The Health Benefits of Vitamin B Complex

Vitamin B complex is a supplement that usually delivers eight of the B vitamins: B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin). Found naturally in meat, leafy greens, dairy, beans, peas, and whole or fortified grains, B vitamins are water-soluble and play essential roles in certain bodily functions, such as helping your body make energy from the food you eat and forming red blood cells.

benefits of B vitamins
Verywell / Joshua Seong

Health Benefits

Each of the eight vitamins in vitamin B complex supplements has its own unique set of health benefits. For instance, vitamin B1 is critical for the growth, development, and function of cells in the body. Other vitamins, such as B2, work cooperatively in the body with other B vitamins to convert food into energy. B2 converts B6 into a usable form and aids in niacin production, which is mainly obtained from food and is essential in the proper functioning of cells.

Whilst vitamin B5 breaks down fats and carbohydrates for energy and helps the body use other vitamins, such as riboflavin (found in B2), B6 is involved in immune function and is required by the body to use and store protein and carbohydrates from food in the form of glycogen.

B7 helps the body convert fats, carbohydrates, and proteins from the food you eat into energy. It is also needed to make fatty acids (which help to build and sustain overall health) and maintain bone and hair health. Vitamin B9 is required to help cells produce and maintain DNA (the genetic material found in all body cells), while B12 is important for protein metabolism.

Keep in mind, not everyone requires vitamin B supplementation. Speak with your health care provider if you believe supplementation may benefit you. Depending on your individual needs, your provider may advise you to take a specific B vitamin supplement, such as B6 or B12, instead of a vitamin b complex supplement.

Converts Food Into Energy

Most B vitamins are involved in the process of converting food into energy. Some help to metabolize carbohydrates and others aid in breaking down fat and/or protein.

While this is an essential process, that's not to say taking a vitamin B complex supplement will boost your energy. Although B vitamins are essential for your body, the effect is different when they are consumed in the form of dietary supplements rather than food. A B-complex supplement may fill a specific vitamin gap or deficiency, however, it cannot provide energy in the form of calories like a food source.

B vitamins involved: B1, B2, B3, B5, B6, B7, and B12

Supports Brain Health

Research shows that B vitamins support just about every aspect of brain health. While all B vitamins promote healthy brain function, a 2016 review published in Nutrients indicates that vitamins B6, B9, and B12 in particular play a role in homocysteine metabolism, which helps reduce the risk of cognitive decline and dementia. In particular, B12 supports healthy DNA structures, which is important during fetal development and the prevention of chronic disease and cancer.

Vitamin B6 supports both brain development and function, while vitamin B9 can reduce the risk of birth defects in the brain and spine, such as spina bifida.

B vitamins involved: B1, B2, B3, B5, B6, B7, B9, B12

Produces Red Blood Cells

Some B vitamins, particularly vitamin B12, play an essential role in the formation of red blood cells. Healthy red blood cells are needed to transport oxygen to every part of the body, and when there's a vitamin B12 deficiency, the body will struggle to produce enough red blood cells, often leading to anemia.

Vitamins B2 and B9 are also needed for red blood cell production and growth. While vitamin B5 plays a role in red blood cell production, it also helps reduce the amount of cholesterol produced by the body. And vitamin B6, which is required for more than 100 different enzyme reactions in the body, aids in the formation of hemoglobin, which also allows red blood cells to carry oxygen through the blood.

B vitamins involved: B2, B5, B6, B9, B12

Promotes Nervous System Health

Vitamin B2 helps maintain health of the eyes, nervous system, and skin. It also aids in the conversion of food into energy and helps enzymes in the body function properly—not to mention, it makes and repairs DNA, and helps with the optimal function of the digestive and nervous systems.

B vitamins involved: B1, B2, B3, B6, B12

Supports Hormone Production

Vitamins B3 and B5 are needed for the production of hormones in the adrenal glands, such as sex and stress hormones. On the other hand, vitamin B6 stimulates neurotransmitters and hormones that influence mood and regulate the body's biological clock.

B vitamins involved: B3, B5, B6

May Reduce Stress

Research shows that certain B vitamins may help to alleviate stress. For instance, a 2019 study published in Nutrients determined that vitamin B supplementation can benefit mood, though more research on the dietary patterns and micronutrient statuses of broader populations is needed to make an evidence-based recommendation.

B vitamins involved: B1, B2, B3, B5, B6, B7, B9, B12

May Prevent Migraines

Vitamin B supplementations have been found to prevent migraines in some people, such as in a 2015 report that analyzed the effects of vitamin B supplementation on individuals with migraines. The authors determined that reducing homocysteine levels with folic acid (the synthetic form of folate) and vitamins B6 and B12 may help reduce symptoms associated alongside migraine with aura— meaning a recurring headache with sensory disturbances.

However, the report notes that more rigorous research is required to determine the safety and efficacy of B vitamin supplementation as a preventative measure for people with chronic migraine headaches.

B vitamins involved: B2, B6, B9, B12

Possible Side Effects

Although vitamin B complex supplements are water-soluble and are not retained in the body for long, large doses in supplement form can cause certain side effects. There is a daily tolerable intake level (UL) for some B vitamins (which is above what most people need) but it is not established for all of the B vitamins.

