Vitamin B Complex Benefits

The eight vitamins that comprise the vitamin B complex are commonly consumed supplements, with benefits ranging from cellular health and cognition to mood and migraines. 

Let’s take a closer look at how the B complex vitamins may improve health, any potential side effects, and the recommended dosages for each.

What Is Vitamin B Complex?

Vitamin B complex is a term encompassing the eight B vitamins:

• Vitamin B1 (thiamin): Thiamin is vital for energy metabolism, as it plays a significant role in the Krebs cycle—a series of steps called aerobic respiration by which our cells produce energy from food.
• Vitamin B2 (riboflavin): Riboflavin acts as a cofactor to help metabolize carbs, fats, and protein into cellular energy. It also has been found to function as an antioxidant, boosting the immune system and supporting skin health.
• Vitamin B3 (niacin): Niacin is also needed for energy metabolism as it is a precursor to NAD+, a coenzyme required by every one of our cells for energy production, mitochondrial function, and DNA repair. It also helps with healthy nerve function.
• Vitamin B5 (pantothenic acid): Pantothenic acid is involved with cellular energy metabolism and synthesizing the neurotransmitter acetylcholine, which is involved with muscle contraction, memory, motivation, and learning.
• Vitamin B6 (pyridoxine): B6 helps with cognition, mood, immunity, nerve function, and the breakdown of carbohydrates, proteins, and fats. Vitamin B6 converts homocysteine into methionine. Homocysteine is an amino acid that, when elevated, increases the risk of dementia, heart disease, and stroke. 
• Vitamin B7 (biotin): Biotin is essential for healthy hair, nails, and nerve function. It also is involved with gene regulation, cell signaling, and promoting the metabolism of fatty acids, glucose, and amino acids. 
• Vitamin B9 (folate or folic acid): Folate is crucial for fetal development, as it prevents neural tube defects like spina bifida. It’s also needed for DNA repair, red blood cell formation, and converting homocysteine to methionine. 
• Vitamin B12 (cobalamin): B12 is needed to form healthy red blood cells and DNA and plays a role in the brain and nervous system, as it’s required for the development, myelination, and function of nerves. (Myelination refers to the addition of a fatty sheath surrounding nerve fibers that improve the rate of signal conduction.) 

While most B complex supplements contain all eight of these vitamins, others may have just a few, depending on what the vitamin B supplement is intended to do. 

Top 6 Potential Health Benefits of Vitamin B Complex

1. Reduces Fatigue

As all of the B vitamins (except folate) play a vital role in energy metabolism, supplementing with B complex may help to improve energy—but likely only if you are lacking in one of the B vitamins. 

Due to some of the B complex’s role in producing healthy red blood cells (especially vitamin B12), fatigue is a common symptom of inadequate intake.

When the body does not have enough red blood cells, oxygen can’t circulate to all of the body’s tissues, resulting in weakness, tiredness, and, eventually, anemia.

However, even subclinical inadequate levels (meaning yet to be diagnosable or evident on lab testing) of some B vitamins may cause fatigue or low energy.

Some research has found that supplementing with B vitamins improves energy in athletic situations. For example, a small study of ultra-marathon runners found that those who took riboflavin supplements had faster times and quicker muscle recovery than those who took a placebo. 

B complex supplements may also benefit people with chronic fatigue syndrome.

In a 2019 study, people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)—a complex illness that causes long-lasting extreme fatigue—supplemented with high doses of vitamin B12 for three months. About two-thirds of people had increases in serum vitamin B12 levels alongside significant improvements on both a physical functioning scale and a fatigue scale.

2. Improves Mood and Stress

Some B vitamins are linked to better mood and reduced prevalence of depression and anxiety. The B complex vitamins most associated with mood improvements are B6, B9, and B12. 

In a systematic review of 18 studies, eleven of the trials reported a positive effect of B vitamins for improving overall mood or a facet of mood, with the most significant improvements on stress. 

They also found that B complex worked the best in “at-risk” people, meaning populations at higher risk of poor B vitamin status or poor mood. 

The hypothesis is that these B vitamins reduce homocysteine levels, as high homocysteine is a risk factor for depression and low mood.

3. May Protect Against Cognitive Decline

The research is far from conclusive here, but some evidence suggests that several B complex vitamins (namely, B6, B9, and B12) could be associated with preventing cognitive decline with age. 

Like with the relation to mood, this may be due to the B vitamins’ role in lowering homocysteine, an amino acid linked to neurodegeneration when elevated. 

In a meta-analysis of 95 studies with 46,175 participants, people without dementia who supplemented with B vitamins had significantly lower rates of developing cognitive decline.

The researchers also concluded that lower folate and higher homocysteine levels increased the risk of dementia; however, higher dietary B12 or B6 intake was not.

4. Reduces Anemia

Although iron is the micronutrient most associated with anemia, there are other types of anemia that certain B vitamins are linked with. 

