The first 1000 days of early life refers to the period from conception through the child’s second birthday [1
]. Optimal nutrition during this time is essential for supporting critical periods of fetal growth and development, maternal health (including the postpartum period and lactation), and for fueling infant and toddler growth (until two years of age). Failure to provide key nutrients during the first 1000 days of life can result in developmental shortfalls such as a lifelong deficit in brain function. To help optimize development and to fuel a healthy pregnancy, all essential nutrients should be included in the diet. This review distinguishes eight key nutrients and describes the unique role that each play during the first 1000 days of life, including carotenoids (lutein + zeaxanthin), choline, folate, iodine, iron, the omega-3 fatty acids, and vitamin D. Other nutrients, including B vitamins, magnesium, vitamin A and other trace minerals, are discussed, as they relate to topics such as maternal, infant and toddler nutrient deficiency and supplementation.
The upcoming 2020–2025 Dietary Guidelines for Americans (DGA) will make specific recommendations for children, and it is important to provide accurate scientific information to support health influencers, such as dietitians and other health professionals, in the field of nutrition. Therefore, the purpose of this review is to 1) summarize the available scientific evidence regarding physiological and nutritional requirements during the first 1000 days of early life; 2) describe scientific data on the benefits of dietary nutrition supplements; and 3) provide professionals with a nutritional guidance document on pregnancy through early childhood.
3. Why Nutrition Matters: Maternal Physiological Changes and the Role of Nutrition
The physiological changes that occur during pregnancy are unique in the life of women. These changes are normal adaptations that occur to nurture the developing fetus and to prepare the mother for a healthy labor and delivery [2
]. These changes begin immediately after conception and affect organ systems including the cardiovascular, endocrine, gastrointestinal, hematological, respiratory, and skeletal system [3
]. For women who experience a normal and healthy pregnancy, these changes typically resolve after birth with minimal residual effects. Table 1
provides an overview of the major physiological changes that occur during pregnancy.
Physiological changes during pregnancy result in changing nutritional needs. During the first 2–8 weeks of pregnancy, foundational growth of the fetus occurs, and the nutrition status of the mother impacts early embryonic development, organogenesis, and neural development. During the second and third trimesters, fetal nutrients accumulate to be used after birth; therefore, it is critical to have an adequate supply of all essential nutrients. While it is important to recognize that all essential nutrients are required to support a healthy pregnancy and early childhood development, due to the scope of this review, we will focus on the role of eight key nutrients, including carotenoids (lutein + zeaxanthin), choline, folate, iodine, iron, omega-3 fatty acids and vitamin D.
The first 1000 days of life represents the time from pregnancy through the child’s second birthday.
Mothers undergo major physiological changes to maintain pregnancy and prepare for a healthy labor and delivery; these changes begin after conception and affect all organ systems’ development, but especially the fetal cardiovascular, endocrine, gastrointestinal, hematological, respiratory and skeletal systems.
Optimal nutrition status during pregnancy is critical, as it impacts early embryonic development, organogenesis and neural development.
Nutrients such as the carotenoids (lutein + zeaxanthin), choline, folate, iodine, iron, omega-3 fatty acids and vitamin D play critical roles during fetal development.
3.1. Optimal Nutrition to Help Sustain A Healthy Pregnancy and Critical Periods of Development
Pregnancy places unique demands on a woman’s body with additional energy and increased intake of nutrients required to help support optimal fetal development [5
] (Table 2
). The body can be extremely sensitive to damage caused by internal and external harmful exposures (alcohol, medications, environmental toxins), and these exposures can trigger major or minor functional and structural fetal defects (Figure 2
). Similarly, the body is sensitive to diet and nutrition. For example, in the presence of a healthy diet that delivers adequate amounts of key macro and micronutrients, fetal growth and development typically thrive [1
Adequate nutrition is especially critical for normal central nervous system development. Neurological development is extremely rapid during the first 1000 days of life, with changes occurring from post conception (day 18) up until age two. Nerve cells proliferate at an extremely rapid pace, especially during early fetal development [6
]. This growth culminates in a network of billions of neurons and trillions of neural connections by the time of birth [6
]. During fetal and early childhood development, the prefrontal cortex, hippocampus, and sensory systems undergo tremendous development that will not be able to occur later in life [1
] (Figure 2
Regarding energy requirements during pregnancy, extra calories should come from nutrient-dense foods to support a healthy pregnancy weight gain [5
]. To help meet nutrient requirements, expectant mothers should consume foods that provide carotenoids (lutein + zeaxanthin), choline, folate, iodine, iron, omega-3 fatty acids, and vitamin D. In this section, we describe the role of each nutrient during pregnancy, as well as each nutrient’s role during critical periods of growth and development, where information is available.
