Risk of low vitamin B6 status in infants breast-fed exclusively beyond six months

Assessment of vitamin B6 status in never-pregnant, pregnant and postpartum women and their infants

PURPOSE

Pyridoxal 5´-phosphate (PLP) is the main form of vitamin B6 in humans and functions a coenzyme for more than 160 different enzymatic reactions. The purpose of the study was to find plasma PLP concentrations, which ensure an optimal vitamin B6 status determined by a metabolic marker, in never-pregnant, pregnant and lactating women and their infants.

METHODS

In an observational, prospective study, plasma PLP and the metabolic marker, HKr (hydroxykynurenine/(kynurenic acid + anthranilic acid + xanthurenic acid + hydroxyanthranilic acid) were assessed in women (n = 114) from pregnancy week 18 to 6 months postpartum and related to infant status. Never-pregnant women 18-40 years (n = 127) were included as controls.

RESULTS

Compared to controls, plasma PLP decreased during pregnancy and increased postpartum, while HKr increased from week 18 to 6 weeks postpartum, indicating maternal vitamin B6 insufficiency during this period. In never-pregnant women, HKr increased gradually with plasma PLP < 100 nmol/L, and in pregnancy week 28 a sharp increase in HKr was seen at plasma PLP < 30 nmol/L. Despite correcting for maternal vitamin B6 status, infant median plasma PLP decreased with months of exclusive breastfeeding.

CONCLUSIONS

Plasma PLP and kynurenine concentrations differ substantially between never-pregnant, pregnant and postpartum women and infants. A plasma PLP concentration in the range of 50-100 nmol/L seems to ensure an optimal vitamin B6 status for never-pregnant women, whereas a plasma PLP > 30 nmol/L in pregnancy week 28 ensures an adequate vitamin B6 status during pregnancy and lactation. Infant vitamin B6 status at age 6 months is inversely correlated to number of months of exclusive breastfeeding.

Macronutrient balance and micronutrient amounts through growth and development

Nutrition is essential for human growth, particularly in newborns and children. An optimal growth needs a correct diet, in order to ensure an adequate intake of macronutrients and micronutrients. Macronutrients are the compounds that humans consume in largest quantities, mainly classified in carbohydrates, proteins and fats. Micronutrients are instead introduced in small quantities, but they are required for an adequate growth in the pediatric age, especially zinc, iron, vitamin D and folic acid. In this manuscript we describe the most important macro and micronutrients for children's growth.

Revised D-A-CH Reference Values for the Intake of Vitamin B6

BACKGROUND

The Nutrition Societies of Germany, Austria, and Switzerland as the joint editors of the "D-A-CH reference values for nutrient intake" have revised the reference values for vitamin B6 in summer 2019.

SUMMARY

For women, the average requirement (AR) for vitamin B6 intake was derived on the basis of balance studies using a pyridoxal-5'-phosphate (PLP) plasma concentration of ≥30 nmol/L as a biomarker of an adequate vitamin B6 status. The recommended intake (RI) was derived considering a coefficient of variation of 10%. The RIs of vitamin B6 for men, children, and adolescents were extrapolated from the vitamin B6 requirement for women considering differences in body weight, an allometric exponent, growth factors as appropriate, and a coefficient of variation. For infants aged 0 to under 4 months, an estimated value was set based on the vitamin B6 intake via breast feeding. The reference value for infants aged 4 to under 12 months was extrapolated from the estimated value for infants under 4 months of age and the average vitamin B6 requirement for adults. The reference values for pregnant and lactating women consider the requirements for the foetus and the loss via breast milk. Key Messages: According to the combined analysis of 5 balance studies, the AR for vitamin B6 to ensure a plasma PLP concentration of ≥30 nmol/L is 1.2 mg/day for adult females and the extrapolated AR for adult males is 1.3 mg/day. The corresponding RIs of vitamin B6 are 1.4 mg/day for adult females and 1.6 mg/day for adult males, independent of age. For infants, the estimated value is 0.1 mg/day and 0.3 mg/day, depending on age. The AR of vitamin B6 for children and adolescents ranges between 0.5 and 1.5 mg/day, and the RI is between 0.6 mg/day and 1.6 mg/day. During pregnancy, the AR is 1.3 mg/day in the first trimester and 1.5 mg/day in the second and third trimesters; the RI is 1.5 mg/day in the first trimester and 1.8 mg/day in the second and third trimesters. For lactating women, the AR is 1.3 mg/day and the RI is 1.6 mg/day.

