Assessment of vitamin B-6 estimated average requirement and recommended dietary allowance for adolescents aged 13-15 years using vitamin B-6 intake, nutritional status and anthropometry

Because of limited available information, the Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) of vitamin B-6 for adolescents were recently estimated by extrapolation from adult values. To determine vitamin B-6 requirements and to provide recommendations for intakes, vitamin B-6 intake, nutritional status and anthropometry were studied in 134 healthy adolescents (63 boys and 71 girls) aged 13-15 y in Tainan, Taiwan. Direct and indirect vitamin B-6 indicators were measured in plasma, erythrocytes and urine. The anthropometric data of the adolescents in this study were similar to those of the first Nutrition and Health Survey in Taiwan (NAHSIT), conducted from 1993 to 1996, showing the normal growth and development of this adolescent group. All subjects had plasma pyridoxal-5'-phosphate (PLP) concentrations > or = 20 nmol/L, indicating an adequate vitamin B-6 status. The mean dietary vitamin B-6 intakes of boys and girls were 1.04 +/- 0.24 and 0.83 +/- 0.26 mg/d, respectively. Vitamin B-6 status indicators, including plasma PLP, erythrocyte alanine activity coefficient (EALT-AC), aspartate aminotransferase activity coefficient (EAST-AC) and urinary 4-pyridoxic acid (4-PA), were correlated with vitamin B-6 intake (r = 0.84, -0.84, -0.77 and 0.86, respectively, P < 0.01). Adequate values of plasma PLP (> or = 20 nmol/L), EALT-AC (<1.25), EAST-AC (<1.8) and urinary 4-PA (>3.0 micromol/d) were used to determine the EAR according to the Dietary Reference Intake committee methodology. The present study suggests that vitamin B-6 EAR (RDA) for adolescent boys and girls aged 13-15 y are 1.07 (1.28) and 0.90 (1.08) mg/d, respectively.     

Vitamin B6 status assessment in relation to dietary intake in high school students aged 16-18 years

The vitamin B6 status of high school students and its relationship with dietary intake were investigated in this cross-sectional study by face-to-face interview. A total of 157 healthy students aged 16-18 years (eighty-three boys and seventy-four girls) were randomly recruited from two out of nineteen senior high schools in Tainan, Taiwan. Vitamin B6 intakes were calculated from three 24-h dietary records. Direct and indirect vitamin B6 status indicators were measured in plasma, erythrocytes and urine. The anthropometric data, being similar to those of the first Nutrition and Health Survey in Taiwan (1993-1996), showed the normal growth and development of these students. All students except one girl (28.7 nmol/l) had plasma pyridoxal-5'-phosphate (PLP) levels >35 nmol/l, indicating an adequate vitamin B6 status. The mean dietary vitamin B6 intakes of boys and girls were 1.04 (sd 0.29) and 0.96 (sd 0.27) mg/d, respectively. Vitamin B6 status indicators, including plasma PLP, erythrocyte alanine aminotransferase activity coefficient (EALT-AC), aspartate aminotransferase activity coefficient (EAST-AC) and urinary 4-pyridoxic acid (4-PA), were correlated with vitamin B6 intake. Students with adequate values of plasma PLP (>35 nmol/l), EALT-AC ( < 1.25), EAST-AC ( < 1.8) and urinary 4-PA (>3.0 micromol/d) had median intakes of 1.08 and 1.01 mg/d, respectively, for boys and girls. This study suggests that vitamin B6 requirements for boys and girls aged 16-18 years were approximately 1.1 and 1.0 mg/d, respectively.     

