Vitamin B1

Vitamin B1, also known as thiamine, was the first B vitamin discovered, leading to its name. It is an essential water-soluble vitamin that plays a critical role in converting nutrients into energy and maintaining healthy nerve function.

Thiamine's active form, thiamine pyrophosphate (TPP), serves as a crucial cofactor (coenzyme) for several enzymes involved in glucose metabolism. Without adequate thiamine, cells cannot efficiently convert carbohydrates into energy, leading to cellular energy crisis.

The vitamin is particularly important for tissues with high metabolic demands, including the brain, heart, and skeletal muscles. The brain consumes 20% of the body's glucose but comprises only 2% of body weight, making it especially vulnerable to thiamine deficiency.

Historically, thiamine deficiency was common in populations relying heavily on polished white rice, leading to the deficiency disease beriberi. This discovery led to the identification of the "anti-beriberi factor" - later named vitamin B1. Today, deficiency is rare in developed countries due to food fortification, but certain populations remain at risk.

Beyond preventing deficiency, thiamine supplementation may benefit people with diabetes, heart failure, and Alzheimer's disease, though research is ongoing. The vitamin has an excellent safety profile with no established upper limit due to lack of toxicity.

Thiamine's biological activity depends on its conversion to thiamine pyrophosphate (TPP), also called thiamine diphosphate. This phosphorylated form serves as an essential cofactor (coenzyme) for several key enzymes:

1. Pyruvate Dehydrogenase Complex: Converts pyruvate (from glucose breakdown) into acetyl-CoA, which enters the Krebs cycle for energy production. Without TPP, pyruvate cannot enter the mitochondria and accumulates, leading to lactic acidosis.

2. α-Ketoglutarate Dehydrogenase: A critical enzyme within the Krebs cycle itself. Thiamine deficiency impairs this enzyme, reducing ATP production and causing oxidative stress.

3. Transketolase: An enzyme in the pentose phosphate pathway that generates ribose (for RNA/DNA synthesis) and NADPH (for antioxidant defense and fatty acid synthesis).

In the nervous system, thiamine plays unique roles beyond energy metabolism:

• It is involved in nerve impulse transmission through regulation of sodium channels and neurotransmitter release
• It is essential for synthesizing acetylcholine, a key neurotransmitter for memory and muscle function
• It maintains nerve membrane integrity through myelin maintenance

The high metabolic demand of the brain makes it particularly vulnerable to thiamine deficiency. The brain relies heavily on glucose for energy, and when thiamine is deficient, the brain experiences both energy failure and accumulation of toxic metabolites like lactate.

Thiamine is found in a variety of whole foods. Fortified grains are a major source in many countries.

Thiamine deficiency causes beriberi, characterized by cardiovascular and neurological symptoms. Severe deficiency causes Wernicke-Korsakoff syndrome.

RDA varies by age and sex: adult men 1.2 mg/day, adult women 1.1 mg/day. Requirements increase with higher carbohydrate intake and alcohol consumption.

Thiamine is available as thiamine hydrochloride (HCl) or thiamine mononitrate. Benfotiamine is a lipid-soluble form with better bioavailability for peripheral nerves.