Vitamin B

B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism.

Updated: April 11, 2019

B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism.  Dietary supplements containing all eight of these vitamins are referred to as a vitamin B complex. B-complex supplements usually pack all eight B vitamins into one pill. Individual B vitamin supplements are referred to by the specific number or name of each vitamin, such as B1, B2, B3, B5, B6, B7, B9 and B12.
As B vitamins are water-soluble, your body does not store them. For this reason, your diet must supply them each day.

Functions and Deficiency:

B vitamins have many important functions and are vital for maintaining good health. Although all of these vitamins share some characteristics, they all have unique functions and are needed in different amounts.

B1 (thiamine):

Thiamine plays an essential role in metabolism by helping convert nutrients into energy. The richest food sources include pork, sunflower seeds and wheat germ.
Deficiency causes beriberi. Symptoms of this disease of the nervous system include weight loss, emotional disturbances, Wernicke encephalopathy (impaired sensory perception), weakness and pain in the limbs, periods of irregular heartbeat, and edema (swelling of bodily tissues). Heart failure and death may occur in advanced cases. Chronic thiamin deficiency can also cause alcoholic Korsakoff syndrome, an irreversible dementia characterized by amnesia and compensatory confabulation.

B2 (riboflavin):

Riboflavin helps convert food into energy and also acts as an antioxidant. Foods highest in riboflavin include organ meats, beef and mushrooms.
Deficiency causes ariboflavinosis. Symptoms may include cheilosis (cracks in the lips), high sensitivity to sunlight, angular cheilitis, glossitis (inflammation of the tongue), seborrheic dermatitis or pseudo-syphilis (particularly affecting the scrotum or labia majora and the mouth), pharyngitis (sore throat), hyperemia, and edema of the pharyngeal and oral mucosa.

B3 (niacin):

Niacin plays a role in cellular signaling, metabolism and DNA production and repair. Food sources include chicken, tuna and lentils.
Deficiency, along with a deficiency of tryptophan causes pellagra. Symptoms include aggression, dermatitis, insomnia, weakness, mental confusion, and diarrhea. In advanced cases, pellagra may lead to dementia and death (dermatitis, diarrhea, dementia, and death).

B5 (pantothenic acid):

Pantothenic acid helps your body obtain energy from food and is also involved in hormone and cholesterol production. Liver, fish, yogurt and avocado are all good sources.
Deficiency can result in acne and paresthesia, although it is uncommon.

B6 (pyridoxine):

Pyridoxine is involved in amino acid metabolism, red blood cell production and the creation of neurotransmitters. Foods highest in this vitamin include chickpeas, salmon and potatoes.
Deficiency causes seborrhoeic dermatitis-like eruptions, pink eye and neurological symptoms (e.g. epilepsy)

B7 (biotin):

Biotin is essential for carbohydrate and fat metabolism and regulates gene expression. Yeast, eggs, salmon, cheese and liver are among the best food sources of biotin.
Deficiency does not typically cause symptoms in adults but may lead to impaired growth and neurological disorders in infants. Multiple carboxylase deficiency, an inborn error of metabolism, can lead to biotin deficiency even when dietary biotin intake is normal.

B9 (folate):

Folate is needed for cell growth, amino acid metabolism, the formation of red and white blood cells and proper cell division. It can be found in foods like leafy greens, liver and beans or in supplements as folic acid.
Deficiency results in a macrocytic anemia, and elevated levels of homocysteine. Deficiency in pregnant women can lead to birth defects.

B12 (cobalamin):

B12 is vital for neurological function, DNA production and red blood cell development. B12 is found naturally in animal sources like meats, eggs, seafood and dairy.
Deficiency results in a macrocytic anemia, elevated methylmalonic acid and homocysteine, peripheral neuropathy, memory loss and other cognitive deficits. It is most likely to occur among elderly people, as absorption through the gut declines with age. The autoimmune disease pernicious anemia is another common cause. It can also cause symptoms of mania and psychosis. In rare extreme cases, paralysis can result.
Since all of these vitamins are found in a wide variety of foods, most people get the recommended amounts of these vitamins through diet alone. However, factors like age, pregnancy, dietary choices, medical conditions, genetics, medication and alcohol use can be a factor for deficiency of B vitamins.
These conditions can affect how your body absorbs and uses B vitamins. In these circumstances, supplementing with B vitamins may be necessary. Nutritional supplements that contain all eight B vitamins are referred to as B-complex vitamins.


