Understanding B Vitamins
Thursday, November 12, 2009
The water-soluble B vitamins are collectively referred to as B complex. They include thiamin (B1), riboflavin (B2), niacin or niacinamide (B3), pyridoxine (B6), folic acid, vitamin B12, biotin and pantothenic acid (B5). In addition, choline, inositol and PABA (para-aminobenzoic acid) are compounds that are not technically B vitamins, but which have related functions and so are often included with B complex products. Each of the B vitamins has its own functions to serve in the body; but, in general, they play a role in energy metabolism and promote homeostasis when the body is under stress. The use of the entire B complex is recommended, since the individual B vitamins affect one another’s absorption, metabolism and excretion.1
Energizing Vitamin
Each of the B vitamins is converted into coenzymes in the body. These B vitamin coenzymes are involved, directly or indirectly, in energy metabolism. Some facilitate the energy-releasing reactions themselves within the mitochondria; others help build new cells to deliver the oxygen and nutrients that permit the energy pathways to run. Research shows thiamin is essential for the oxidative decarboxylation of the multienzyme branched-chain ketoacid dehydrogenase complexes of the citric acid cycle; riboflavin is required for the flavoenzymes of the respiratory chain; NADH is synthesized from niacin and is required to supply protons for oxidative phosphorylation; pantothenic acid is required for coenzyme A formation, and is also essential for alpha-ketoglutarate and pyruvate dehydrogenase complexes as well as fatty acid oxidation; and biotin is the coenzyme of decarboxylases required for gluconeogenesis and fatty acid oxidation.2 Folic acid and choline are believed to be central methyl donors required for mitochondrial protein and nucleic acid synthesis through their active forms.3
Active individuals with poor or marginal nutritional status for a B vitamin may have decreased ability to perform exercise at high intensity. Exercise stresses metabolic pathways that depend on thiamine, riboflavin and B6. Consequently, the requirements for these vitamins may be increased in athletes and active individuals.4 In fact, exercise could increase the need for these micronutrients in several ways: through decreased absorption of the nutrients; by increased turnover, metabolism or loss of the nutrients; through biochemical adaptation as a result of training that increases nutrient needs; by an increase in mitochondrial enzymes that require the nutrients; or through an increased need for the nutrients for tissue maintenance and repair. Other research suggests exercise may increase the requirements for riboflavin and vitamin B6, and possibly for folic acid and vitamin B12.5 Biochemical evidence of deficiencies in some of these vitamins in active individuals has been reported, including riboflavin and B6.6 Exercise appears to decrease nutrient status even further in active individuals with preexisting marginal vitamin intakes or marginal body stores. Thus, active individuals who restrict their energy intake or make poor dietary choices are at greatest risk for poor B vitamin status, and should consider supplementing with B complex vitamins
Stressed Out
B complex vitamins are intimately involved in the function of the nervous system,7 and so can play a role in helping to counter some of the negative effects of stress. In fact, the ability of humans to respond to stresses can be influenced by nutritional status—including the status of key B vitamins.8 Studies have shown B1 and B6 together are especially necessary for workers whose activity is associated with nervous/emotional stress.9,10
Research on individual B vitamins reveals important roles where stress and the nervous system are concerned. For example, B1 was found to reduce the effects of catabolic (i.e., breaking down tissues) stress hormones resulting from surgery.11 It also protected the adrenal glands from functional exhaustion. Pantothenic acid is intimately involved in adrenal function, and the production of adrenal hormones associated with stress.12 Niacinamide has been found to reduce certain neurological damage caused by oxidative stress,13 as well as to prevent heart disturbances that resulted from emotional/painful stress.14,15 Vitamin B6 deficiency has been found to be related to increased psychological distress in recently bereaved men;16 supplementation with B6 is suggested as part of an overall program for stress.17 Vitamin B12 is also necessary for nervous system functioning, and a deficiency can lead to fatigue and degeneration of peripheral nerves.18
1. Whitney E, Rolfes S. “Understanding Nutrition, Ninth Ed.” Belmont, CA: Wadsworth/Thomson Learning; 2002.
2. Depeint F et al. “Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism.” Chem Biol Interact. 2006;163(1-2):94-112.
3. Depeint F et al. “Mitochondrial function and toxicity: role of B vitamins on the one-carbon transfer pathways.” Chem Biol Interact. 2006;163(1-2):113-32.
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6. Manore MM. Op cit.
7. Whitney E, Rolfes S. Op cit.
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12. Kutsky R. “Handbook of Vitamins and Hormones.” New York: Van Nostrand Reinhold Company; 1973:208.
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14. Meerson FZ, Manukhina EB, Dosmagambetova RS. “[Disorders of contractile function and adrenoreactivity of the portal vein in emotionally-painful stress and experimental myocardial infarct and their prevention by means of membrane protectors].” Kardiologiia 1984; 24(4):104-8.
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16. Baldewicz T et al. “Plasma pyridoxine deficiency is related to increased psychological distress in recently bereaved homosexual men.” Psychosom Med. 1998; 60(3):297-308.
17. Teggin AF, van Niekerk JP. “Manifestations and management of stress.” S Afr Med J. 1981;59(21):751-2.
18. Whitney E, Rolfes S. Op cit.
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24. Woodside JV et al. “Antioxidants, but not B-group vitamins increase the resistance to low-density lipoprotein to oxidation: a randomised, factorial design, placebo-controlled trial.” Atherosclerosis. 1999; 144(2):419-27.
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26. Suliman ME et al. “Effects of high-dose folic acid and pyridoxine on plasma and erythrocyte sulfur amino acids in hemodialysis patients.” J Am Soc Nephrol. 1999; 10(6):1287-96.
27. Mansoor MA et al. “Plasma total homocysteine response to oral doses of folic acid and pyridoxine hydrochloride (vitamin B6) in healthy individuals. Oral doses of vitamin B6 reduce concentration of serum folate.” Scand J Clin Lab Invest. 1999; 59(2):139-46