Assessment of vitamin B-6 status in young women consuming a controlled diet containing four levels of vitamin B-6 provides an estimated average requirement and recommended dietary allowance

The Recommended Dietary Allowance (RDA) of vitamin B-6 for young women was recently reduced from 1.6 to 1.3 mg/d based on an adequate plasma pyridoxal phosphate (PLP) concentration of 20 nmol/L. To assess vitamin B-6 requirements and suggest recommendations for intake, seven healthy young women consumed a controlled diet providing 1.2 g protein/kg body weight for a 7-d adjustment period (1.0 mg vitamin B-6/d) and three successive 14-d experimental periods (1.5, 2.1 and 2.7 mg/d, respectively). Direct and indirect vitamin B-6 status indicators were measured in plasma, erythrocytes and urine. Indicators most strongly correlated with vitamin B-6 intake [i.e., plasma and erythrocyte PLP, urinary 4-pyridoxic acid (4-PA) and total vitamin B-6] were regressed on vitamin B-6 intake and the dietary vitamin B-6 to protein ratio. Inverse prediction using adequate and baseline values estimated vitamin B-6 requirement. Adequate values were determined for plasma PLP and urinary 4-PA from baseline values of 60 previous subjects, using the statistical method suggested by Sauberlich. The current study suggests a vitamin B-6 Estimated Average Requirement (EAR) for young women of 1.1 mg/d or 0.016 mg/g protein, and a RDA of 1.5 mg/d or 0.020 mg/g protein. When results from this study are combined with data from four other recent studies, the combined data predict an EAR of 1.2 mg/d or 0.015 mg/g protein, and a RDA of 1.7 mg/d or 0.018 mg/g protein. This study suggests that the current vitamin B-6 RDA may not be adequate.     

Plasma pyridoxal 5'-phosphate concentration is correlated with functional vitamin B-6 indices in patients with rheumatoid arthritis and marginal vitamin B-6 status

Many patients with rheumatoid arthritis (RA) have low plasma pyridoxal-phosphate (PLP) but a normal erythrocyte aspartate aminotransferase activity coefficient (alpha EAST), a measure of vitamin B-6 status in the erythrocytes, compared with healthy subjects. The goal of the present study was to examine the correlations of PLP levels in these two compartments (plasma and erythrocytes) with other established indices of vitamin B-6 status, and to determine which indicator better reflects functional status of vitamin B-6 in patients with RA. Multiple indices of vitamin B-6 status were measured in 33 patients with RA. Plasma PLP, urinary 4-pyridoxic acid (4-PA), net increase in plasma total homocysteine after a methionine load (DeltatHcy) and net increase in urinary xanthurenic acid after a tryptophan load (DeltaXA) were log-transformed to reach normality for statistical analyses. We found that log-plasma PLP levels were inversely correlated with both log-DeltatHcy (r = -0.368, P = 0.035) and log-DeltaXA (r = -0.333, P = 0.05). Plasma PLP was not correlated with alpha EAST or urinary 4-PA excretion. In contrast, erythrocyte PLP was inversely correlated with alpha EAST (r = -0.431, P = 0.012) and positively correlated with log-4-PA (r = 0.475, P = 0.005), but erythrocyte PLP was not correlated with the outcomes of a methionine or tryptophan load test. Erythrocyte PLP and log-4-PA, but not plasma PLP, were correlated with dietary intake of vitamin B-6 after adjusting for protein intake (r = 0.420, P = 0.015 and r = 0.333, P = 0.05, respectively). We suggest that in patients with RA, plasma PLP levels are a better diagnostic indicator of functional vitamin B-6 status than erythrocyte PLP levels.     

Vitamin B6 intakes and status assessment of elderly men and women in Taiwan.

