Zinc and infant nutrition☆
Introduction
Infancy is a critical phase of life that requires adequate nutrition to sustain growth and development. Pioneers in the field of zinc biology identified many years ago that at birth, a neonate has only small pools of metabolically available zinc, as evidenced by early onset growth failure in conditions of zinc restriction, despite the presence of normal tissue zinc levels [1]. Thus establishing the zinc requirements for infants has been of great importance. This chapter discusses the importance of zinc nutrition, sources of dietary zinc and its bioavailability, requirements for mineral supplementation, risk factors for zinc deficiency, the effects of zinc deficiency and its contribution to the global burden of disease. The consequences of mutations and epigenetic changes to key zinc transporters provide insights into the cellular mechanisms regulating zinc homeostasis that are of particular importance to the health and development of infants and young children.
Section snippets
Essentiality of zinc
Zinc has many diverse roles in biological processes. At the cellular and molecular level, zinc is required for the structural and catalytic function of hundreds of enzymes that regulate the major metabolic pathways of the body [2]. As a structural component of transcription factors [3], zinc has a key role in regulation of gene expression and is involved in signal transduction and neuronal transmission [4], [5]. Numerous cellular processes require zinc including cell proliferation,
Nutrition and body zinc status
The concept of body zinc status is based on the notion of acquisition of zinc that is sufficient for optimal biological processes. Body zinc status may be a consequence of dietary zinc intake, phytate consumption, gastrointestinal health, rate of zinc excretion and reabsorption, and other factors, many of which are not clear [13]. As there are numerous biological functions of zinc, many measures of zinc status have been considered, including zinc levels blood, urine, hair, feces, sweat, and
Dietary zinc requirements of infants
Dietary requirements for essential nutrients including zinc provide estimates of whether intakes are adequate for optimal body function. The RDA (recommended dietary allowance) is the daily intake amount of a nutrient that is considered to be sufficient to meet the requirements of 97.5% of healthy individuals over the age of 6 months. RDAs for zinc vary between different countries and range from 1.5 to 2 mg/day for 0–6 months of age, 3–8 mg/day for 7–12 months of age and 4–9 mg/day for 1–3 year
Zinc in human breast milk and infant formulas
Neonates are born with a substantial storage of zinc (25% of total body zinc) bound primarily to metallothioneins in the liver, that accumulate in the last trimester of gestation [26], [27], [28]. These hepatic zinc reserves are progressively reduced until they reach a constant level at approximately 4 months of age [28], [29]. However, unlike iron and copper, the major source of zinc in the neonatal period is breast milk [29]. The zinc concentration in human milk is highest in colostrum
Zinc bioavailability in milk
Stable isotope studies and zinc loading tests show that human milk has a greater zinc bioavailability than cow’s milk and infant formulas [40], [41]. Zinc absorption in healthy adults was on average 41% from human milk, 28% from cow’s milk, 31% from casein-based formula and only 14% from soy based formula [40]. A higher fractional absorption of zinc from human milk (54%) was found in infants [50]. An important factor in zinc bioavailability is the whey-to-casein ratio as zinc is more
Dietary factors influencing zinc nutrition in infants
Micronutrient interactions can affect zinc bioavailability and absorption. This can be through competition of transport processes or through zinc chelation. Iron supplements may interfere with zinc absorption [63], [64]. Cadmium can inhibit zinc absorption while some amino acids including histidine and methionine increase zinc absortion [65]. Dietary zinc bioavailability is influenced by many food constituents including phytate, a plant ligand of inositol phosphate that is present in cereals
Vegetarianism
Meat and seafood are major sources of dietary zinc, while the zinc in plant-based diets containing folate, fibre and phytochemicals, is less available [68]. Although grains, nuts and seeds can provide amounts of zinc similar to those found in animal tissues, adult populations with vegetarian diets have been found to have low zinc intakes [69], [70], [71], [72] and in some cases reduced serum zinc levels [73]. Other studies on adults show no effects of vegetarian diets on serum zinc [70], [72],