The carotenoids lutein and zeaxanthin play important roles during the development of the infant eye and brain. Lutein and zeaxanthin have been found to accumulate in the eye of fetuses as early as 17 to 22 weeks of gestation [13
]. Therefore, the mother must have adequate lutein consumption to supply her own needs along with the needs of her unborn child. Studies have shown that lutein is not only present and often the predominant carotenoid in the mother’s bloodstream during pregnancy, but that lutein concentration typically increases during pregnancy, while levels of other carotenoids remain fairly constant [16
Lutein levels in both cord blood and maternal plasma peak during the third trimester, a period of active retinal and neural development [18
]. Lutein has also been found to be present at higher amounts in cord blood compared to other carotenoids [16
]. Additionally, of the carotenoids present in the placenta, lutein and zeaxanthin were the most prevalent and levels were significantly correlated with levels in maternal serum and infant cord blood [22
]. Placenta and umbilical cord blood rely on the mother’s dietary intake, thereby reemphasizing the importance of maternal nutrition during pregnancy.
Lutein and zeaxanthin have established roles as antioxidants and visual filters. Their presence in the eye may serve as a protective factor against oxidative damage during early development due to the high metabolic activity of this tissue, abundance of long-chain polyunsaturated fatty acids, and vascularity. Beyond protection, these carotenoids also support neuronal development via stabilizing microtubules [23
], enhancing gap junction communication [24
], improving vasculature [25
], and stabilizing and modifying the permeability of membranes [26
Choline, a precursor to acetylcholine, is an essential nutrient that aids in cell membrane signaling and transporting lipids via lipoproteins [27
]. Choline is also required to synthesize phospholipids including phosphatidylcholine and sphingomyelin, both of which are essential components of cell membranes. During pregnancy, the requirements for choline increase because of elevated maternal demand and the rapid division of fetal cells [28
]. Choline can also influence stem cell proliferation and choline insufficiency can promote cellular apoptosis. As a result of insufficiency, brain and spinal cord structure may be altered, increasing the risk for neural tube defects [27
Beyond its ability to synthesize neurotransmitters and molecules necessary for normal functioning of the human body, choline also plays a vital role in cognitive development. During the later stages of pregnancy, the hippocampus (the memory center of the brain) develops and continues to develop after birth and up until four years of age. A lack of choline in the maternal diet during critical periods of fetal development may cause lifelong changes in a child’s brain structure and function, including the hippocampus. New evidence also suggests that sufficient maternal choline intake during pregnancy and lactation can have long-lasting beneficial neurocognitive effects on the offspring [29
Furthermore, cross-sectional data also reveal that consumption of choline from foods and beverages is not optimal. Data from What We Eat in America, NHANES 2015–2016, demonstrate that women of childbearing age, 20 years and over, consume about 287 mg per day of choline from foods and beverages, which is considerably below the Adequate Intake (AI) recommendation of 425 mg per day for non-pregnant women and even further below the recommendation for pregnant women (450 mg per day). Ensuring that women of childbearing age receive optimal amounts of choline in their diet should be made a public health priority, to decrease risk for neural tube defects and to foster the healthy growth and development of young children [30
Folate is a B-vitamin important for both fetal and maternal health, functioning as a coenzyme critical for DNA synthesis and amino acid metabolism. Folate is a generic term that includes both the naturally occurring forms of the vitamin (from food) or folic acid, a form commonly found in dietary supplements and fortified foods. For women of childbearing age, folate is critical to normal neural tube development (the area from which the brain and spinal cord form) in the fetus within 28 days of conception. One of the other major functions of folate is that it provides single carbon units for the synthesis of nitrogenous bases (purine and pyrimidine) and amino acid metabolism, making folate essential for DNA synthesis [31
]. This metabolic pathway is also important for erythropoiesis, which is rapidly surging during pregnancy to help increase the mother’s blood volume in preparation for the fetus.