B vitamins supplements are required in the Following cases:

Pregnant or Breastfeeding Women:

The requirement of Vitamin B, especially B12 and folate increases during pregnancy to support fetal development. As B12 or folate deficiency in pregnant or breastfeeding women can lead to severe neurological damage or birth defects in the fetus or infant, supplementing with a B-complex vitamin is crucial in women who are pregnant or breastfeeding.

Older Adults:

The ability to absorb vitamin B12 decreases and your appetite declines as you grow old. Therefore, making it difficult for some people to get enough B12 through diet alone. Deficiency in B12 has been linked to increased rates of depression and mood disturbances in elderly people. Deficiencies in vitamin B6 and folate are also common in these people.

Medical Conditions:

People with certain medical conditions, such as celiac disease, cancer, Crohn’s disease, alcoholism, hypothyroidism and anorexia, are more susceptible to developing B vitamins and other nutrient deficiencies. People who have undergone certain weight-loss surgeries are more likely to be deficient in B vitamins. Also, the MTHFR genetic mutation can affect how your body metabolizes folate and can lead to a folate deficiency and other health issues.
All of these people are advised to supplement with a B-complex vitamin to correct or avoid deficiencies.

Certain Medications:

Certain medications can lead to a deficiency in B vitamins. These include:

  • proton pump inhibitors, which are medications that lower stomach acid, can decrease the absorption of B12
  • metformin, a popular diabetes drug, can decrease levels of both B12 and folate
  • Birth control pills can also deplete several B vitamins, including B6, B12, folate and riboflavin


As Vitamin B12 is naturally found in animal products like meat, dairy, eggs and seafood, vegetarians could be at risk of developing a B12 deficiency if they don't get enough of this vitamin through fortified foods or supplements.
Therefore, people who choose to follow diets that eliminate animal products are advisable to take a daily B-complex vitamin to get enough of these important nutrients.

Signs of vitamin B deficiency:

The most common signs of vitamin B deficiency, specific to individual B vitamins, are given below:

Vitamin B6 deficiency:

  •     Anemia
  •     Skin disorders such as seborrheic dermatitis
  •     Inflammation of the mouth (oral ulcers)
  •     Soreness and cracks at the corners of the mouth, chapped lips
  •     Tingling or numbness in hands and feet
  •     Irritability, confusion and depression

Vitamin B9 deficiency (folate or folic acid):

  •     Anemia
  •     Increased risk of birth defect (in pregnancy)
  •     Mood changes (irritability, forgetfulness)
  •     Sore mouth and diarrhea

Vitamin B12 deficiency:

  •     Anemia
  •     Tingling or numbness in hands and feet
  •     Memory lapses
  •     Mood changes (mental confusion, agitation)
  •     Unsteadiness and poor muscle coordination

Although a vitamin B supplement may be beneficial in certain cases, it is always best to seek dietary sources first. Discuss any supplements you want to take with your healthcare professional before starting it.

Best Food Sources of Vitamin B:

You can get all eight B vitamins from a variety of foods:

  •     Whole grains (brown rice, barley, millet)
  •     Meat (red meat, poultry, fish)
  •     Eggs and dairy products (milk, cheese)
  •     Legumes (beans, lentils)
  •     Seeds and nuts (sunflower seeds, almonds)
  •     Dark, leafy vegetables (broccoli, spinach, kai lan)
  •     Fruits (citrus fruits, avocados, bananas)

Uses & Effectiveness:

Although certain conditions make it necessary for some people to supplement with B-complex vitamins, taking a B-complex supplement may be helpful even for people who don't have an increased need for these nutrients. B-complex vitamins help reduce:

Symptoms of Anxiety or Depression:

Deficiency of B vitamins, including B12, B6 and folate, have been linked to an increased risk of depression. B-complex vitamin supplements may help improve symptoms of depression or anxiety. However these are not a cure for mental health issues. B vitamins may also enhance treatment response when given in combination with antidepressant medication. Supplementing patients with a vitamin containing B12, B6 and folic acid led to a more enhanced and sustained antidepressant response.

Stress and Boost Mood:

B-complex vitamins are often used to reduce fatigue and boost mood as these can lift your spirits and improve your cognitive performance. Supplementing with a multivitamin containing high levels of B-complex vitamins can reduce stress and mental fatigue.
This supplement has been used in following health conditions:

Wound Healing:

Thiamine (vitamin B1), pantothenic acid (vitamin B5), and other B vitamins have all been shown to play a role in wound healing. So, a high-potency B vitamin supplement is recommended to promote wound healing.

