What is thiamine?

Thiamine, also known as vitamin B1, is an essential, water-soluble vitamin from the B complex that plays a crucial role in energy metabolism, nerve function, and mental performance. Since the body cannot store thiamine and it is continuously excreted in urine, regular intake through food or supplements is necessary.

Thiamine was identified as the first B vitamin discovered, hence its name “B1”. It is found mainly in whole grains, legumes, meat (especially pork), and nuts. In its active form – thiamine pyrophosphate (TPP) – it acts as a coenzyme in numerous biochemical reactions that release energy from carbohydrates and amino acids.

A thiamine deficiency can have far-reaching consequences, since organs with high energy demands – especially the brain, heart, and muscles – depend on a constant energy supply.

How does thiamine work in the body?

1. Energy production from carbohydrates:
Thiamine is an essential component of the pyruvate dehydrogenase complex, an enzyme that enables the conversion of carbohydrates into energy (ATP). Without thiamine, glucose cannot be efficiently used in the mitochondria, leading to energy deficiency, fatigue, and muscle weakness.

2. Supporting the nervous system:
Thiamine plays a central role in signal transmission between nerves and muscles. It is necessary for the synthesis of neurotransmitters such as acetylcholine, which are responsible for memory, concentration, and motor control.
A deficiency can lead to nerve damage, numbness, coordination problems, or even neurological disorders such as beriberi or Wernicke-Korsakoff syndrome.

3. Heart and muscle function:
Thiamine supports heart muscle contraction and helps maintain healthy cardiovascular function. A thiamine deficiency can lead to enlarged heart, edema, and shortness of breath because the heart works less efficiently.

4. Supporting amino acid and fatty acid metabolism:
Thiamine is involved in the utilization of amino acids and the breakdown of fatty acids. It therefore supports the supply of energy from various nutrient sources.

5. Antioxidant effect and protection against cellular stress:
Thiamine indirectly contributes to the reduction of oxidative damage because, as a coenzyme, it optimizes energy metabolism and supports the formation of reducing equivalents (NADPH) - substances that protect cells from free radicals.

Benefits of thiamine

  • Converts carbohydrates into energy and supports energy metabolism

  • Promotes normal nerve and brain function

  • Supports heart and muscle function

  • Contributes to mental performance and concentration

  • Reduces fatigue and exhaustion

  • Protects cells from oxidative stress

  • Improves glucose utilization and supports blood sugar balance

Recommended daily intake

According to the German Nutrition Society (DGE):

  • Men: 1.2–1.3 mg per day

  • Women: 1.0–1.1 mg per day

  • Increased requirements for athletes, pregnant and breastfeeding women, and people with a high carbohydrate intake.

Since thiamine is water-soluble, it is easily lost during cooking - gentle cooking or steaming is therefore recommended.

Natural sources of thiamine

  • Whole grains (oats, spelt, wheat germ, brown rice)

  • Legumes (lentils, peas, beans)

  • Pork, poultry

  • Sunflower seeds, nuts (especially cashews)

  • Potatoes, asparagus, spinach

Deficiency symptoms

A thiamin deficiency can result from inadequate nutrition, chronic alcohol abuse, digestive disorders, or increased physical exertion.
Symptoms:

  • Fatigue, muscle weakness

  • Irritability, concentration problems

  • Loss of appetite

  • Heart problems, edema

  • Neurological disorders (e.g., tingling, numbness, ataxia)

Severe deficiencies lead to diseases such as:

  • Beriberi (dry form: nerve damage; wet form: heart failure)

  • Wernicke-Korsakoff syndrome (especially in alcoholics—with memory loss and disorientation)

Overdose and safety

An overdose is practically impossible, since excess thiamin is excreted in the urine.
Even high doses (>50 mg) are well tolerated and are generally used therapeutically for deficiency.

Conclusion

Thiamin (vitamin B1) is a key factor in energy production, nerve function, and heart health. Without adequate thiamin intake, the body cannot efficiently convert carbohydrates into energy, which can quickly lead to noticeable fatigue, especially in active people, athletes, or those with an unbalanced diet.

A balanced diet rich in whole grains, legumes, and high-quality protein sources reliably meets the body's needs. As a supplement, thiamin helps promote energy, concentration, muscle strength, and mental clarity—essential for vitality and performance in everyday life and training.

Sources

  1. German Nutrition Society (DGE). (2020): Reference values for nutrient intake – Thiamin.

  2. Lonsdale D. (2006): A review of the biochemistry, metabolism and clinical benefits of thiamin(e) and its derivatives. Evid Based Complement Alternat Med, 3(1), 49–59.

  3. Singleton CK, Martin PR. (2001): Molecular mechanisms of thiamine utilization. Curr Mol Med, 1(2), 197–207.

  4. Frank LL. (2015): Thiamin in clinical practice. J Parenter Enteral Nutr, 39(5), 503–520.