Iodine is a micronutrient that works in tandem with the thyroid gland. The thyroid gland uses iodine from food to make two thyroid hormones including thyroxine (T4) and triiodothyronine (T3). During pregnancy, iodine requirements are increased by ≥ 50% due to increases in maternal thyroid hormone production necessary to supply to the fetus, which does not have a fully functional thyroid gland until 20 weeks gestation [1
]. In the fetus, iodine is important for normal brain and nervous system development [33
Iron is a trace mineral that is required for fetal growth and development, because it serves as a cofactor for enzymes involved in oxidation–reduction reactions, which occur in cellular metabolism. Iron is also a major component of hemoglobin, the protein that allows red blood cells to carry oxygen throughout the body. The neonatal brain is in an active metabolic state consuming about 60% of total body oxygen (in comparison, the adult brain consumes about 20% of total body oxygen); therefore, pregnant women have high demands for iron. Pregnancy also requires a large expansion in blood volume to meet the demands of the growing fetus.
A prospective cohort study compared nutrient intake levels during pregnancy to recommended intake levels and found that none of the pregnant women (n
= 200) achieved the recommendation for dietary iron [34
]. Meeting the iron recommendation of 27 mg per day is especially important during the last trimester of pregnancy, since the fetus accumulates iron for use during early life.
Research has shown that if pregnant women are iron deficient, and, consequently, iron is not available to the infant in the first six months of life, there can be lifelong irreversible neurological effects [35
]. Furthermore, women who meet iron requirements during pregnancy may provide an advantageous impact on cognitive development in their children [36
]. In the first year of life, iron continues to play a vital role in neurodevelopment. During this time, the brain experiences a considerable transformation, becoming a complex organ. Several neurodevelopmental processes occur, including synaptogenesis, the organization of neurotransmitter systems, and the onset of myelination, especially within the hippocampus, visual and auditory systems. Iron is also associated with critical cellular processes in the brain, including the maintenance of neural cell energy and neurotransmitter homeostasis. Collectively, because the brain continues to develop during infancy and early childhood, iron may have an influence on cognitive ability and behavior [36
3.1.6. Omega-3 Fatty Acids
Omega-3 fatty acids include alpha-linolenic acid (ALA, 18:3n3), eicosapentaenoic acid (EPA, 20:5n3, docosapentaenoic acid (DPAn3, 22:5n3) and docosahexaenoic acid (DHA, 22:6n3) [38
]. All of these are significant dietary components, however, EPA and DHA will be the primary focus of our discussion, with DHA being the principal omega-3 found in mammalian tissues. ALA, an essential omega-3 fatty acid, is enzymatically converted in vivo to EPA (which can subsequently be converted to DHA). However, due to enzymatic competitive inhibition, this process is inefficient. Therefore, direct consumption of DHA is optimal to achieve ideal circulating levels [39
Omega-3 fatty acids, DHA in particular, are important for supporting a healthy pregnancy. There is an active transport of DHA and other polyunsaturated lipids across the placenta [40
] to support the high demands for fetal growth, especially during the last trimester [41
]. Crawford, et al., have described the process where there is an increased concentration of DHA going from mothers’ bloodstream to the fetal bloodstream to the fetal brain as “biomagnification”. This process is suggested to provide for optimal fetal brain development and rapid accumulation of a high concentration of nervous system DHA [43
Mothers who have healthy intakes of DHA give birth to infants with more bloodstream DHA and better visual function as measured by visual evoked potentials [44
]. The continued intake of EPA and DHA are also important for the maintenance of the mother’s cardiovascular health, as they mitigate several risk factors for disease, including lowering triglycerides and LDL, raising HDL and modulating blood pressure, heart rate and arterial compliance [45
]. The level of omega-3 fatty acids in the mother’s bloodstream during pregnancy has been shown to correlate with insulin levels [46
] and adiposity [47
]. Newer lines of inquiry have indicated that prenatal DHA during the second half of pregnancy alters the infant epigenome (gene activity changes that do not affect the DNA sequence) and can alter developmental programming [48
3.1.7. Vitamin D
During pregnancy, vitamin D plays a vital role in fetal growth and development by supporting the skeletal system, and the formation of tooth enamel, and by aiding in calcium regulation [49
