Thiamine (B1) Deficiency

Thiamine (vitamin B1) is a water-soluble vitamin with a key role in energy metabolism. When intake falls, absorption fails or losses rise, deficiency can develop. Its best-known forms are beriberi, which mainly affects the peripheral nerves and the heart, and Wernicke encephalopathy, an acute brain condition that can progress to Korsakoff syndrome, a lasting memory disorder. Severe deficiency was long regarded as a problem of infants in low-income rice-eating communities and of adults with alcohol dependence. A 2021 review of non-alcohol cases in high-income countries identified 81 adults with confirmed deficiency linked to cancer, gastrointestinal disease, heart failure, obesity, bariatric surgery, diuretics, repeated vomiting, thiamine-free parenteral nutrition and restrictive diets. Most improved, partly or fully, after intravenous thiamine. No single blood test is universally agreed, and the signs vary, so the condition is often missed. Guidelines therefore tell clinicians to suspect Wernicke encephalopathy in any setting that can lead to thiamine deficiency, not only in people who drink heavily. Suspected cases are treated with thiamine given by injection or drip, not by waiting for a supplement to work.

• •Loss of appetite and weight loss
• •Muscle weakness and wasting
• •Tingling, numbness or burning in the hands and feet (peripheral neuropathy)
• •Confusion and short-term memory loss
• •Breathlessness and leg swelling from heart failure (wet beriberi)
• •Abnormal eye movements or double vision
• •Unsteady walking and poor coordination (cerebellar signs)
• •Severe short-term memory loss with confabulation (Korsakoff syndrome)

• •Heavy, long-term alcohol use
• •Bariatric surgery, especially in the first months
• •Prolonged vomiting, including hyperemesis gravidarum
• •Long-term loop diuretic use
• •Disease-related malnutrition (cancer, gut disease)
• •Parenteral nutrition that lacks thiamine
• •Diets built on polished rice or other low-thiamine staples
• •Food insecurity or very restrictive diets
• •HIV/AIDS and other catabolic illness
• •Diabetes, which raises thiamine loss in urine

Deficiency arises in one of three ways: too little thiamine coming in, poor absorption, or high losses. Intake falls with famine, diets built on polished rice or other low-thiamine staples, food insecurity and monotonous or restrictive diets. Alcohol reduces absorption of thiamine, the liver's stores of it and its conversion to its active form, which is why chronic alcohol use is the most common cause in highly industrialised countries. Persistent vomiting, bariatric surgery and some gut diseases cut absorption and intake together. Diuretics and, in diabetes, increased clearance by the kidneys raise losses. In pregnancy with severe vomiting (hyperemesis gravidarum), one systematic review of case reports found that women became thiamine-depleted between 10 and 15 weeks of gestation.