Vitamin B6 (Pyridoxine):

include pyridoxine, pyridoxal, pyridoxamine, and their 5` – phosphate derivatives. Vitamin B6, in the form of pyridoxal phosphate (PLP), acts as a coenzyme for more than 100 enzymes involved in the metabolism of amino acids, synthesis of heme and neurotransmitters, and metabolism of glycogen, lipids, steroids, and other vitamins, including conversion of tryptophan to vitamin B3.

Functions of Vitamin B6:

1. It involves in the metabolism of amino acids and lipids.
2. It promotes production of neurotransmitters especially gamma aminobutyric acid (GABA) in the brain.
3. It is required for the conversion of tryptophan to vitamin B3 and arachidonic acid to prostaglandin E2.
4. As a coenzyme, it has a key role in the production of melatonin, serotonin, and dopamine.
5. It helps maintain sodium and potassium balance.
6. It promotes the production of red blood cells.
7. It is required for maintaining optimal levels of magnesium inside the cells.
8. It is important for the absorption of amino acids from the intestine and their transfer into the cells.
9. It facilitates the breakdown of glycogen into glucose in the liver and muscles.
10. It regulates the metabolism of acetylcholine, norepinephrine, and histamine.
11. It has a key role in liver detoxification.
12. It is necessary for the conversion of homocysteine to cystathionine.

Food Sources and Absorption:

Plants contain vitamin B6 in the form of pyridoxine, whereas animal sources contain PLP and pyridoxamine phosphate. The best animal sources of vitamin B6 are organ meats, especially the liver. Fish, chicken and egg yolks are good sources as well. Plant sources are wheat germ, whole grains, legumes, nuts, potatoes, prunes, bananas, cauliflower, collard greens, mustard greens, bell peppers, mushroom, cabbage, avocado, and spinach. It is also produced in the intestine by floral bacteria.

Vitamin B6 is absorbed well from the small intestine, and excess vitamin B6 is eliminated in the urine. The vitamin B6 in plant sources is less bioavailable than that in animal sources. A small amount is stored in the muscles.

Since it is very sensitive to ultraviolet and heat, it is easily destroyed by sunlight and cooking.

Athletic Benefits of Vitamin B6:

1. Supports glycogen breakdown in glucose to generate energy.
2. Aids building muscles by involving in the metabolism of amino acids and synthesis of natural steroid hormones.
3. May prevent from muscle spasms and cramps by increasing the bioavailability of magnesium.
4. May be beneficial in pre – competition anxiety.
5. Vitamin B6 in conjunction with vitamins B9 and 12 are the most important cofactors in the conversion of creatine into creatine phosphate (CP).

Non – Athletic Benefits of Vitamin B6:

Vitamin B6 may be beneficial in the following conditions:

1. Anemia.
2. Autism.
3. Asthma.
4. Age – related cognitive decline.
5. Carpal tunnel syndrome.
6. Canker sore.
7. Depression and anxiety.
8. Dysmenorrhea.
9. Morning sickness.
10. Premenstrual syndrome (PMS).
11. Postpartum blue.
12. Muscle fatigue and soreness.
13. Schizophrenia.
14. Vertigo.
15. Fibrocystic breast disease.
16. Parkinson`s disease.
17. High homocysteine levels.
18. Kidney stones of calcium oxalate type.
19. Gestational diabetes.
20. Water retention.
21. Female infertility.
22. Overdose with barbiturate medications.
23. Carbon monoxide toxicity.
24. Epilepsy.
25. Skin problems, such as psoriasis, dermatitis, dandruff, and acne, especially premenstrual.
26. Irradiation therapy.

Deficiency of Vitamin B6:

Symptoms of vitamin B6 deficiency appear when dietary daily intake is less than 0.2 mg or blood level of PLP is less than 20 nmol/L. They include fatigue, muscle weakness, irritability, depression, confusion, anemia, seborrhea, inflammation of the tongue, neuropathy, convulsions, and personality changes. Low levels of vitamin B6 in the blood are associated with inflammation, elevated levels of C – reactive protein (CRP), increased blood levels of homocysteine, and increased risk of cardiovascular disease.

The contributing factors to deficiency of vitamin B6 are:

1. Alcoholism.
2. Asthma.
3. Elderly people.
4. Depression.
5. Poor digestion.
6. Birth control pills.
7. Hormone replacement therapy.
8. Peptic ulcer.
9. Pregnancy.
10. Smoking.
11. Medications: isoniazid, gentamycin, penicillamine, hydralazine, reserpine, theophylline, and cyclosporine.

Dosage and Side Effects:

For the RDA of vitamin B6 in adults, see the table below. The performance daily intake (PDI) in athletes and physically active adults is 20 – 200 mg. The safe upper limit for vitamin B6 is 100 mg per day, although no side effects have been reported with high dietary intakes. However, supplementing with large doses of vitamin B6 could cause impaired coordination, numbness and tingling.

Large doses of vitamin B6 (250 – 500 mg per day) would be needed in carpal tunnel syndrome, multiple sclerosis, Parkinson`s disease, epilepsy, neuropathies, carbon monoxide poisoning, and drug overdose with barbiturates.

                     The Recommended Daily Allowance (RDA) for Vitamin B6

Interactions:

1. L – dopa: vitamin B6 interferes with the action of this medication. If you are taking this medication, do not take vitamin B6.
2. Amiodarone: vitamin B6 may increase amiodarone – induced photosensitivity.
3. Anti – epilepsy medications (phenobarbital and phenytoin): vitamin B6 decreases their effectiveness by increasing their liver metabolism.
4. Aspirin and NSAIDs: vitamin B6 may increase the risk of bleeding.
5. Anticoagulants or blood thinners (Coumadin, heparin, and Plavix): vitamin B6 may increase the risk of bleeding.
6. Ginkgo biloba: vitamin B6 may increase the risk of bleeding.