There is a great deal of biological activity for which this group of vitamins is responsible, and there is also a great deal of overlap between the respective functions of each vitamin in the B-complex family. However, most of the overlap is centered around the metabolism of the three macronutrients (protein, carbohydrates and fat). Other tasks more specific to certain members of the B-complex group of vitamins include support for the brain and central nervous system, the growth and development of red blood cells, the maintenance of healthy skin and muscle tone, immune function and hormone activity. Metaphorically speaking, the B-complex family of vitamins can be described as the ‘transmission fluid' of the complex automobile that is the human body.

Vitamin B1 ( a.k.a. thiamin): Thiamin is required to convert glucose and amino acids into energy as well as to develop red blood cells and maintain muscle tissue. Thiamin is converted by the body into its active coenzyme form thiamin pyrophosphate (TPP). TPP is a catalyst for pyruvate dehydrogenase (PDH), a key enzyme responsible for the conversion of pyruvate into the all-important acetyl-CoA, which is central to the Kreb's Cycle that in turn generates cellular respiration. In ‘underdeveloped' countries, B1 deficiencies are usually found where foods made from white flour are staples. In the ‘developed' world, where such foods are often fortified with thiamin, the main reasons for deficiencies are alcohol consumption (which impairs thiamin absorption) and poor dietary choices. The most serious deficiencies can lead to degenerative nerve disorders such as beriberi and Wernicke-Korsakoff syndrome, diseases also common among chronic alcoholism.

Thiamin deficiency has also been linked to Type II Diabetes, particularly in the formation of advanced glycation endproducts (AGEs), which occur at an abnormally high rate among diabetics. Simply put, AGEs are cellular proteins that are damaged as a result of being exposed to glucose without the mediating action of a co-enzyme. Increased AGE occurrence is also commensurate with the aging process. Benfotiamine is a lipid-soluble form of thiamin that has been shown in studies to be 5 times more bioavailable than regular thiamin. In fact, clinical trials have demonstrated that benfotiamine can improve nerve function by 30% and decrease nerve pain by 50% among diabetics.

Vitamin B2 (a.k.a. Riboflavin): While playing a role in the energy metabolism of carbohydrates, fats, and proteins, B2 is particularly active in skin and vision health. B2 has long been used as an adjunct in the treatment of neonatal jaundice and has recently been added to anti-migraine protocols as well. Ariboflavinosis is the specific condition caused by riboflavin deficiency and its symptoms include sores around the mouth and swelling of the throat, cheilosis (cracks on the lips), and glossitis (inflammation of the tongue).

Vitamin B3 (a.k.a. Niacin): The derivatives of B3 form the basis of the oxidized and reduced forms of Nicotinamide Adenine Dinucleotide (NAD+ and NADH). The interaction between these coenzymes forms part of the basis (along with the aforementioned acetyl-CoA) of the Kreb's cycle, generating cellular respiration and energy in the form of ATP. B3 also plays an essential role in DNA repair, removing toxic chemicals from the body, and assisting in hormone production. Niacin is also effective at inhibiting the release of low-density lipoproteins (or LDL [bad] cholesterol) into the blood from the liver, making it a treatment of choice for hyperlipidemia.

Deficiency in B3 (combined with a deficiency in the essential amino acid tryptophan) can lead to a disease known as pellagra, characterized by deramatitis, insomnia, diarrhea, weakness and progressive dementia. Most niacin supplements are in nicotinic acid form, which has been associated with a ‘flushing' effect, an unpleasant warming and itching of the skin when taken at significant doses. Inositol hexanicotinate is a form of niacin that is free of this effect.

Vitamin B5 (a.k.a. Pantothenic acid): B5 is needed to form coenzyme A (later becoming acetyl-CoA), which is central to the Kreb's cycle and subsequent cellular respiration and energy production. Prior to this, however, pantothenic acid must first be converted into pantethine in the body, and the isolation of pantethine in supplement form has been able to produce results in clinical trials not seen with conventional pantothenic acid supplements (often in the form of calcium pantothenate or pantothenic acid). These results include lowered total and LDL (bad) cholesterol levels.

Vitamin B6 (a.k.a. Pyridoxine): Vitamin B6 is most commonly known as pyridoxine, but in fact B6 is comprised of three organic forms, namely pyridoxal, pyridoxine, and pyridoxamine. Each represents a different stage in the body's metabolism of this important vitamin. Pyridoxal-5'-phosphate, or P5P, represents the advanced stage of this metabolism, the stage at which B6 has been converted into a coenzyme, a catalyst for at least 113 known essential enzymatic reactions in the body. These include the metabolism of all endogenous amino acids, including such particularly crucial ones as tyrosine, glutamine, cysteine and glycine. P5P is also important for the proper metabolism of essential fatty acids as well as the formation of red blood cells and neurotransmitters, making P5P a factor in optimal cognitive function as well. Notable features of the latter include the fact that P5P is required to convert tryptophan into serotonin as well as to release glucose from glycogen.

Indeed, a deficiency in vitamin B6 can lead to anemia, depression, dermatitis, hypertension, elevated levels of homocysteine and water retention, insomnia, premenstrual tension, irritability, muscle twitching, convulsions, and kidney stones. B6 has been successfully studied for its ability to enhance the immune system and alleviate the symptoms of autism, carpal tunnel syndrome (CTS), anemia, premenstrual syndrome (PMS), hyperhomocysteinemia and other conditions. While the aforementioned studies used conventional B6 supplementation (mainly pyridoxine hydrochloride), it must be remembered that only the P5P converted from pyridoxine can be used for nitrogen and protein metabolism and heme synthesis. This underlines the potential for P5P in supplement form, especially in cases where the body's ability to synthesize it from its organic B6 forms is compromised in any way. In fact, it was found that in patients with impaired liver function, only 33% responded to pyridoxine hydrochloride supplementation with an increase in plasma P5P, where as all of the patients receiving P5P supplementation experienced an increase.

