Thiamine, also known as Vitamin B1, is a water-soluble nutrient with an important role in the human body. It is found naturally in foods, added to others, and available as a dietary supplement. Since the body does not produce thiamine, a consistent dietary intake is necessary to maintain its levels.
Thiamine’s Essential Functions
Thiamine acts as a coenzyme, assisting enzymes in energy metabolism. It helps convert carbohydrates, fats, and proteins into adenosine triphosphate (ATP), the primary energy source for cells. Without sufficient thiamine, the body struggles to efficiently convert carbohydrates into usable energy.
Thiamine also supports proper nerve function. It is involved in synthesizing neurotransmitters, like acetylcholine, which are chemical messengers for nerve signals. This nutrient also aids in muscle contraction and the conduction of nerve signals.
Beyond energy and nerve function, thiamine supports heart health. A deficiency can lead to impaired heart function, potentially contributing to conditions like congestive heart failure. Thiamine helps maintain mitochondrial size and ATP levels in the heart.
Understanding Low Thiamine Levels
Low thiamine levels primarily result from insufficient dietary intake, especially with diets high in processed carbohydrates. Chronic alcoholism is a significant factor, impairing absorption and increasing excretion. Malabsorption issues from gastrointestinal surgeries or conditions like Crohn’s and celiac disease also contribute. Additionally, conditions like hyperthyroidism can increase the body’s need for thiamine, and some medications, including certain diuretics, can lead to increased thiamine excretion.
Symptoms of low thiamine levels can be vague and often mimic other conditions. These may include:
- Neurological symptoms: Confusion, irritability, short-term memory loss, and ataxia (loss of muscle coordination).
- Peripheral neuropathy: Tingling or loss of sensation, particularly in the hands and feet.
- Cardiovascular symptoms: Rapid heart rate, an enlarged heart, and swelling in the lower legs due to fluid retention.
- General symptoms: Fatigue, weakness, loss of appetite, and nausea or vomiting.
Severe and prolonged thiamine deficiency can lead to specific conditions. Beriberi affects the nervous and cardiovascular systems, with two main types: wet beriberi impacting the heart and circulatory system, potentially causing heart failure; and dry beriberi affecting the nervous system, leading to muscle weakness, numbness, and difficulty walking. Infantile beriberi can occur in breastfed infants of deficient mothers. Another severe manifestation is Wernicke-Korsakoff syndrome, a brain disorder most commonly seen in individuals with chronic alcohol use disorder. This syndrome includes Wernicke encephalopathy, an acute disorder characterized by confusion, visual problems, and ataxia, often followed by Korsakoff syndrome, a chronic memory disorder marked by severe memory loss.
Measuring Thiamine Status
Thiamine levels are assessed clinically through various diagnostic tests, as symptoms can be non-specific. The erythrocyte transketolase activity (ETKA) assay is a common indirect marker of thiamine status. This test measures the activity of the enzyme transketolase in red blood cells, which requires thiamine diphosphate (ThDP). In thiamine deficiency, transketolase activity is reduced, and adding ThDP will cause a greater increase in enzyme activity. A normal ETKA coefficient is 0%–15%, while values of 15%–25% indicate marginal deficiency and over 25% suggest deficiency.
Direct measurement of thiamine or its phosphorylated derivatives, particularly thiamine diphosphate (TDP), in whole blood is also used. Whole blood is preferred because most thiamine in blood is found within red blood cells as TDP, reflecting the body’s stores. Normal whole blood thiamine pyrophosphate levels range from 70 to 180 nmol/L, though specific laboratory ranges may vary. Levels below 70 nmol/L suggest deficiency. Urinary excretion of thiamine can provide information on recent dietary intake, but it does not reliably indicate the body’s thiamine stores.
Maintaining Healthy Thiamine Levels
Maintaining adequate thiamine levels primarily involves consuming a balanced diet rich in thiamine. Excellent dietary sources include:
- Whole grains: Brown rice, whole wheat bread, and oats.
- Legumes: Beans, lentils, and peas.
- Pork.
- Nuts, seeds, and certain fish like salmon.
- Fortified foods: Many breakfast cereals and bread products.
Thiamine supplementation may be considered for diagnosed deficiencies or for individuals with specific risk factors, but always under medical guidance. For mild deficiencies, oral thiamine supplements may be recommended. In more severe cases, particularly with conditions like Wernicke encephalopathy, intravenous thiamine might be necessary before transitioning to oral therapy. The specific dosage and duration depend on the individual’s condition and the doctor’s assessment.
Thiamine toxicity from food sources is extremely rare because it is a water-soluble vitamin. The body efficiently absorbs less of the nutrient when intake is very high and readily excretes any excess in the urine. Even from supplements, toxicity is very rare. While there is no established upper intake level, taking 100 mg or less per day of thiamine supplements is generally considered unlikely to cause harm. In rare instances of extremely high doses, mild and temporary side effects might occur, but severe adverse effects are uncommon.