-Occurring Symptoms in Autism Spectrum Disorder. Medicina (Kaunas). 2020 May 20;56(5):245. doi: 10.3390/medicina56050245. PMID: 32443822; PMCID: PMC7279218.