Studies have indicated that vitamin B6 status decreases with age. However, little is known about vitamin B6 status of elderly people in Taiwan. The purpose of this study was to assess vitamin B6 status of elderly Taiwanese and to examine the effect of protein on various indices of vitamin B6 status in the elderly. Thirty-nine men (mean age = 69.9 +/- 4.2 years) and 55 women (mean age = 69.5 +/- 3.9 years) completed a 24-h diet recall. The mean total vitamin B6 intake (men: 1.7 +/- 0.9 g/day; women: 1.6 +/- 1.2 g/day) was higher than the 1998 US Dietary Reference Intakes (DRI) and the current Taiwan Recommended Daily Nutrient Allowance (RDNA). Dietary energy and protein intakes were not related to any vitamin B6 status parameters in any sex groups and the pooled group. Vitamin B6 intake correlated only with erythrocyte aspartate transaminase activity coefficient (EAST-AC) in the pooled (r = -0.214, p < 0.05) group. There were no significant differences in plasma pyridoxal 5'-phosphate (PLP), erythrocyte alanine transaminase activity coefficient (EALT-AC), and EAST-AC between sex groups. Although elderly subjects had adequate mean plasma PLP concentrations, 59% of men and 55% of women had plasma PLP concentrations lower than a cutoff of 20 nmol/L. The mean EALT-AC was < 1.25 in two groups with adequate vitamin B6 status. However, 23% of men and 18% of women had EALT-AC values > 1.25. The mean EAST-AC value of subjects was higher than the suggested value (< 1.8) for inadequate vitamin B6 status. The incidence of biochemical vitamin B6 deficiency in our elderly is probably more relevant from other causes than from dietary intake of protein and vitamin B6.     

Vitamin B-6 requirements of elderly men and women

The vitamin B-6 requirements of 12 men and women over 60 y old were studied. The protocol consisted of a 5-d baseline period and four experimental periods during which the subjects successively received 0.003, 0.015, 0.0225 and 0.03375 mg of vitamin B-6/(kg body wt.d). Dietary protein was 1.2 or 0.8 g/(kg body wt.d). At 5- or 6-d intervals, xanthurenic acid (XA) after a 5-g L-tryptophan load and 4-pyridoxic acid (4-PA) in 24-h urine, erythrocyte aspartate aminotransferase activity coefficient (EAST-AC) and plasma pyridoxal-5'-phosphate (PLP) were measured. These measurements were abnormal during vitamin B-6 depletion but returned to normal during repletion. Men who ingested approximately 120 g protein/d required 1.96 +/- 0.11 mg of vitamin B-6 to normalize XA; women who ingested 78 g protein/d required 1.90 +/- 0.18 mg of vitamin B-6 to normalize XA. To attain normal levels of EAST-AC and 4-PA in men, 2.88 +/- 0.17 mg of vitamin B-6 were needed; to normalize PLP, 1.96 +/- 0.11 mg of vitamin B-6 were required. Women required 1.90 +/- 0.18 mg or more of vitamin B-6 to normalize these measurements. Vitamin B-6 requirements were not decreased in two of three subjects who ingested 54 g of protein daily. Thus, vitamin B-6 requirements of elderly men and women are about 1.96 and 1.90 mg/d, respectively.     

Vitamin B-6 status and bioavailability in vegetarian women

It has been hypothesized that the vitamin B-6 status of vegetarians and nonvegetarians may differ in relation to bioavailability of vitamin B-6. Fasting blood samples and 24-h urine collections were obtained from 13 Seventh-day Adventist (SDA) vegetarian and 16 non-SDA nonvegetarian women aged 50-83 y. The two groups were further subdivided into vitamin users and nonusers. Dietary intake was estimated from a 3-d diet record. Plasma pyridoxal 5'-phosphate (PLP) was measured by an enzymatic method. Vitamin B-6 intakes were similar and provided 85% of the RDA for both groups. The vegetarians consumed significantly more crude fiber than the nonvegetarians. No significant differences were found between the two groups for plasma PLP, urinary 4-pyridoxic acid, and urinary vitamin B-6 among vitamin nonusers or for age categories within groups. There appeared to be no adverse effect of fiber on the availability or metabolism of vitamin B-6 between these free-living groups.     

Effect of age on changes in plasma, erythrocyte, and urinary B-6 vitamers after an oral vitamin B-6 load

We investigated the effect of age on indices of vitamin B-6 metabolism in 36 fasting males aged 25-35, 45-55, and 65-75 y who ingested 17.15 mumol vitamin B-6. There were no significant differences among groups in dietary vitamin B-6 intake, base-line erythrocyte pyridoxal 5'-phosphate (PLP), and total vitamin B-6 concentrations, and 24-h and base-line urinary excretion of total vitamin B-6 and 4-pyridoxic acid (4-PA). Base-line plasma PLP and total vitamin B-6 were higher (p less than 0.05) in the youngest group. Increased serum alkaline phosphatase (AP) and decreased dietary vitamin B-6 intake were correlated with decreased base-line plasma PLP and total vitamin B-6. Changes in plasma and erythrocyte PLP concentrations and excretion of 4-PA and total vitamin B-6 postload were not different among groups. Indices of vitamin B-6 absorption, phosphorylation, and excretion were not affected by age.     

