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Vitamin B6 for Eyes, Brain and Body

Friday, May 30, 2008


Vitamin B6 is a water-soluble vitamin discovered in 1930 during nutrition studies on rats. It must be obtained from the diet or from supplements because humans cannot synthesize B6. It plays a vital role in the function of over 100 enzymes that catalyze essential chemical reactions in the human body.

Red blood cell function

 

B6 functions as a coenzyme in the synthesis of heme, a component of hemoglobin, which is critical to red blood cells ability to transport oxygen throughout the body. It can also influence gene expression by interacting with various transcription (signaling) factors that can inhibit platelet aggregation.

The nervous system

The synthesis of the brain-dependent neurotransmitter, serotonin, from the amino acid tryptophan, is catalyzed by a B6 dependent enzyme. Other neurotransmitters, including dopamine, norepinephrine and GABA are synthesized using B6-dependent enzymes.

 

B6 is an important co-factor in systemic dry eye formulations because it stimulates the neurotransmitters associated with the blink response and the ocular surface tear production neuronal loop, as well as being a major co-factor in both Omega-6 and Omega-3 essential fatty acid delta-6-desaturase and delta-5-desaturase metabolism.

Hormone function

Steroid hormones, such as estrogen and testosterone, dramatically affect the body by binding to steroid hormone receptors in the nucleus of the cell, which alters gene transcription. Vitamin B6 binds to steroid receptors and inhibits inappropriate signaling of steroid hormones. A number of studies suggest that B6 deficiency may be implicated in steroid hormone related diseases, including breast cancer and prostate cancers.

The homocysteine /B vitamin connection

Elevated levels of homocysteine, a by product of methionine metabolism, is now considered a marker of cardiovascular disease, including heart disease and stroke. Elevated homocysteine is also a marker associated with the progression of dry macular degeneration to wet macular degeneration, and the progression of Alzheimer’s and Parkinson’s disease.

 

Healthy people utilize two different pathways to metabolize homocysteine. One simply converts homocysteine back to methionine and is dependent on folic acid and vitamin B12, which is the pathway most written about. The other pathway, and more important in my opinion, converts excess homocysteine to the amino acid cysteine, which the kidneys flush from the body. This metabolism requires three B vitamin-dependent enzymes, made up of B6, B12 and folate. It has been suggested that the B vitamin, choline and it's metabolite, betaine, are also players in this sophisticated metabolic process.

Immune function

B6 deficiency has been associated with impaired immune function, especially in the elderly, because production of immune system white blood cells called lymphocytes, and an anti-inflammatory protein called interleukin-2 (IL-2) are dependent on vitamin B6 intake.

 

Severe B6 deficiency is uncommon, although recent studies suggest that women who take birth control pills are almost always deficient in vitamin B6. Those who consume large amounts of protein in their daily diets have an increased requirement for vitamin B6 because it's also a coenzyme for amino acid metabolism.

Kidney stones

A group of more than 85,000 women without a prior history of kidney stones were followed for over 14 years and those who consumed 40 mg or more of vitamin B6 daily cut the risk of developing kidney stones by two thirds, compared to those who consumed 3 mg or less on a daily basis.

 

A study published in this month’s American Journal of Clinical Nutrition that looked at the epidemiology of vitamin B6 status in the US population suggests that women of childbearing age have significantly lower levels of vitamin B6 than those of comparably aged men, and most oral contraceptive users have extremely low levels of B6.

This study reinforces our recommendation that all women on birth control pills and those of child bearing age (think neural tube defects) supplement with a full-spectrum multiple that includes efficacious amounts of the entire complex of B vitamins.

Ellen Troyer, MT MA
Biosyntrx CEO /  Chief Research Officer


PEARL

The Food & Nutrition Board of the Institute of Medicine has set the safe upper limit (UL) for vitamin B6 at 100 mg per day. B6 is a natural diuretic and some people (mostly women) have been known to take excessive amounts for special occassions. There have been no adverse B6 events reported to my knowledge, but we still don't recommend this as a regular event.

BioTears Oral Capsules include 20 mg of vitamin B6 in each four-gelcap daily dose.
Oculair includes 50 mg of vitamin B6 in each four-capsule recommended daily dose.
Macula Complete includes 50 mg of B6 in each six-capsule recommended daily dose.

Both full-spectrum multiples include the complete complex of B vitamins, including choline and betaine.

Oculair also includes 800 mcg of folic acid and 50 mcg of vitamin B12 in each daily dose, as methylcobalamin, the form of oral B12 with the highest absorption rate.

Macula Complete also includes 800 mcg of folic acid and one full mg of vitamin B12 in each recommended daily dose, as methylcobalamin. We increased the amount of B12 in Macula Complete because we lose some of our ability to produce gastric intrinsic factor as we age, which is necessary to absorb vitamin B12.

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References

Plasma pyridoxal 5-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. Savaria Morris,M, Picciano M, et al. The American Journal of Clinical Nutrition, May 2008, vol 87 No 5, 1446-1454 [abstract]

DNA damage from micronutrient deficiencies is likely to be a major cause of cancer. Ames BN, Mutat Res 2001 Apr 18;475(1-2):7-20. [abstract]

Multivitamin/mineral supplementation improves plasma B vitamin status and homocysteine concentration in healthy older adults consuming a folate-fortified diet. McKay DL, Perrone G, et al. J Nutr 200 Dec; 130(12);3090-6 [abstract]

Vitamin B-6 deficiency impairs interleukin 2 production and lymphocyte proliferation in elderly adults. Meydani SN, Ribaya-Mercado JD, Russell RM, Sahyoun N, Morrow FD, Gershoff SN. Am J Clin Nutr. 1991;53(5):1275-1280. (PubMed)

Intake of vitamins B6 and C and the risk of kidney stones in women. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. J Am Soc Nephrol. 1999;10(4):840-845. (PubMed)

Food and Nutrition Board, Institute of Medicine. Vitamin B6. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington D.C.: National Academies Press (National Academies Press)