Written by Tara Boustany on
August 4, 2021
Reading Time: 13 minutes

Medically Reviewed by our Medical Affairs Team

Written by Tara Boustany on:

Do you feel tired and sluggish and losing a lot of focus lately?

The body needs B vitamins to make energy from food, help cells grow and divide properly, keep your skin healthy and maintain a strong immune system.

Without proper B vitamins levels, you could feel tired or have trouble thinking clearly. That’s why it is important to supplement your diet with the right vitamins and minerals.

Different Types of B Vitamins

B vitamins are essential for energy production, so it’s no surprise that fatigue is one of the most common symptoms of Vitamin B deficiency. There are eight B vitamins. Together they are called the Vitamin B complex. They include:

Continue reading to learn more about the many uses and benefits of B vitamins.

Thiamin (Vitamin B1)

Thiamin, also known as Vitamin B1, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement.

Thiamin role in the body:

  • Break down of carbohydrates (sugar) from foods
  • Create brain chemicals (neurotransmitters)
  • Produce fatty acids
  • Synthesize hormones

Food sources of thiamin:

Dosages:

In adults, the recommended dose is 1.2mg daily for men and 1.1mg daily for women. For pregnancy and lactation, the recommended dose is 1.4mg daily.

The largest daily dose unlikely to cause adverse side effects in the general population is unknown. This is due to a lack of reports showing negative effects from high thiamin intakes.

Thiamin cannot be stored in the body, so you should get it from your diet.

Thiamin deficiency:

Most people meet the required amount of thiamin through their diets, and thiamin deficiency is rare.

Causes of thiamin deficiency:

  • Low intake of thiamin containing foods
  • Decreased gut absorption
  • Increased losses in urine. Examples of thiamin loss in the urine include alcohol abuse and diuretic use.

Symptoms of mild to moderate thiamin deficiency:

Severe Thiamin deficiency:

Beriberi is a form of severe thiamin deficiency. It causes muscle loss and reduced feeling in the hands and feet (peripheral neuropathy). Beriberi can eventually lead to deadly fluid build-up in the heart and lower limbs.

Also, Beriberi is classified as ‘wet’ and ‘dry’ beriberi. ‘Dry’ beriberi affects the nervous system while ‘wet’ beriberi affects the cardiovascular system.

Wernicke-Korsakoff syndrome (WKS) is another form of severe thiamin deficiency. It is often seen with alcohol abuse. It causes symptoms that are like those of Alzheimer’s disease.

They include confusion, loss of muscle coordination, and peripheral neuropathy. WKS can lead to Wernicke’s encephalopathy (WE), which can be life-threatening. A 2017 review found that people with WE may benefit from high doses of thiamin.

Compromised gastrointestinal problems can lead to both types of deficiencies. Examples include celiac disease, bariatric surgery, or HIV/AIDs.

Thiamin toxicity:

Thiamin does not have an established toxic level. Even if you eat a lot of it, your body will only absorb the thiamin that’s useful and get rid of any excess amount through the urine.

Riboflavin (Vitamin B2)

Riboflavin, also known as Vitamin B2, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement. Gut bacteria can produce small amounts of riboflavin, but not enough to meet dietary needs.

Riboflavin role in the body:

  • Energy production
  • Break down fats, drugs, and steroid hormones
  • Tryptophan conversion into niacin (vitamin B3)
  • Vitamin B6 conversion into a coenzyme that the body needs

Food sources of riboflavin:

Since UV light destroys riboflavin, foods rich in this vitamin should be kept out of direct sunlight.

Dosages:

In adults, riboflavin recommended dose is about 1.3mg daily for men and 1.1mg daily for women. For pregnancy, the recommended dose is 1.4mg daily. For lactation, the recommended dose is 1.6mg daily.

The largest daily dose unlikely to cause adverse side effects in the general population is unknown. This is due to a lack of reports observing a toxic level from food sources or long-term intakes of high-dose dietary supplements.

Riboflavin cannot be stored in the body, so you should get it from your diet.

Riboflavin deficiency:

Riboflavin helps enzymes work in the body, and a lack of riboflavin can lead to health problems.

Causes of riboflavin deficiency:

Riboflavin deficiency is rare. It mainly occurs with other vitamin deficiencies such as during malnutrition. Thyroid problems can also increase the risk of a deficiency. 

Symptoms of riboflavin deficiency:

Riboflavin toxicity:

A toxic level of riboflavin has not been established yet. The gut has a limited capacity to absorb riboflavin, and excess amounts are excreted in the urine. Excess intake of riboflavin, usually from supplements, can cause urine to become bright yellow.