Children of Latino immigrants, 4-8 years, in rural Nebraska are adequate in vitamin B-6

Plasma concentrations of B-6 vitamers and homocysteine as well as erythrocyte alanine aminotransferase activity coefficients and vitamin B-6 (dietary + supplement) intakes of apparently healthy young Latino children of immigrant parents living in rural Nebraska were determined and differences determined by gender. Thirty-five Latino children (16 males and 19 females), aged 4-8 years, were included in the study. Nutrient intake information was obtained from the children's parents utilizing two nonconsecutive 24-hour food recalls. No differences were observed by gender with regard to vitamin B-6 intakes, plasma concentrations of B-6 vitamers and homocysteine, and erythrocyte alanine aminotransferase activity coefficients. The intakes of all children met the Recommended Dietary Allowance for vitamin B-6. Plasma pyridoxal 5'-phosphate concentrations, plasma homocysteine concentrations, and erythrocyte alanine aminotransferase activity coefficients of the children were (mean +/- SD) 83.71 +/- 37.35 nmol/L, 6.81 +/- 1.63 micromol/L, and 1.08 +/- 0.06, respectively. All the Latino children of immigrant parents in this study had values indicative of adequate vitamin B-6 status.     

Influence of age and sex on vitamin B-6 vitamer distribution and on vitamin B-6 metabolizing enzymes in Wistar rats

Vitamin B-6 vitamer distribution and activities of vitamin B-6 metabolizing enzymes were evaluated in aging male and female Wistar rats fed a purified diet (containing 250 g of casein and 6 mg of pyridoxine hydrochloride per kg) from weaning until 31 mo of age. Plasma pyridoxal 5'-phosphate (PLP) concentration became lower with increasing age, with the largest decrease in the 1st yr of life. An age-related change in vitamin B-6 distribution between the various tissues examined was observed: B-6 vitamer content increased in heart and brain, whereas PLP content decreased in gastrocnemius muscle, kidney and liver. The decrease in muscle PLP content occurred in concert with a decrease in muscle glycogen phosphorylase activity. Urinary 4-pyridoxic acid (4-PA) excretion increased with age, especially in female rats, in parallel with an increase in liver pyridoxal oxidase and pyridoxal dehydrogenase activities. Age-related changes in vitamin B-6 distribution were probably not causally related to changes in activity of vitamin B-6 metabolizing enzymes; they were regarded as consequences of changes in protein metabolism. The higher urinary 4-PA excretion in older rats may reflect a lower vitamin B-6 requirement; however, the lower PLP content of gastrocnemius muscle may indicate an age-related decrease in vitamin B-6 body stores.     

The effect of wheat bran on the bioavailability of vitamin B-6 in young men

The effect of cooked wheat bran on the bioavailability of vitamin B-6 (B-6) was determined in 10 men, aged 20 to 35 years. The subjects consumed a constant diet with and without the addition of 15 g wheat bran during three successive 18-day periods in a switch-back design. Half of the subjects received the additional bran during periods 1 and 3; the other half consumed the bran during period 2. The bran and nonbran diets supplied, respectively, 1.69 and 1.66 mg of B-6 daily. Plasma total B-6 and pyridoxal phosphate (PLP), urinary 4-pyridoxic acid (4-PA), and urinary and fecal B-6 were determined at regular intervals during each period. Bran significantly increased fecal B-6 (P less than 0.05) and decreased urinary 4-PA (P less than 0.01). Bran also significantly depressed plasma B-6 (P less than 0.01) and PLP (P less than 0.05). These results indicate that the addition of 15 g of wheat bran to the diet decreased the bioavailability of B-6. Since this decrease was modest, never exceeding 17% (based on urinary 4PA and B-6), this amount of bran will not adversely affect B-6 status when intake of the vitamin is adequate.     

