Vitamin B6 nutriture during pregnancy and lactation. I. Vitamin B6 intake, levels of the vitamin in biological fluids, and condition of the infant at birth.

Vitamin B6 nutriture was assessed during pregnancy and lactation to determine possible relationships among vitamin B6 intake, levels of the vitamin in biological fluids and the condition of the infant at birth. Vitamin B6 levels were measured in maternal serum and in urine at 5 and 7 months gestation and at delivery, in cord serum and in milk at 3 and 14 days postpartum. Intake of vitamin B6, less than the Recommended Dietary Allowances (1974) for pregnancy and lactation, 2.5 mg/day, resulted in lower levels of the vitamin in maternal serum at delivery and in cord serum than higher intakes. Mothers whose infants had unsatisfactory Apgar scores at 1 min, (less than 7) had significantly low intakes of vitamin B6 and lower levels of the vitamin in both serum and milk than mothers whose infants had satisfactory scores, (greater than or equal to 7). At 5 months gestation, levels of vitamin B6 in maternal serum were significantly correlated with levels of the vitamin in cord serum and in milk at 14 days postpartum. This stage of gestation precedes the period of rapid growth of the central nervous system of the fetus, and is, therefore, a critical time for the assessment of maternal vitamin B6 nutriture.     

The effect of vitamin B6 deficiency on food intake, growth, and renal function in chronically azotemic rats

Chronically uremic patients appear to have an increased nutritional requirement for vitamin B6, and vitamin B6 deficiency occurs frequently when such individuals do not receive supplements of this vitamin. Since manifestations of vitamin B6 deficiency in renal failure are not well defined, this study examined two aspects of the chronic renal failure syndrome which might be influenced by vitamin B6: impaired growth and progressive loss of renal function. We examined food intake, weight gain, the food efficiency ratio, degree of azotemia, and renal function in chronically azotemic rats pair-fed for 6 weeks either a vitamin B6-deficient diet or a diet containing a surfeit of vitamin B6. In the azotemic vitamin B6-deficient rats, as compared to the azotemic B6-replete rats, there was evidence of reduced appetite, decreased weight gain, a lower food efficiency ratio, increased azotemia, and a reduced glomerular filtration rate as estimated from the urea clearance or the mean of the urea and creatinine clearances. These findings suggest that vitamin B6 deficiency may contribute to decreased food intake, reduced growth, and lower renal function in animals with chronic renal insufficiency.     

Effect of exercise on the metabolism of vitamin B6 and some PLP-dependent enzymes in young rats fed a restricted vitamin B6 diet

The effect of exercise on vitamin B6 metabolism and PLP-dependent enzymes was studied in rats fed a diet with or without vitamin B6. Metabolism of some amino acids (citrulline, arginine, ornithine and threonine) inhibited in the B6-deficient rats was normalized during exercise. Exercise was also effective in storing vitamin B6 in the body by lowering excretion of vitamin B6, when intake of vitamin B6 was restricted. Aspartatae aminotransferase activity was higher in the red portion of the gastrocnemius muscle than that of the white one, whereas glycogen phosphorylase activity was vice versa and furthermore glycogen content in the white portion was very low in the vitamin B6-deficient rat. From the data obtained, it has been suggested that the red and white portions of the gastrocnemius muscle seemed to be more important in metabolizing amino acids and hydrolyze glycogen, respectively.     

Effects of different levels of vitamin B-6 supplementation on vitamin B-6 concentrations in human milk and vitamin B-6 intakes of breastfed infants

Vitamin B-6 has been reported to vary in concentration in human milk in response to changes in maternal intake of the vitamin. This study examined the effects of such changes on the breastfed infants' intake of vitamin B-6. Lactating mothers received 0, 2.5, 10.0 or 20.0 mg pyridoxine X HCl (PN X HCl) for 3 consecutive days in addition to dietary sources. Dietary intakes of vitamin B-6 (mean = 1.8 +/- 0.2 mg/day) were similar among the four groups. Vitamin B-6 was determined in milk samples from each feeding and milk intakes of infants were estimated by test-weighing. Nonsupplemented mothers had lower vitamin B-6 in their milk (93 +/- 8 micrograms/L) and vitamin B-6 intake of their infants was lower (0.06 +/- 0.01 mg/day) compared to other groups. Maternal supplementation with 2.5, 10.0 or 20.0 mg PN X HCl was paralleled by vitamin B-6 levels in milk of 192 +/- 16, 247 +/- 25 and 413 +/- 45 micrograms/L, respectively, and by vitamin B-6 intakes of breastfed infants of 0.12 +/- 0.02, 0.22 +/- 0.02 and 0.28 +/- 0.03 mg/day, respectively. When maternal intakes of vitamin B-6 approximated 20.0 mg/day, breastfed infants were unlikely to receive the current RDA of 0.3 mg vitamin B-6/day.     

