Vitamin B6, also called pyridoxine, is one of 8 B vitamins. All B vitamins help the body convert food (carbohydrates) into fuel (glucose), which is "burned" to produce energy. These B vitamins, often referred to as B complex vitamins, also help the body metabolize fats and protein. B complex vitamins are necessary for healthy skin, hair, eyes, and liver. They also help the nervous system function properly.

All the B vitamins are water-soluble, meaning that the body does not store them.

Vitamin B6 helps the body make several neurotransmitters, chemicals that carry signals from one nerve cell to another. It is essential for normal brain development and function, and helps the body make the hormones serotonin and norepinephrine (which influence mood) and melatonin (which helps regulate the body clock).

Along with vitamins B12 and B9 (folic acid), B6 helps control levels of homocysteine in the blood. Homocysteine is an amino acid that may be associated with heart disease. B6 also is necessary for proper absorption of vitamin B12 and for the production of red blood cells and cells of the immune system.

It is rare to have a significant deficiency of B6, although many studies indicate many people may be mildly deficient, especially children and the elderly. Certain medications can also cause low levels of B6 in the body. Symptoms of serious deficiency include muscle weakness, nervousness, irritability, depression, difficulty concentrating, and short-term memory loss.

Heart Disease

Several observations have caused researchers to wonder about the relationship between vitamin B6 and heart disease. People who don't get enough B6 in their diet have a higher risk of heart disease. Low dietary intake of vitamin B6 is associated with higher risk of having heart disease. And as mentioned, B6 plays a role in lowering levels of homocysteine in the blood. High levels of homocysteine appear to be associated with heart disease, but it's not clear exactly what the relationship is. Nor is it clear whether lowering levels of homocysteine will reduce risk of heart disease. Until more is known, the best action is to get enough B6 through your diet, and to take supplements if recommended by your doctor.

Nausea and Vomiting during pregnancy

Several studies, including one large double-blind, placebo-controlled study, indicate that a daily dose of 30 mg of B6 may help reduce morning sickness. However, other studies have found no benefit. If you are pregnant, be sure to ask your doctor before taking any supplements, including vitamin B6.

Depression

Vitamin B 6 elevates levels of serotonin in the blood. Because low levels of serotonin are associated with depression, and some antidepressant medications work by raising levels of serotonin, it has been proposed that vitamin B6 might help reduce symptoms of depression. But well-designed studies are needed to show whether there is any true benefit.

Premenstrual Syndrome (PMS)

Some studies show that vitamin B6 may help improve PMS symptoms -- however, most of these studies were poorly designed, and some that were better designed found no benefit from B6. However, some health care providers and their female patients report improvement in PMS from using vitamin B6. It is possible that response to vitamin B6 may be based on the individual. Until more research is completed, talk with your doctor about whether using B6 is appropriate and safe for you. Then, if taking the vitamin, follow your symptoms closely. It can take up to 3 months until any change is noticeable.

Carpal Tunnel Syndrome

Some early studies suggested that B6 might help reduce inflammation and symptoms of carpal tunnel syndrome, but not all studies have shown it to be effective.

Rheumatoid Arthritis

Low levels of vitamin B6 have been associated with rheumatoid arthritis, and some studies indicate that people with RA may need more vitamin B6 than healthy people, because chronic inflammation may lower B6 levels. Eating a balanced diet, including a complete vitamin B complex, is a good idea for anyone with a chronic illness, such as rheumatoid arthritis. Talk to your doctor before taking B6 supplements.

Good dietary sources of vitamin B6 include chicken, turkey, tuna, salmon, shrimp, beef liver, milk, cheese, lentils, soybeans, spinach, carrots, brown rice, bran, sunflower seeds, wheat germ, and whole-grain flour.

Vitamin B6 can be found in multivitamins (including children's chewable and liquid drops), B complex vitamins, or can be sold individually. It is available in a variety of forms, including tablets, softgels, and lozenges. Vitamin B6 is also sold under the names pyridoxal, pyridoxamine, pyridoxine hydrochloride, and pyridoxal-5-phosphate.