Analyzed vitamin B-6 intakes of pregnant and postpartum lactating and nonlactating women

Daily dietary food composites were collected for three consecutive days from 36 women (23 who planned to breast feed their infants and 13 who planned to formula feed their infants) at approximately the 37th week of pregnancy and at one, three, and six months postpartum. When the food composites were collected, each woman also kept detailed food intake records. Daily protein and energy intakes were calculated from the records. Representative aliquots of the homogenized food composites were analyzed microbiologically for total vitamin B-6. The data from the composite analyses indicate that the daily dietary intakes of vitamin B-6 for both groups of women in late pregnancy through six months postpartum were substantially less than the Recommended Dietary Allowances (RDAs). During pregnancy, the women who planned to breast feed their infants consumed diets which provided 54% of the RDA. The women who planned to formula feed their infants consumed diets which provided only 44% of the RDA for vitamin B-6 for pregnant women. At one, three, and six months postpartum, the diets of the lactating women provided 61% of their RDA for vitamin B-6, and the diets of the nonlactating women provided a mean of 46%. Of the 402 daily dietary composites analyzed, only 6% met or exceeded the RDA for vitamin B-6 for the women while they were pregnant or postpartum, either lactating or nonlactating.     

The effect of dietary protein on the metabolism of vitamin B-6 in humans

Eight men, aged 21-31 yr, were fed semipurified diets containing 0.5 (low), 1.0 (medium) and 2.0 (high) g protein/kg body weight; vitamin B-6 intake was kept constant at 1.6 mg/d. Each level of protein was fed for 15 d. Urinary vitamin B-6 (UB-6), urinary 4-pyridoxic acid (4-PA), plasma total vitamin B-6 (PB-6) and plasma pyridoxal 5'-phosphate (PLP) were determined every third day. Means are reported for all subjects of values determined during the second half of each period. Concentration of urinary and plasma vitamin B-6 compounds were negatively correlated with protein intake: the correlation coefficient of nitrogen intake with 4-PA was -0.69 (P less than 0.01); with PLP, -0.45 (P less than 0.05); and with PB-6, -0.48 (P less than 0.05). The decrease in UB-6 was not statistically significant. These results indicate that with increased intake of dietary protein, vitamin B-6 is retained in the body for increased catabolism of amino acids. When evaluating vitamin B-6 requirements or status in humans, protein intake must be considered.     

Dependence of vitamin B-6 status assessment on alcohol intake among elderly men and women (Dutch Nutrition Surveillance System)

To obtain more insight into the effect of moderate alcohol intake on vitamin B-6 status indicators, we studied the associations of alcohol intake (unadjusted and adjusted for intake of vitamin B-6 and protein) with the erythrocyte aspartate aminotransferase activation coefficient (EAST-AC) and plasma pyridoxal 5'-phosphate (PLP) level. Data obtained from men (n = 224) and women (n = 217) aged 65-79 (nationwide sample in the Netherlands) were used for this purpose. Although alcohol intake (a maximum of 21% of the energy came from alcohol) tended to be positively associated with PLP, this association never reached statistical significance (p greater than or equal to 0.05). EAST-AC was inversely associated with alcohol intake, whether or not it was adjusted for vitamin B-6 and protein intake. Similar results were found for the total EAST activity (after adding PLP) or apoenzyme activity; the basal EAST activity (before adding PLP) or holoenzyme activity was not associated with the alcohol intake. These results indicate that caution is needed in the interpretation of the specificity of EAST-AC (i.e., the degree to which EAST-AC is unaffected by other factors) as an indicator of vitamin B-6 intake.     