]. There is also some emerging evidence to support a role for vitamin D in fetal immune development and function [49
]. During pregnancy, maternal calcium is mobilized, and subsequent utilization increases to meet the demands of fetal bone mineralization. As a result, several physiological adaptations take place, including increased serum calcitriol, vitamin D binding protein, placental vitamin D receptor (VDR) and renal and placental CYP27B1 (the enzyme that produces the bioactive form of vitamin D) to maintain normal serum levels of 25(OH)D and calcium. Maternal 25(OH)D crosses the placenta and is the main form of vitamin D for the fetus. Additionally, vitamin D escalates calcium absorption and placental calcium transport during pregnancy, while also regulating immune system function and modulating inflammation. All these effects indicate how important vitamin D is during gestation [50
]. Several observational studies show a relationship between inadequate serum 25(OH)D in pregnant women and adverse neonatal and pregnancy outcomes including preeclampsia, small for gestational age (SGA), preterm birth and gestational diabetes mellitus [51
Pregnancy is a period of increased nutrient demands, when optimal nutrition is critical for maturing, proliferating, and differentiating cells throughout the fetus.
Carotenoids play a key role in brain, eye and nervous system development.
Choline fuels cell growth and proliferation, as well as nervous and cognitive system development.
Adequate intakes of folate prior to and during pregnancy may help to prevent neural tube defects. Folate also plays a key role in DNA synthesis and amino acid metabolism.
Iodine helps produce thyroid hormones, that are transferred to the fetus early in life.
Iron is a major component of hemoglobin, a protein that allows red bloods cells to transport oxygen throughout the body.
Omega-3 fatty acids are crucial for the development of the nervous system and eye, and overall fetal growth.
Vitamin D supports the skeletal system, helps to regulate calcium levels by increasing calcium absorption, and may negate adverse pregnancy outcomes including preeclampsia, SGA, preterm birth and gestational diabetes mellitus.
Ensuring that women of childbearing age receive optimal nutrition should be a priority for health professionals.
3.2. The Postpartum Period: Feeding Baby
Scientific organizations including the American Academy of Pediatrics (AAP) and the Academy of Nutrition and Dietetics (AND) recommend exclusive breastfeeding for six months, with continuation for one year or more, as desired by the mother [52
]. A World Health Organization review along with an opinion paper published by the European Food Safety Authority (EFSA) described that exclusive breast feeding by well-nourished mothers for six months can meet the needs of most healthy infants for energy, protein, and for most vitamins and minerals, with the exception of vitamin K and vitamin D, both of which can be addressed by supplementation [54
Lactating women require nutrients in increased amounts in comparison to non-pregnant women, including vitamins A, E, B6, B12, choline, folate, iodine, lutein and zeaxanthin, zinc, omega-3 fatty acids, as well as increased amounts of fiber and protein (Table 2
). Nutrients that are low in breast milk include zinc, iron, and vitamin D. Several scientific organizations recommend supplemental vitamin D to infants, and especially to exclusively breastfed infants. Infants receive most of the required amount of vitamin D from sun exposure, and the rest from formula or breast milk [53
]. For breastfeeding mothers, only minimal amounts of maternal serum 25(OH)D are transferred to human breast milk; therefore, to provide sufficient vitamin D content in breast milk for the infant, the vitamin D intake of the mother during lactation has to be much higher compared to the intake during pregnancy. Overall, mothers who choose to breastfeed can consider micronutrient supplementation [1
While breastfeeding is considered the gold standard for feeding infants, it is not always possible for all mothers to achieve. Potential barriers to breastfeeding include overall discomfort, improper latching, lack of knowledge or uncertainty about breastfeeding, and the stress of returning to work [57
]. Breast milk and formula provide infants with water, carbohydrates, human milk oligosaccharides, essential fatty acids, proteins, carotenoids, and vitamins and minerals [58
]. Human milk contains nutrients, growth factors and cells important for brain development that formula lacks, however, formula contains vitamin D, iron, and omega-3s that may be insufficient in breast milk, especially if the mother is deficient [1
]. It is important for families to consult with health professionals to develop a feeding plan that gives the mother and baby the best chance for health and healthy development.
