What Happens When You Are Low on Thiamine (Vitamin B1)? Symptoms and Treatment

Thiamine, also known as vitamin B1, is an essential micronutrient for your body. Low thiamine may cause wet and dry beriberi, Wernicke-Korsakoff syndrome, and other conditions.

Thiamine, also known as vitamin B1, is an essential micronutrient for your body. It's needed in minute amounts but performs several vital functions in the body. Like other B vitamins, thiamine is a water-soluble vitamin. Your body can't store much of it or make it. You have to consume this vitamin regularly to maintain good health and prevent the problems and symptoms of deficiency.  

This vitamin plays important roles in energy metabolism. It is also vital for the health of your nervous system. Vitamin B1 is needed for the synthesis of myelin and neurotransmitters (acetylcholine), both vital for nervous system function.

Most of the thiamine in your body is thiamine diphosphate (also known as thiamine pyrophosphate). This compound is an essential cofactor for several enzymes involved in amino acid, glucose, and lipid metabolism.

These thiamine-dependent enzymes are essential for metabolizing carbohydrates and amino acids to form adenosine triphosphate (ATP), the energy molecule of the cells. Thiamine deficiency causes oxidative damage, a lack of ATP, and cell death. Organs with high energy needs are the first to be affected when this vitamin is deficient. These organs include the brain, heart, nerves, liver, pancreas, and muscles. 

Vitamin B1 is found in many foods. Good sources are:

• Whole grain bread
• Peas
• Oranges and bananas. Most fruits have little thiamine.
• Nuts
• Meat
• Fish

Some cereals and infant formulas are fortified with thiamine. Dairy has little thiamine, and this is further reduced by pasteurization. Heating food destroys thiamine — bread contains less of it than grain. This vitamin is water-soluble, and throwing away the water used in cooking food removes thiamine.

Thiamine is absorbed from the small intestine. It is stored in the liver but in small amounts. You need to consume vitamin B1 regularly to avoid deficiency.

The recommended nutrient intake (RNI) of thiamine is 1.2 milligrams a day for men and 1.1 milligrams a day for women. Pregnant and breastfeeding women need more — they should have 1.4 and 1.5 milligrams a day, respectively. Children need lesser amounts:

Infants: 0.2 to 0.3 milligrams a day

1 to 3 years: 0.5 milligrams a day

4 to 6 years: 0.6 milligrams a day

7 to 9 years: 0.9 milligrams a day.

Children over 10: same as adults. 

Greater consumption of this vitamin has no adverse effects. Thiamine is usually plentiful in food, but you can get it as supplements by itself or as multivitamin tablets.

Thiamine is widespread in food, and deficiency rarely happens in people eating a balanced diet. People eating a diet based on polished rice or cassava are at risk of thiamine deficiency. Heavy consumption of alcohol, severe malnutrition, advanced acquired immunodeficiency syndrome (AIDS), and bariatric surgery can also cause vitamin B1 deficiency. 

Vitamin B1 deficiency causes different types of disorders.

"Wet" beriberi

This is a disorder seen mainly in infants and young children. There is heart failure and swelling of the feet (edema). "Wet" refers to the fluid in the lungs because of heart failure. This condition can be fatal.

"Dry" beriberi

This disorder is caused by vitamin B1 deficiency in older children and adults. This disorder chiefly affects the nervous system. There is weight loss, confusion, memory loss, and muscle weakness in the early stages. The reflexes are slow. Weakness, inability to move the eyes, loss of balance (ataxia), and cognitive impairment happen as the disorder progresses. 

Wernicke-Korsakoff syndrome

The acute stage of this disorder is Wernicke's encephalopathy, which affects the brain and nerves. It is fatal in about 20% of people. The other form of this disorder is Korsakoff's psychosis which causes memory loss, confusion, and disorientation. About a quarter of people with such symptoms don't recover with thiamine treatment. 

Mixed manifestations

Thiamine deficiency does not always fit into one or other of these disorders. Infants often have nervous system disorders, and adults also have heart failure. 

Weakness is frequent in thiamine deficiency. It is caused by a combination of muscle loss and peripheral nerve disease. Other common manifestations are nausea, loss of appetite, vomiting, tiredness, and sleepiness. Infants are often fussy. Changes in personality, loss of memory, headache, constipation, and burning feet may develop.

Severe thiamine deficiency can have long-lasting effects. These include hearing loss, heart damage, nerve and brain damage, and liver damage. Untreated thiamine deficiency can cause death.

Other conditions

Some medical disorders are not caused by vitamin B1 deficiency but are worsened by it. Some of these are Alzheimer's disease, diabetes, and heart failure. High-dose thiamine partially reverses some symptoms.

Your doctor will treat vitamin B1 deficiency by prescribing tablets to take orally. You can have thiamine with your meals or without. The usual dose for mild deficiency is 25 to 100 milligrams daily. Your doctor will prescribe 100 milligrams two or three times a day for severe deficiency. Your doctor will prescribe a dose for your child after weighing them.

Severe symptoms of thiamine deficiency may need treatment by injection. Your doctor will administer 50 to 100 milligrams intravenously on the first day, followed by 10 milligrams intramuscularly every day for a week. After this, they will prescribe 3 to 5 milligrams of thiamine a day by mouth for six weeks or more.

Your doctor will monitor your symptoms and blood levels while you take the treatment. Once your deficiency is cured, they'll prescribe a lower dose to prevent deficiency from happening again.

Thiamine is generally well-tolerated, but you may have a stomach ache, diarrhea, or nausea. These side effects are usually mild and don't last long. 

Look out for:

Skin rash

Wheezing

Tightness in the throat or chest

Swelling on the mouth, lips, tongue, or face

You may be having a severe allergic reaction (anaphylaxis) and should go to a hospital immediately.

You shouldn't drink alcohol while taking this vitamin. Thiamine is generally safe during pregnancy and while you're breastfeeding, but if your baby is premature, talk to your doctor about taking B1 supplements. 

Thiamine deficiency is often not considered and diagnosed in developed countries because malnutrition is rare, and several foods are fortified with this vitamin. If you are at risk for thiamine deficiency because of alcohol use, AIDS, or another condition. Early treatment can reverse the effects of deficiency and avoid permanent organ damage.