Dietary intake of total and glycosylated vitamin B-6 and the vitamin B-6 nutritional status of unsupplemented lactating women and their infants

The mean dietary intakes of total and glycosylated vitamin B-6, determined from analysis of 3-d diet composites collected from 30 lactating women, were 8.63 +/- 4.04 and 1.33 +/- 0.85 mumol/d (mean +/- SD), respectively. A comparison of linear regression models that either included or excluded dietary glycosylated vitamin B-6 content indicates that the intake of glycosylated vitamin B-6 had little, if any, effect upon maternal plasma pyridoxal 5'-phosphate concentration and maternal urinary excretion of total vitamin B-6 and 4-pyridoxic acid. On the basis of guidelines from the literature for evaluating biochemical indices of vitamin B-6 nutriture, the women appeared to be consuming adequate amounts of the vitamin. The mean breast-milk concentrations of total and glycosylated vitamin B-6 were 733 and 18 nmol/L, respectively. Infant plasma pyridoxal 5'-phosphate concentration was 54 +/- 44 nmol/L (mean +/- SD) and all infants had lengths and weights appropriate for age.     

Effects of different levels of vitamin C intake on the vitamin C concentration in human milk and the vitamin C intakes of breast-fed infants

The influence of maternal intake of vitamin C on the vitamin C concentration in human milk and on the vitamin C intakes of breast-fed infants has not been demonstrated conclusively. This study examined these influences of diet and supplementation in 25 lactating women administered 90 mg of ascorbic acid for 1 day followed by 250, 500 or 1000 mg/day for 2 days or unsupplemented for 1 day followed by either 0 or 90 mg ascorbic acid supplement for 2 days. Vitamin C content in milk and urine was determined by the 2,4-dinitrophenylhydrazine method. Vitamin C intakes of infants were calculated from milk volume, as determined by the test-weighing method and from vitamin C levels in milk samples obtained at each feeding. Total maternal intakes of vitamin C, which exceeded 1000 mg/day or 10-fold the RDA for lactation (100 mg/day), did not significantly influence the vitamin C content in milk or the vitamin C intakes of infants. However, maternal vitamin C intake was positively correlated (r = 0.7) with maternal urinary excretion. These differences in milk and urine response to vitamin C intake suggest a regulatory mechanism for vitamin C levels in milk.     

Differences in vitamin B6 status indicator responses between young and middle-aged women fed constant diets with two levels of vitamin B6

The responses of adult women to two levels of vitamin B6, was conducted with five young and eight middle-aged subjects. A constant diet (2.3-2.4 mg vitamin B6 per day) was fed for four weeks followed by three weeks of the same diet supplemented with 8.0 mg pyridoxine. Plasma pyridoxal 5'-phosphate (PLP), plasma and urinary vitamin B6, and urinary 4-pyridoxic acid (4-PA) were determined. The older women had significantly lower plasma PLP, plasma and urinary vitamin B6 and slightly higher urinary 4-PA values on normal vitamin B6 intakes. With supplementation, only the difference in urinary total vitamin B6 remained significant. Tryptophan load tests revealed no significant between-group differences in xanthurenic acid or kynurenic acid excretion. These results demonstrate an age-related difference in vitamin B6 status indicators in women under controlled dietary intake of vitamin B6.     

叶酸联合维生素B6/B12心对脑缺血半暗带区影响

目的 研究叶酸(FA)、维生素B6(VB6)和维生素B12(VB12)对局灶性脑缺血-中脑动脉闭塞(MCAO)大鼠缺血半暗带区(ischemie penumbra,IP)的影响.方法 将SD大鼠随机分为中脑动脉闭塞模型组(MCAO)、MCAO+叶酸组(MCAO+FA)和MCAO+复合维生素(叶酸+VB6+VB12)组(MCAO+CV);预防性给药28 d后,手术制备各组大鼠大脑中动脉闭塞(MCAO)模型,造成局灶性脑缺血,对脑部进行磁共振(MRI)扫描,观察预防性给予叶酸及其联合VB6及VB12,对缺血半暗带区的改善效果.结果 缺血后6 h,半暗带区表观弥散系数(ADC):MCAO+FA组为0.61±0.04,MCAO+CV组为0.63±0.04,均高于MCAO组的0.50±0.05(P<0.05),2组平均弥散系数(DCavg)依次为0.74±0.04,0.77±0.06,均高于MCAO组的0.67±0.04(P<0.05),MCAO组部分各向异性值(FA)为0.80±0.06,高于MCAO组的0.62±0.04(P<0.05).结论 补充叶酸能使脑缺血半暗带区向正常灌注区发展,抑制缺血核心区的扩大,联合补充VB6和VB12效果更佳.     