Niacin (Vitamin B3)

Niacin, also known as Vitamin B3, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement. Niacin comes in 2 forms: nicotinic acid and nicotinamide. Both are found in food. The body can also convert tryptophan (an amino acid) to nicotinamide.

Niacin role in the body:

Niacin works in the body as a coenzyme, with more than 400 enzymes dependent on it for various reactions. These enzymes help with:

  • Converting the energy in carbohydrates, fats, and proteins into a form the body can use
  • The body’s cellular metabolism
  • Cell-to-cell communication
  • DNA expression in cells

Good food sources of niacin:

Dosages:

Niacin is measured in milligrams of niacin equivalents (mg NE). One NE equals 1 milligram of niacin. In adults, the recommended dose is about 16mg NE daily for men and 14mg NE daily for women. For pregnancy, the recommended dose is 18mg NE daily. For lactation, it is 17mg NE daily.

The largest daily dose unlikely to cause adverse side effects in adults is 35mg.

Niacin cannot be stored in the body, so you should get it from your diet.

Niacin supplements:

Niacin dietary supplements come in the form of nicotinic acid or nicotinamide. They often provide more than the recommended daily doses, causing flushing.

They also come as prescription medications to treat high cholesterol. They usually come in an extended-release form of nicotinic acid to allow gradual absorption and to avoid flushing.

Niacin deficiency:

A deficiency in niacin is rare because of its presence in many foods, both from animals and plants.

Causes of Niacin deficiency:

Niacin deficiency is more likely to be caused by problems that affect the absorption of niacin or tryptophan.

  • Alcoholism
  • Disorders of the digestive system
  • Prolonged treatment with Isoniazid (a drug used for the treatment of tuberculosis)

Symptoms of severe Niacin deficiency

Niacin toxicity:

Toxicity when eating foods containing niacin is uncommon. However, long-term use of high-dose niacin supplements increases the risk of toxicity.

A typical sign is a  reddened skin flush with itchiness or tingling on the face, arms, and chest. Flushing is caused largely by high-dosage nicotinic acid supplements, rather than with nicotinamide.

Other signs of niacin toxicity include:

Pantothenic acid (Vitamin B5)

Pantothenic acid, also known as Vitamin B5, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement. Gut bacteria can produce some riboflavin, but not enough to meet dietary needs.

Pantothenic acid role in the body:

  • Create new coenzymes, proteins, and fats.
  • Carried by red blood cells and used in a variety of processes for energy and metabolism.

Food sources of Pantothenic acid:

Dosages:

In adults, Pantothenic acid recommended dose is about 5mg daily for men and women. For pregnancy, the recommended dose is 6mg daily. For lactation, it is 7mg daily.

The largest daily dose unlikely to cause adverse side effects in the general population for Pantothenic acid is unknown. This is due to a lack of reports observing a toxic level from food sources or long-term intakes of high-dose dietary supplements.

Pantothenic acid cannot be stored in the body, so you should get it from your diet.

Pantothenic acid deficiency:

Pantothenic acid deficiency is rare because of its presence in many foods, both from animals and plants.

Causes of Pantothenic acid deficiency:

  • Malnutrition.
  • Pantothenate kinase-associated neurodegeneration 2 mutation: a mutation where Pantothenic acid cannot be metabolized.

Symptoms of Pantothenic acid deficiency:

Pantothenic acid toxicity:

A toxic level of Pantothenic acid has not been established yet. But, rarely, stomach upset or mild diarrhea has been reported with very large doses of 10 grams daily.

Pyridoxine (Vitamin B6)

Vitamin B6, or Pyridoxine, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement.

Pyridoxine role in the body:

Pyridoxal 5’ phosphate (PLP) is the active form of Vitamin B6. It assists more than 100 enzyme reactions. The body needs vitamin B6 for:

  • Amino acid metabolism
  • Break down of carbohydrates and fats
  • Brain function
  • Immune function

Food sources of Pyridoxine:

Dosages:

For men: Aged 14 to 50: 1.3mg daily, Aged 51+: 1.7mg daily

For women: Aged 14 to 18: 1.2mg daily; Aged 19 to 50: 1.3mg daily; Aged 51+: 1.5mg daily. For pregnancy, the recommended dose is 1.5mg daily. For lactation, the amount increases to 2.0mg daily.

The largest daily dose unlikely to cause adverse side effects in adults is 100mg daily. In children and adolescents, the dose is slightly lower. This high level of Pyridoxine can only be achieved by taking vitamin supplements.

You should get your daily need for Vitamin B6 from your diet.

Pyridoxine deficiency:

Niacin deficiency is rare because of its presence in many foods. It can develop because extensive processing can deplete foods of vitamin B6.

