The Vitamin B Series, Vitamin B6

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Vitamin B6, also known as pyridoxine, is part of the vitamin B group of essential nutrients. The vitamin was first discovered in 1934 by Paul György, a Hungarian-born scientist, whilst conducting research on a skin disease (dermititis acrodynia) in rats. Other studies were showing a deficiency in this substance led to sudden, involuntary contraction of muscles in dogs, pigs and rats [1]. In 1938, Samuel Lepkovsky isolated vitamin B6 from rice bran. In 1939, Leslie Harris and Karl Folkers revealed the structure of vitamin B6 and showed that it was a pyridine derivative. In 1945, Snell was able to identify the two forms of vitamin B6, pyridoxal and pyridoxamine, from his development of microbiological growth assays. Vitamin B6 was named pyridoxine to indicate its structural similarities to pyridine.

What is the prevalence of vitamin B6 deficiency?

Most children, adolescents and adults in the United Kingdom and United States consume an adequate amount of vitamin B6, although deficiency is seen in some populations. The mean B6 intake in men and women, taken from the National Diet and Nutrition Survey in the UK, significantly surpassed the recommended daily intake by ~50% [2]. Mean intakes in the United States show adequate consumption of B6, on average, according to an analysis of data from the 2003-2004 National Health and Nutrition Examination Survey [3]. Keep in mind these studies focus on mean intakes, and some individuals may be consuming lower than the mean intake, with some reports of marginally low B6 status of some groups in the United States [6].

It should be noted that 24% of people in the United States who do not take supplements containing B6 have low plasma PLP concentrations (less than 20 nmol/L) when blood samples are analysed. Further analysis of blood samples and plasma concentrations in other studies show B6 deficiency is most common among those who are alcohol dependent, obese, pregnant, or those with preeclampsia, eclampsia, malabsorption syndromes, celiac disease, crohn’s disease, and ulcerative colitis [4][5].

What foods contain vitamin B6?

The best plant-based sources are chickpeas, fortified breakfast cereals, potatoes, bananas, bulgur, squash, dried fruit, avocadoes and spinach. Top animal-based sources are turkey, chicken, pork, beef, tuna, salmon and cottage cheese. Adults in westernised societies achieve the majority of their dietary vitamin B6 from fortified cereals, beef, poultry, starchy vegetables, and non-citrus fruits [7].

Bioavailability of vitamin B6 from animal sources is 90-100%, with nearly all of the nutrient available for utilization. As plant foods are higher in fiber, they generally have a 5-10% reduced bioavailability. Plant foods which contain vitamin B6 in the form of pyridoxine glucoside have significantly decreased consumption of 75-80%, due to glucoside presence having a negative interaction with B6 uptake [8].

What are the symptoms of vitamin B6 deficiency?

Vitamin B6 deficiency, when maintained over long periods, can result in mood changes, anxiety, irritability, confusion, muscle pains and low energy. Due to B6’s close interaction with components of the nervous system, neuropsychiatric disorders such as seizures and migraines have also been reported when B6 levels are inadequate. Insufficient amounts of B6 can also worsen symptoms of anaemia, as well produce skin disorders, such as a rash or cracks around the mouth.

How much do you need per day?

Age

Male

Female

Pregnancy

Lactation

0-6 months

0.1 mg

0.1 mg

6-12 months

0.3 mg

0.3 mg

1-3 years

0.5 mg

0.5 mg

4-8 years

0.6 mg

0.6 mg

9-13 years

1.0 mg

1.0 mg

14-18 years

1.3 mg

1.2 mg

1.9 mg

2.0 mg

19-50 years

1.3 mg

1.3 mg

1.9 mg

2.0 mg

51+ years

1.7 mg

1.5 mg

[4]

What are the health benefits of vitamin B6?

Vitamin B6 is broken down in the body to its coenzyme forms, Pyridoxal 5’ phosphate (PLP) and pyridoxamine 5’ phosphate (PMP). These coenzymes are involved in over 100 metabolic reactions in the body, regarding a variety of functions. PLP and PMP are essential for amino acid metabolism, and also play a role in reactions involving lipid and carbohydrate metabolism.

