Thiamine Deficiency Symptoms & Dangers You Don’t Want to Ignore

Thiamine deficiency - Dr. Axe

Vitamin B1, which is also referred to as thiamine, is a coenzyme used by the body to metabolize food for energy and to maintain proper heart and nerve functions. Thiamine has the important role of helping us digest and extract energy from the foods we eat by turning nutrients into useable energy in the form of adenosine triphosphate (ATP). Thus, a thiamine deficiency is something you definitely want to avoid.

What happens if you get too little vitamin B1? Without high enough levels of thiamine, the molecules found in carbohydrates and proteins (in the form of branched-chain amino acids) cannot be properly used by the body to carry out various important functions.

What are some symptoms of vitamin B1 deficiency? A thiamine deficiency (also referred to as beriberi) can cause weakness, chronic fatigue, heart complications, psychosis and nerve damage. The best way to prevent thiamine deficiency is to eat whole foods that supply high amounts of B vitamins, particularly thiamine foods. Thiamine can be found in many commonly eaten foods, including certain whole grains, beans, nuts, nutritional yeast, organ meats like liver and other meats. Additionally, it is included in many vitamin B complex supplement products, which is good news in preventing a thiamine deficiency.

What Is Thiamine?

Thiamine (vitamin B1) is a water-soluble vitamin that is used in nearly every cell in the body. It is especially important for supporting energy levels and a healthy metabolism. Thiamine is technically a sulfur-containing derivative of thiazole and pyrimidine. It is used in combination with other B vitamins, which make up the “B vitamin complex,” to regulate important functions of the cardiovascular system, endocrine system and digestive system.

The human body cannot produce thiamine, so we must ingest it from our diet to prevent thiamine deficiency. What is the disease caused by a deficiency of thiamine? A thiamine deficiency can cause a disorder called beriberi, which has been seen in certain undernourished populations for thousands of years. Beriberi can lead to muscle wasting and severe cardiovascular problems, including an enlarged heart.

Thiamine deficiency is not very common in Western, developed nations. It’s believed that most adults meet their daily thiamine requirement, and with supplementation included, some adults may get significantly more than their required daily intake.

Today, in developed nations like the Unites States, we most commonly see a thiamine deficiency in alcoholics, which is known as Wernicke-Korsakoff syndrome. Why do many alcoholics develop thiamine deficiency? Chronic alcohol consumption can cause inadequate nutritional thiamine intake, decreased absorption of thiamine from the gastrointestinal tract and impaired ability for cells to use thiamine. (1) Most alcoholics that are diagnosed with this disorder also report not eating much food in addition to drinking a lot of alcohol, which is a big contributing factor to thiamine deficiency symptoms.

Thiamine Deficiency Symptoms

What are the symptoms of low thiamine? Clinical thiamine deficiency symptoms (or symptoms of beriberi) can include: (2)

  • Rapid weight loss
  • Poor appetite
  • Colitis
  • Ongoing digestive problems, such as diarrhea
  • Nerve damage
  • Burning in the feet (particularly severe at night)
  • Nerve inflammation (neuritis)
  • Fatigue and low energy
  • Decrease in short-term memory
  • Confusion
  • Irritability
  • Muscle weakness, muscle wasting, cramps, pains in the legs and stiffness
  • Mental changes, such as apathy or depression
  • Cardiovascular effects, such as an enlarged heart

What happens if you don’t have enough thiamine in your body? Your brain, heart, and other tissues and organs suffer from low thiamine levels. High concentrations of thiamine are normally found in skeletal muscles and in the heart, liver, kidneys and brain. Thiamin deficiency causes degeneration of peripheral nerves and parts of the brain, including the thalamus and cerebellum. Deficiency can also reduce blood flow, cause vascular resistance, increase swelling and cause heart to become dilated.