Causes of Pyridoxine deficiency:

  • Protein-energy undernutrition
  • Malabsorption
  • Alcoholism
  • Use of pyridoxine-inactivating drugs (antiseizure drugs, isoniazid, cycloserine, hydralazine, corticosteroids, penicillamine)
  • Excessive loss during hemodialysis

Symptoms of Pyridoxine deficiency:

Mild deficiency in Pyridoxine may have no symptoms. But, prolonged or severe deficiency can lead to the following:

Some conditions interfere with the absorption of Vitamin B6 and can increase the risk of deficiency:

  • Kidney disease
  • Had a kidney transplant
  • Celiac disease, ulcerative colitis, Crohn’s disease, and other autoimmune intestinal disorders
  • Rheumatoid arthritis and other autoimmune inflammatory disorders.
  • Alcohol dependence

Pyridoxine toxicity:

Toxicity when eating foods containing Pyridoxine is uncommon. Even if you eat a lot of it, your body will only absorb the thiamin that’s useful and get rid of any excess amount through the urine. However, toxicity can occur from long-term supplementation doses greater than 1000mg daily.  Symptoms include:

  • Neuropathy in feet and hands
  • Ataxia (loss of control of body movements)
  • Nausea

Symptoms usually subside after decreasing the dosage to normal levels.

Biotin (Vitamin B7)

Vitamin B7, commonly known as Biotin, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement.

Biotin is usually added to hair, nail, and skin supplements. Yet, there is not enough evidence to conclude whether taking biotin supplements helps with hair, nails, or skin.

Biotin role in the body:

  • Break down fats, carbohydrates, and protein
  • Cell-to-cell communication
  • DNA regulation

Food sources of Biotin:

Dosages:

Biotin’s adequate intake level in adults is about 30mcg daily for men and women. For pregnancy, the recommended amount is also 30mcg daily. For lactation, the amount increases to 35mcg daily.

The largest daily dose unlikely to cause adverse side effects in the general population is unknown. This is due to a lack of reports observing a toxic level from food sources or high-dose supplements.

Biotin deficiency:

A deficiency in Biotin is rare because of its presence in many foods.

Causes of biotin deficiency:

Alcoholism increases the risk of biotin deficiency since alcohol blocks its absorption. Alcoholism is also usually associated with poor dietary intake.

Mild deficiency occurs in about a third of pregnant women despite eating healthy. The reason behind this is not clear.

Symptoms of biotin deficiency:

Biotin toxicity:

No evidence in humans has shown toxicity of biotin even with high intakes. A toxic level of biotin has not been established yet. The gut has a limited capacity to absorb biotin, and excess amounts are excreted in the urine.

Folate/folic acid (Vitamin B9)

Vitamin B9, commonly known as Folate, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement in the form of folic acid.

When women have normal levels of folate before and during pregnancy, the fetus has a lower risk of neural tube defects. These birth defects usually affect the brain and the spinal cord.

Folate role in the body:

  • Help form red blood cells
  • DNA replication
  • Vitamin metabolism
  • Amino acid metabolism
  • Proper cell division

Food sources of Folate:

Folic acid, the synthetic form of Vitamin B9, is better absorbed than folate. As of January 1998, folic acid was added to foods commonly eaten, such as bread, cereals, pasta, rice, and other grain products. This program has increased the average folic acid intake by about 100 mcg/day.

Good sources of folate include:

Dosages:

Folate is measured in micrograms (mcg) of dietary folate equivalents (DFE).

In adults, the recommended dose is about 400mcg DFE daily for men and women.

For pregnancy, the recommended dose is 600mcg DFE daily. For lactation, it is 500mcg DFE daily.

Alcohol may impair the absorption of folate. People who regularly drink alcohol should aim for at least 600mcg DFE of folate daily.

The largest daily dose unlikely to cause adverse side effects in adults for folic acid from fortified food or supplements is set at 1,000mcg a day. This does not include folate from food.

Folate cannot be stored in the body, so you should get it from your diet or dietary supplements.

Folate deficiency:

A folate deficiency is rare because it is found in a wide range of foods. However, the following conditions may put people at increased risk:

Causes of Folate deficiency:

  • Alcoholism: Alcohol prevents the absorption of folate and accelerates its excretion from the body. People with alcoholism also tend to eat poor diets low in folate-containing foods
  • Pregnancy: The need for folate increases during pregnancy due to its role in fetal development.
  • Digestive disorders that cause malabsorption: Examples include celiac disease and inflammatory bowel disease. They can also interfere with the absorption of folate.
  • Intestinal surgeries: involving the digestive organs or that reduce the normal level of stomach acid. They can also interfere with the absorption of folate
  • Genetic variants: People carrying a variant of the gene MTHFR are not able to convert folate to its active form.

