The Benefits of B Complex Vitamins

A B complex vitamin usually delivers eight of the B vitamins: B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folic acid), and B12 (cobalamin).

Found naturally in meat, leafy greens, dairy, beans, peas, and whole or fortified grains, B complex vitamins help your body make energy from the food you eat, form red blood cells, and play an essential role in certain bodily functions. Take a closer look at the benefits, signs of deficiency, and food sources for each of these B complex vitamins.

benefits of B vitamins
Verywell / Joshua Seong

B1 (Thiamine)

Health Benefits

  • Critical for the growth, development, and function of cells in the body
  • Helps the body use carbohydrates from food to produce energy
  • Needed for the health of the brain, muscles, and nervous system

Symptoms of Deficiency

  • Beriberi
  • Cardiovascular symptoms
  • Fatigue
  • Irritability
  • Short-term memory loss
  • Weakness
  • Weight loss

Food Sources

Common food sources of vitamin B1 include fortified breakfast cereal, enriched and whole-grain products (bread, breakfast cereals, rice, noodles, and flour), wheat germ, pork, trout, black beans, mussels, and tuna.

B2 (Riboflavin)

Health Benefits

  • Keeps the eyes, nervous system, and skin healthy
  • Helps convert food into energy
  • Needed for red blood cell production and growth
  • Works with other B vitamins (helps convert B6 into a usable form and aids in niacin production)

Symptoms of Deficiency

  • Cracks at the corners of the mouth
  • Hair loss
  • Sensitivity to light
  • Skin disorders
  • Sore throat
  • Swelling of the mouth and throat
  • Swollen, cracked lips

Food Sources

Common food sources of vitamin B2 include milk and dairy products, fortified breakfast cereals, beef liver, clams, portobello mushrooms, almonds, and chicken.

B3 (Niacin)

Health Benefits

  • Aids in the conversion of food into energy
  • Helps enzymes in the body function properly by helping the body use other B vitamins and make and repair DNA (the genetic material found in all body cells)
  • Helps with the function of the digestive and nervous systems and skin
  • Needed for the production of hormones, such as sex and stress hormones

Symptoms of Deficiency

  • Canker sores
  • Depression
  • Digestive problems
  • Fatigue
  • Inflamed skin
  • Pellagra
  • Poor circulation
  • Vomiting

Food Sources

Common food sources of vitamin B3 include eggs, fish, fortified bread and cereal, rice, nuts, milk and dairy, chicken, beef, turkey, lamb, organ meats, peanuts.

B5 (Pantothenic Acid)

Health Benefits

  • Breaks down fats and carbohydrates for energy
  • Helps the body use other vitamins, such as riboflavin
  • Plays a role in the production of sex and stress hormones in the adrenal glands and neurotransmitters
  • Vitamin B5 is needed for the production of red blood cells and cholesterol

Symptoms of Deficiency

  • Burning feet
  • Depression
  • Fatigue
  • Insomnia
  • Irritability
  • Stomach pains
  • Upper respiratory tract infections
  • Vomiting

Food Sources

Common food sources of vitamin B5 include meat, avocado, broccoli, kale, eggs, milk, mushrooms, fortified cereals, organ meats, poultry, potatoes, and legumes.

B6 (Pyridoxine)

Health Benefits

  • Involved in immune function and brain development and function
  • Needed by the body to use and store protein and carbohydrates from food (in the form of glycogen, stored energy in the muscles and liver)
  • Required for more than 100 enzyme reactions in the body. It aids in the formation of hemoglobin (a substance in red blood cells that carries oxygen through the blood) and neurotransmitters and hormones that influence mood and regulate the body's clock

Symptoms of Deficiency

  • Depression
  • Difficulty concentrating
  • Irritability
  • Muscle weakness
  • Nervousness
  • Short-term memory loss

Food Sources

Common food sources of vitamin B6 include chickpeas, beef liver, tuna, salmon, chicken breast, fortified breakfast cereal, potatoes, turkey, fruits (except citrus), and beef.

B7 (Biotin)

Health Benefits

  • Helps the body convert the fats, carbohydrates, and proteins in the food that you eat into energy
  • Needed to make fatty acids
  • Promotes growth and bone and hair health

Symptoms of Deficiency

  • Brittle nails
  • Dry eyes
  • Hair thinning or loss
  • Muscle pain
  • Skin rashes around the eyes, nose, mouth, or other mucous membranes

Food Sources

Common food sources of vitamin B7 include beef liver, egg yolk, wheat germ, pork, beef, sunflower seeds, sweet potato, almonds, whole-grain foods, sardines, spinach, and broccoli.

