Vitamin B1 (Thiamine)

General Info


Thiamin is primarily absorbed in the middle portion of the small intestine. Conditions causing intestinal inflammation such as milk or wheat food allergies can inhibit the body's ability to absorb thiamin.

Dietary Origins

All animal and plant foods contain vitamin B1, but only in small amounts. The richest sources are brewer's yeast and organ meats. Whole cereal grains comprise the most important dietary source of vitamin B1 in human diets.


Vitamin B1, also known as thiamine, was the first of the B vitamins to be discovered in the 1900s. Vitamin B1 plays a vital role in the conversion of blood sugar to energy. Its metabolic activities primarily affect the nerves, muscles, and cardiovascular system. Because it is a water-soluble vitamin, it must be replenished daily. Beriberi is the classical vitamin B1 deficiency syndrome. It is more prevalent in Asian countries where polished rice is the staple diet. When beriberi occurs in the United States, it is most commonly seen in severely malnourished infants and elderly people. In adults, alcoholism, malabsorption syndromes and diets consisting primarily of highly processed, refined foods can be causes of vitamin B1 deficiency.

Toxicities & Precautions


There are no known toxicities or precautions associated with vitamin B1.

Functions in the Body

Amino Acid Conversion

Involved in converting amino acids to, enzymes, hormones, and proteins.

Carbohydrate Metabolism

Plays a role in the conversion of blood sugar into biological energy.


An important tool used in the maintenance of muscular function, especially the heart.


Role in maintenance of nerve tissues, nerve function, and nerve transmission. Involved in the synthesis of acetylcholine in nerve cell membranes.

Symptoms & Causes of Deficiency

Thiamine deficiency tends to be very rare in the United States. Most Americans acquire the Recommended Daily Allowance from fortified and enriched food sources in their diet. These foods include bread, bread products, grains, and prepared cereals. With the exception of lactating females, fewer than 5% of all individuals in the United States had dietary intakes lower than the Estimated Average Requirement. Deficiencies of vitamin B1 manifest primarily as disorders of the neuromuscular, gastrointestinal, and cardiovascular systems. Nerve degeneration can cause muscular weakness, calf muscle tenderness, and fatigue. Gastrointestinal symptoms can include anorexia, indigestion, and weight loss. Cardiovascular symptoms include edema, increased pulse rate, and palpitations. Deficiencies in the elderly can produce depression, irritability, and memory loss.