What is it?
Vitamin B1 is a water-soluble vitamin and unused vitamins leave your body through your urine. As your body does not store this vitamin you need a regular supply in your diet or through supplementation.
B1 is often used in combination with other B vitamins, and found in many vitamin B complex products. Some people who have liver problems, consume a lot of alcohol, or have other health conditions may not absorb B1 properly. 
What it does
Vitamin B1 is essential for normal growth and development and helps to maintain proper functioning of the heart, nervous system and digestive systems. Thiamine is required by our bodies to properly use carbohydrates, is essential for energy production and nerve cell function and promotes muscle tone.
Alcoholics, or those with very heavy refined carbohydrate consumption, tend to be deficient in vitamin B1. Deficiency in Vitamin B1 may lead to loss of appetite, weakness, nervousness irritability, insomnia, weight loss, aches and pains, mental depression and constipation. In children it may result in impaired growth.
Natural sources of vitamin B1 include dried yeast, rice husks, whole wheat, oatmeal, peanuts, pork, most vegetables and milk. It is common for thiamin to be added to white bread; however, orthomolecular practitioners and researchers generally consider this to be a less than ideal source due to the negative effects of white flour on the body.
Recommended Dietary Allowance (RDA)
Canada’s RDA can be found here.
Molecular Dosage Range
Thiamin is the anti-polyneuritis or anti-beriberi vitamin. It is used as an adjunct in the treatment of certain depressions and is specific for Wernicke-Korsakoff disease. Molecular practitioners may recommend megadose levels ranging from 100 to 3,000 mg. per day, but this is rare.
, site reviewed Aug. 23, 2016
 Hoffer, Abram, PH.D., M.D. and Walker, Morton, D.P.M. Orthomolecular Nutrition: New Lifestyle for Super Good Health. Keats Publishing Inc., Connecticut: 1978. Pg. 121 – 122.