Vitamin B1 (Thiamine)

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Subject: Vitamin B1 (Thiamine)

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Definition

  • Thiamine, first named “the antiberiberi factor” in 1926, has a historical value due to the very early description of beriberi in the Chinese medical texts, as far back as 2697 bc. Thiamine is found in larger quantities in food products such as yeast, legumes, pork, rice, and cereals. Milk products, fruits, and vegetables are poor sources of thiamine. The thiamine molecule is denatured at high pH and high temperatures. Hence, cooking, baking, and canning of some foods as well as pasteurization can destroy thiamine. Thiamine is an essential vitamin required for carbohydrate metabolism, brain function, and peripheral nerve myelination. Thiamine deficiency has been associated with three disorders: Beriberi (infantile and adult), Wernicke-Korsakoff syndrome, and Leigh syndrome.

  • Normal range: 70–180 nmol/L.

Use

  • Assessment of thiamine deficiency: Thiamine measurement is appropriate in patients with behavioral changes, eye signs, gait disturbances, delirium, and encephalopathy; or in patients with questionable nutritional status, especially those who appear at risk and who also are being given insulin for hyperglycemia.

  • Investigation of suspected beriberi.

  • Monitoring the effects of chronic alcoholism.

Interpretation

Increased In

  • Leukemia

  • Polycythemia vera

  • Hodgkin disease

Decreased In

  • Alcoholism with and without liver disease

  • Deficient diet

  • Chronic febrile infections

  • Prolonged diarrhea

  • Diabetes

  • Carcinoid syndrome

  • Hartnup disease

  • Pellagra

Limitations

  • Whole blood is the preferred specimen for thiamine assessment. Approximately 80% of thiamine present in whole blood is found in RBCs.

  • Drugs that may decrease vitamin B1 levels include glibenclamide, isoniazid, and valproic acid.

  • Diets high in freshwater fish and tea, which are thiamine antagonists, may cause decreased vitamin B1 levels.

  • Thiamine deficiency can be assessed by measuring the blood thiamine concentration, erythrocyte thiamine transketolase (ETKA), or transketolase urinary thiamine excretion (with or without a 5-mg thiamine load). Most laboratories now measure blood thiamine concentration directly, in preference to the ETKA method. The ETKA method is a functional test, and results are influenced by the hemoglobin concentration.

 
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