Vitamin B12 in human colostrum and milk. Quantitation of the vitamin and its binder and the uptake of bound vitamin B12 by intestinal bacteria

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.

Micronutrients in Human Milk: Analytical Methods

Exclusive breastfeeding is recommended by the WHO for the first 6 mo of life because human milk protects against gastrointestinal infections and supplies balanced and adequate nutrient contents to the infant. However, reliable data on micronutrient concentrations in human milk are sparse, especially because some micronutrients are affected by maternal diet. Microbiological and competitive protein-binding assays, nuclear magnetic resonance or inductively coupled plasma spectroscopy, and chromatographic analyses are among the methods that have been applied to human-milk micronutrient analysis. However, the validation or evaluation of analytical methods in terms of their suitability for the complex human-milk matrix has been commonly ignored in reports, even though the human-milk matrix differs vastly from blood, plasma, or urine matrixes. Thus, information on the validity, accuracy, and sensitivity of the methods is essential for the estimation of infant and maternal intake requirements to support and maintain adequate milk micronutrient concentrations for healthy infant growth and development. In this review, we summarize current knowledge on methods used for analyzing water- and fat-soluble vitamins as well as iron, copper, zinc, iodine, and selenium in human milk and their different forms in milk; the tools available for quality control and assurance; and guidance for preanalytical considerations. Finally, we recommend preferred methodologic approaches for analysis of specific milk micronutrients.

Analyzing B-vitamins in Human Milk: Methodological Approaches

According to the World Health Organization (WHO), infants should be exclusively breastfed for the first six months of life. However, there is insufficient information about the concentration of nutrients in human milk. For some nutrients, including B-vitamins, maternal intake affects their concentration in human milk but the extent to which inadequate maternal diets affect milk B-vitamin content is poorly documented. Little is known about infant requirements for B-vitamins; recommendations are generally set as Adequate Intakes (AI) calculated on the basis of the mean volume of milk (0.78 L/day) consumed by infants exclusively fed with human milk from well-nourished mothers during the first six months, and the concentration of each vitamin in milk based on reported values. Methods used for analyzing B-vitamins, commonly microbiological, radioisotope dilution or more recently chromatographic, coupled with UV, fluorometric and MS detection, have rarely been validated for the complex human milk matrix. Thus the validity, accuracy, and sensitivity of analytical methods is important for understanding infant requirements for these nutrients, the maternal intakes needed to support adequate concentrations in breast milk. This review summarizes current knowledge on methods used for analyzing the B-vitamins thiamin, riboflavin, niacin, vitamin B-6 and pantothenic acid, vitamin B-12, folate, biotin, and choline in human milk, their chemical and physical properties, the different forms and changes in concentration during lactation, and the effects of deficiency on the infant.

Competitive chemiluminescent enzyme immunoassay for vitamin B12 analysis in human milk

Recent discoveries of matrix interferences by haptocorrin (HC) in human milk and serum show that past analyses of vitamin B12 in samples with high HC content might have been inaccurate (Lildballe et al., 2009; Carmel & Agrawal, 2012). We evaluated two competitive enzyme-binding immunoassays for serum/plasma (IMMULITE and SimulTRAC-SNB) for B12 analysis in human milk. B12-recovery rates (United States Environmental Protection Agency, 2007) were determined to be 78.9 ± 9.1% with IMMULITE and 225 ± 108% (range 116-553%) using SimulTRAC-SNB, most likely due to the presence of excess HC. HC-interferences were not observed with the IMMULITE assay, rendering previously reported mandatory HC-removal (Lildballe et al., 2009) unnecessary. Linearity continued at low B12-concentrations (24-193 pM; r(2)>0.985). Milk B12 concentrations from Bangladeshi women (72-959 pM) were significantly lower than those from California (154-933 pM; p<0.0001) showing IMMULITE's robustness against the complex milk matrix and its ability to measure low milk B12 concentrations.

