[1] Wet beriberi affects the cardiovascular system, resulting in a fast heart rate, shortness of breath, and leg swelling.

[1] Dry beriberi affects the nervous system, resulting in numbness of the hands and feet, confusion, trouble moving the legs, and pain.

[8] Risk factors include a diet of mostly white rice, alcoholism, dialysis, chronic diarrhea, and taking high doses of diuretics.

[11] Symptoms of beriberi include weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart rate.

[6] Wernicke's encephalopathy is the most frequently encountered manifestation of thiamine deficiency in Western society,[14][15] though it may also occur in patients with impaired nutrition from other causes, such as gastrointestinal disease,[14] those with HIV/AIDS, and with the injudicious administration of parenteral glucose or hyperalimentation without adequate B-vitamin supplementation.

[16] This is a striking neuro-psychiatric disorder characterized by paralysis of eye movements, abnormal stance and gait, and markedly deranged mental function.

[2] It may also be caused by shortcomings other than inadequate intake – diseases or operations on the digestive tract, alcoholism,[23] dialysis or genetic deficiencies.

[33][34] The number of people with Wernicke's disease may be even higher, considering that early stages may have dysfunctions prior to the production of observable lesions at necropsy.

[37][38] Leigh disease (subacute necrotising encephalomyelopathy) is an inherited disorder that affects mostly infants in the first years of life and is invariably fatal.

[39] Mutations in the SLC19A3 gene have been linked to biotin-thiamine responsive basal ganglia disease,[40] which is treated with pharmacological doses of thiamine and biotin, another B vitamin.

[23] Workers on Chinese squid ships are at elevated risk of beriberi due to the simple carbohydrate-rich diet they are fed and the long period of time between shoring.

One of the earliest is by Ge Hong in his book Zhou hou bei ji fang (Emergency Formulas to Keep up Your Sleeve) written sometime during the third century.

Better known examples of early descriptions of "foot qi" are by Chao Yuanfang (who lived during 550–630) in his book Zhu bing yuan hou lun (Sources and Symptoms of All Diseases)[57][58] and by Sun Simiao (581–682) in his book Bei ji qian jin yao fang (Essential Emergency Formulas Worth a Thousand in Gold).

The link to white rice was clear to Western doctors, but a confounding factor was that some other foods like meat failed to prevent beriberi, so it could not be easily explained as a lack of known chemicals like carbon or nitrogen.

[63] In 1882, Takaki learned of a very high incidence of beriberi among cadets on a training mission from Japan to Hawaii, via New Zealand and South America.

With the support of the Japanese Navy, he conducted an experiment in which another ship was deployed on the same route, except that its crew was fed a diet of meat, fish, barley, rice, and beans.

[63] This emphasis on varied diet contradicted observations by other doctors, and Takaki's carbon-based etiology was just as incorrect as similar theories before him, but the results of his experiment impressed the Japanese Navy, which adopted his proposed solution.

[65] In 1897, Christiaan Eijkman, a Dutch physician and pathologist, published his mid-1880s experiments showing that feeding unpolished rice (instead of the polished variety) to chickens helped to prevent beriberi.

The following year, Sir Frederick Hopkins postulated that some foods contained "accessory factors"—in addition to proteins, carbohydrates, fats, and salt—that were necessary for the functions of the human body.

In 1935, Robert R. Williams isolated and cheaply synthesized thiamine from rice bran, based on discoveries he had made as a researcher in Manila's Bureau of Science in 1910.

[70] Although the identification of beriberi as a deficiency syndrome was proven beyond a doubt by 1913, a Japanese group headed by Mori Ōgai and backed by Tokyo Imperial University continued to deny this conclusion until 1926.

They employed various social tactics to denounce vitamin deficiency experiments and prevent them from being published, while beriberi ravaged the Japanese Army.

In response to this severe loss of life, in 1907, the Army ordered the formation of a Beriberi Emergency Research Council, headed by Mori.

Symptoms of PEM include a profuse, but transient, diarrhea, listlessness, circling movements, stargazing or opisthotonus (head drawn back over neck), and muscle tremors.

[79] The most common cause is high-carbohydrate feeds, leading to the overgrowth of thiaminase-producing bacteria, but dietary ingestion of thiaminase (e.g., in bracken fern), or inhibition of thiamine absorption by high sulfur intake are also possible.

This is often a problem observed in captivity when keeping garter and ribbon snakes that are fed a goldfish-exclusive diet, as these fish contain thiaminase, an enzyme that breaks down thiamine.

[82] Thiamine deficiency has been identified as the cause of a paralytic disease affecting wild birds in the Baltic Sea area dating back to 1982.

Researchers noted, "Because the investigated species occupy a wide range of ecological niches and positions in the food web, we are open to the possibility that other animal classes may develop thiamine deficiency, as well."[83]p.

12006 In the counties of Blekinge and Skåne, mass deaths of several bird species, especially the European herring gull, have been observed since the early 2000s.

In April 2012, the County Administrative Board of Blekinge found the situation so alarming that they asked the Swedish government to set up a closer investigation.