Revised D-A-CH-reference values for the intake of zinc

BACKGROUND

The Nutrition Societies of Germany, Austria and Switzerland as the joint editors of the 'D-A-CH reference values for nutrient intake' have revised the reference values for zinc in July 2019.

METHODS

For infants aged 0 to under 4 months, an estimated value was set based on the zinc intake via breast feeding. For all other age groups, the reference values were calculated using the factorial method considering endogenous zinc losses via intestinal losses, urine, faeces, skin and sweat, semen in men and the additional zinc requirements to build up body weight in children and adolescents as well as in pregnant women. Due to the strong influence of phytate intake on zinc absorption, the recommendations for the intake of zinc for adults are derived depending on low (0.5 mmol/day, corresponding to 330 mg/day), moderate (1.0 mmol/day, corresponding to 660 mg/day) and high (1.5 mmol/day, corresponding to 990 mg/day) phytate intake. The reference values for lactating women take into account the zinc loss via breast milk.

RESULTS AND CONCLUSION

For adults, pregnant and lactating women, the recommended intake values for zinc range from 7 mg/day to 16 mg/day, depending on sex and dietary phytate intake.

The relationship between plasma albumin, alkaline phosphatase and pyridoxal phosphate concentrations in plasma and red cells: Implications for assessing vitamin B6 status

BACKGROUND

Plasma concentrations of most vitamins decrease as part of the systemic inflammatory response (SIR). Thus low plasma values do not necessarily indicate deficiency. Vitamin B6 status is usually assessed by measurement of pyridoxal phosphate (PLP) in plasma, although vitamin concentrations in blood cells tend to be better markers of cellular stores. In health, plasma PLP appears to be determined primarily by intake, its binding to albumin, and its hydrolysis by alkaline phosphatase (ALP).

OBJECTIVE

To examine, using in vitro studies, the effect of albumin concentration and ALP activity on PLP concentration in plasma and red blood cells of healthy subjects (HS) and critically ill patients (CI).

DESIGN

Heparin and EDTA (ALP inhibited) whole blood samples from HS (n = 8) and CI (n = 26) were incubated with PLP. Concentration of PLP in plasma and red cells was measured. Albumin and ALP levels were determined in plasma.

RESULTS

In PLP incubated heparin samples, there was a strong direct relationship between albumin in the concentration range 10-44 g/L and increase in plasma PLP concentration (r_s = 0.93, P < 0.001) and an inverse relationship with increase in red cell PLP concentration (r_s = -0.90, P < 0.001). In contrast, ALP activity was inversely associated with increase in plasma PLP concentration (r_s = -0.42; P = 0.013) and directly associated with red cell PLP concentration (r_s = 0.49; P = 0.003).

CONCLUSIONS

Plasma albumin concentration and to a lesser extent ALP activity influences PLP concentration in plasma and red cells. In conditions associated with low albumin (e.g. SIR) or altered ALP activity, red cell PLP measurements are more likely to be reliable than plasma measurements in differentiating true from apparent vitamin B6 deficiency and to guide vitamin B6 supplementation.

Overview of Nutrients in Human Milk

The WHO recommends exclusive breastfeeding for the first 6 mo of life to promote optimal infant health and development. Understanding the micro- and macronutrient concentrations of human milk and how each nutrient fluctuates with lactational stage, maternal factors, and supplementation is imperative for supporting good breastfeeding practices. Where maternal undernutrition compromises human milk quality, a thorough awareness of the effectiveness of interventions can direct efforts to achieve both maternal and infant nutrient sufficiency. This review of current knowledge covers trends in nutrient concentrations over the course of lactation and describes the influence of maternal intake, status, supplementation, and other factors on human milk concentrations of each nutrient.

