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Vitamin B refers to not one, but eight different vitamins. All B vitamins play a role in converting food into energy in the body. Each vitamin also has a unique role in a person's health.
Vitamin B-complex supplements include all of the essential B vitamins in one pill. Some contain 100 percent of the recommended daily allowance (RDA) of every B vitamin. Others contain higher doses of some or all of these vitamins.
Many people get all the vitamin B they need from a varied, healthful diet, but others benefit from taking a vitamin B-complex supplement.
Vitamin B-complex supplements should include all of the essential B vitamins.
If a product contains the vitamin B complex, it should have some of each of the following:
Vitamin B-1 – thiamin
Vitamin B-1 is vital to the healthy growth and function of organs, including the brain and heart.
Vitamin B-2 – riboflavin
The body needs vitamin B-2 to break down fats and drugs.
Vitamin B-3 – niacin
The body needs niacin to maintain healthy skin, nerves, and digestion. Doctors sometimes prescribe high doses of niacin to help improve cholesterol levels.
Vitamin B-5 – pantothenic acid
Vitamin B-5 is essential for the health of the brain and nervous system.
Vitamin B-6 – pyridoxine
Vitamin B-6 helps the body make new red blood cells, which carry oxygen throughout the body. It also helps keep the immune system strong.
Vitamin B-7 – biotin
Biotin is essential for healthy hair, nails, and nerve function.
Vitamin B-9 – folic acid
The body uses folic acid — or folate, its natural form — to make DNA and genetic material. During pregnancy, folic acid may reduce the risk of certain birth defects.
Vitamin B-12 – cobalamin
The body's nerve and blood cells require vitamin B-12. Adequate levels of B-12 also prevent pernicious anemia, which is a deficiency of this nutrient.
Many B-complex supplements contain about 100 percent of the RDA of each of the eight B vitamins.
However, some contain very high levels of certain B vitamins. Before taking a high-dose supplement, talk with a clinician.
The following are RDAs for each of the B vitamins, in milligrams (mg) or micrograms (mcg), according to The National Institutes of Health Office of Dietary Supplements. Older adults may require higher dosages of some B vitamins.
| Males | Females | During pregnancy | During breastfeeding |
| Vitamin B-1 | 1.2 mg | 1.1 mg | 1.4 mg | 1.4 mg |
| Vitamin B-2 | 1.3 mg | 1.1 mg | 1.4 mg | 1.6 mg |
| Vitamin B-3 or dietary equivalents | 16 mg | 14 mg | 18 mg | 17 mg |
| Vitamin B-5 | 5 mg | 5 mg | 6 mg | 7 mg |
| Vitamin B-6 | 1.3 mg | 1.5 mg | 1.9 mg | 2.0 mg |
| Vitamin B-7 | 30 mcg | 30 mcg | 30 mcg | 35 mcg |
| Vitamin B-9 or dietary equivalents | 400 mcg | 400 mcg | 600 mcg | 500 mcg |
| Vitamin B-12 | 2.4 mcg | 2.4 mcg | 2.6 mcg | 2.8 mcg |
Vitamin B-complex supplements may help with certain health problems. If a person has any of the conditions listed below, they may benefit from taking a supplement that contains B vitamins:
Migraine episodes
Some research suggests that certain B vitamins could help prevent migraine with aura, specifically:
- vitamin B-6
- vitamin B-9
- vitamin B-12
The researchers also suggest that vitamin B-2 could help prevent migraine by influencing mitochondrial dysfunction, which occurs at the cellular level.
Authors of a review study from 2017 looked at the effects of vitamin B-2 on migraine. They report that this vitamin is well-tolerated and effective at reducing migraine frequency in adults, though they recommend further research.
Depression and anxiety
Authors of a study from 2018 state that vitamin B-12 levels play an important role in the development and presentation of depression and anxiety. They report that participants with depression or anxiety had lower levels of B-12 than their control counterparts.
A meta-analysis found that B vitamins could help with depression in certain cases. The researchers said that taking some B vitamins regularly for several weeks to years could reduce the risk of depression relapse.
A small-scale study in India also suggested that B-9 and B-12 deficiencies play a role in depression and anxiety.
Skin wounds
B vitamins may help the skin heal.
One study found that, when applied to the skin, these vitamins helped wounds heal more effectively. Another study found that B-12 improved wound healing in mice with diabetes.
Canker sores
Vitamin B-12 may be helpful in treating canker sores, also known as oral ulcers. A double-blind study found that a B-12 ointment relieved pain better than a placebo.
PMS
Some evidence suggests that taking a combined supplement of B-6 and calcium improves symptoms of premenstrual syndrome (PMS).
A systematic review and meta-analysis also found vitamin B-6 to be helpful in controlling physical and psychological PMS symptoms.
The following sections look at who may benefit from taking vitamin B-complex supplements.
Pregnant women
Pregnant women may benefit from taking vitamin B-complex supplements.
B vitamins are particularly important during pregnancy, when a woman should take in least 400 mcg of folic acid every day. Ideally, this would also occur in the months before getting pregnant.
In addition, pregnant women should be consuming folate — the natural form of folic acid — from food sources. Getting the recommended amounts of folic acid and folate reduces the risk of birth defects involving the brain and spinal cord, according to the Centers for Disease Control and Prevention (CDC).