Thiamine deficiency - Dr. Axe


What causes low thiamine levels? It’s believed that thiamine may not properly be absorbed by people who deal with the following conditions/diseases: (3)

  • Liver problems
  • Alcoholism
  • Anorexia and other eating disorders that result in malnutrition
  • Older age, due to factors like low dietary intake, chronic diseases, use of multiple medications and low absorption of thiamine
  • Consumption of medications that are known to disrupt thiamine absorption
  • Gastrointestinal issues, including prolonged diarrhea and vomiting
  • Diabetes, which seems to increase clearance of thiamine by the kidneys
  • Having had bariatric surgery, which can lead to under-eating and absorption problems
  • A poor diet high in refined foods and lacking vegetables, whole grains, nuts, beans and seeds
  • Fever, strenuous exercise and other “stressful” demands on the body
  • High consumption of foods that may interfere with thiamine absorption (including raw seafood, tea and coffee)
  • Potentially pregnancy, which increases the demand for all B vitamins (and most other nutrients)

Certain substances in coffee and tea, called tannins, can react with thiamine by turning it into a form that is difficult for the body to absorb. This may potentially lead to digestive problems and a thiamine deficiency. This is rarely seen in Western populations and is believed to only occur when someone drinks a very large amount of caffeine, leading to caffeine overdose. Most researchers believe that the interaction between coffee and tea and thiamine is likely nothing to worry about unless someone’s diet is very low in thiamine and also vitamin C. This is because vitamin C seems to prevent the interaction between thiamine and the tannins in coffee and tea.

Research also shows that raw, freshwater fish and shellfish can contain chemicals that destroy thiamine. This has been seen in people who eat high amounts of raw seafood, but cooked fish and seafood do not cause the same problem.

Some research suggests that certain nuts called areca (betel) nuts can change thiamine chemically so it doesn’t work as well. At this time there isn’t much research to conclude how thiamine may interact with any other medicines, so before taking a supplement, talk with your health professional if you take any medications.

Vitamin B1 Benefits

Why is thiamine good for you? Below are the major benefits of vitamin B1/thiamine:

1. Maintains a Healthy Metabolism

Thiamine is needed to make ATP, the body’s main energy-carrying molecule, within the mitochondria of cells. It helps in the conversion of carbohydrates into glucose, which is the preferred source of energy that the body runs off of to keep your metabolism running smoothly. Thiamine also helps break down proteins and fats too. (4)

We know that the coenzymatic form of thiamine is involved in two main types of metabolic reactions within the body: decarboxylation and transketolation. After eating something containing thiamine, it is transported in the blood and plasma and then used by the cells to convert energy.

Thiamine also plays an important role in the production of red blood cells, which are used for ongoing energy. Because thiamine and other B vitamins are naturally energy-boosting and required to produce ATD from foods, you will often find B vitamin complex supplements labeled as “energy boosting” or “healthy metabolism” products. Ingesting thiamine in supplement form is also sometimes given to patients to help correct metabolic disorders associated with genetic diseases.

2. Prevents Nerve Damage

Without enough “fuel” from our diets going toward the function of our nervous system, we can experience nerve damage that can result in trouble moving, learning and remembering information. Thiamine is needed to convert carbohydrates from our food, and the main role of carbohydrates is to provide energy for the body, especially for the brain and nervous system. Thiamine is specifically needed for a system of enzyme reactions called pyruvate dehydrogenase, which works to oxidize sugars that we eat. (5)

Thiamine also helps with proper development of myelin sheaths, which wrap around nerves to protect them from damage and death.

3. Supports a Healthy Cardiovascular System

Having enough thiamine in the body is essential for producing the neurotransmitter called acetylcholine. This is used to relay messages between the nerves and the muscles, our heart being one of the main muscles that relies on these crucial signals.

In order to maintain proper cardiac function and healthy heartbeat rhythms, the nerves and muscles must be able to use bodily energy to keep signaling to each other. Recent studies have shown that thiamine can be useful in fighting heart disease because it helps maintain healthy ventricular function and treat heart failure. (6)

4. Boosts Immunity

Thiamine helps maintain the muscle tone along the walls of the digestive tract, where much of the immune system is actually located. Digestive health is important for thiamine absorption because a healthy digestive tract allows your body to extract nutrients from food better, which are used to boost immunity and defend you from becoming sick. Thiamine helps in the secretion of hydrochloric acid, which is essential for the complete digestion of food particles and absorption of nutrients. (7)

5. Helps Treat Alcoholism

Thiamine helps decrease the risk for developing the specific brain disorder called Wernicke-Korsakoff syndrome (WKS). WKS symptoms include involuntary muscle movement, nerve damage, lethargy and trouble walking. This brain disorder is related to low levels of thiamine and is often seen in alcoholics, especially those who have poor diets as well. (8) Alcohol negatively impacts the body’s ability to absorb thiamine from foods.

It is believed that between 30 percent to 80 percent of alcoholics have thiamine deficiency. High doses of thiamine have been shown to help to decrease symptoms of alcohol withdrawal.