Potential host-defense role of a human milk vitamin B-12-binding protein, haptocorrin, in the gastrointestinal tract of breastfed infants, as assessed with porcine haptocorrin in vitro

BACKGROUND

Limited information exists on the biological role of a vitamin B-12-binding protein, haptocorrin, in human milk. The expression of haptocorrin by human mammary epithelial cells and its presence in human milk suggest a potential physiologic function in breastfed infants.

OBJECTIVE

We investigated the extent to which haptocorrin could withstand proteolytic degradation and exert antimicrobial activity under in vitro conditions designed to simulate the gastrointestinal tract of breastfed infants.

DESIGN

An in vitro model that simulates infant gastric and intestinal digestion was developed. The structural stability of porcine haptocorrin after exposure to digestive enzymes (pepsin and pancreatin) was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot analysis, column chromatography, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The antimicrobial activity of haptocorrin was determined by incubating haptocorrin with enteropathogenic Escherichia coli O127 strain 2348/69 and monitoring bacterial growth.

RESULTS

The structural analysis of haptocorrin exposed to enzymes did not show a decrease in molecular weight, which indicated that haptocorrin can survive proteolytic degradation. Both haptocorrin exposed to digestive enzymes and undigested haptocorrin inhibited the growth of enteropathogenic E. coli and did so to a similar extent. Thus, haptocorrin in vitro not only retains its structure after exposure to proteases but also exhibits antimicrobial activity.

CONCLUSION

These results suggest that haptocorrin may exert a host-defense function against pathogens in the gastrointestinal tracts of breastfed infants.

Transfer of drugs and other chemicals into human milk

The American Academy of Pediatrics places emphasis on increasing breastfeeding in the United States. A common reason for the cessation of breastfeeding is the use of medication by the nursing mother and advice by her physician to stop nursing. Such advice may not be warranted. This statement is intended to supply the pediatrician, obstetrician, and family physician with data, if known, concerning the excretion of drugs into human milk. Most drugs likely to be prescribed to the nursing mother should have no effect on milk supply or on infant well-being. This information is important not only to protect nursing infants from untoward effects of maternal medication but also to allow effective pharmacologic treatment of breastfeeding mothers. Nicotine, psychotropic drugs, and silicone implants are 3 important topics reviewed in this statement.

Nutritional vitamin B12 deficiency in a breastfed infant following maternal gastric bypass

Breastfed infants of women who have had gastric or intestinal bypass procedures may develop nutritional deficiencies. We describe a 10-month-old exclusively breastfed white male infant who presented with vomiting, failure to thrive, and megaloblastic anemia. He was found to have vitamin B12 deficiency. His mother had undergone a gastric bypass procedure for morbid obesity 2 years prior to her pregnancy with this child. She had subclinical vitamin B12 deficiency, with an abnormal Schilling test that corrected with the addition of intrinsic factor. Therefore, we believe that the mother's gastric bypass had caused a decrease in available intrinsic factor, resulting in subclinical vitamin B12 deficiency and decreased breast milk B12. Although she was asymptomatic, her breastfed infant developed symptomatic B12 deficiency. This is the first reported case of a maternal gastric bypass resulting in vitamin B12 deficiency in an infant. These mothers should receive vitamin supplements, including vitamin B12, during and after pregnancy, and may require parenterally administered vitamin B12.

Breast milk as a source of vitamins, essential minerals and trace elements

Human breast milk provides all of the vitamins and essential minerals and trace elements (micronutrients) that are required by the normal term infant, until weaning. With a few exceptions, excessive micronutrient supplies to the mother, or a moderate deficiency in her diet, do not greatly alter the supply to the infant. Thus, the infant is well-protected by maternal homeostatic processes, although the mechanisms of these are not yet well understood. Considerable progressive changes in concentration occur for some of the micronutrients during the course of lactation. Because the concentration of these nutrients, and of other substances that modify their absorption by the infant, such as binding proteins, differs considerably between human milk, animal milk and, hence, commercial milk formulae, there is great interest in the quantitative significance of micronutrient supplies, and their variability in breast milk, in the quest for improvement of commercial formulations. The aim of this review is to summarize the available information about the factors that determine breast milk contents of micronutrients.