Who Is Most at Risk for Vitamin B1 Deficiency?

Vitamin B1, often called thiamine, is a water-soluble vitamin belonging to the group of B vitamins. It plays a key role in energy metabolism in the body.

Vitamin B1 is a colorless organosulfur molecule that dissolves in the blood and is transported throughout the body. It is not naturally produced by the human body and must be obtained from dietary foods or supplements.

Vitamin B1 helps with the following:

• Heart function
• Carbohydrate and energy-yielding metabolism
• Neurological development and function
• Muscle contraction

Vitamin B1 is available as supplements or in multivitamins, including pills, soft gels, and lozenges. Thiamine can be administered intravenously in extreme cases of deficiency.

Thiamine needs are closely tied to carbohydrate consumption. 

Carbohydrates contribute 65% or more of the energy in most diets. However, the contribution of a diet to total energy content rather than energy produced from carbohydrates alone is low.

The recommended daily allowance (RDA) for thiamine is based on the following:

• Assessment of the effects of varying levels of dietary thiamine on the occurrence of clinical signs of deficiency
• Urinary excretion of thiamine
• Erythrocyte transketolase activity

Thiamine deficiency can cause a wide range of symptoms depending on its severity. Common symptoms of vitamin B1 deficiency include:

• Nausea and vomiting
• Headache
• Muscle weakness
• Shortness of breath especially when lying down
• Difficulty walking
• Leg pain and swelling
• Rapid heart rate (tachycardia)
• Reduced immunity
• Weight loss
• Difficulty sensing vibrations, especially in the hands and feet
• Garbled or slurred speech or inability to speak
• Confusion
• Memory loss
• Depression
• Generalized pain
• Jerky eye movements

Complications of vitamin B1 deficiency include:

• Heart failure
• Worsening diabetic neuropathy
• Permanent nerve damage
• Encephalopathy
• Coma
• Psychosis

• Dry beriberi: Dry beriberi can cause nerve and muscular dysfunctions to develop. Symptoms may include:
  • Prickling (pins-and-needles) sensation in the toes
  • Burning sensation in the feet, especially at night
  • Leg cramps and discomfort
  • Muscles weakness and wasting or thinning (atrophy)
• Wet beriberi: Wet beriberi causes heart problems, such as a rapid heart rate, shortness of breath, and edema (swelling) that mainly affects the legs. Eventually, heart function declines and results in heart failure. Besides fluid buildup in the legs (edema), heart failure can affect the lungs and cause pulmonary edema.
• Wernicke-Korsakoff syndrome: This is the result of various brain abnormalities caused by thiamine deficiency, especially in people who consume excessive amounts of alcohol. Brain abnormalities can exist without any symptoms until something further increases the thiamine deficiency. Wernicke-Korsakoff syndrome has two stages.
  • Wernicke encephalopathy: If left untreated, symptoms may lead to coma and even death. Symptoms include:
    • Disorientation
    • Lethargy
    • Trouble walking
    • Vision difficulties, such as nystagmus (involuntary eye movements) and eye muscle weakness
  • Korsakoff psychosis: This is characterized by recent onset memory loss, disorientation, and a tendency to make up facts to fill in memory gaps (confabulation).
• Infantile beriberi: Infantile beriberi affects newborns (typically between 3-4 weeks) who are nursed by thiamin-deficient individuals. Heart failure can develop unexpectedly in these babies. They may experience aphonia (some loss of voice) and lack certain reflexes.

If you suspect thiamine deficiency, you can improve your levels by making dietary changes:

• Reduce alcohol consumption: Alcohol reduces dietary thiamine absorption and can damage the intestinal lining, leading to even greater malabsorption.
• Avoid caffeine: Coffee and tea can interfere with thiamine absorption.
• Reduce your sugar intake: High sugar consumption can cause your body to require extra thiamine to metabolize the glucose.
• Eat lean meat: Vitamin B1 is found in abundance in lean pork. Three ounces of lean pork contains 0.5 mg of thiamin, which is 40% of the daily intake for adults
• Increase your intake of whole foods: Vitamin B1 is found in whole grains, peas, lentils, eggs, and potatoes. Avoid refined grains since these are leached of thiamine during the manufacturing process.

Vitamin B1 is not known to interact with any drugs, but several medications can lower thiamine levels. Individuals who use these or other drugs regularly should speak with their healthcare providers about their thiamine levels:

• Furosemide: Furosemide is a loop diuretic, which increases urine output to treat edema and hypertension and has been connected to thiamine deficiency. Clinical trials are needed to evaluate if thiamine supplements can help prevent thiamine deficiency in people who take loop diuretics.
• Digoxin: Lab studies report that digoxin (a medicine used to treat cardiac problems) may impair the ability of heart cells to absorb and utilize vitamin B1. This is more likely when digoxin is coupled with furosemide. 
• Fluorouracil: Fluorouracil is a chemotherapy drug that is often used to treat colorectal and other solid tumors Several cases of beriberi or Wernicke's encephalopathy have been linked to this medication. The drug increases thiamine metabolism and blocks the synthesis of thiamine diphosphate, the active form of thiamin. Some of these symptoms could be reversed by taking thiamine supplements.
• Phenytoin: Preliminary research suggests that some people using phenytoin have reduced amounts of thiamine in their blood. This is not true for everyone who takes phenytoin. Ask your doctor if you need a thiamine supplement while on phenytoin.