Vitamin B12 or folate deficiency can cause megaloblastic anemia, which leads to abnormally large and oval-shaped (not round) red blood cells. 

Without enough healthy and functional red blood cells, your tissues and organs don’t get enough oxygen, causing weakness, fatigue, shortness of breath, tingling in the extremities, and trouble walking. 

Therefore, supplementing with folic acid and B12 (not necessarily the entire complex) can reduce the risk of megaloblastic anemia and improve red blood cell function.

5. May Reduce Migraine Episodes

Vitamins B6, B9, and B12 may also be able to prevent migraine episodes or reduce their severity, although the research is limited. 

In a randomized controlled trial of 52 people with migraine with aura (one that causes sensory disturbances like vision changes, blind spots, or flashes of light), those who took B vitamin supplements containing 2mg of folic acid, 25mg of vitamin B6, and 400mcg of vitamin B12 for six months had reductions in migraine-related disability from 60% to 30%.

The B vitamin group also had reduced headache frequency and pain severity. Again, this may be linked to lowering homocysteine, as people in the B complex group had reduced homocysteine levels by 39%. 

Plus, a study of women with premenstrual-related chronic or episodic migraines found that a supplement of vitamins B1, B6, and B12 led to significant reductions in the severity of menstrual-related migraine attacks and was well-tolerated.

In those with chronic migraines, the average intensity of their menstrual-related migraine attacks reduced from 6.7 on a 10-point scale down to 3.2. In women with episodic migraines, the severity of attacks lowered from 7.2 to 3.7, indicating significant improvements from taking vitamins B1, B6, and B12. 

6. Reduces Nerve Pain

Just a few of the B vitamins are thought to help with nerve pain or neuropathy: vitamins B1, B6, and B12. 

These are considered the “neurotropic B vitamins” due to their involvement with the nervous system. 

Vitamins B1, B6, and B12 protect nerves against oxidative stress and damage, maintain myelin health, promote nerve cell survival, provide essential energy to nerve cells, and more.

Conversely, a vitamin B deficiency in B1, B6, or B12 is linked to nerve degeneration, pain, and neuropathy.

Therefore, supplementing with these B vitamins may support nerve repair, reduce neuropathy and its associated pain, and promote nerve regeneration.

For example, one study found that people with diabetic neuropathy who took 600mg per day of benfotiamine (a more bioavailable thiamin precursor) had reduced neuropathic pain and improvements in their condition. 

Similarly, vitamin B12 was found to alleviate pain by increasing nerve regeneration and decreasing ectopic nerve firing (which causes neuropathic pain) in a systematic review of 24 studies.

Vitamin B Complex Recommended Dosage

The Food and Nutrition Board has set either an RDA (Recommended Dietary Allowance) or AI (Adequate Intake) for vitamins and minerals.

The RDA is the average daily nutrient intake level needed to meet the requirements of 97-98% of healthy people. The AI is an intake level that is assumed to be nutritionally adequate for most people, but the available evidence is insufficient to develop an RDA.

For the B vitamin family, these are the established RDAs or AIs for adult males and females: 

Vitamin B Complex Side Effects

Although vitamin B complex supplements are water-soluble vitamins and don’t accumulate in the body (except B12), some can cause side effects when taken in excess. 

The most common B complex side effects are skin flushing or digestive issues, but there are other concerns when taking B vitamins in excessively high doses. 

While it is unlikely that the general population could overdose on supplemental thiamin, high doses of vitamin B1 orally may cause nausea, while excessive amounts of riboflavin may cause harmless orange discoloration in the urine.

High doses of supplemental niacin (1 to 3 grams per day) in the form of nicotinic acid have been shown to cause skin flushing, impaired vision, abdominal pain, high blood sugar, and liver failure. 

High-dose supplemental nicotinic acid can also increase uric acid levels, which is a risk factor for gout.

Other potential side effects of having too much niacin include dizziness, high or low blood pressure, fatigue, headache, and nausea. 

Excessively large doses of pantothenic acid (15-20 grams per day) can cause an upset stomach and diarrhea, but no other adverse effects have been reported.

Chronic and excessive consumption of vitamin B6 can lead to severe neurological symptoms. 

Overdoses of vitamin B6 can cause neuropathy in the hands and feet, unsteady gait, light sensitivity, skin rashes and lesions, nausea, heartburn, ataxia (loss of control of body movements), and impaired reflexes.

Excessive folic acid (the synthetic form of folate) can negatively affect mental function, in addition to causing insomnia, irritability, and digestive issues.

Taking too much biotin or vitamin B12 is known to cause acne in some people. 

Some vitamin B complex supplements contain very high doses of some of the vitamins (10,00% of the RDA or more). If you’re unsure about taking too much of any one B vitamin, consult your doctor or healthcare provider.

Vitamin B Complex FAQs