Vitamin B1

In its early stage, thiamin deficiency can cause weight loss and anorexia, confusion, short-term memory loss, and other mental signs and symptoms; muscle weakness; and cardiovascular symptoms (such as an enlarged heart).

The most common effect of thiamin deficiency is beriberi, which is characterized mainly by peripheral neuropathy and wasting. People with this condition have impaired sensory, motor, and reflex functions. In rare cases, beriberi causes congestive heart failure that leads to edema in the lower limbs and, occasionally, death. Although beriberi is rare in the United States and other developed countries, people in these countries do occasionally develop the condition. Administration of supplemental thiamin, often parenterally, quickly cures beriberi.

A more common manifestation of thiamin deficiency in the United States is Wernicke-Korsakoff syndrome. This disorder is about 8–10 times more common in people with chronic alcoholism than in the general population, but it can also develop in patients who have severe gastrointestinal disorders, rapidly progressing hematologic malignancies, drug use disorders, or AIDS. In many patients, Wernicke-Korsakoff syndrome has two phases. The first, acute, and life-threatening stage, Wernicke’s encephalopathy, is usually characterized by peripheral neuropathy. Without treatment, up to 20% of people with Wernicke’s encephalopathy die; those who survive develop Korsakoff’s psychosis, although some people with Korsakoff’s psychosis have not previously had Wernicke’s encephalopathy. Korsakoff’s psychosis, an effect of chronic thiamin deficiency, is associated with severe short-term memory loss, disorientation, and confabulation (confusion between real and imagined memories). At this chronic state of the disorder, parenteral thiamin treatment does not lead to recovery in about one-quarter of patients.