Vitamin B6 supplementation may alter plasma free fatty acid (FFA) and amino acid concentrations during exercise without affecting endurance, according to this study conducted on 11 trained men. Blood was drawn pre, during (60 min), post, and post-60 min of exercise, and plasma was analyzed for glucose, lactate, glycerol, free fatty acids, catecholamines, and amino acids. Mean FFA concentrations changed over time in the tests, and the only significant changes in amino acid concentrations were for lower tyrosine and methionine concentrations in T2B6 relative to TIC at post-60 min of exercise and postexercise, respectively.
Virk RS, Dunton NJ, Young JC, Leklem JE: Effect of vitamin B-6 supplementation on fuels, catecholamines, and amino acids during exercise in men, Med Sci Sports Exerc 1999 Mar;31(3):400-8
Large doses of vitamin B6 may reduce the risk of kidney stone formation in women, according to this study conducted on 85,557 women over a period of 14 years. A total of 1078 incident cases of kidney stones were documented during the follow-up period, indicating that a high intake of vitamin B6 was inversely associated with risk of stone formation. While some evidence suggests that vitamin C may increase risk of kidney stones, this study found that vitamin C intake was not associated with risk.
Curhan GC, Willett WC, Speizer FE, Stampfer MJ: Intake of vitamins B6 and C and the risk of kidney stones in women, J Am Soc Nephrol 1999 Apr;10(4):840-5
To determine the effectiveness of pyridoxine for nausea and vomiting of pregnancy.
There was a significant decrease in the mean of posttherapy minus baseline nausea scores in the pyridoxine compared with that in the placebo group (t test, p = 0.0008). There was also a greater reduction in the mean number of vomiting episodes, but the differences did not reach statistical significance (p = 0.0552).
Pyridoxine is effective in relieving the severity of nausea in early pregnancy.
Pyridoxine for nausea and vomiting of pregnancy: a randomized, double-blind, placebo-controlled trial. Vutyavanich-T; Wongtra-ngan-S; Ruangsri-R. Am-J-Obstet-Gynecol. 1995 Sep; 173(3 Pt 1): 881-4.
Concerns about vitamin B-6 adequacy in neonatal nutrition relate to critical functions of the vitamin in development.
The vitamin B-6 concentration of milk and estimated intakes of the vitamin by breast-fed infants paralleled maternal supplements (ie, 2 and 27 mg). Plasma and erythrocyte measurements of infants correlated with their vitamin B-6 intakes; values were highest for infants given vitamin B-6 supplements and those that wee formula-fed. Vitamin B-6 adequacy was questionable for unsupplemented breast-fed infants of mothers in the 2-mg supplemented groups.
Vitamin B-6 adequacy in neonatal nutrition: associations with preterm delivery, type of feeding, and vitamin B-6 supplementation. Kang-Yoon-SA; Kirksey-A; Giacoia-GP; West-KD. Am-J-Clin-Nutr. 1995 Nov; 62(5): 932-42.
The use of vitamin B-6 may ease the symptoms of premenstrual syndrome, according to the results of nine trials involving 940 women. However, an excess of B-6 can cause nerve damage, and researchers do not recommend that women depend on vitamin B-6 alone to cure PMS. In doses of up to 100 mg, though, the vitamin may help to keep estrogen levels under control by aiding in the metabolism of hormones. PMS affects about 40% of women of childbearing age.
Wyatt, Katrina M.; et al: British Medical Journal; 1999; 318:1375-81
Erythrocyte and plasma B-6 vitamer concentrations were determined
All subjects had fasting plasma pyridoxal-5'-phosphate (PLP) concentrations indicative of adequacy. Erythrocyte B-6 vitamer and 4-pyridoxic acid (4-PA) concentrations of all three groups were not significantly different. Nonusers had significantly higher plasma PLP concentrations than did smokers, whereas PLP concentrations of chewers were intermediate between the two groups. Chewers had significantly higher concentrations of plasma pyridoxamine-5'-phosphate (PMP) than other groups. Plasma pyridoxal, pyridoxine, pyridoxamine, and 4-PA concentrations of the three groups were not significantly different. Differences in some B-6 vitamer concentrations in plasma but not in erythrocytes were observed between tobacco users and nonusers.
Erythrocyte and plasma B-6 vitamer concentrations of long-term tobacco smokers, chewers, and nonusers. Giraud-DW; Martin-HD; Driskell-JA. Am-J-Clin-Nutr. 1995 Jul; 62(1): 104-9.
