Is thiamine a B vitamin?

Thiamine is a B Vitamin

Yes, thiamine is definitively classified as a B vitamin, specifically vitamin B1. 1

Classification and Properties of Thiamine

• Thiamine, also known as vitamin B1, is a water-soluble vitamin that belongs to the B vitamin complex 1, 2
• It exists in several forms in the body, with thiamine diphosphate (ThDP) being the active form that serves as a coenzyme for several metabolic processes 1
• Thiamine is essential for carbohydrate metabolism, energy production, and proper functioning of the nervous system 1, 3

Biochemical Role and Function

• Thiamine functions as a coenzyme in the catabolism of carbohydrates and amino acids and plays an antioxidant role 4
• It is a key component in the production of energy (ATP) as a catalyst in the Krebs cycle 4, 3
• Thiamine pyrophosphate (TPP) is the active coenzyme form that serves as an antiberiberi substance 5
• It participates in the synthesis of neurotransmitters and has important roles in both central nervous system and immune system function 4, 3

Dietary Sources and Requirements

• Main dietary sources include whole grains, legumes, meats, nuts, fortified foods, enriched cereals and breads, lean pork, and small amounts in most nutritious foods 1
• The Recommended Dietary Allowance (RDA) for adults is 1.1-1.2 mg/day 1
• For enteral nutrition, guidelines recommend providing 1.5-3 mg per day of vitamin B1 in patients receiving 1500 kcal per day 1
• For parenteral nutrition, at least 2.5 mg per day should be provided 1

Deficiency and Clinical Implications

• Thiamine deficiency can lead to serious conditions including Wernicke-Korsakoff syndrome, beriberi, optic neuropathy, and other disorders 1, 4
• Clinical manifestations of deficiency include neuritis, edema, cardiac failure, hoarseness, anorexia, restlessness, and aphonia (symptoms of beriberi) 1
• Deficiency can occur in various clinical situations including malnutrition, alcoholism, diabetes, congestive heart failure, and after bariatric surgery 1, 4
• In cases of suspected deficiency, thiamine status should be determined by measuring red blood cell or whole blood thiamine diphosphate (ThDP) 1

Supplementation Guidelines

• For mild deficiency, 10 mg per day for one week is recommended 1, 6
• For acute deficiency or in emergency/intensive care settings, higher doses of 100-300 mg/day IV are recommended for 3-4 days 1, 7
• In patients with suspected reduced food intake or high alcohol consumption, thiamine 100-300 mg/day should be administered either orally or IV 1
• For patients who have undergone bariatric surgery, additional thiamine supplementation may be necessary to prevent deficiency 1, 7

Safety and Administration

• Thiamine has no established upper limit for toxicity, with excess being excreted in urine 7, 6
• It can be administered orally, enterally, or intravenously, with the IV route being most efficient for acute deficiency 1
• High doses exceeding 400 mg may cause mild side effects such as nausea, anorexia, and mild ataxia 7, 8
• Rare cases of anaphylaxis have been reported with high intravenous doses 7

Thiamine's classification as vitamin B1 is well-established in medical literature and clinical practice, with clear guidelines for its use in various clinical scenarios.