Studies have shown a link between vitamin B6 intake and the reduction in homocysteine levels in the blood, which may decrease risk of cardiovascular disease. A large study involving 5500 adults, known as the HOPE 2 trial, showed a 25% decreased stroke risk when participants were supplemented with vitamin B6 (50mg/day), vitamin B12 (1mg/day), and folic acid (2.5mg/day) for 5 years, compared to placebo [9]. However, it is difficult to evaluate the degree to which vitamin B6 has on such beneficial effects due to the combination of supplements involved in the study not allowing isolated results between the given nutrients. Studies that do only use B6 supplementation (40mg/day), such as the Norwegian Vitamin Trial and the Western Norway B Vitamin Intervention Trial, showed no benefit of vitamin B6 supplementation on cardiovascular events.

Adequate vitamin B6 intake is also linked to improving cognitive function, and reducing cognitive decline in the elderly. Those with higher serum B6 concentrations seem to produce better analytical memory scores when tests are completed on 50+ year old adults, although data is limited [10]. Contradicting data is also available, with a Cochrane review finding no evidence that short-term vitamin B6 supplementation, 5-12 weeks, improves cognitive function or mood in the two studies involved [11]. More data is needed to evaluate this link.

More conclusive evidence is seen regarding B6’s effect on nausea and vomiting in pregnancy, commonly known as “morning sickness”. In two randomized, placebo-controlled trials, 30-75 mg of pyridoxine per day significantly decreased nausea in pregnant women who were previously reporting symptoms of nausea [12][13]. Vitamin B6 may have a pronounced effect on nausea when combined with doxylamine (antihistamine), with a study associating a 70% reduction in nausea and vomiting in pregnant women when these two supplements were combined [14].

Vitamin B6 is found mainly in chickpeas, cereals, potatoes, and various meats. It has benefits on protein metabolism, reducing nausea, and may have an impact on reducing the rate of strokes and improving cognitive function. A lack of vitamin B6 may result in mood changes, irritability, low energy, and skin issues. Deficiency is not common, but prevalent enough for people to assess their intakes and ensure they are consuming adequate amounts. Supplementation may be necessary for some individuals, and is a good idea for pregnant women looking to reduce the occurrence of morning sickness.

 

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  1. Rosenburg IH. (2012). A history of the isolation and identification of vitamin B(6). Ann Nutr Metab.
  2. Gregory J, Foster K, Tyler H, Wiseman H. (1990). The Dietary and Nutritional Survey of British. Adults. London. HMSO
  3. Morris MS, Picciano MF, Jacques PF, Selhub J. (2008). Plasma pyridoxal 5’-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. Am J Clin Nutr
  4. Institute of Medicine. (1998). Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. National Academy Press
  5. Mackey A, Davis S, Gregory J. (2005). Vitamin B6, Modern Nutrition in Health and Disease. 10th ed. Baltimore. MD: Lippincott Williams & Wilkins
  6. McCormick D. (2006). Vitamin B6. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. 9th ed. Washington, DC: International Life Sciences Institute
  7. Subar AF, Krebs-Smith SM, Cook A, Kahle LL. (1998). Dietary sources of nutrients among US adults, 1989 to 1991. J Am Diet Assoc
  8. Reynolds. RD. (1988). Bioavailability of vitamin B-6 from plant foods. Am J Clin Nutr.
  9. Saposnik G, Ray JG, Sheridan P, McQueen M, Lonn E. (2009). Homocysteine-lowering therapy and stroke risk, severity, and disability: additional findings from the HOPE 2 trial. Stroke
  10. Riggs KM, Spiro A, Tucker K, Rush D. (1996). Relations of vitamin B-12, vitamin B-6, folate, and homocysteine to cognitive performance in the Normative Aging Study. Am J Clin Nutr
  11. Malouf R, Grimley Evans J. (2003). The effect of vitamin B6 on cognition. Cochrane Database Syst Rev
  12. Niebyl JR. (2010). Clinical practice. Nausea and vomiting in pregnancy. N Engl J Med
  13. Matthews A, Dowswell T, Haas DM, Doyle M, O’Mathuna DP. (2010). Interventions for nausea and vomiting in early pregnancy. Cochrane Database Syst Rev
  14. ACOG (American College of Obstetrics and Gynecology). (2004). Practice Bulletin: nausea and vomiting of pregnancy. Obstet Gynecol

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