Deficiency in vitamin B6 may lead to increased homocysteine levels and a decreased rate of protein metabolism in the liver, according to this animal study. Researchers fed rats with serine and either a low-pyridoxine diet or an adequate pyridoxine diet, then analyzed levels of homocysteine and protein metabolism products in blood and other fluids. Rats deficient in vitamin B6 exhibited greater levels of homocysteine, lower levels of enzymes needed for protein metabolism, and lower levels of proteins produced in serine metabolism than found in rats with adequate vitamin B6 levels.
Martinez M, Cuskelly GJ, Williamson J, Toth JP, Gregory JF 3rd: Vitamin B-6 deficiency in rats reduces hepatic serine hydroxymethyltransferase and cystathionine beta-synthase activities and rates of in vivo protein turnover, homocysteine remethylation and transsulfuration., J Nutr 2000 May;130(5):1115-23
Hyperhomocysteinemia & Vitamin B6
Vitamin B6 may help to lower homocysteine levels in patients with adequate levels of riboflavin and folate, according to this double-blind, randomized study conducted on 22 healthy elderly subjects. Patients received supplements of folic acid for 6 weeks and riboflavin for 18 weeks prior to treatment with vitamin B6. After this repletion time, patients then received 1.6 mg/d vitamin B6 or placebo for 12 weeks. Subjects who supplemented with vitamin B6 exhibited lower-than-baseline fasting homocysteine levels
McKinley MC, et al: Low-dose vitamin B-6 effectively lowers fasting plasma homocysteine in healthy elderly persons who are folate and riboflavin replete, Am J Clin Nutr 2001 Apr;73(4):759-64
Vitamin B6 may hinder colon tumor formation, according to this study performed on male ICR mice. The mice were fed special diets for 22 weeks that included 1, 7, 14, or 35 mg pyridoxine (PN) HCl/kg to determine if increasing amounts of vitamin B6 ingestion resulted in higher suppression of tumor growth. For the first ten weeks of their diet, mice were injected with azoxymethane (5mg/kg body) to promote colon tumorigenesis. The diets including 7, 14, and 35 mg PN HCl/kg were found to reduce the levels of c-myc and c-fos proteins and decrease the number of resulting colon tumors. The authors suggest that higher intakes of vitamin B6 lessen the risk of colon tumor formation by reducing cell proliferation.
Komatsu Si S, Watanabe H, Oka T, Tsuge H, Nii H, Kato N: Vitamin B6-supplemented diets compared with a low vitamin B6 diet suppress azoxymethane-induced colon tumorigenesis in mice by reducing cell proliferation, J Nutr 2001 Aug;131(8):2204-2207
Tardive dyskinesia is an abnormal condition characterized by involuntary, repetitious movements of the muscles of the face, limbs, and trunk. It usually affects older people who have been treated for long periods of time with phenothiazine, a dopamine-blocker. Vitamin B6 supplements may help ameliorate the symptoms of tardive dyskinesia, according to this double-blind study conducted on fifteen schizophrenia patients. The patients, who met specific research diagnostic criteria, were randomly assigned to receive vitamin B6 supplements or placebo for four weeks. The patients' progress was measured weekly by the Exptrapyramidal Symptom Rating Scale. During the third week of treatment, participants receiving supplements showed significantly more improvement than those receiving placebo.
Lerner V, et al: Vitamin B(6) in the treatment of tardive dyskinesia: a double-blind, placebo-controlled, crossover study, Am J Psychiatry 2001 Sep;158(9):1511-4
Schizophrenia & Vitamin B-6
Although vitamin B6 is important in the synthesis of certain neurotransmitters, it may not influence psychotic symptoms in schizophrenia or schizoaffective disorder, according to this study. In this nine-week long double-blind, placebo-controlled study, fifteen patients were randomly assigned to receive placebo or vitamin B6. Doses began at 100 mg/day the first week and increased by 100 mg/day each of the three remaining weeks. The patients were assessed once a week using the Positive and Negative Syndrome Scale for schizophrenia. No major differences in the mental states of the patients were seen between the vitamin B6 and placebo groups. The authors suggest that studies involving more participants with a shorter duration of illness could better clarify the efficacy of vitamin B6 in treating psychotic symptoms in schizophrenia.
Lerner V, Miodownik C, Kaptsan A, Cohen H, Loewenthal U, Kotler M: Vitamin B6 as add-on treatment in chronic schizophrenia and schizoaffective patients: a double-blind, placebo-controlled study, J Clin Psychiatry 2002 Jan;63(1):54-8
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