Vitamin B-6 inadequacy is prevalent in rural and urban Indonesian children

The vitamin B-6 status of Indonesian children was evaluated by determining their dietary vitamin B-6 intakes, erythrocyte alanine aminotransferase activity coefficients and plasma pyridoxal phosphate (PLP) concentrations. Thirty-eight third-grade elementary school children (ages = 8-9 y) in rural and 39 in urban areas of Bogor, West Java, Indonesia, voluntarily served as subjects. The subjects included 39 male and 38 female students. The mean vitamin B-6 intake of the subjects was 0.57 mg/d. Fifty-five percentage of the children reported consuming <0.5 mg/d of vitamin B-6 (the 1998 Estimated Average Requirement for those 4-8 y). Erythrocyte alanine aminotransferase activity coefficients >/= 1.25 were observed in 30%, and plasma PLP concentrations 相似文献   

Vitamin B6 supplementation increases immune responses in critically ill patients

OBJECTIVE: To investigate whether vitamin B6 supplementation has a beneficial effect on immune responses in critically ill patients. DESIGN: A single-blind intervention study. SETTING: The study was performed at the Taichung Veterans General Hospital, the central part of Taiwan. SUBJECTS: Fifty-one subjects who stayed over 14 days in the intensive care unit completed the study. Subjects were not treated with any vitamin supplement before the intervention. INTERVENTIONS: Patients were randomly assigned to one of three groups, control (n = 20), a daily injection of 50 mg vitamin B-6 (B6 -50, n=15), or 100 mg vitamin B-6 (B6 -100, n = 16) for 14 days. MAIN OUTCOME MEASURES: Plasma pyridoxal 5'-phosphate (PLP), pyridoxal (PL), 4-pyridoxic acid (4-PA), erythrocyte alanine (EALT-AC) and aspartate (EAST-AC) aminotransaminase activity coefficient, and urinary 4-PA were measured. The levels of serum albumin, hemoglobin, hematocrit, high-sensitivity C-reactive protein (hs-CRP) and immune responses (white blood cell, neutrophils, total lymphocytes count (TLC), T- (CD3) and B-(CD19) lymphocytes, T-helper (CD4) and suppressor (CD8) cells) were determined. RESULTS: Plasma PLP, PL, 4-PA and urinary 4-PA concentrations significantly increased in two treated groups. T-lymphocyte and T-helper cell numbers and the percentage of T-suppressor cell significantly increased on day 14 in the B6 -50 group. Total lymphocyte count, T-helper and T-suppressor cell numbers, the percentage of T-lymphocyte cells and T-suppressors significantly increased in the B6 -100 group at the 14th day. There were no significant changes with respect to immune responses in the control group over 14 days. CONCLUSIONS: A large dose of vitamin B6 supplementation (50 or 100 mg/day) could compensate for the lack of responsiveness of plasma PLP to vitamin B6 intake, and further increase immune response of critically ill patients. SPONSORSHIP: This study was supported by the National Science Council, Taiwan, Republic of China (NSC-92-2320-B-040-026).     

Vitamin B6 intakes and status of mechanically ventilated critically ill patients in Taiwan

OBJECTIVE: To assess vitamin B6 intake and status of critically ill patients. The relationship between vitamin B6 status indicators and the severity of illness and outcome in these patients was also examined. DESIGN: Prospective clinical study. SETTING: The study was performed at the Taichung Veteran General Hospital, in the central part of Taiwan. SUBJECTS: Ninety-four patients in the intensive care unit (ICU) entered the study and 46 patients successfully completed this study. INTERVENTIONS: No intervention. MAIN OUTCOME MEASURES: Vitamin B6 intake was recorded for 14 days. Vitamin B6 status was assessed by direct measures (plasma pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and urinary 4-pyridoxic acid (4-PA)) and indirect measures (erythrocyte alanine (EALT-AC) and aspartate (EAST-AC) aminotransaminase activity coefficient). The severity of illness (APACHE II score), the length of ventilation dependency, and the length of ICU and hospital stay were recorded. RESULTS: Patients had an adequate mean vitamin B6 intake (16.26+/-19.39 mg) during the 14 day study. Mean vitamin B6 intake was significantly higher on day 14 than on day 1 (P<0.001). However, plasma PLP and PL concentrations significantly decreased at the 14th day after admission (P<0.05). Erythrocyte alanine aminotransaminase activity coefficient and EAST-AC did not change significantly. Urinary 4-PA significantly increased at the 14th day (P<0.001). No significant relationships were found between APACHE II scores and clinical outcomes (the length of ICU and hospital stay, the length of ventilation dependency) of patients, vitamin B6 intake or status indicators. CONCLUSIONS: Critically ill patients received nutritional support in the ICU, and had sufficient mean vitamin B6 intake and adequate vitamin B6 status. Therefore, the severity of illness and the results should not be affected by vitamin B6 status. However, we have noted that plasma PLP and PL concentrations significantly decreased while vitamin B6 intake significantly increased on day 14. Critical clinical conditions and complex metabolism in the critically ill may account for the reduction of plasma PLP and PL. Since vitamin B6 deficiency causes profound effects on immune system function, dietary or supplemented vitamin B6 intake is suggested for hospitalized patients.     