People who eat a balanced diet containing good sources of vitamin B6 should be able to meet the daily requirement without taking a supplement. Vitamin supplements should always be taken with water, preferably after a meal. As with all medications and supplements, check with a health care provider before giving vitamin B6 supplements to a child.

Daily recommendations for dietary vitamin B6 are listed below.

Pediatric

• Newborns to 6 months: 0.1 mg (adequate intake)
• Infants 7 months to 1 year: 0.3 mg (adequate intake)
• Children 1 - 3 years: 0.5 mg (RDA)
• Children 4 - 8 years: 0.6 mg (RDA)
• Children 9 - 13 years: 1 mg (RDA)
• Males 14 - 18 years: 1.3 mg (RDA)
• Females 14 - 18 years: 1.2 mg (RDA)

Adult

• 19 to 50 years: 1.3 mg (RDA)
• Males 51 years and older: 1.7 mg (RDA)
• Females 51 years and older: 1.5 mg (RDA)
• Pregnant females: 1.9 mg (RDA)
• Breastfeeding females: 2.0 mg (RDA)

Prevention of heart disease and lowering of homocysteine levels: 3.0 mg per day.

Larger doses have been used to treat some of the conditions discussed above, but you should not take doses above 100 mg per day without a doctor's supervision.

Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider.

Very high doses (200 mg or more per day) of vitamin B6 can cause neurological disorders, such as loss of sensation in the legs and imbalance. Discontinuing high doses usually leads to a complete recovery within 6 months.

There have been rare reports of allergic skin reactions to high doses of vitamin B6 supplements.

Other side effects can include sensitivity to sunlight, nausea, abdominal pain, and loss of appetite.

If you are being treated with any of the following medications, you should not use vitamin B6 supplements without first talking to your health care provider.

Drugs that reduce levels of B6 in the body -- If you take any of these medications, be sure to get enough B6 in your diet:

• Cycloserine (Seromycin), used to treat tuberculosis
• Hydralazine (Apresoline), used to treat high blood pressure
• Isoniazid, used to treat tuberculosis
• Penicillamine, used to treat rheumatoid arthritis
• Theophylline (TheoDur), used to treat asthma

Antibiotics, Tetracycline -- All B complex vitamins, including vitamin B6, interfere with the absorption and effectiveness of antibiotic tetracycline. You should take tetracyclien at different times from vitamin B6 and other B vitamins.

Antidepressant Medications -- Taking vitamin B6 supplements may improve the effectiveness of certain tricyclic antidepressants such as nortriptyline (Pamelor), especially in elderly people. Other tricyclic antidepressants include amitriptyline (Elavil), desipramine (Norpramin), and imipramine (Tofranil).

On the other hand, antidepressants called monoamine oxidase inhibitors (MAOIs) may reduce blood levels of vitamin B6. Examples of MAOIs include phenelzine (Nardil) and tranylcypromine (Parnate).

Chemotherapy drugs -- Vitamin B6 may reduce certain side effects of 5-fluorouracil and doxorubicin, medications used to treat cancer, without reducing the effectiveness of the chemotherapy. Talk to your doctor before taking any supplement if you are undergoing chemotherapy.

Erythropoietin (EPO) -- Erythropoietin therapy, used to treat severe anemia, may decrease vitamin B6 levels in red blood cells and may require B6 supplementation.

Levodopa (L-dopa)-- Vitamin B6 reduces the effectiveness of levodopa, a medication used to treat Parkinson's disease. However, your doctor may be able to determine a dose of B6 that can help reduce side effects of levodopa without interfering with the drug's action. Taking vitamin B6 along with levodopa should be done only under the strict guidance of a physician.

Phenytoin (Dilantin) -- Vitamin B6 reduces the effectiveness of phenytoin, a medication used to treat seizures.

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