Effects of seven low-dose combined contraceptives on vitamin B6 status

The effect of seven low-dose oral contraceptive preparations on vitamin B6 status was investigated in 55 women. All preparations contained about the same amount of ethinylestradiol but differed in the content and type of progestagen. The following preparations were investigated: monophasic and triphasic levonorgestrel, monophasic and biphasic desogestrel, monophasic norethisterone, monophasic cyproterone acetate and triphasic gestodene. The vitamin B6 status was evaluated by measuring erythrocyte glutamate oxaloacetate transaminase (EGOT) activity and its degree of in vitro stimulation. From these two variables the total EGOT activity was calculated. In addition plasma pyridoxal-5'-phosphate (PLP) levels were estimated. After six months' treatment, EGOT activity and the calculated total EGOT activity were increased, but no changes were observed in the degree of in vitro stimulation (which is a more reliable parameter). Plasma PLP levels initially decreased during the first three months of treatment but after six months a return to normal levels was observed. Differences between the seven preparations were not found. We conclude from these results that the low-dose preparations investigated in this study have no any adverse effects on vitamin B6 status.     

Evaluation of vitamin B6 intake and status of 20- to 64-year-old Koreans

BACKGROUND/OBJECTIVES

Recent research regarding vitamin B₆ status including biochemical index is limited. Thus, this study estimated intakes and major food sources of vitamin B₆; determined plasma pyridoxal 5''-phosphate (PLP); and assessed vitamin B₆ status of Korean adults.

MATERIALS/METHODS

Three consecutive 24-h diet recalls and fasting blood samples were collected from healthy 20- to 64-year-old adults (n = 254) living in the Seoul metropolitan area, cities of Kwangju and Gumi, Korea. Vitamin B₆ intake and plasma PLP were analyzed by gender and by vitamin B₆ supplementation. Pearson''s correlation coefficient was used to determine associations of vitamin B₆ intake and plasma PLP.

RESULTS

The mean dietary and total (dietary plus supplemental) vitamin B₆ intake was 1.94 ± 0.64 and 2.41 ± 1.45 mg/day, respectively. Median (50th percentile) dietary intake of men and women was 2.062 and 1.706 mg/day. Foods from plant sources provided 70.61% of dietary vitamin B₆ intake. Only 6.3% of subjects consumed total vitamin B₆ less than Estimated Average Requirements. Plasma PLP concentration of all subjects was 40.03 ± 23.71 nmol/L. The concentration of users of vitamin B₆ supplements was significantly higher than that of nonusers (P < 0.001). Approximately 16% of Korean adults had PLP levels < 20 nmol/L, indicating a biochemical deficiency of vitamin B₆, while 19.7% had marginal vitamin B₆ status. Plasma PLP concentration showed positive correlation with total vitamin B₆ intake (r = 0.40984, P < 0.0001).

CONCLUSIONS

In this study, vitamin B₆ intake of Korean adults was generally adequate. However, one-third of subjects had vitamin B₆ deficiency or marginal status. Therefore, in some adults in Korea, consumption of vitamin B₆-rich food sources should be encouraged.     

Folate and vitamin B(6) intake and risk of acute myocardial infarction in Italy

BACKGROUND: Folate and vitamin B6 intake has been associated with reduced risk of coronary heart disease, but studies are not consistent. OBJECTIVE: The relation between folate and vitamin B6 intake and the risk of acute myocardial infarction (AMI) was assessed in a Mediterranean population. DESIGN: A hospital-based case-control study was conducted in Milan, Italy, between 1995 and 1999. Information was collected by interviewer-administered questionnaires. Adjusted odds ratios (ORs) and 95% confidence intervals (CI) were obtained by multiple logistic regression models. SUBJECTS: Cases were 507 patients with a first episode of nonfatal AMI, and controls were 478 patients admitted to hospital for acute conditions. RESULTS: Compared to patients in the lowest tertile of intake, the ORs for those in the highest tertile were 0.56 (95% CI 0.35-0.88) for folate and 0.34 (95% CI 0.19-0.60) for vitamin B6. The OR was consistently below unity in strata of sex, age, alcohol, methionine, tobacco smoking, coffee, hypertension and family history of AMI; the inverse association was apparently stronger for vitamin B6 in regular alcohol drinkers than in no or occasional drinkers. Compared to subjects with a low intake of both micronutrients, the OR was 0.29 for those with a high intake of both. Compared to subjects reporting no or occasional alcohol drinking and low methionine and folate intake, the OR was 0.28 in regular drinkers with high methionine and high folate intake. The corresponding value for vitamin B6 was 0.25. CONCLUSIONS: A high intake of folates, vitamin B6 and their combination is inversely associated with AMI risk. SPONSORSHIP: Partly supported by "Ministero della Salute" (Contract No. 177, RF 2001).     