6. Prevents Brain Disorders

Thiamine helps bridge the gap between the brain/body connection. It can help defend against a type of brain damage called cerebellar syndrome. Health care providers also sometimes give high doses of thiamine to patients to prevent certain memory disorders that are commonly seen in thiamine-deficient people, including those experiencing alcohol withdrawal or coming out of a coma. (9) It is also linked with decreasing the risk of Alzheimer’s disease. (10)

7. Enhances Learning

Thiamine is a crucial vitamin for increasing focus, energy, fighting chronic stress and possibly preventing memory loss. Studies have linked thiamine deficiency to problems learning and retaining information. One study out of the U.K. showed that thiamine caused quick reaction times and feelings of clear-headedness in those taking tests. (11)

8. Helps Keep a Positive Mood

Thiamine improves the body’s ability to withstand stress, which is one reason why B vitamins are often called the “anti-stress” vitamins. A lack of energy can contribute to a poor mood and motivation. Thiamine is needed to boost your mood and defend against depression and anxiety because of its positive effects on the brain. (12)

It can ward off inflammation and help maintain healthy brain function that is responsible for decision making in the brain. Healthy nerve function is crucial for controlling stress and anxiety and boosting your mood.

9. Helps Prevent Vision Problems

Some research has shown that thiamine can help to defend against vision problems, such as cataracts and glaucoma. This is due to its ability to influence nerve and muscle signaling, which is important in relaying information from the eyes to the brain. (13)

Best Thiamine Foods

What foods contain thiamine? Below are the best food sources of thiamine/vitamin B1 (percentages are based on the adult RDA of 1.2 milligrams daily): (14)

  1. Nutritional Yeast — 2 tablespoons: 9.6 milligrams (640 percent DV)
  2. Seaweed (Such as Spirulina) — 1 cup seaweed: 2.66 milligrams (216 percent DV)
  3. Sunflower Seeds — 1 cup: 2 milligrams (164 percent DV)
  4. Macadamia Nuts— 1 cup: 1.6 milligrams (132 percent DV)
  5. Black Beans — 1/3 cup dried, or about 1 cup cooked: 0.58 milligram (48 percent DV)
  6. Lentils — 1/3 cup dried, or about 1 cup cooked: 0.53 milligram (44 percent DV)
  7. Organic Edameme/Soybeans — 1/3 cup dried, or about 1 cup cooked: 0.53 milligram (44 percent DV)
  8. Navy Beans — 1/3 cup dried, or about 1 cup cooked: 0.53 milligram (44 percent DV)
  9. White Beans —1/3 cup dried, or about 1 cup cooked: 0.53 milligram (44 percent DV)
  10. Green Split Peas — 1/3 cup dried, or about 1 cup cooked: 0.48 milligram (40 percent DV)
  11. Pinto beans — 1/3 cup dried, or about 1 cup cooked: 0.46 mg (39 percent DV)
  12. Mung Beans — 1/3 cup dried, or about 1 cup cooked: 0.42 milligram (36 percent DV)
  13. Beef Liver — 1 3 oz. piece cooked: 0.32 milligram (26 percent DV)
  14. Asparagus — 1 cup cooked: 0.3 milligram (25 percent DV)
  15. Brussels Sprouts — 1 cup cooked: 0.16 milligram (13 percent DV)

Supplements and Dosage

How much thiamine do you need a day? According to the USDA, the RDA for adults is 1.2 milligrams a day for men and 1.1 milligrams per day for women. (15) To prevent deficiency, humans require a minimum of 0.33 milligrams of thiamine for every 1,000 calories they consume each day.

As with all nutrients, it’s best to try to obtain them from actual whole food sources as opposed to supplements whenever possible. Thiamine deficiency does not seem to be common, according to studies, so for the average person, supplementing with extra thiamine is not necessary.

Vitamin B1 is normally included in Vitamin B complex supplements. Most complex supplements include vitamin B1 (thiamine), vitamin B2(riboflavin), vitamin B3 (niacin/niacinamide), vitamin B5 (pantothenic acid), vitamin B6vitamin B12  and other vitamins that work together to produce energy through effective food absorption.

