Thiamine, also called vitamin B1, has several important roles in the body. It is essential for converting carbohydrates into energy and is needed for the functioning of the nervous system and muscles, including the heart. Thiamine deficiency is rare in the general population but can occur in chronic alcohol abusers and people with gastrointestinal diseases and chronic diseases such as AIDS. Possible consequences of thiamine deficiency include damage to the nerves, heart and brain.
Thiamine is present in moderate amounts in meats, fish, legumes and whole grains. Fruits, vegetables and dairy products contain small amounts of thiamine. In Western countries, many flours, breads, pastas and cereals are fortified with thiamine, because much of what is available in grains is lost during processing. Certain foods, including shellfish, fresh fish and raw meat, contain enzymes called thiaminases that destroy thiamine. A diet very low in thiamine or high in thiaminases is capable of causing thiamine deficiency.
Thiamine deficiency can have a number of short-term and long-term consequences. In general, the heart and nervous system are more sensitive to deficiency than other organs and bodily systems are. The first symptoms of deficiency can appear very quickly, because the body can store only a limited supply of the vitamin. If dietary intake does not fulfill the body’s needs, stored thiamine can be used up in as little as two weeks. The first symptoms that can appear include fatigue, muscle cramps and weakness, unsteady gait and difficulty walking, sleep disturbance, poor memory and tachycardia. Without treatment, symptoms can progress quickly to beriberi, a disease that occurs when thiamine deficiency affects the nervous system, or an associated deficiency syndrome.
One of the most common syndromes associated with thiamine deficiency is Wernicke’s encephalopathy, which causes symptoms such as paralysis of eye muscles, abnormal gait, memory impairment and confusion. This disease often is associated with a type of psychosis called Korsakoff syndrome. So-called Wernicke-Korsakoff syndrome often develops in chronic alcohol abusers, typically as a result of reduced dietary intake combined with a decreased uptake of thiamine from the gastrointestinal tract and impaired thiamine storage in the liver.
There are three distinct types of beriberi: dry, wet and infantile. Symptoms of dry beriberi are caused by nerve damage and include impairment of reflexes, movement and interpretation of sensory input. People with wet beriberi have mental confusion and muscle wasting and can develop cardiac symptoms such as congestive heart failure, an enlarged heart and tachycardia. Infantile beriberi can develop in a child who is breastfed by a woman with thiamine deficiency, with possible symptoms including tachycardia, vomiting and convulsions. Symptoms of all three types of beriberi tend to improve very quickly when high-dose thiamine treatment is administered, but damage done to the heart or nervous system is not always reversible.
