How Does Vitamin B Complex Help Your Body?

The B vitamins are water-soluble and need to be consumed regularly to support good health.
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B vitamins are vital for cell metabolism and every physiological function in your body, but since they're water-soluble, your body is unable to store them. This means that, if you can't get all the essential B vitamins from your diet, or if you have certain medical conditions, taking a B complex supplement is a wise choice, ensuring your body gets the nutrients it needs.



Each of the unique vitamins in B complex has a defined role in the overall health of your bodily functions. Vitamin B complex has an impact on your energy levels, cell metabolism, brain function and immune system.

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What Is Vitamin B Complex?

A nutritional supplement that contains all eight of the essential water-soluble vitamins, with the exception of vitamin C, is known as vitamin B complex. The B vitamins share some chemical characteristics and often coexist in some foods, but each works independently and has a different role in contributing to your health. The vitamins in B-complex include:

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  • thiamine (vitamin B1) — essential for DNA and creation of energy and closely linked to the activity of other B vitamins
  • riboflavin (vitamin B2) — helps cleanse your blood and acts as an antioxidant

  • niacin (vitamin B3) — needed for communication between cells and vital for energy production

  • pantothenic acid (vitamin B5) — helps your liver cope with toxins and helps generate energy

  • pyridoxine (vitamin B6) — for your immune system, contributes to oxygen circulation

  • biotin (vitamin B7) — for healthy cells, regulates inflammation and protects the development of babies

  • folic acid (vitamin B9) — essential for your brain, lowers risk of heart disease and cancer, prevents birth defects

  • cobalamins (vitamin B12) — for the health of your blood cells, nervous system and DNA structure


Read More​: Foods High in B Vitamins

How Much Do You Need?

Vitamin B complex supplements are available in pill, powder, liquid, time-released and chewable forms. Some are formulated for specific age groups or gender. Some are designed to support certain requirements, such as boosting energy or relieving stress. Other vitamins may be included in a B-complex supplement, such as vitamin C.


Each vitamin in B-complex supplements is unique and required in different amounts, often dependent on gender and age. The recommended daily allowance outlined by the Dietary Guidelines lists the RDA for each B vitamin ranging from 3 micrograms per day for vitamin B12 to 18 milligrams per day for vitamin B3. It's important to check the label on your supplement to avoid taking excessive amounts of any vitamin, especially when it isn't needed.

Read More​: How Much Is Too Much Vitamin B Complex?


Who’s at Risk for Deficiency?

Some conditions and your lifestyle can affect your body's vitamin stores and increase the need for taking a daily B-complex vitamin to help ensure you maintain adequate levels of important nutrients. Alcohol abuse decreases absorption, so excessive drinking may lead to a deficiency. A vitamin-B deficiency can also be the result of ingesting a tapeworm from contaminated food that's not fully cooked due to the parasite sapping the nutrients from your body.



Vegetarians or people on a strict vegan diet who eliminate animal products are often deficient in B vitamins, especially vitamin B12. Pregnant and breastfeeding women have an increased demand for B vitamins, particularly B12 and folate. Not getting enough of these vitamins can result in a deficiency and possible harm to a newborn baby.

Effect of Drugs and Medications

Certain prescription drugs, including some antiseizure medications, can restrict the absorption of vitamin B complex. Proton pump inhibitors, which lower stomach acid, and metformin, a diabetes drug, can decrease absorption ability. Oral contraceptives can also deplete several B vitamins, including B6, B12 and folate, according to University Health News.


Medical Conditions May Reduce Absorption

Medical conditions that cause a decreased ability to absorb nutrients can result in a deficiency and the need for a B-complex supplement. As you age, you may have a reduction in stomach acid. Diseases, such as celiac or Crohn's disease, may inhibit your ability to absorb vitamins from food. Individuals who have undergone surgery, such as for weight loss, gastric bypass or removal of part of the small intestine, or patients undergoing hemodialysis for kidney disease, may have difficulty with absorption, according to Mayo Clinic.


Read More​: Symptoms of Low B12

B Complex to Reduce Stress

Vitamin B complex has been found useful in reducing fatigue and stress as well as improving mood. Researchers have identified a link between vitamin B levels and brain atrophy and cognitive ability.

An Australian trial examined the effects of B vitamins on stress and mood variables with full-time employees in the workplace. Incorporating the role of B vitamins as antioxidants, the study investigated the relationship between maintaining cognitive ability and general health. Published in the Nutrition Journal in 2014, evidence concluded that dietary supplementation of B vitamins may be viable in reducing occupational stress, increasing work productivity and decreasing absenteeism.


Improve Anxiety or Depression

Depression is the most common type of mental illness in Americans. Studies investigating nutrition to sustain mood and depressive disorders have found that B-complex vitamins may be helpful in improving symptoms of depression. A placebo-controlled trial studied 60 adults diagnosed with major depression to evaluate the effect of vitamin B complex on improving depressive and anxiety symptoms.

Results of the study, published in the journal ISRN Psychiatry in 2013, showed modest improvements in mood and mental health with the use of vitamin-B supplementation. The conclusion was that dietary supplements may be effective for alleviating depression, mood symptoms and improving quality of life.

Treat Yeast Infection

Vitamin B complex is needed for healthy cell replication, which is particularly important when cells are attacked with infection. Symptoms of inflammation from infection may be relieved by vitamin B complex as evidenced in a study to find an effective therapy for vulvovaginal candidiasis (VVC). VVC is a fungal infection in women with symptoms of inflammation and painful discomfort during urination.

The 2017 study examined the effect of vitamin B complex, in combination with conventional treatments, to alleviate the symptoms of complicated vulvovaginal candidiasis. Findings, published in the journal Biomedicine & Pharmacotherapy, showed a significantly higher reduction in inflammation and increased antifungal effect in the group that received a co-administration of oral B-complex vitamins. Results showed a correlation between highest vitamin B-complex dosage and lowest inflammatory scores.

Complications From Toxicity

Because the vitamins in B complex are water soluble, any excess your body doesn't use is excreted, so it's unlikely you'll experience a vitamin B overdose or toxic effect. If you experience bright yellow urine after taking B complex, surplus riboflavin is the culprit.

In rare situations, taking megadoses of certain B vitamins may cause adverse health effects. High intake of niacin (vitamin B3) supplements may bring on abdominal pain, gout, nausea, rapid heartbeat, itching, skin flushing and even acute liver failure, according to the journal Case Reports in Pediatrics.

High doses of pyridoxine (vitamin B6) can cause symptoms associated with neuropathy, including nerve damage, numbness, tingling or burning. A study published in Toxicology in Vitro found that the symptoms of vitamin B6 overdose are similar to those of vitamin B6 deficiency. Excessive vitamin B6 can also lead to skin lesions, oversensitivity to light, gastrointestinal symptoms and reduced ability to sense pain or extreme temperatures, warns Mayo Clinic.

Read More​: B-Complex Vitamin Toxicity