AAP and AND recommend exclusive breastfeeding for 6 months, with continuation for ≥1 year, or as desired by mother.
Health professionals should be aware of the differences between breast milk and formula to help families make healthy feeding plans for their infants.
Lactating mothers have increased nutrient needs, and they may be deficient in iron, zinc, and vitamin D.
While breast milk is the gold standard for feeding, breastfeeding or formula feeding can be the primary source of nutrition for the growing child.
4. Nutrition for the Growing Child, 0–24 Months
Infants change dramatically in the first 24 months of life and each child can vary considerably in terms of their growth, development, and feeding patterns (Figure 2
). Immediately after birth, newborns lose about 5%–10% body weight, until about two weeks of age, when they have established good feeding patterns, begin to gain weight, and grow. From birth until two years of age, infants and toddlers have extremely high metabolic rates and calorie needs. Newborns, for example, require about 50 calories per pound daily to support rapid growth and a high basal metabolic rate. After two to three months of age, calorie needs decrease to about 40 calories per pound and remain at this level until the age of three [59
Complementary foods are defined as solids or liquids other than breast milk or infant formula. The introduction of complementary foods represents a period when breast milk or formula alone is no longer enough to meet the nutritional demands of infants, usually at four to six months of age [54
]. During this time, breast milk or formula should be continued, but infants should be offered complementary foods with a variety of flavors and textures; this is necessary for both nutritional and developmental reasons [54
]. In terms of specific nutrients required by growing children, Table 3
provides the Dietary Reference Intakes (DRI) for key nutrients required for healthy growth and development (by stage). Nutrients such as fat, including the essential fatty acids, linoleic and alpha-linolenic acids, are an important determinant of energy supply throughout the first year of life and should be well supplied in the diet. Even though a DRI has not been established for carotenoids such as lutein and zeaxanthin, there is a growing body of evidence that these nutrients are important for the development of the visual and neural systems and have a positive impact on health outcomes [20
At six months of age, requirements for other nutrients, such as iron and zinc, increase dramatically (Table 3
). By this time, the infant’s internal stores are depleted and the need for iron and zinc increases, as the physiological requirement per kg body weight becomes greater than later in life [54
]. Due to the quick growth and metabolic rate during this stage, the nutrient density of foods offered in the diet needs to be high. Dairy products, pulses, and leafy green vegetables should be included in the diet when possible, since they are key sources of protein, calcium, and vitamin D, which are required to support the growth of healthy bones and prevent rickets [54
]. Furthermore, foods that provide adequate levels of vitamin A, C, B6, B12, and folate are particularly important to include in toddlers’ diets, as they can help to prevent major nutrient-related deficiencies, enhance non-heme iron absorption, and foster healthy growth and development [54
]. A study of US toddlers between 18 and 36 months indicates a very low DHA intake of about 20 mg per day which is consistent with NHANES reports of intakes of 20 mg/day in children under 6 years of age [60
]. Correcting this deficiency led to an improvement in their respiratory health [60
By 6 months of age, infant iron and zinc stores are depleted, therefore foods that contain these nutrients should be preferentially offered.
From 6 months onward, growth and development continue to be rapid, and nutrients such as protein, calcium and vitamin D are required for accretion of skeletal mass and to help prevent nutritional rickets.
Omega-3 fatty acids, specifically DHA, are required for continued brain and eye development.
Carotenoids, such as lutein and zeaxanthin, continue to play key roles in eye and neural development.
