What is thiamine?
Thiamine (also spelled as thiamin) is a water-soluble essential nutrient. Thiamine is denoted as vitamin B1 and is placed under the B complex group.
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Its deficiency results in debilitating diseases like beriberi, optic neuropathy, Wernicke's encephalopathy and Korsakoff’s psychosis. Untreated thiamine deficiency can be fatal.As a water-soluble nutrient, any excess thiamine intake is excreted and the human body stores may last for a couple of weeks. Hence daily intake of the nutrient is necessary to ward off its deficiency related diseases. Yeast, whole grains, oatmeal, flax, sunflower seeds, brown rice and several vegetables are naturally rich in thiamine. The Recommended Dietary Allowances in several countries is set at about 1.0 mg.
In whole grains, vitamin B1 is found mostly in the outer layers of the grain (bran) and also in the germ. Whole 100 grams wheat flour contains up to 0.55 mg of thiamine. Processing and refining removes much of the nutrient and processed white wheat flour contains only 0.06 mg of thiamine.
Thiamine functions
Its phosphate derivatives such as thiamine diphosphate (ThDP) and thiamine triphosphate (ThTP) are coenzymes. They are involved in several metabolic and cellular processes. Vitamin B1 is involved in various aspects of cell metabolism such as energy production, RNA synthesis, lipid biosynthesis and neurotransmitter synthesis. Vitamin B1 facilitates neurotransmitter release, affecting acetylcholine, dopamine and noradrenaline. The enzymes associated with the citric acid cycle and oxidation of pyruvate, α-ketoglutarate and branched chain amino acids are dependent on the cofactor or coenzyme role of thiamine diphosphate.ThDP is the coenzyme for metabolic enzymes, cytosolic transketolase, pyruvate dehydrogenase complex and oxoglutarate dehydrogenase complex. It is vital for oxidative metabolism and any decrease in oxidative metabolism can lead to cell death.
"The brain heavily relies on oxidative metabolism for the synthesis of ATP, making this organ particularly sensitive to thiamine deficiency."
Thiamine deficiency causes
The foremost cause of vitamin B1 deficiency is inadequate intake. Malnutrition, starvation, diseases of malabsorption, major surgeries and systemic diseases are the other causes for developing insufficiency of thiamine in the body. Gastric bypass surgery, prolonged intensive care and intravenous therapy without vitamin supplementation, "hunger strikes", consuming polished rice as main food item and habitual consumption of large quantities of sweet food will exacerbate an existing clinical or subclinical thiamine deficiency.Certain components in food such as sulfites (preservative), thermolabile thiaminases (present in raw fish and shellfish), caffeic acid, chlorogenic acid and tannic acid react with vitamin B1, rendering it unabsorbable. Chronic alcoholism and the associated severe malnutrition is the cause of thiamine deficiency diseases like Korsakoff’s psychosis and Wernicke-Korsakoff syndrome in developed countries, particularly, the United States.
There are several inherited disorders of ThDP-dependent enzymes. Mutations in the SLC19A2 gene cause thiamine-responsive megaloblastic anemia disease. It is an an autosomal recessively inherited condition. SLC19A2 gene provides instructions for making thiamine transporter 1 protein, which transports thiamine into cells. Mutations in SLC19A2 gene hampers the transport of the nutrient into the cells, causing chronic deficiency. Biotin-thiamine-responsive basal ganglia disease is caused by mutations in the SLC19A3 gene. It is an autosomal inherited condition affecting the transport of vitamin B1 into cells.