Vitamin B12 (a.k.a. Cyanocobalamin): Vitamin B12 has distinguished itself among the B-vitamins with the volumes of research attributable to its specific effects on neurological health. B12 is also very important to the methylation cycle. The successful studies with B12's neuroprotective and neurogenerative benefits were conducted with the methylcobalamin (the active coenzyme) form of B12.

Folic acid is needed for the synthesis of new red blood cells (which carry oxygen throughout the body) and DNA. Folic acid is often prescribed during pregnancy, as it reduces the risk of neural tube defects such as spina bifida in the fetus. A deficiency can also lead to megaloblastic anemia, a specific form of anemia caused by the inhibition of DNA synthesis in red blood cell production, as well as elevated levels of homocysteine. Biotin is another B vitamin that is inolved in the metabolism of protein, carbohydrates and fats, and finally, although not strictly a vitamin, choline is an essential nutrient that is often grouped with the B-complex. Choline is a nitrogen-based organic compound that is found in the lipids of cell membranes. As such, it plays an important role in the structural integrity of cells as well as in the movement of essential lipids across cell membranes and in the synthesis of the key neurotransmitter acetylcholine.

In summation, the B-complex family of vitamins is essential to processing and disseminating the fuel required to keep the evolutionist miracle known as the human body in constant operation. Maintaining the proper intake of this group of vitamins is indeed essential for keeping that operation as optimal as possible for as long as possible.

References

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Bertolini S, Donati C, Elicio N, et al. "Lipoprotein changes induced by pantethine in hyperlipoproteinemic patients: adults and children." Int J Clin Pharmacol Ther Toxicol. 1986 Nov; 24(11): 630-7.

Kira J, Tobimatsu S, Goto I. Vitamin B12 metabolism and massive-dose methyl vitamin B12 therapy in Japanese patients with multiple sclerosis. Intern Med. 1994 Feb; 33(2): 82-6.

Vitamin B6 (pyridoxine and pyridoxal 5'-phosphate) - monograph. Altern Med Rev. 2001 Feb;6(1):87-92.

Dietary vitamin b6 intake and the risk of colorectal cancer.
Cancer Epidemiol Biomarkers Prev. 2008 Jan;17(1):171-82.
Theodoratou E, Farrington SM, Tenesa A, McNeill G, Cetnarskyj R, Barnetson RA, Porteous ME, Dunlop MG, Campbell H.

Vitamin B6, a coenzyme in the folate metabolism pathway, may have anticarcinogenic effects. Laboratory and epidemiologic studies support the hypothesis of its protective effect against colorectal cancer (CRC). The aim of this large Scottish case-control study, including 2,028 hospital-based cases and 2,722 population-based controls, was to investigate the associations between dietary and supplementary intake of vitamin B6 and CRC. Three logistic regression models adjusted for several confounding factors, including energy, folate, and fiber intake, were applied in the whole sample and after age, sex, cancer site, folate, MTHFR C677T (rs1801133), MTHFR A1298C (rs1801131), MTR A2756G (rs1805087), and MTRR A66G (rs1801394) stratification (analysis on genotypes on 1,001 cases and 1,010 controls less than 55 years old). Moderately strong inverse and dose-dependent associations in the whole sample were found between CRC risk and the intake of dietary and total vitamin B6 in all three models [model III: odds ratio (OR), 0.77; 95% confidence interval (95% CI), 0.61-0.98; P for trend = 0.03; OR, 0.86; 95% CI, 0.69-1.07; P for trend = 0.12]. In addition, meta-analyses of published studies showed inverse associations between vitamin B6 and CRC (combined relative risk, 0.81; 95% CI, 0.68-0.96; test for overall effect P = 0.01; combined odds ratio, 0.67; 95% CI, 0.60-0.75; test for overall effect P < 0.00001). Analysis within the stratified subgroups showed similar associations apart from a stronger effect among those who were 55 or younger. Evidence from larger cohort and experimental studies is now required to confirm and define the anticarcinogenic actions of vitamin B6 and to explore the mechanisms by which this effect is mediated.

Vitamin B complex and homocysteine in chronic renal failure.
Nutr Hosp. 2007 Nov-Dec;22(6):661-71.
Sánchez C, Planells E, Aranda P, de la Cruz AP, Asensio C, Mataix J, Llopis J.


Metabolic, biochemical, and hormonal changes occur in chronic renal failure usually associated with hyponutrition states. In predialysis patients, knowing the nutritional state about water-soluble vitamins such as thiamine, riboflavin, pyridoxine, cianocobalamine, and folic acid is becoming more and more important since some of the manifestations of chronic renal failure may be due to the deficiency of some of these water-soluble vitamins. The metabolic pathways in which most of these vitamins participate are interrelated and it is difficult to understand how the individual deficits of each vitamin affect renal pathology. This work aims at reviewing not only this issue but also the status of these water-soluble vitamins that different authors have found in groups of predialysis patients. On the other hand, the issue on the high prevalence of hyperhomocysteinemia in chronic renal failure as the main mortality risk factor due to cardiovascular pathologies as well as the implication of these vitamins in the metabolism of homocysteine, and consequently in plasma levels of this metabolite in predialysis patients is reviewed.

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