Canker Sores:

People with recurrent canker sores may have a B vitamin deficiency. Supplementing with vitamins B1, B2, and B6 can provide relief.

Acne Rosacea:

Acne rosacea has improved with oral supplements or injections of B vitamins in some cases.

Alcohol Withdrawal:

It is possible that successful treatment of B-complex vitamin deficiencies may actually reduce alcohol cravings.

Athletic Performance:

B-complex vitamins are needed to produce energy from carbohydrates. Exercisers may have slightly increased requirements for some of the B vitamins, including vitamins B2, B6, and B5. Athletic performance can be improved by taking these supplements.  However, most athletes obtain enough B vitamins from their diet without supplementation.

Attention Deficit–Hyperactivity Disorder:

B vitamins have been used for ADHD. High amounts of B vitamins have shown mixed results in relieving ADHD symptoms.


A combination of hydrochloric acid supplement and a vitamin B-complex supplement can help treat people with hives.

Indigestion, Heartburn, and Low Stomach Acidity:

Many minerals and vitamins require adequate concentrations of stomach acid to be absorbed optimally. These include iron, zinc, and B-complex vitamins, and folic acid.
People with achlorhydria (no stomach acid) or hypochlorhydria may therefore be at risk of developing various nutritional deficiencies, can contribute to the development of a wide range of health problems. It is advisable to take a recommended supplement in these cases.

Indigestion, Heartburn, and Low Stomach Acidity, and Vitamin B12 Deficiency:

People who have inadequate absorption of vitamin B12 due to low stomach acid are advisable to take supplement with vitamin B complex which can help correct a deficiency.


Postmenopausal women who combined hormone replacement therapy with B vitamins and other nutrients and dietary changes can increase their bone density. In addition, they need to avoid processed foods, limit protein intake, emphasize vegetable over animal protein, and limit consumption of salt, sugar, alcohol, coffee, tea, chocolate, and tobacco.

Premenstrual Syndrome:

B vitamin deficiencies are linked to PMS. So some women may benefit from supplementing with B-complex vitamins for symptom relief.

Tardive Dyskinesia:

Taking vitamin B-complex along with other nutrients can help prevent the development of tardive dyskinesia.


PABA, a compound commonly found in B-complex vitamins, has been shown to repigment skin affected by vitiligo.


Each B vitamin has a specific recommended daily amount. The recommended dose varies depending on gender, age and other variables like pregnancy.
The recommended daily intake (RDI) for B vitamins are as follows:

For Women:

  • B1 (Thiamine)    1.1 mg   
  • B2 (Riboflavin)    1.1 mg   
  • B3 (Niacin)    14 mg   
  • B5 (Pantothenic acid)    5 mg (RDI not established; Adequate Intake, or AI, provided)   
  • B6 (Pyridoxine)    1.3 mg   
  • B7 (Biotin)    30 mcg (AI)   
  • B9 (Folate)    400 mcg   
  • B12 (Cobalamin)    2.4 mcg

For Men

  • B1 (Thiamine) 1.2 mg
  • B2 (Riboflavin) 1.3 mg
  • B3 (Niacin) 16 mg
  • B5 (Pantothenic acid) 5 mg (AI)
  • B6 (Pyridoxine) 1.3 mg
  • B7 (Biotin) 30 mcg (AI)
  • B9 (Folate) 400 mcg
  • B12 (Cobalamin) 2.4 mcg

It is important to choose a B-complex supplement based on your individual requirements for each B vitamin. Pregnant and lactating women need higher amounts of B vitamins, while infants and children need less. You may need to supplement with higher doses to correct the deficiency.

Side Effects:

B-complex vitamins are likely safe when taken in recommended dose. As B vitamins are water-soluble, it is safe even if you consume more of these nutrients through diet alone or by taking a B-complex supplement. However, taking supplements that contain excessively high and unnecessary quantities of B-complex vitamins could lead to serious side effects.
These include:

  • High doses of supplemental B3 (niacin) may lead to vomiting, high blood sugar levels, skin flushing and even liver damage.
  • High doses of B6 can cause nerve damage, light sensitivity and painful skin lesions.
  • Excess of B-complex supplements can turn urine bright yellow. This is because your body is getting rid of excess vitamins that it can't use. Nothing serious lies in discolored urine.

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