beriberi

beriberi, nutritional disorder caused by a deficiency of thiamin (vitamin B₁) and characterized by impairment of the nerves and heart. General symptoms include loss of appetite and overall lassitude, digestive irregularities, and a feeling of numbness and weakness in the limbs and extremities. (The term beriberi is derived from the Sinhalese word meaning “extreme weakness.”) In the form known as dry beriberi, there is a gradual degeneration of the long nerves, first of the legs and then of the arms, with associated atrophy of muscle and loss of reflexes. In wet beriberi, a more acute form, there is edema (overabundance of fluid in the tissues) resulting largely from cardiac failure and poor circulation. In infants breast-fed by mothers who are deficient in thiamin, beriberi may lead to rapidly progressive heart failure.

The cardiac symptoms, in both infants and adults, generally respond promptly and dramatically to the administration of thiamin. When neurological involvement is present, the response to thiamin is much more gradual; in severe cases, the structural lesions of the nerve cells may be irreversible.

Thiamin normally plays an essential role as a coenzyme in the metabolism of carbohydrates; in its absence, pyruvic acid and lactic acid (products of carbohydrate digestion) accumulate in the tissues, where they are believed to be responsible for most of the neurological and cardiac manifestations.

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Thiamin occurs widely in food but may be lost in the course of processing, particularly in the milling of grains. In East Asian countries, where polished white rice is a dietary staple, beriberi has been a long-standing problem. The history of the recognition, the cause, and the cure of beriberi is dramatic and is well documented in medical literature. In the 1880s the Japanese navy reported that beriberi had been eradicated among its sailors as a result of adding extra meat, fish, and vegetables to their regular diet. Before that time, almost half of the sailors were likely to develop beriberi, and many died of it. In 1897 Christiaan Eijkman, working in the Dutch East Indies (now Indonesia), found that a beriberi-like disease could be produced in chickens by feeding them a diet of polished rice. British researchers William Fletcher, Henry Fraser, and A.T. Stanton later confirmed that beriberi in humans was also related to the consumption of polished white rice. In 1912 Casimir Funk demonstrated that beriberi-like symptoms induced in pigeons could be cured by feeding them white rice that was supplemented with a concentrate made from rice polishings. Following this discovery he proposed that this, as well as several other conditions, were due to diets that were deficient in specific factors that he called “vitamines,” later called vitamins.

The prevention of beriberi is accomplished by eating a well-balanced diet, since thiamin is present in most raw and untreated foods. The incidence of beriberi in Asia has markedly decreased because an improved standard of living has allowed a more varied diet and partly because of the gradual popular acceptance of partially dehusked, parboiled, and enriched rice—forms that contain higher concentrations of thiamin. In Western countries, thiamin deficiency is encountered almost solely in cases of chronic alcoholism.