B9 (Folic Acid)

Health Benefits

  • Helps your body make red blood cells
  • Needed to help cells make and maintain DNA
  • Reduces the risk of birth defects in the brain and spine, such as spina bifida

Symptoms of Deficiency

  • Diarrhea
  • Forgetfulness
  • Gingivitis
  • Irritability
  • Loss of appetite
  • Poor growth
  • Shortness of breath
  • Tongue inflammation

Food Sources

Common food sources of vitamin B9 (folate) include spinach, beef liver, broccoli, Brussels sprouts, beans and legumes, asparagus, orange juice, peanuts, avocado, dark leafy greens, fortified cereals, and salmon.

B12 (Cobalamin)

Health Benefits

  • Helps keep the nervous system and red blood cells healthy
  • Important for protein metabolism
  • Required for the formation of red blood cells and DNA

Symptoms of Deficiency

  • Constipation
  • Fatigue
  • Lack of appetite
  • Megaloblastic anemia
  • Nerve damage
  • Numbness and tingling in the fingers and toes
  • Weakness
  • Weight loss

Food Sources

Common food sources of vitamin B12 are found primarily in animal foods, such as beef liver (and other organ meats), clams and other shellfish, beef, chicken, fish, eggs, milk, and other dairy products, and some fortified cereals.


With a key role in converting food into fuel, proponents claim that B complex vitamins can help with a variety of conditions, including anxiety, depression, heart disease, and premenstrual syndrome (PMS).

In addition, some people take a vitamin B complex to increase energy, enhance mood, improve memory, boost skin and hair health and stimulate the immune system.

While most people who eat a varied diet get enough B vitamins from food, some people are at an increased risk of deficiency, particularly those who are over the age of 50, take antacid medication, or have celiac disease, Crohn's disease, gastritis, or other digestive disorders.

If you have had stomach or weight loss surgery, drink alcohol regularly, or follow a vegetarian or vegan diet, you may be more prone to a deficiency. Pregnant and breastfeeding women may need more vitamins B6, B12, and folic acid.

B Complex Side Effects

Although B complex supplements are water-soluble and do not stay in the body for long, large doses of the vitamins in supplement form can cause certain side effects:

  • B3 (niacin): Skin flushing or pain, elevated blood sugar levels, and liver toxicity
  • B6 (pyridoxine): B6 may cause nerve damage, skin lesions, worsening of kidney function, and increased risk of heart attack, stroke, and death in people with diabetes and advanced kidney disease. Studies have associated high doses of vitamin B6 with a slightly increased risk of hip fracture and increased risk of lung cancer (when taken with vitamin B12).
  • B9 (folic acid): Vitamin B6 can result in kidney damage, increased insulin resistance in offspring, lower natural killer cell activity in older women, and may be associated with increased risk of some cancers. It also may mask the diagnosis of a vitamin B12 deficiency.
  • B12 (cobalamin): Vitamin B12 has been found to speed the decline in kidney function and increase the risk of cardiovascular events in people with impaired kidney function. High doses of vitamin B12 taken with folic acid have been associated with a greater risk of cancer and mortality, along with acne and rosacea in some people.

There is a daily tolerable intake level (UL) for each B vitamin, which is above what most people need. Getting more than the UL increases your chances of side effects.

A Word From Verywell

To stay healthy, most people can get what they need by eating a varied, balanced diet filled with delicious foods naturally rich in B vitamins, such as leafy greens, nuts, beans and legumes, whole grains, lean protein, mushrooms, and eggs. There isn't solid evidence to support taking excessive amounts of B vitamins if you're not deficient in them.

If you're not getting enough of a B vitamin from your diet, taking a vitamin B supplement may be beneficial for some people. Deficiency in B vitamins can cause a number of symptoms, including tiredness, anemia, loss of appetite, depression, abdominal pain, muscle cramps, hair loss, and eczema.

Just be sure to consult your health care provider to find out whether a B complex supplement is right for you (and if so, the appropriate amount considering the total daily amount you are getting from food and supplements). 

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Article Sources
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  4. NIH. Folate B9. Updated March 11, 2020.

  5. Oliai araghi S, Kiefte-de jong JC, Van dijk SC, et al. Folic acid and Vitamin B12 supplementation and the risk of cancer: Long-term follow-up of the B Vitamins for the prevention of osteoporotic fractures (B-PROOF) trial. Cancer Epidemiol Biomarkers Prev. 2019;28(2):275-282. doi:10.1158/1055-9965.EPI-17-1198

  6. Brescoll J, Daveluy S. A review of vitamin B12 in dermatology. Am J Clin Dermatol. 2015;16(1):27-33. doi:10.1007/s40257-014-0107-3

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