If you are going to take a supplement that contains thiamine, look for a high-quality product that is made from real food sources. Below is the RDA for vitamin B1 (thiamine) supplementation, according to the USDA:

  • Infants: 0–6 months, 0.2 mg; infants 7–12 months, 0.3 mg
  • Children: 1–3 years, 0.5 mg; children 4–8 years, 0.6 mg; children 9–13 years, 0.9 mg
  • Adult men: 1.2 mg
  • Adult women: 1.1 mg
  • Pregnant and breastfeeding women: 1.4–1.5 mg

The typical dose for severe thiamine deficiency can be up to 300 milligrams per day, although this is only prescribed by doctors and used in certain cases. High doses of thiamine are given to those with thiamine deficiency to prevent complications. Up to 10 to 30 milligrams a day can be given to treat neuropathy, 100 milligrams via IV once a day for several days can be given to treat edema and cardiovascular complications, and 50 to 100 milligrams may be given by IV to those with Wernicke-Korsakoff syndrome.

For reducing the risk of getting cataracts, a daily dietary intake of approximately 10 milligrams of thiamine is recommended.

Thiamine dosage - Dr. Axe

How to Increase Intake

The richest food sources of thiamine include various beans, nuts, seeds, seaweed (or spirulina powder) and yeast — especially “nutritional yeast,” which is a seasoning commonly used by vegetarians that naturally tastes similarly to cheese. Some types of meats and meat organs, including liver, also contain smaller amounts, as do certain whole grains like oats and barley.

Thiamine is usually found in most whole-grain and enriched grain products like breads, pastas, rice and fortified cereal grains. These foods are enriched with thiamine, meaning thiamine is added into the food synthetically.

While some of these foods do naturally contain thiamine in their whole, unprocessed form, a lot of the foods’ natural vitamins are lost during the refining process and therefore must be added back in after. In products where thiamine is added to the food synthetically, you will usually see the words “enriched” or “fortified.” Unlike processed products, whole foods like nuts, beans and seeds naturally contain a high amount of thiamine

What is a good source of thiamine if you’re a vegetarian or vegan (you avoid eating meat)? Most fruits and vegetables do not provide very high amounts of thiamine, although some like peas and tomatoes do contain low or moderate amounts. Other kinds like asparagus, potatoes, mushrooms, romaine lettuce, spinach, Brussels sprouts and eggplant include small amounts of B vitamins like thiamine, so when you consume high amounts of these you are getting a good dose. If you avoid meat and organs meats, the best way to get enough thiamine is to regularly eat yeast, sea vegetables, nuts, seeds and beans/legumes (I recommend soaking/sprouting them first).

To help increase your intake of thiamine, try adding foods that are naturally high in thiamine to your diet in these ways:

  • Have a salad of leafy greens stopped with beans, nuts and seeds
  • Try making a Tangy Bean Salad or Pea Salad
  • Make homemade miso soup and add dried seaweed or other sea vegetables
  • Whip up a batch of Black Bean Brownies
  • Try making some split pea soup or a bean-based chili or soup
  • Top some steel cut oats with sunflower seed butter and berries

Risks and Side Effects

Can you overdose on vitamin B1? In other words, in very high amounts, is thiamine poisonous?

As of now, there have been very few confirmed cases of very serious adverse effects reported after taking too much thiamine. There is not much concern over consuming too much thiamine at one time because it is a water-soluble vitamin, and it’s believed that only a small percentage of a high dose of thiamine is actually absorbed by the body.

The excess levels that the body does not need results in urinary excretion of the vitamin within a few hours. Extra vitamin B1 in supplement form will not cause damage in the body, but it also isn’t necessarily one of the most crucial nutrients to obtain in supplement form either.

Final Thoughts

  • Thiamine (vitamin B1) is a water-soluble vitamin that is important for supporting energy levels, cognitive health, heart functions and a healthy metabolism.
  • What happens when you have a thiamine deficiency? Thiamine is present in all cells of the body, so thiamine deficiency affects all organ systems, especially cells of the nervous system and heart. Inadequate thiamine intake can lead to cardiovascular complications, cognitive problems, fatigue, nerve damage, muscle weakness and interfere with the body’s defense against oxidative stress.
  • People at an increased risk of developing thiamine deficiency include alcoholics, those with anorexia, people with liver damage or liver disease, and those eating too little calories or lots of processed/refined foods.
  • How much B1 can you take a day? The recommended intake of thiamine for adults is 1.2 mg/day for men and 1.1 mg/day for women. Most people consuming enough calories get this amount from their diets without needing to supplement.
  • Can you overdose on thiamine? Thiamine is water-soluble and therefore excess amounts are urinated out. Extra vitamin B1 in supplement form will not cause damage in the body, but it also isn’t necessarily or usually beneficial.

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