Symptoms of Folate deficiency:

Folate toxicity:

Toxicity when eating foods containing Folate is extremely uncommon.

Folic acid supplementation of more than 1,000 mcg daily is not advised. This is because higher amounts can mask a vitamin B12 deficiency.

If you choose folic acid supplements, make sure you keep the dosage low. This means 400mcg a day or less. You will likely get additional folic acid from fortified foods and natural folate in food.

The amount of folic acid in a multivitamin does not usually cause any harm. It might help prevent some diseases, especially in people who do not get enough folate from their diets, and in individuals who drink alcohol.

Cobalamin (Vitamin B12)

Vitamin B12, commonly known as Cobalamin, is a water-soluble vitamin. It is found in some foods, can be added to food, and is sold as a supplement in the form of folic acid.

Cobalamin role in the body:

  • Help form red blood cells
  • DNA synthesis
  • Brain and neurological function
  • Fat and protein metabolism

Food sources of Cobalamin:

Dosages:

In adults, Cobalamin the recommended amount is about 2.4micrograms (mcg) daily for men and women. For pregnancy, the recommended amount is 2.6mcg daily. For lactation, it is 2.8mcg daily.

The maximum daily dose unlikely to cause adverse side effects in the general population is unknown. This is due to a lack of reports observing a toxic level from food sources or long-term intakes of high-dose supplements.

However, research suggests that supplements of 25 mcg daily or higher may increase the risk of bone fractures.

Cobalamin deficiency:

A cobalamin deficiency is rare because it is found in a wide range of foods. But, cobalamin is not found in fruit, vegetables, and grains. Thus, vegans may not get enough of it.

Measuring vitamin B12 in the blood is not an accurate method to determine whether someone has a deficiency. This is because people with a deficiency can show normal B-12 blood levels. Blood levels of methylmalonic acid and homocysteine are the best way to indicate a vitamin B12 deficiency.

In cases of severe vitamin B12 deficiency pernicious anemia, doctors may prescribe B12 injections in the muscle.

Causes of cobalamin deficiency:

  • Avoiding animal products: Animal-based foods are the only sources of vitamin B12. Avoiding these foods increases the risk of a vitamin B12 deficiency. This is why vegans or vegetarians should include B12-fortified foods or a B12 supplement in their diets. Pregnant women should also consider this, as the fetus requires vitamin B12 to prevent birth defects.
  • Lack of intrinsic factor: Pernicious anemia is an autoimmune disease that attacks gut cells and intrinsic factor. Intrinsic factor is crucial for vitamin B12 absorption. Taking high-dose vitamin B12 supplements will not solve the problem, as the intrinsic factor is unavailable to absorb it.
  • Inadequate stomach acid: stomach acid is needed to liberate vitamin B12 from food. Some medications used to decrease stomach acidity can lead to vitamin B12 deficiency. These include proton-pump inhibitors, H2 blockers, or other antacids.
  • Intestinal surgeries: Surgeries that affect the stomach or the ileum can increase the risk of a deficiency.
  • Digestive disorders: Examples include Crohn’s and celiac disease. They both negatively impact the digestive tract and can lead to deficiency.

Signs and symptoms of cobalamin deficiency:

Thiamin toxicity:

No evidence in humans has shown toxicity of cobalamin even with high intakes. A toxic level of cobalamin has not been established yet. The gut has a limited capacity to absorb cobalamin, and excess amounts are excreted in the urine.

Generally, taking up to 1000mcg orally daily to treat a deficiency is considered safe. However, before starting supplements of any kind it is important to talk to your doctor.

Is there a link between ADHD and B vitamins?

A study on pregnant women showed that those who do not get enough folate are more likely to give birth to children suffering from ADHD.

Another study found that taking magnesium and vitamin B6 for 2 months reduced hyperactivity and aggressiveness. It also improved school attention. Also, when the Mg-B6 treatment was stopped, symptoms of the disease reappeared in few weeks together with a decrease in Mg values.

Also, one study on adults suffering from ADHD showed that lower levels of the vitamins B2, B6, and B9 were associated with the ADHD diagnosis.

Also, lower levels of B2 and B6 were associated with a higher symptom load. Yet, lower vitamin B6 and B9 levels were associated with smoking, which may have influenced the results. But, further studies are needed to determine whether B vitamins supplementation may play a role in the treatment of ADHD.

In Conclusion

The B vitamins are a collection of eight water-soluble vitamins. They play diverse and essential metabolic functions. B vitamins cannot be stored in the human body, and you should get adequate amounts from your diet.

Some dietary supplements can interact with some underlying conditions and medications. Always talk to your doctor before you add any supplements to your routine. You should also see your doctor if you think you have a deficiency in one of the B vitamins.

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