Nutritional deficiencies during normal growth

Nutritional deficiencies have always been a major consideration in pediatrics. Although the classic forms of many of the well-documented nutritional deficiencies are memorized during training as a physician, nutritional deficiencies that can occur in otherwise asymptomatic normally growing children are often overlooked. The two most common deficiencies seen in children who are growing normally are iron and vitamin D deficiencies. These deficiencies are surprisingly common and can have a significant impact on the overall health of a child. This article reviews these nutritional deficiencies and other less commonly seen deficiencies in children who are otherwise growing normally.

Relation between pyridoxal and pyridoxal phosphate concentrations in plasma, red cells, and white cells in patients with critical illness

BACKGROUND

Evidence suggests that the relation between plasma and red cell vitamin B-6 concentrations is perturbed as part of the systemic inflammatory response in critically ill patients.

OBJECTIVE

The aim was to examine the cross-sectional and longitudinal interrelations between pyridoxal (PL) and pyridoxal phosphate (PLP) concentrations in plasma and red and white cells in patients with critical illness.

DESIGN

PLP and PL concentrations were measured by HPLC in plasma and red and white cells in normal subjects (n = 126) and critically ill patients (n = 96) on admission and on follow-up.

RESULTS

On admission, compared with the controls, median plasma PLP and PL (P < 0.001 and < 0.01, respectively) and red cell PLP and PL (P < 0.001 and < 0.05, respectively) and their ratio (PLP:PL) in plasma and red cells (P < 0.001 and < 0.01, respectively) were significantly lower in the critically ill. In critically ill patients, plasma PLP:PL was significantly lower than red cell PLP:PL (P = 0.001) and white cell PLP:PL (P = 0.008). Plasma PL concentration was directly associated with both red cell PL (r(s) = 0.73, P < 0.001) and white cell PL (r(s) = 0.68, P < 0.001). Red cell PL and white cell PL were directly associated with red cell PLP (r(s) = 0.82, P < 0.001) and white cell PLP (r(s) = 0.68, P < 0.001), respectively. Longitudinal measurements (n = 48) were similar.

CONCLUSIONS

The relation between plasma PLP and PL was significantly perturbed in critical illness. This effect was less pronounced in red and white cells. Therefore, these results confirm the hypothesis that intracellular PLP concentrations are more likely to be a reliable measure of status than are plasma measurements in the critically ill patient.

B vitamins: proposed fortification levels for complementary foods for young children

The B vitamins, except for folate, can be classified as group I nutrients during lactation. Nutrients in this category share the following characteristics: low maternal intake or stores during lactation reduce the concentration in human milk, and infants' stores are readily depleted. For some of these nutrients, the infants' stores at birth may be depleted by maternal deficiency during pregnancy. The prevalence of some B vitamin deficiencies, especially deficiencies of riboflavin and vitamin B-12, is probably much higher than is usually assumed. Taken together, these considerations emphasize the importance of supplying adequate amounts of B vitamins to infants and young children. Recommendations are made here on the amounts and densities of B vitamins that should be present in fortified complementary foods fed to children aged 6-24 mo. The values are based on the difference between recommended daily intakes and the amount that the child will receive from maternal milk using estimates reported in the literature. There are few concerns about the potential toxicity of any of these vitamins at the levels likely to be added to complementary foods. If there are losses during food preparation or concentrations of the vitamins are low in human milk, the estimates provided may need to be increased. The adequacy of these recommendations must be evaluated thoroughly.

Vitamin B-6 content of breast milk and neonatal behavioral functioning

OBJECTIVE

To determine if vitamin B-6 intakes of mothers influence the B-6 vitamer content of transition milk and if correlations exist between the vitamin B-6 content of the milk and the infants' neurobehavioral functioning.

DESIGN

Transition milk samples were collected from mothers 8 to 11 days after delivery for B-6 vitamer analysis. Neurobehavioral functioning of the neonates was determined at that time. A 24-hour recall was used in estimating vitamin B-6 intakes of the mothers.

SUBJECTS

A convenience sample of low-income, lactating women (n = 25) who had normal pregnancies.

MAIN OUTCOME MEASURES

B-6 vitamers were measured in the mothers' transition milk samples. Neurobehavioral functioning was assessed using the Brazelton Neonatal Behavioral Assessment Scale (NBAS), and the Center for Epidemiologic Studies Depression Scale was used to evaluate maternal depression.

