Effects of Vitamin B1(Thiamine) Deficiency

Thiamine deficiency produces the following effects in animals:

  1. The growth of young animal is retarded.
  2. There is anorexia and other gastrointestinal abnormalities.
  3. Polyneuritis, especially marked in pigeons. The pigeons cannot fly, walk or even stand; there is head retardation, i.e. opisthotons, death follows after some times.

   Effects of Vitamin B1 (Thiamine) Deficiency In Human Beings 

Beriberi: Beriberi means ‘I cannot’ which points out to the facts that the patient suffers from severe weakness and even paralysis. This disease was found to be associated with eating polished rice and was very common in the Far East where rice is the staple diet. Beriberi is nowadays quite uncommon even in Far East and is usually found in infants and pregnant and lactating women. In the west, beriberi is occasionally seen in alcoholics but the manifestation in these cases from those in the East. The reason for this regional difference in the clinical picture of beriberi is not know.

Beriberi occurs in three main forms:

  1. Wet beriberi: This is an acute disease; cardiac failure of high output type and edema are the principal signs.
  2. Dry beriberi: This is a more chronic disease of adults in which polyneuropathy is the principal feature.
  3. Infantile beriberi: This occurs in the first year of life and is marked by cardiovascular abnormalities.

The various features of beriberi are discussed below:

  1. Polyneuropathy: There is myelin degeneration of peripheral nerves with loss of axoplasm. Posterior colums of the spinal cord may also undergo degeneration; there may also be seen retro-bulbar neuritis with blindness. The onset is insidious. There is easy fatigability, pain and weakness of muscles. Later the muscles atrophy. There may be toe drop, foot drop and wrist drop. Reflexes, e.g. knee jerk disappear. Paresthesias and anesthesias are common particularly over the lower extremities. Burning feet syndrome may be seen. Walking becomes difficult and the patient becomes bedridden.
  2. Cardiovascular Features: Palpitation, tachycardia, precordial pain and dyspnea are common. Edema is usually present and may be due to heart failure and hypoproteinemia. There may be pericardial effusion. Death may result suddenly with or without exertion. Pathologically, the heart is enlarged due to its dilatation and there is swelling and vacuolization of cardiac fibers. Characteristic E.C.G changes are observed.
  3. Gastrointestinal Features: These include anorexia and diarrhea leading to weight loss.
  4. Cerebral Lesions: These occur only in the Occident where the disease occurs in alcoholics. These lesions have never been found in oriental cases. The lesions include bilateral hemorrhages in the hypothalamus and especially in mamillary bodies. Manifestations of Wernicke’s encephalopathy are seen which include confusion, apathy, drowsiness, nystagmus, ataxia, and opthalmoplegia.

In the blood, pyruvic acid level is found to be raised especially after exercise and glucose intake. This is due to a decreased rate of the reaction, pyruvic acid àacetyl-S—CoA, which needs thiamine pyrophosphate as a coenzyme. The ratio, blood lactic acid; blood pyruvic acid is also abnormally increased.

   Factors Affecting Requirements of Vitamin B1 (Thiamine)

The requirements of thiamine are increased in the following conditions:

  1. When metabolic activities are increased, e.g. in fever, hyperthyroidism and muscular exercise.
  2. When carbohydrates form a much greater formation of the caloric intake.

On the other hand, the dietary intake of fats, protein and alcohol decreases its requirement because of a thiamine-sparing action. The deficiency of thiamine seen in chronic alcoholism is due to low intake and not due to increased requirements of thiamine. This vitamin is not stored in the body in appreciable amounts.

Untoward Reaction to Thiamine

Some persons collapse and may even die after an injection of thiamine. This is due to hypersensitivity to this substance (anaphylactic shock). Less severe toxic effects are nervousness, tremors, tachycardia and sweating.