7. The Role of the Microbiome in Pregnancy, the Postnatal Period, and the Growing Child
The first 1000 days of life are a critical period of development, and all aspects of environment may play a role in shaping future health, including the microbiome [307
]. Bacterial colonization may begin early, during fetal development. It has been previously thought that the uterus is sterile and the first encounter of the infant with microbes happens during delivery. However, there is recent literature that has identified microbes from placenta [308
], amniotic fluid [308
], umbilical cord [309
], and meconium [310
]. Microbiome changes in composition and diversity begin in the first trimester and continue to change through the third trimester [311
]. These changes are usually associated with metabolic syndrome and disorders, however, in the case of pregnancy they are considered to be beneficial for pregnant women, since they would support the growth of the fetus and also potentially help with energy demands during the lactation period [311
Since pregnancy itself is associated with transformation of the gut microbiota towards what is usually considered an obesogenic microbiota, there are also studies in which the impact of gestational diabetes (GDM) and/or obesity on gut microbiota has been assessed. GDM has been shown to be associated with further changes in the gut microbiota; Actinobacteria have been shown to be enriched, similarly to species within genera Collinsella
. Moreover, even after adjustment for BMI before pregnancy, five OTUs were different between women with GDM and healthy pregnant women of which Butyricicoccus
was negatively associated with insulin sensitivity and Akkermansia
spp. was associated with lower insulin sensitivity [312
After delivery, it takes several months for the mother’s gut microbiota to return to the pre-pregnancy state. It has been shown that delivery and lactation don’t significantly alter the gut microbiota, at least for the first month [313
]. Moreover, the gut microbiota of mothers with GDM did not return to a “normal” state, even after 8 months postpartum [312
]. One important microbial population after the delivery is milk microbiota. It has been proposed that a bacterial entero-mammary pathway enables the milk microbiota to exist. Streptococcaceae, Staphylococcaceae, and Bifidobacteriaceae families have been reported to form the core milk microbiota [314
]. However, the milk microbiota varies between different geographical locations and delivery mode. For example, Chinese women have been shown to have a high abundance of Actinobacteria, whereas Spanish women have been shown to have a high abundance of Bacteroidetes. Moreover, women having a cesarean birth have been shown to have a high abundance of Proteobacteria [315
Vaginal, oral, and skin microbiota of the mother will also have an impact on the seeding of the infant’s microbiota. Healthy vaginal microbiota is dominated by lactobacilli, and, unlike other microbial populations within the human being, lower α-diversity is associated with healthier vaginal microbiota. Moreover, studies have shown that disturbed vaginal microbiota may impact the length-for-age Z
-score (LAZ), and therefore influence the growth of the infant [316
]. The importance of oral and skin microbiota in pregnancy has been studied less, but they have been shown to affect the initial colonization of bacteria within an infant gut [317
Bacterial colonization of the infant gastrointestinal tract is influenced by mode of delivery, prematurity, type of feeding (breast feeding vs. formula feeding), antibiotic treatment of the child or the mother, lifestyle, and geographical location [318
]. The earliest colonizers are usually facultative anaerobic bacteria such as Enterobacteriaceae, Streptococcaceae and Staphylococcaceae, whereas later colonizers tend to be strict anaerobes, e.g., Bifidobacterium
spp., and clostridia, regardless of the infant’s geographical origin and methods used for the detection [311
] (Figure 3
). It has also been shown that the mother-to-infant microbial transmission has been compromised in infants born by caesarean, since only 41% of the fecal infant early colonizers (at species level) were found from the mother’s fecal microbiota, whereas, in the case of vaginal delivery, 72% of the species were found from the mother’s fecal microbiota [319
]. Caesarean birth has also been shown to alter microbial β-diversity, as compared to vaginally-delivered infants. Moreover, in a recent study it was shown that a decrease in Bacteroidetes in caesarean infants was also associated with an altered metagenomic landscape during the first year of life. Since Bacteroides
spp. are an important species with regards to regulation of intestinal immunity, these changes could have long-lasting health implications [320
Immediately after birth, within the first 24 h, high microbial species diversity in the infant have been observed, but this decreases during the first week of life [317