STATISTICAL ANALYSES PERFORMED

Pearson correlation coefficients were used to assess if statistically significant relationships existed between variables. The Mann-Whitney test was used to determine if median group values were significantly different.

RESULTS

The major B-6 vitamer in transition milk was pyridoxal. Mothers with vitamin B-6 intake greater than the median value had a significantly higher median pyridoxal level in their breast milk than did the mothers with intakes below the median value. All except one mother had a dietary vitamin B-6 intake that exceeded the Recommended Dietary Allowance. Infant scores on habituation (r = .94, P < .05) and autonomic stability (r = .34, P < .05) subscales of the NBAS were positively correlated with milk pyridoxal values.

APPLICATIONS/CONCLUSIONS

Vitamin B-6 is important for normal behavioral functioning of infants. The mothers' vitamin B-6 intake affects vitamin B-6 levels of breast milk and the need for consuming recommended levels of vitamin B-6 should be emphasized to all pregnant and lactating mothers.

Oxalate, citrate, and sulfate concentration in human milk compared with formula preparations: influence on urinary anion excretion

BACKGROUND

Nephrocalcinosis is not uncommon in preterm infants, and elevated urinary oxalate excretion is known to be one of the main risk factors. When oxalate excretion was found to be higher in formula-fed than in human milk-fed infants, the formulas' oxalate content was thought to be responsible.

METHODS

The oxalate concentration in human milk (21 samples obtained during lactogenesis; 17 samples obtained during established lactation) and of 16 formula preparations was examined. Citrate and sulfate concentrations were also measured, because both anions influence urinary saturation.

RESULTS

The mean (+/- SE) oxalate content of human milk increased approximately 27% from early lactogenesis (70.4 +/- 6.4 micromol/1) to established lactation (96.4 +/- 9.5 micromol/l; p < 0.05). The latter was not different from the mean oxalate concentration of formula (98.2 +/- 11.4 micromol/l), however a fourfold range of measurements was recorded in both groups. The mean citrate content of human milk increased only slightly after early lactogenesis (2.66 +/- 0.22 mmol/l), but remained significantly lower than in formula (3.34 +/- 0.23 mmol/l; p < 0.05). The mean sulfate concentration did not increase and was 13 times lower in human milk (52.1 +/- 9.5 micromol/l) than in formula (688.7 +/- 95.4 micromol/l; p < 0.0001).

CONCLUSIONS

The higher oxalate excretion in formula-fed infants is not because of the milk's oxalate concentration. Urinary citrate and sulfate excretion may be influenced by their higher concentrations in formula preparations, which may be of clinical importance in the population that is at risk for development of nephrocalcinosis.

Self-selected diets of lactating women often fail to meet dietary recommendations

OBJECTIVE

To assess longitudinally nutrient intakes of lactating women during the postpartum period.

DESIGN

Dietary data from lactating women were collected by means of 2-day food records at 3 and 6 months postpartum. Intake of energy and selected nutrients was tabulated and compared with dietary standards.

SUBJECTS

The 52 lactating women enrolled in the study lived in a university community, were apparently healthy, had a body mass index within normal range, were successfully nursing a term infant, and planned to nurse for at least 6 months.

STATISTICAL ANALYSES PERFORMED

Paired t tests and Stuart-Maxwell chi(2) analyses.

RESULTS

Mean energy intakes were below the Recommended Dietary Allowance. Mean intakes of most nutrients met or exceeded recommended standards except for zinc and vitamins D and E at both 3 and 6 months postpartum. Calcium and folate intakes were also below standards at 6 months. Although mean iron intake exceeded the standard at both measurement times, there was a significant decline from 3 to 6 months. Relative frequencies of mothers meeting various percentages of standards differed significantly from 3 to 6 months for calcium; iron; folate; and vitamins E, D, and B-6. At 6 months, significant increases were noted in the number of women reporting calcium, folate, and vitamin B-6 intakes at less than one half of the recommended amounts.

APPLICATIONS/CONCLUSIONS

Guidance for lactating women should stress food sources of nutrients likely to be limited in their diets: calcium; zinc; folate; and vitamins E, D, and B-6.