Vitamin B6
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Vitamin B6

Vitamin B6 is a water-soluble vitamin. Water-soluble vitamins are stored in the body in very limited amounts, and are excreted through the urine. Therefore, it is a good idea to have them in your daily diet. Vitamin B6 exists in three major forms: pyridoxine, pyridoxal, and pyridoxamine. Pyridoxal phosphate (PLP) is the coenzyme form of B6. A coenzyme enables an enzyme to catalyze a reaction. PLP is an essential coenzyme for many protein metabolism reactions.

Functions

Vitamin B6's functions include:

  • Helping amino acid and protein metabolism
  • Enabling red blood cell metabolism
  • Helping the nervous system function efficiently
  • Helping the immune system function efficiently
  • Converting tryptophan (an amino acid) to niacin (a vitamin)
  • Enabling the breakdown of glycogen to glucose
  • Aiding in the metabolism, transportation, and distribution of selenium
  • Assisting in the metabolism of calcium and magnesium

Recommended Intake:

Age Group (in years)Recommended Dietary Allowance
FemalesMales
1-30.5 milligrams (mg)0.5 mg
4-80.6 mg0.6 mg
9-131.0 mg1.0 mg
14-181.2 mg1.3 mg
14-18 Pregnancy1.9 mgn/a
14-18 Lactation2.0 mgn/a
19-501.3 mg1.3 mg
19-50 Pregnancy1.9 mgn/a
19-50 Lactation2.0 mgn/a
51 +1.5 mg1.7 mg

Vitamin B6 Deficiency

Primary deficiency of vitamin B6 is rare—most foods contain the vitamin. Secondary deficiency may result in certain situations, including malabsorption, alcoholism, some medications, and cigarette smoking. Symptoms of vitamin B6 deficiency include:

  • Skin inflammation and irritation
  • Glossitis (sore or inflamed tongue)
  • Confusion
  • Depression
  • Irritability and nervousness
  • Fatigue and sleepiness
  • Cheilosis (cracking and scaling of the lips)
  • Convulsions
  • Anemia

Vitamin B6 Toxicity

The tolerable upper intake level (UL) for vitamin B6 from dietary sources and supplements combined is 100mg per day. Symptoms of vitamin B6 toxicity include:

  • Muscle incoordination
  • Numbness of the hands and feet
  • Impaired reflexes
  • Abnormal plasma amino acid levels

Major Food Sources

FoodServing Size Vitamin B6 Content
(mg)
Fortified breakfast cereal¾ cup 0.50 - 2.0
(check Nutrition Facts label)
Oatmeal, instant1 packet.74
Potato, baked with skin1 medium.70
Banana1 medium.68
Chicken breast, roasted, no skin3.5 ounces.60
Garbanzo beans½ cup.57
Tomato paste, canned½ cup.50
Pork loin, broiled3.5 ounces.45
Top sirloin, broiled3.5 ounces.45
Halibut, broiled3 ounces.34
Rainbow trout, cooked3 ounces.29
Brown rice, cooked1 cup.28
Sweet potato, baked with skin1 medium.27
Sunflower seeds, dry roasted1 ounce.23
Avocado½ cup.20
Kidney beans, cooked½ cup.18
Lentils, cooked½ cup.18
Tuna, canned in water3 ounces.18
Peanut butter2 Tbs.15
Lima beans, cooked½ cup.10
Soybeans, cooked½ cup.05

Health Implications

Populations at Risk for Vitamin B6 Deficiency

The following populations may be at risk for vitamin B6 deficiency and may require a supplement:

  • The Elderly—many older adults have low blood levels of vitamin B6, which may occur from low intake of the vitamin or accelerated hydrolysis and oxidation of the vitamin.
  • People Who Consume Excessive Amounts of Alcohol—alcohol impairs the conversion and enhances the hydrolysis of the vitamin.
  • People Who Smoke Cigarettes—cigarette smoking disturbs vitamin B6 metabolism, which contributes to a deficiency. Studies have shown the vitamin level to normalize within two years of quitting smoking.

Vitamin B6, Homocysteine, and Heart Disease

Homocysteine is an amino acid normally found in the blood. However, studies have shown that elevated blood levels of homocysteine can be a risk factor for heart disease and stroke. Because vitamins B6, B12, and folic acid are required for the metabolism of homocysteine, it is thought that a deficiency of any of the three may increase the level of homocysteine in the blood. One would think that taking these vitamins as supplements may offer protection from heart disease. However, clinical intervention trials are needed to clearly determine this.

Areas of Research That Have Not Been Supported by Clinical Data

  • Headache and Depression—vitamin B6 is needed for the synthesis of neurotransmitters, including serotonin. Low levels of serotonin have been found in individuals suffering from depression and migraine headaches. This led researchers to look at the relationship between vitamin B6, headaches, and depression. So far, vitamin B6 supplements have not proved effective in relieving either.
  • Premenstrual Syndrome (PMS)—there has been much anecdotal evidence that vitamin B6 can help relieve the symptoms of PMS (depression, irritability, bloating, mastalgia). However, clinical trials have failed to support this idea.
  • Carpal Tunnel Syndrome—the idea that vitamin B6 can help with carpal tunnel syndrome has been around for about 30 years. Scientific studies have never been able to show this to be true. In fact, there are documented cases of neuropathy caused by excessive amounts of vitamin B6 taken for carpal tunnel syndrome.
  • Morning Sickness—there has been some evidence that high levels of B6 can help allieviate the symptoms, such as nausea, of morning sickness during pregnancy.

Tips for Increasing Your Vitamin B6 Intake

To help increase your intake of vitamin B6:

  • Sprinkle kidney beans or garbanzo beans on a salad
  • Opt for a fortified breakfast cereal—one that is high in fiber—in the morning
  • Slice a banana into your oatmeal or cereal
  • If you take a vitamin supplement, make sure it contains vitamin B6

RESOURCES:

American Dietetic Association
http://www.eatright.org

Nutrition.gov
http://www.nutrition.gov

CANADIAN RESOURCES:

Canadian Council on Food and Nutrition
www.ccfn.ca

Dietitians of Canada
http://www.dietitians.ca/

References:

Facts about dietary supplements. National Institutes of Health website. Available at: http://www.nih.gov/.

Food and Nutrition Information Center, US Department of Agriculture website. Available at: http://www.usda.gov/wps/portal/usdahome.

The Nutrition Desk Reference. Keats Publishing;1995.



Last reviewed June 2008 by Dianne Scheinberg MS, RD, LDN

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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