]. The fecal microbiota of vaginally delivered babies has been shown to be enriched in Bacteroides
spp., and Escherichia
spp. (Figure 3
), whereas the fecal microbiota of babies delivered by Caesarean birth has been shown to be enriched with Enterobacter
spp., and Veillonella
Importantly, some of the early colonizers are transient, for example Haemophilus parainfluenzae
and Prevotella melanonigenica
, were found in the infant fecal sample at day one but were not found at subsequent sampling points [319
]. Since these bacterial species are not usually associated with fecal/gut microbiota, they most likely originated from body sites of the mother than the gastrointestinal (GI) tract [317
]. Bacterial species that are associated with the GI tract, e.g., Bacteroides vulgatus
, Bifidobacterium longum,
and Bifidobacterium breve
, were found throughout the follow-up period of 4 months [319
]. In addition, vaginal species, which totaled up to 16% of infant fecal microbiota at day 1, were under detection limits at 1 week of age [317
By the end of the first year of life, when the child has already started to eat the same foods as the adults and ceased breastfeeding, the gut microbiota starts to converge towards a profile characteristic of the adult microbiota (Figure 3
). However, the fecal bacterial diversity is still lower [319
]. In a cohort from the U.S., it has been shown that the relative abundance of Bifidobacterium
spp., and Erysipelotrichaceae decreases, whereas the relative abundance of Faecalibacterium
spp. and Clostridiales increases between 1 year of age and 2 years of age [320
]. By the end of the second to third year, the phylogenetic composition evolves even more towards the adultlike composition [320
]. Moreover, the gut microbiota will continue to evolve. It has been shown in children and adolescents that, even though the microbiota starts to resemble that of adults, there are still differences from the adult microbiome in the microbial diversity and microbial pathways throughout childhood [321
The gut microbiota changes during pregnancy and continues to evolve during the postpartum phase. Changes in microbial diversity and composition have been noted from the first to third trimesters.
The mother’s fecal, vaginal, oral and skin microbiota have a direct impact on the infant’s microbiota
Bacterial colonization of the infant’s gastrointestinal tract is influenced by mode of delivery (vaginal vs. caesarean)
By the end of the first year of life, gut microbiota begins to converge towards an “adult like” profile. Microbiome changes continue through childhood.
The first 1000 days of life represents a critical period for healthy growth and development. This review has found that, while all essential nutrients are required to support a healthy pregnancy, eight key nutrients, including carotenoids (lutein + zeaxanthin), choline, folate, iodine, iron, omega-3 fatty acids and vitamin D, are necessary throughout the stages of gestation, during the postpartum period, and through the 2nd birthday. This review has also identified that little information exists regarding the prevalence of nutrient deficiencies for infants and toddlers in the USA. Nutrient deficiency in this age group is of concern because it can have long-term consequences on growth and development and may also impact wellness as an adult. Therefore, it is critical that we begin to close this knowledge gap by studying children more.
In terms of supplementation, very little information has been reported in the literature on maternal postnatal health. This makes it challenging for healthcare providers to guide post-partum mothers on their nutritional transition to motherhood. Similarly, for infants and toddlers, research on nutrient supplementation is limited, and more work is especially needed on nutrients that play key roles in visual and cognitive development, such as the carotenoids, iron, vitamin D, and omega-3 fatty acids.
Finally, an evolving area of research relative to this review topic, is the role of the microbiome from pregnancy through the child’s second birthday. From this review, we’ve learned that the gut microbiota adapts during pregnancy and continues to evolve during the postpartum phase. The bacterial colonization of the infant’s gastrointestinal tract is influenced by the mode of delivery, however, by the end of the first year of life, the gut microbiota appears more adult-like.
While much remains to be discovered in the areas of nutrient supplementation, nutrient deficiencies, and the changing gut microbiota, expectant mothers should continue to work with nutrition gatekeepers and qualified healthcare practitioners. Achieving a diet plan that provides flexibility in planning while still meeting nutrient requirements for carotenoids (lutein + zeaxanthin), choline, folate, iodine, iron, omega-3 fatty acids and vitamin D is critical. Expectant mothers who fall short on these nutrients may consider taking a supplement to help fill their dietary gap.