Thiamine, also called vitamin B1, helps cells convert food into energy and supports normal nerve function. Severe deficiency can cause beriberi or the neurological emergency known as Wernicke encephalopathy.

Who is at risk?

Deficiency is uncommon where foods are fortified, but risk rises with severe malnutrition, alcohol-use disorder, prolonged vomiting, malabsorption, bariatric surgery, dialysis or other conditions that affect intake and absorption.

Possible effects

“Dry” beriberi mainly affects nerves and may cause weakness, numbness or difficulty walking. “Wet” beriberi affects the cardiovascular system and can cause swelling, breathlessness and heart failure. Symptoms overlap with many other conditions.

The NIH Office of Dietary Supplements lists whole and fortified grains, pork, fish, legumes, seeds and nuts as thiamine sources.

Treatment

Suspected severe deficiency needs prompt medical treatment. Route and dose depend on the clinical situation, and thiamine may need to be given before or alongside glucose in high-risk patients. Food alone is not a substitute for urgent treatment when neurological or cardiac symptoms are present.