Effect of maternal zinc status on infant health
Although 82% of all pregnant women worldwide are estimated to be zinc deficient [76], zinc levels in human milk were found to be unrelated to maternal zinc status as measured by maternal plasma zinc levels [77], and the zinc status of the lactating mother does not influence transfer of zinc into milk [78], [79], [80], [81], [82], [83], [84], [85]. Additionally, the majority of studies show no correlation between maternal age, parity or smoking habits on zinc levels in milk [78], [86], [87], [88]
Zinc deficiency in infants
Zinc deficiency is a prevalent condition in countries with poor nourishment and particularly affects infants and young children. Due to the numerous roles of zinc in cell growth, differentiation and function and the lack of body stores, the infant is particularly susceptible to the adverse effects of zinc deficiency. Zinc deficiency accounts for the deaths of over half a million infants and children under 5 years of age, per year [13]. The WHO estimates that 800,000 deaths per year are due to
Zinc supplementation
Preterm babies represent approximately about 12% of births in USA, and have a higher risk of micronutrient deficiency than term babies [113]. Zinc fortification of this group has been recommended [114]. Preterm babies are recommended to have zinc supplements ranging from 200 to 500 μg/kg/day for infants born between 27 and 40 weeks gestation [22]. Very low birthweight premature infants, less than 1.5 kg at birth are recommended to have supplementation of 10 mg Zn/day beginning at week 1 until
Genetic conditions in infants that are associated with zinc deficiency
The most frequently occurring form of zinc deficiency is due to nutritional insufficiency. Rarer forms of zinc deficiency that are inherited may be found in exclusively breast-fed babies, who present with symptoms characteristic of nutritional zinc deficiency, including dermatitis, diarrhoea, alopecia, loss of appetite, impaired immune function and neuropsychiatric changes [109], [123]. This type of zinc deficiency (transient neonatal zinc deficiency) is caused by reduced levels of zinc in the
References (165)
- et al.
J. Biol. Chem.
(1987) - et al.
J. Trace Elem. Med. Biol. Organ Soc. Minerals Trace Elem.
(2006) J. Nutr.
(1996)- et al.
J. Nutr.
(2003) - et al.
Clin. Chim. Acta Int. J. Clin. Chem.
(2012) Nutr. Res.
(2000)- et al.
Early Hum. Dev.
(2013) - et al.
J. Pediatr.
(2006) J. Nutr.
(1989)- et al.
Am. J. Clin. Nutr.
(1994)
J. Chromatogr. A
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Talanta
Nutr. Res.
J. Nutr.
J. Nutr.
J. Trace Elem. Med. Biol. Organ Soc. Minerals Trace Elem.
Adv. Food Nutr. Res.
J. Am. Dietetic Assoc.
J. Adolesc. Health Off. Publ. Soc. Adolesc. Med.
Am. J. Clin. Nutr.
J. Am. Dietetic Assoc.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
Am. J. Clin. Nutr.
J. Nutr.
Proc. Nutr. Soc.
Biochemistry
Science
Nature
Mol. Cell. Biochem.
J. Cell. Physiol.
Biochem. J.
Annu. Rev. Biochem.
Br. J. Nutr.
Metallomics Integr. Biometal Sci.
Paediatr. Int. Child Health
Br. J. Nutr.
Food Nutr. Bull.
J. Clin. Diagn.Res. JCDR
BMC Pediatr.
Tohoku J. Exp. Med.
Nutr. Clin. Pract. Off. Publ. Am. Soc. Parenter. Enter. Nutr.
Acta Paediatr.
Cited by (80)
Accumulation characteristics of metals in human breast milk and association with dietary intake in northeastern China
2024, Science of the Total EnvironmentEffects of Zinc Supplementation on Metabolomic Profiles in Tanzanian Infants: A Randomized Trial
2024, Journal of NutritionStudy on the zinc ions binding to human lactoferrin
2023, Journal of Molecular StructureEncapsulins from Ca. Brocadia fulgida: An effective tool to enhance the tolerance of engineered bacteria (pET-28a-cEnc) to Zn<sup>2+</sup>
2022, Journal of Hazardous MaterialsCitation Excerpt :Owing to their flexibility, accumulation, and non-biodegradability, heavy metal ions are difficult to remove from wastewater and have become one of the most severe environmental pollutants (Han et al., 2016; Peligro et al., 2016; Raval et al., 2016). Zn, as a crucial element in cellular functions, participates in more than 1000 enzymatic reactions and 2000 transcription factors (Olza et al., 2017; Ackland and Michalczyk, 2016). About 30–1000 mg/L Zn2+ in wastewater is discharged from industrial activities (Daverey et al., 2014), and such excessive amounts of Zn2+ might be highly toxic to cells (Lu and Chiu, 2006).
Potential Micronutrient Deficiencies in the First 1000 Days of Life: The Pediatrician on the Side of the Weakest
2024, Current Obesity Reports
- ☆
This article is part of a Special Issue entitled The Cutting Edge of Zinc Biology, edited by Shinya Toyokuni, Taiho Kambe, and Toshiyuki Fukada.