In vivo and in vitro inhibition of B16 melanoma growth by vitamin B6

The effect of vitamin B6 on the growth of B16 melanoma cells in vivo and in vitro was studied. B16 melanoma cells grown for three days in medium supplemented with 5.0 mM pyridoxine or 0.5 mM pyridoxal showed an 80% reduction in cell proliferation compared with control culture. Cells cultured for six hours in medium supplemented with 0.5 mM pyridoxal took up and incorporated 13 and 32% less [3H]thymidine, respectively, than did control cultures. A 17% reduction in [3H]glucose uptake was observed at this time point. When the incubation time was decreased to three hours, an inhibition of cellular uptake of [3H]thymidine (22%), [3H]uridine (14%), and [3H]glucose (15%) was observed; however, little or no inhibition in incorporation was detected. In in vivo studies, mice pretreated with pyridoxal for two weeks and then injected with B16 melanoma cells had a 62% reduction in tumor weight compared with controls at the end of a three-week period. If tumors were first established in mice and then treated with pyridoxal for six days, a 39% reduction in tumor growth was observed. There were no differences observed in body weights or liver weights in any of the animal groups. These results indicate that supraphysiological doses of vitamin B6 can inhibit the growth of B16 melanoma cells both in vitro and in vivo. The exact mechanism by which pyridoxal exerts its inhibitory effect was not ascertained, but experiments suggest that the vitamer may be acting on the plasma membrane to reduce precursor transport into the cell.     

孕期摄入维生素D对婴幼儿哮喘发生率影响的系统回顾和荟萃分析

目的 进行孕期摄入维生素D对婴幼儿哮喘发生率影响的系统分析。方法 检索中国知网、万方数据库、维普科技期刊数据库、PubMed数据库、OVID数据库,收集国内外关于孕期摄入维生素D对婴幼儿哮喘发生率影响的研究进行Meta分析。结果 5篇前瞻性队列研究文献和4篇RCT文献纳入研究。1)对5项前瞻性队列研究进行描述性分析显示,孕期饮食维生素D摄入量高的孕妇比摄入量低的孕妇其后代发生哮喘及喘息的几率较小,差异均具有统计学意义。2)对4项RCT中的2项进行Meta分析,共1 355组孕妇-婴幼儿纳入研究,其中补充维生素D组683例,安慰剂对照组672组,结果显示补充维生素D组的孕妇比安慰剂组的孕妇后代发生婴幼儿哮喘的风险较小(OR=0.71,95%CI:0.54～0.92,P=0.01)。结论 孕期摄入较大剂量的维生素D有助于减少婴幼儿哮喘的发生率。     

Dietary intake of vitamin B(6) and risk of breast cancer in Taiwanese women

Background

B vitamins, including vitamin B₆, are coenzymes that are important for DNA integrity and stability. Deficiencies in B vitamins may promote tumor carcinogenesis.

Methods

We examined the association of dietary vitamin B₆ intake with overall breast cancer risk and breast cancers stratified by hormone receptor status. This case-control study included 391 breast cancer cases and 782 control subjects enrolled at the Tri-Service General Hospital in Taipei, Taiwan. Energy-adjusted intake of vitamin B₆ was derived from a food frequency questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression.

Results

As compared with women in the lowest tertile, the multivariate-adjusted ORs for breast cancer among women in the second and highest tertiles of vitamin B₆ intake were 0.78 (95% CI, 0.64–2.52) and 0.64 (0.26–0.92), respectively. In addition, higher vitamin B₆ intake was associated with a significantly lower risk of developing ER-negative breast tumors.

Conclusions

Our findings suggest that higher intake of vitamin B₆ is associated with a reduction in breast cancer risk, particularly ER-negative tumors.Key words: breast cancer, ER-defined breast tumors, 1-carbon metabolism, vitamin B₆