B1 deficiency symptoms

What are the symptoms of thiamin deficiency?

According to NIH, in the early stage weight loss and loss of appetite, confusion, short-term memory loss and other mental symptoms, muscle weakness and heart-related findings (such as an enlarged heart) can occur. Beriberi is the most common effect of thiamin deficiency; it is characterized mainly by peripheral neuropathy and muscle wasting, and sensory, motor and reflex functions are impaired. Rarely it leads to congestive heart failure with edema, and to death. ^[1]

None of these findings is specific to thiamin; the pictures can also occur in other diseases. For this reason, new symptoms in a person in a risk group are evaluated together.

Why is Wernicke encephalopathy an emergency?

EFSA reports that impairment of metabolic functions in the brain can lead to Wernicke encephalopathy; that it is described clinically by eye findings, ataxia and impaired consciousness; and that it can be followed by Korsakoff syndrome, which involves amnesia, disorientation and often confabulation. ^[2] Fiorentini and colleagues state that untreated Wernicke encephalopathy can progress to Korsakoff syndrome, a permanent cognitive impairment, and that the picture is a severe, potentially life-threatening condition. ^[4]

The 2010 EFNS guideline describes this picture as a disease that is “preventable and treatable but often not diagnosed during life.” The main points of the guideline are as follows: ^[3]

• It notes that findings can look different in people who use alcohol and those who do not; although the disease is more common with alcohol, it says that it should be considered in every clinical situation that can lead to thiamin deficiency.
• For clinical diagnosis in people who use alcohol, it looks for two of the following four findings: dietary deficiency, eye signs, cerebellar dysfunction, altered mental state or mild memory impairment. It notes that MRI can be used to support the diagnosis.
• It considers thiamin indicated for suspected or manifest Wernicke encephalopathy, preferably intravenously, before any carbohydrate is given (level of recommendation C). The guideline defines a specific regimen; this regimen is determined by the physician and is not given here. It rates the general safety of thiamin as very good (level B).
• It recommends giving parenteral thiamin to everyone in a risk group who presents to the emergency department as a good practice point.

For this reason, Wernicke encephalopathy is treated as an emergency in which thiamin treatment is recommended at the level of suspicion and which is managed by a physician. This page gives no doses.

The classic triad may not be present in every case

In a review of 82 cases of Wernicke encephalopathy developing due to hyperemesis gravidarum (case reports and case series from 66 publications), eye findings were present in 93.9% of cases (77/82), ataxia in 74.4% (61/82) and confusion in 76.8% (63/82); muscle weakness was reported in 43.9%, reflex abnormalities in 51.2% and memory impairment in 30.5%. That is, not every finding was present in every case. Hospital admission occurred at a mean of 14.6 weeks of gestation, after vomiting lasting a mean of 6.6 weeks; encephalopathy appeared at a mean of 16.5 weeks. These are a review of case reports; they describe the picture that emerges, not its frequency. ^[4]

Who gets thiamin deficiency?

What is intake like in Türkiye?

In the analysis of TÜBER (Türkiye Dietary Guidelines) 2022 based on TBSA 2017 data, 1.6% of individuals aged 15 and over had B1 intake below the estimated average requirement (EAR). In women the rate rose with age (6.5% in women aged 65 and over; 9.5% in women aged 75 and over). This is an intake distribution based on a nutrition survey; it is not a blood level measurement and cannot be interpreted as the frequency of deficiency. ^[5]

Do symptoms resolve when the deficiency is corrected?

NIH reports that thiamin supplementation, often given intravenously, rapidly improves beriberi. ^[1] In Wernicke encephalopathy, however, the outcome depends on delay: if untreated, the picture can progress to Korsakoff syndrome, that is, a cognitive impairment that can be permanent; in the review of 82 cases with hyperemesis gravidarum, thiamin was given in almost all cases, but data on clinical course and birth outcomes were often missing. ^[4] For this reason, the generalization “thiamin was given, the problem was solved” cannot be made: the outcome depends on the delay in diagnosis and the stage of damage.

Prevention and monitoring

The 2010 EFNS guideline recommends monitoring thiamin status for at least 6 months after bariatric surgery and parenteral thiamin support, and giving parenteral thiamin to everyone in a risk group who presents to the emergency department. NIH, for its part, states that whether thiamin supplements prevent deficiency in people using loop diuretics needs to be determined by clinical studies; that is, there is no proven prevention regimen for every risk group. ^{[3] [1]}

Deficiency in infants

EFSA reports that infantile beriberi can be seen in infants aged 2–6 months breastfed by thiamin-deficient mothers, and that thiamin deficiency has also been described in infants fed a soy-based infant formula that contains no thiamin. ^[2]

How is deficiency measured?

According to EFSA, the erythrocyte transketolase activity coefficient (αETK, “TDP effect”) is a functional test; below 1.15 generally reflects adequate thiamin status. NIH reports that the TDP effect is generally 0–15% in healthy people, 15–25% in borderline deficiency, and above 25% in deficiency. Total thiamin in whole blood, serum and erythrocytes and erythrocyte TDP levels have also been investigated; EFSA states that there are no established cutoff values for these markers and that 24-hour urinary thiamin is not reliable on its own. ^{[2] [1]}

EFNS recommends that total thiamin measurement from blood be done immediately before thiamin is given; that is, the measurement rests on a sample taken before treatment starts. The guideline puts clinical findings and MRI forward for diagnosis. ^[3]