Vitamins >> Vitamin B1 - Deficiency Symptoms

Beriberi, the disease resulting from severe thiamin deficiency, was described in Chinese literature as early as 2600 B.C. Thiamin deficiency affects the cardiovascular, nervous, muscular, and gastrointestinal systems. Beriberi has been termed dry, wet, and cerebral, depending on the systems affected by severe thiamin deficiency.

Dry berberi

The main feature of dry (paralytic or nervous) beriberi is peripheral neuropathy. Early in the course of the neuropathy "burning feet syndrome" may occur. Other symptoms include abnormal (exaggerated) reflexes, diminished sensation and weakness in the legs and arms. Muscle pain and tenderness and difficulty rising from a squatting position have also been observed. Severely thiamin deficient individuals may experience seizures.

Wet beriberi

In addition to neurologic symptoms, wet (cardiac) beriberi is characterized by cardiovascular manifestations of thiamin deficiency, which include rapid heart rate, enlargement of the heart, severe swelling (edema), difficulty breathing, and ultimately congestive heart failure.

Cerebral beriberi

Cerebral beriberi may lead to Wernicke's encephalopathy and Korsakoff's psychosis. The diagnosis of Wernicke's encephalopathy is based on a "triad" of signs, which include abnormal eye movements, stance and gait abnormalities, and abnormalities in mental function, which may include a confused apathetic state or a profound memory disorder termed Korsakoff's amnesia or Korsakoff's psychosis. Thiamin deficiency affecting the central nervous system is referred to as Wernicke's disease when the amnesic state is not present and Wernicke-Korsakoff syndrome (WKS) when the amnesic symptoms are present along with the eye movement and gait disorders. Most WKS sufferers are alcoholics, although it has been observed in other disorders of gross malnutrition, including stomach cancer and AIDS. Administration of intravenous thiamin to WKS patients generally results in prompt improvement of the eye symptoms, but improvements in motor coordination and memory may be less, depending on how long the symptoms have been present. Recent evidence of increased immune cell activation and increased free radical production in the areas of the brain that are selectively damaged suggests that oxidative stress plays an important role in the neurologic pathology of thiamin deficiency.

Causes of thiamin deficiency

Thiamin deficiency may result from inadequate thiamin intake, an increased requirement for thiamin, excessive loss of thiamin from the body, consumption of anti-thiamin factors in food, or a combination of factors.

Inadequate intake: Inadequate consumption of thiamin is the main cause of thiamin deficiency in underdeveloped countries. Thiamin deficiency is common in low-income populations whose diets are high in carbohydrate and low in thiamin (e.g., milled or polished rice). Breast fed infants whose mothers are thiamin deficient are vulnerable to developing infantile beriberi. Alcoholism, which is associated with low intake of thiamin among other nutrients, is the primary cause of thiamin deficiency in industrialized countries.

Increased requirement: Conditions resulting in an increased requirement for thiamin include strenuous physical exertion, fever, pregnancy, breastfeeding, and adolescent growth. Such conditions place individuals with marginal thiamin intake at risk for developing symptomatic thiamin deficiency. Recently, malaria patients in Thailand were found to be severely thiamin deficient more frequently than non-infected individuals. Malarial infection leads to a large increase in the metabolic demand for glucose, as well as increased demand for the disposal of lactate. The stresses induced by malarial infection could exacerbate thiamin deficiency in individuals already predisposed. HIV-infected individuals, whether or not they had developed AIDS, were also found to be at increased risk for thiamin deficiency. The lack of association between thiamin intake and evidence of deficiency in these HIV-infected individuals suggested they had an increased requirement for thiamin.

Excessive loss: Excessive loss of thiamin may precipitate thiamin deficiency. Individuals with kidney failure requiring hemodialysis lose thiamin at an increased rate, and are at risk for thiamin deficiency. By increasing urinary flow, diuretics may prevent reabsorption of thiamin by the kidney and increase its excretion in the urine. Alcoholics who maintain a high fluid intake and urine flow rate may also experience increased loss of thiamin, exacerbating the effects of low thiamin intake.

Anti-thiamin factors (ATF): The presence of anti-thiamin factors (ATF) in foods also contributes to the risk of thiamin deficiency. Certain plants contain ATF, which react with thiamin to form a product that is oxidized in the body, rendering it inactive. Consuming large amounts of tea and coffee (including decaffeinated), as well as chewing tea leaves and betel nut have been associated with thiamin depletion in humans due to the presence of ATF. Vitamin C and other antioxidants can protect thiamin in some foods by preventing its oxidation to an inactive form. Thiaminases are enzymes that break down thiamin in food. Individuals who habitually eat certain raw freshwater fish, raw shellfish, and ferns are at higher risk of thiamin deficiency because these foods contain a thiaminase, which would normally be inactivated by the heat used for cooking. An acute neurologic syndrome (seasonal ataxia) in Nigeria has been associated with thiamin deficiency precipitated by a thiaminase in African silkworms, a traditional high-protein food for some Nigerians.

The Recommended Dietary Allowance (RDA)

The RDA for thiamin, revised in 1998, was based on the prevention of deficiency in generally healthy individuals.

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