Pregnant women also need plenty of vitamin B-12. Studies show that vitamin B-12 deficiency can lead to early pregnancy loss, low birth weight, high blood pressure in the woman, and fetal abnormalities.
Vegetarians and vegans
People who follow a vegetarian diet do not eat meat, including beef, poultry, and fish. People following a vegan diet do not eat any animal products, including meat, eggs, and dairy products.
Vegetarian and vegan diets can increase a person's risk of B-12 deficiency. The vitamin is present in many animal-based foods, including meat, eggs, and dairy.
People who eat eggs and dairy products may be getting the B-12 that they need from these foods, but those who eat no animal products may need supplements.
People who have had gastric bypass surgery
Individuals who have undergone gastric bypass surgery, also known as bariatric surgery, often need vitamin supplements.
Research indicates that this surgery increases a person's need for B-12. There is further evidence that many people need a multivitamin that includes B vitamins and other nutrients after this surgery, at least in the short term.
Older adults
People who are 65 or older may benefit from a B-complex supplement.
Research shows that older adults are more susceptible to vitamin B-12 deficiency. Some evidence suggests that having higher levels of B-12 may help slow the aging of the brain, but confirming this finding requires further research.
Low levels of B-12 and folate — a dietary equivalent of folic acid, or vitamin B-9 — may be associated with depression in older people, according to a systematic review and meta-analysis.
In addition, a study involving older Latino adults found that higher B-6 levels were linked to decreased depression symptoms.
People with other health conditions
A person with any of the following health conditions may benefit from a vitamin B-complex supplement:
- alcohol dependence
- an autoimmune condition, such as lupus, rheumatoid arthritis, or type 1 diabetes
- depression
- diabetes
- a malabsorption condition, such as celiac disease or Crohn's disease
- kidney disease
- HIV
- heart disease
- Alzheimer's disease
- AIDS
- cancer
B vitamins are water-soluble. This means that, most of the time, the body excretes extra B vitamins in the urine.
While a standard dosage does not seem to cause harm, excessively high doses of certain B vitamins can be dangerous. Speak with a clinician before taking very high doses of B-complex supplements.
Possible side effects of B-complex vitamins:
- High blood sugar. High doses of nicotinic acid, a synthetic form of vitamin B-3, can raise blood sugar levels. This can interfere with diabetes medications. People with diabetes or high blood sugar should not take high doses of nicotinic acid (measuring 1,000 mg or more).
- Excess nicotinic acid. Too much nicotinic acid can also cause low blood pressure, fatigue, headaches, rashes, and liver damage.
- Excess nicotinamide. High doses of nicotinamide, another form of vitamin B-3, can cause diarrhea and increased bleeding. This can occur in doses of 500 mg per day. Doses higher than 3,000 mg can cause vomiting and liver damage.
- Excess folic acid. Taking more than 1,000 mcg of folic acid a day can mask a type of anemia caused by vitamin B-12 deficiency.
Taking a high-dose B-complex supplement can also turn the urine bright yellow. This effect is temporary and harmless. Once the kidneys get rid of the extra vitamins, the color will return to normal.
A doctor may recommend a certain type of this supplement, depending on a person's health needs.
Some vitamin and supplement companies use independent quality testing of their products. Those that pass may have a seal of approval from an independent testing organization.
This seal does not guarantee that the product is 100-percent safe or effective for everyone, but it means that the product contains what is listed on the label without contaminants.
Some testing organizations and their certifications include:
- ConsumerLab.com's approved quality product seal
- NSF International's dietary supplement certification
- the verified mark of The United States Pharmacopeial Convention, or USP
In most cases, vitamin B does not interact negatively with other medications. However, certain medicines can make a vitamin B deficiency more likely.
These are some examples of medications that can result in low levels of specific B vitamins:
- Blood pressure drugs and chemotherapy drugs can lower a person's B-1 levels.
- Antiseizure medications used for epilepsy can lower B-3, B-6, and B-9 levels.
- Drugs that treat tuberculosis can cause low levels of B-3 and B-6.
- Certain cancer drugs can lower B-9 levels.
- Certain drugs that treat ulcerative colitis can cause low levels of vitamin B-9.
- Certain antibiotics and medicines for ulcers, diabetes, or gastroesophageal reflux disease, or GERD, may lower B-12 levels.
Avocados are a major source of B vitamins.
Some foods contain several B vitamins, and a person needs a varied diet to consume all eight.
People can get all the B vitamins that they need from omnivorous, vegetarian, or vegan diets.
However, animal products are a major source of B vitamins, so people following restricted diets should take steps to ensure that they are getting enough of each vitamin from different dietary sources.
Some of the best food sources of B vitamins include:
- beef
- pork
- fish
- organ meats
- avocados
- leafy greens
- nuts
- legumes
- grains
- milk
- cheese
- yogurt
- enriched and fortified breads and cereals
- mushrooms
Learn more about vegetarian and vegan sources of vitamin B-12 here.
Whenever possible, a person should take in B vitamins by eating a variety of healthful foods. However, some people benefit from taking a B-complex supplement.
People can find these supplements in health or drug stores, or they can choose between brands online.
A B-complex supplement is generally safe when a person takes it as directed. However, only take very high doses of B vitamins under a doctor's guidance.
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