For example, the RDA for thiamin (vitamin B1) is 1.2 milligrams and there is no tolerable upper limit due to there being no adverse effects recorded at intakes above 50 milligram—but that doesn't mean there can't be. The tolerable upper limit for niacin (vitamin B3) is 35 milligrams, for vitamin B6 it's 100 milligrams, and vitamin B9 (folate) is 1000 micrograms.

Consuming more than the UL increases your chances of side effects such as:

  • B3 (niacin): Excess B3 may cause skin flushing or pain, elevated blood sugar levels, and liver toxicity.
  • B6 (pyridoxine): Too much B6 can lead to 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 (folate): A higher than required intake 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 an 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.

Before starting any supplement, you should consult with your healthcare provider.


Although consuming a varied diet is usually sufficient for getting 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 also be more prone to a deficiency. People who are pregnant or breastfeeding may need more vitamins B6, B12, and folate.

The National Institutes of Health (NIH) provides the following recommended daily intakes (RDI) for each of the eight B vitamins:

Recommended Daily Intakes (RDIs) for B Vitamins
Men  Women 
B1 (Thiamin) 1.2 mg 1.1 mg 
B2 (Riboflavin) 1.3 mg 1.1 mg
B3 (Niacin) 16 mg 14 mg
B5 (Pantothenic acid) 5 mg 5 mg
B6 (Pyridoxine) 1.3 mg 1.3 mg
B7 (Biotin) 30 mcg 30 mcg
B9 (Folate) 400 mcg 400 mcg
B12 (Cobalamin) 2.4 mcg 2.4 mcg

Maintaining your RDI of B vitamins can help prevent deficiencies. Depending on which B vitamin(s) you are deficient in, symptoms can include one or more of the following:

  • Anemia
  • Brittle hair and nails
  • Cardiovascular symptoms
  • Depression
  • Difficulty concentrating
  • Fatigue
  • Hair loss
  • Irritability
  • Nervousness
  • Short-term memory loss
  • Skin disorders
  • Upset stomach
  • Weakness
  • Weight loss

What to Look For

In the United States, dietary supplements are not held to the same rigorous testing standards as pharmaceutical drugs. This means that the quality of supplements, like vitamin B complex, may vary from one brand to the next and you can find many different brands of vitamin B supplements at drug stores, grocery stores, health food shops, and online.

When shopping for B vitamins, look for brands that have been tested by an independent certification organization, such as the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International. This can help to ensure quality.

Vitamin B supplements should be stored in a cool, dry place and out of reach of children.

Dietary Sources of B Vitamins

B vitamins are found primarily in animal food sources and fortified cereals, although many vegetables, fruits, nuts, and legumes also contain a certain amount of B vitamins. Here's a look at common food sources, of which you'll notice many overlap.

  • B1 (thiamin): 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): Milk and dairy products, fortified breakfast cereals, beef liver, clams, portobello mushrooms, almonds, and chicken
  • B3 (niacin): Eggs, fish, fortified bread and cereal, rice, nuts, milk and dairy, chicken, beef, turkey, lamb, organ meats, peanuts
  • B5 (pantothenic acid): Meat, avocado, broccoli, kale, eggs, milk, mushrooms, fortified cereals, organ meats, poultry, potatoes, and legumes
  • B6 (pyridoxine): Chickpeas, beef liver, tuna, salmon, chicken breast, fortified breakfast cereal, potatoes, turkey, fruits (except citrus), and beef
  • B7 (biotin): Beef liver, egg yolk, wheat germ, pork, beef, sunflower seeds, sweet potato, almonds, whole-grain foods, sardines, spinach, and broccoli
  • B9 (folate): Spinach, beef liver, broccoli, Brussels sprouts, beans and legumes, asparagus, orange juice, peanuts, avocado, dark leafy greens, fortified cereals, and salmon
  • B12 (cobalamin): Beef liver (and other organ meats), clams and other shellfish, beef, chicken, fish, eggs, milk and other dairy products, and some fortified cereals

A Word From Verywell

To maintain your health, you can get everything you need from eating a varied, balanced diet filled with 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.

However, if you're struggling to consume the RDI of B vitamin from your diet, taking a vitamin B supplement may be beneficial. 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. Consult your healthcare provider to find out whether a vitamin B complex supplement is right for you.

Frequently Asked Questions

  • How much vitamin B complex should you take daily?

    The RDI of each type of vitamin B varies from person to person factoring in sex, age, and pregnancy. For example, men will generally require higher doses of vitamin B1, B2, and B3 than women, while those who are pregnant will need more folate than the RDI. People who follow vegetarian or vegan diets may require supplementation of certain B vitamins, such as B12.

  • How long does it take for vitamin B complex to work?

    Although your body may potentially benefit from vitamin B complex from day one (especially if you have a deficiency), a study on the consumption of the supplement required a four-week intake period to fully understand its effect on depressive symptoms, anxiety, and stress. Therefore, although some may feel the benefits right away, for others it can take longer.

  • When should you take vitamin B complex?

    Water-soluble vitamins (such as B vitamins) require sufficient water for optimal absorption. Therefore, it's generally recommended you take this type of supplement on an empty stomach and with a glass of water. While there is not one optimal time for taking vitamin B complex, since many B vitamins are known for their energy-boosting effects, you may want to take it in the morning.

  • Should you get a vitamin B complex injection?

    Most people do not require a vitamin B complex injection if they're consuming sufficient levels of vitamin B from a varied diet. However, if you feel it might be beneficial in improving general health and energy levels, speak with your healthcare provider to determine if the injection is suitable for you.

23 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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