Vitamin B1 Overdose Symptoms

Vitamin B1, or thiamine, supports normal cell function and helps your body convert food into energy. Thiamine overdose symptoms are unlikely to occur because this vitamin will be excreted in urine when consumed in excess. Vitamin B1 deficiency, on the other hand, can be a lot more harmful.

Fortified cereals are filled with vitamin B1. (Image: Povareshka/iStock/GettyImages)

Tip

Thiamine overdose doesn't cause toxicity. In fact, there is no upper limit for this vitamin. However, you may experience digestive distress.

Beware that thiamine hydrochloride, a synthetic form of vitamin B1, may cause allergic reactions and other side effects. Stomach pain, arrhythmia, eye irritation, vomiting and diarrhea are just a few examples. Discuss with your doctor before taking this drug.

The Role of Vitamin B1

B-complex vitamins play a key role in energy production and metabolism. Some promote growth and development, while others support the formation of red blood cells, keep your brain sharp or act as coenzymes in various biochemical reactions. Thiamine helps your body process the nutrients in food and use them for fuel. It regulates glucose metabolism and supports immune function.

The human body can store approximately 25 to 30 milligrams of thiamine, according to the National Institutes of Health (NIH). About 80 percent of this is stored as thiamine diphosphate and helps your body metabolize fats, carbs and amino acids.

Vitamin B1 also supports normal brain function. That's why low levels of this nutrient in the blood may lead to dementia, memory problems, apathy, fatigue and behavioral changes, among other symptoms. Your brain needs thiamine to transmit nerve signals and function properly.

Luckily, thiamine deficiency is rare. Most foods contain varying doses of this vitamin. Whole grains, legumes, fish, seafood and meat are just a few examples.

Fortified breakfast cereals, for instance, provide 100 percent of the daily value (DV) of thiamin, according to the NIH. White rice boasts around 75 percent of the DV of vitamin B1. If you're looking for low-carb options, fill up on tuna, steak, mussels, yogurt and cheddar cheese. Beware that cooking and processing may reduce thiamine levels in food.

Vitamin B1 Side Effects

As the NIH points out, thiamine overdose is unlikely to cause side effects. If you consume too much of it, the excess will be eliminated in urine. In fact, there is no upper limit for vitamin B1. Doses of up to 50 milligrams appear to be safe.

The recommended daily intake of thiamine is 1.1 milligrams for adult women and 1.2 milligrams for men. Pregnant and nursing women should aim for about 1.4 milligrams per day. Although vitamin B1 is unlikely to cause adverse reactions, stay on the safe side and call the poison control helpline in case of overdose.

Some dietary supplements may contain thiamine hydrochloride, a form of vitamin B1. This compound is also available in injectable form. Its side effects may include skin and eye irritation, respiratory tract irritation, eye damage and spastic paralysis, according to the U.S. National Library of Medicine.

You may also experience rapid heartbeat, abdominal pain, rash, swelling of the face and other allergic reactions. Mild adverse effects, such as nausea, vomiting and diarrhea may occur, too.

Thiamine hydrochloride is prescribed to adults and teenagers with vitamin B1 deficiency. This compound, though, is made in the lab and has a slightly different chemical profile than dietary thiamine. In rare cases, the injectable form may cause cardiac arrest and severe allergic reactions that require emergency treatment.

According to Penn State Health, a common side effect of thiamine overdose is stomach upset. Additionally, taking large doses of thiamine or any other B vitamin for a long time can affect overall B vitamin levels in the bloodstream.

Furthermore, certain medications, such as diuretics, phenytoin and digoxin, may affect thiamine absorption and interfere with your body's ability to use this nutrient. If you're under medical treatment, get regular blood tests to check for deficiencies.

The Dangers of Thiamine Deficiency

Every cell and tissue in your body needs thiamine to function properly. Even the slightest deficiency can affect your health and cause serious problems down the road. In fact, low thiamine levels are often the underlying cause of beriberi, Korsakoff's psychosis, Wernicke-Korsakoff syndrome and other life-threatening conditions, as reported by the NIH.

Many individuals who develop thiamine deficiency experience short-term memory loss, unintentional weight loss, gastrointestinal symptoms and cardiovascular problems. If left unaddressed, this condition can lead to full-blown disorders that affect mental health, motor function and heart health.

Beriberi, for example, may cause tingling or loss of feeling in the limbs, confusion, difficulty walking, elevated heart rate and shortness of breath. Wernicke-Korsakoff syndrome may cause brain damage, affecting your eyesight, memory and motor function. Its symptoms include, but are not limited to, poor balance and coordination, hypotension, hallucinations and short-term memory loss.

What Causes Low Thiamine Levels?

Certain people are more likely to develop vitamin B1 deficiency. This condition tends to occur in heavy drinkers, older adults and individuals with HIV or diabetes. It's estimated that up to 30 percent of seniors and 17 to 79 percent of people with diabetes are deficient in thiamine, according to the NIH.

Another common cause is bariatric surgery, which affects the body's ability to absorb nutrients. This may lead to low thiamine levels in the bloodstream.

Surprisingly, obese people tend to have low levels of thiamine, as reported in a March 2015 review published in Advances in Nutrition. As the scientists point out, obesity isn't necessarily characterized by excess nutrition. In fact, the consumption of junk food, sugary treats, soda and other products with empty calories can lead to malnutrition.

Warning

Poor nutrition is a common cause of thiamine deficiency. This vitamin is found in fish, seafood, meat, oats, wheat germ, nuts, seeds, legumes and whole-grain products. Consume whole foods on a daily basis to meet your nutritional needs.

According to the Advances in Nutrition review, thiamine deficiency may result in heart failure, delirium, paralysis, overall weakness, back pain and emotional lability (rapid, often exaggerated changes in mood). It's estimated that about 76 percent of people with low thiamine levels experience delirium. Other common symptoms include chest pain, irregular heartbeat, low blood pressure, sleep problems, depression, memory loss, anorexia, constipation and even blindness.

A diet based on processed foods is often the culprit behind low thiamine levels. Furthermore, certain polyphenols in coffee and tea can inactivate vitamin B1, while diuretics increase its excretion. Crohn's disease and other disorders that reduce nutrient absorption may lead to deficiencies, too.

As you see, this condition can have a variety of causes, from poor nutrition and alcohol consumption to diabetes. The symptoms of vitamin B1 deficiency are a lot more severe than those associated with thiamine overdose. Prevention is your best defense. Eat a balanced diet, have regular checkups and consult your doctor before taking any medications.

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