Thiamine deficiency symptoms
Thiamine deficiency manifests with several neuromuscular, nervous, psychiatric, visual, dermal and cardiovascular symptoms. Peripheral neuropathy, symmetric impairment of sensory, motor, and reflex functions, axonal neuropathy, sensory ataxia, partial paralysis and sensory loss are some of the effects on the nervous system. The calf muscle tenderness, muscular atrophy, edema, tachycardia, cardiomegaly, and congestive heart failure may also be experienced by the patient. Ocular symptoms include, paralysis of eye movements, bilateral visual loss and impaired colour perception. Neuropsychiatric symptoms include, mental confusion, abnormal gait, amnesia, mental derangement and impairment of conceptual functions.Thiamine deficiency diseases
Vitamin B1 deficiency causes diseases such as beriberi, Wernicke's encephalopathy and Korsakoff’s psychosis, Wernicke-Korsakoff syndrome and optic neuropathy.Beriberi
Beriberi is a neurological and cardiovascular disease brought about by thiamine insufficiency in the body. Dry beriberi, wet beriberi and infantile beriberi are the three types of manifestations of beriberi. Dry beriberi is characterized by peripheral neuropathy. The patient suffers from symmetric impairment of sensory, motor, and reflex functions. The distal ends of the extremities are affected to a greater extent. The patient may complain of tender calf muscle. The patient may also suffer from sensory ataxia.In wet beriberi, there is mental confusion, muscular atrophy, edema, tachycardia, cardiomegaly and congestive heart failure, in addition to dry beriberi symptoms. Infantile beriberi occurs in infants breastfed by thiamine-deficient mothers. They may be suffering from subclinical stage of deficiency of this nutrient. The symptoms include, vomiting, tachycardia, convulsions and cardiac manifestations.
Wernicke's encephalopathy
Wernicke's disease is the presence of neurological symptoms as an effect of thiamine depletion in the central nervous system. The common symptoms are weakness or paralysis of one or more extraocular muscles which are responsible for eye movements (ophthalmoparesis or ophthalmoplegia), lack of voluntary coordination of muscle movements (ataxia), mental confusion and loss of orientation. The patient may also have several of the symptoms of beriberi. He may suffer from hypothermia, pallor and tremor. Thiamine supplementation can lead to improvement of the symptoms and often near complete resolution.Korsakoff’s psychosis
Korsakoff’s psychosis or syndrome is the presence of psychiatric symptoms as an effect of thiamine depletion on the brain. Korsakoff’s psychosis is characterised by memory impairment, inability to form new memories (anterograde amnesia), severe loss of earlier memories (retrograde amnesia), confabulation (invented or distorted memories), blackouts, lack of insight, confusion, loss of interest, indifference and personality changes.These neuropsychiatric effects are caused by generalized cerebral atrophy and damages to the medial thalamus and the posterior hypothalamus. Thiamine deficiency caused by chronic alcoholism and associated severe malnutrition leads to Korsakoff’s disease. Alcohol interferes directly with vitamin B1 absorption in the gastrointestinal tract. Alcohol also affects thiamine storage in the liver, disrupting its transformation into active form. Treating the patient with supplements may lead to slow and incomplete recovery.
Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndrome is a condition wherein both Wernicke's encephalopathy and Korsakoff syndrome exist in the same patient. Wernicke-Korsakoff syndrome is a manifestation of thiamine deficiency-related spectrum of diseases, encompassing beriberi, Wernicke's encephalopathy and Korsakoff's psychosis. It is most common in alcoholics and about 20% of the patients die due to failure in diagnosis and treatment. 75% of the survivors are left with permanent brain damage.Thiamine deficiency disease treatment and prevention
Oral doses of thiamine of 5-10 mg three times per day are recommended for mild deficiency diseases. In seriously ill patients, parenteral forms of vitamin B1 is administered. However it is to be noted that thiamine deficiency is preventable by taking balanced diet and supplements.Advertisements
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References: 1.Bettendorff L, Wins P. Biological functions of thiamine derivatives: Focus on non-coenzyme roles. OA Biochemistry 2013 May 01;1(1):10. 2.Hirsch JA, Parrott J. New considerations on the neuromodulatory role of thiamine. Pharmacology 2012;89(1–2):111-6. 3.Rabbani N, Thornalley PJ. Emerging role of thiamine therapy for prevention and treatment of early-stage diabetic nephropathy. Diabetes Obes Metab 2011 Jul;13(7):577-83. |
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