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.     

Improved vitamin B-6 status is positively related to lymphocyte proliferation in young women consuming a controlled diet

To examine the effect of increased intake levels of vitamin B-6 (B-6) on lymphocyte proliferation and interleukin 2 (IL-2) concentration, young women (n = 7) consumed a constant diet containing 1 mg (5.91 micro mol) B-6/d for a 7-d adjustment period, followed by three 14-d experimental periods during which the daily B-6 intake was 1.5, 2.1 and 2.7 mg (8.86, 12.41 and 15.95 micro mol)/d, respectively. Weekly fasting blood and daily 24-h urine samples were collected. Lymphocyte proliferation and IL-2 production were measured in response to phytohemagglutinin. Vitamin B-6 status improved with increased B-6 intake as measured by plasma pyridoxal 5'-phosphate (PLP) and urinary 4-pyridoxic acid. When subjects consumed 2.1 mg B-6/d for 7 d, lymphocyte proliferation increased by 35% (P < or = 0.05) compared with the mean value after consumption of 1.5 mg B-6/d for 14 d. There was no further enhancement after an additional week of 2.1 and 2.7 mg B-6/d for 2 wk. Lymphocyte proliferation was correlated (P < or = 0.01) with vitamin B-6 intake (r = 0.757), plasma PLP (r = 0.456) and erythrocyte aminotransferase activities (r = -0.361). Plasma IL-2 concentration and in vitro production did not change throughout the study, although five of seven subjects showed increases with intakes of 2.1 and 2.7 mg B-6/d, respectively, compared with the 1.5 mg/d intake. Concentrations of PLP in peripheral blood mononuclear cells were correlated (r = 0.357, P < or = 0.01) with plasma PLP, but not with proliferation. These results show that improving vitamin B-6 status by consuming a B-6 intake higher than the current Recommended Dietary Allowance enhances lymphocyte proliferation.     

Plasma pyridoxal 5'-phosphate concentration and dietary vitamin B-6 intake in free-living, low-income elderly people

Free-living, elderly persons (aged greater than or equal to 60 y, n = 198) were recruited to determine the effects of age, sex, health status, dietary vitamin B-6 intakes, and B-6 supplement use on plasma pyridoxal 5'-phosphate (PLP). Vitamin B-6 intakes were determined from 3-d diet records; supplementation was based on self-reported brand and frequency data. Fasting blood samples were analyzed for PLP. Subjects were primarily low-income Caucasians. There was no linear relationship between dietary vitamin B-6 intake, age, sex or health status, and PLP while accounting for supplemental vitamin B-6 use. PLP, however, was negatively correlated with age (p less than 0.001) in individuals with PLP values between 32 and 90 nmol/L. Vitamin B-6 status was low (PLP less than 32 nmol/L) in 32% of this elderly population (n = 198) and could be attributed to low dietary vitamin B-6 intakes and/or the presence of health problems reported to alter vitamin B-6 status. This research suggests that low vitamin B-6 status is prevalent in low-income, elderly persons, especially those with multiple health problems.