Early Nutrition and Its Effect on Growth, Body Composition and Later Obesity
Introduction
Adequate nutrition during the first years of life is essential to provide a healthy growth pattern, both in the short and long term. The literature in this field has increased considerably since we wrote our first chapter on this topic for the Yearbook 2016. There has been an increasing interest in nutrition during the first 1,000 days and how it can have programming effects. We have not included papers on nutrition during pregnancy but have focused on the first 2 years of life. In high-income countries, the majority of papers focus on the healthy growth pattern and how it might prevent later overweight and obesity. However, there is an increasing number of studies from low- and middle-income countries focusing on how early nutrition can prevent undernutrition. We have also included a few studies on this topic.
Among the many papers published between July 1, 2019 and June 30, 2020, we have chosen 9 papers which we found interesting. Some because they were of outstanding quality and some because they added interesting and important new aspects to a relevant area. The areas we have covered include: (1) Human Milk Composition and Growth (3 papers), (2) Breastfeeding Duration and Growth (3 papers), (3) Protein Content of Infant Formula and Growth (1 paper), and (4) Animal Source Food and Early Growth (2 papers).
Human Milk Composition and Infant Growth
Associations between human milk oligosaccharides and growth in infancy and early childhood
Comments: This paper is commented below with the following paper (Mazzocchi et al.)
Hormones in breast milk and effect on infants’ growth: A systematic review
Comments: Bioactive compounds in human milk are likely to influence infant growth and health. However, knowledge about the specific mechanisms is lacking in most cases, but an increasing number of studies have addressed this. We have chosen two papers, which are providing interesting new information on this topic. The study by Lagström et al. is interesting because they investigate the association between pre pregnancy BMI and human milk oligosaccharides (HMOs) as well as HMOs and infant growth up to the age of 5 years. They included 802 mother-infant pairs and collected a total of 802 breast milk samples at 3 months’ postpartum. Mothers were instructed to express 10 mL milk themselves by manual expression. Milk samples were analyzed for the concentration of each HMO, and the total HMO concentration, diversity, and evenness were calculated. Maternal secretor status was determined with 87% of the mothers being secretors. Infant growth was examined at 3, 6 and 8 months and 1, 2, 3, 4, and 5 years, and all time points were included in the analyses. They found that maternal pre pregnancy BMI was negatively associated with HMO diversity and lacto-N-neo-tetraose (LNnT) in secretor mothers and positively associated with 2′fucosyllactose (2′FL) in both secretor and non-secretor mothers. Interestingly, child height and weight were negatively associated with HMO diversity and LNnT and positively associated with 2′FL up to 5 years, but only in non-secretor mothers. They adjusted for maternal prepregnancy BMI, which suggests an independent relation with growth. The effects of LNnT and 2′FL, which is the most abundant HMO, are of special interest because they are now added to some infant formula. HMO diversity has previously been shown to be negatively associated with total fat mass at 1 month [1], which supports the findings by Lagström and colleagues. Furthermore, in a study of breastfed infants with excessive weight gain, we found that maternal BMI at 5 months’ postpartum was positively associated with concentration of 2′FL and that 2′FL was positively associated with weight velocity up to 5 months and with fat mass index at 5 months, suggesting an effect of HMO composition on fat mass accretion [2]. As pointed out by Lagström and colleagues, the effect of HMO on growth might be mediated through an effect on the gut microbiota, but this needs to be confirmed in other studies.
Many bioactive hormones in human milk can potentially influence growth, some of them through an appetite-regulating effect. Quite a lot of studies have explored this
topic. Some of these hormones could have a role in reducing the risk of overweight and obesity in breastfed infants, although the effect is limited in most reviews on this
topic. Many of the studies on human milk hormones and growth are included in the systematic review by Mazzocchi and colleagues, which aimed to evaluate the impact of appetite- and growth-related hormones in breast milk on infant growth. The authors included 15 observational studies investigating the five hormones leptin, ghrelin,
IGF-1, adiponectin, and insulin. The overall conclusion was contradictive findings of effects on growth and fat deposition. Leptin and adiponectin were the most investigated hormones represented in 13 and 11 studies, respectively. The authors overall conclude contradictive findings also for these hormones. However, 4 of the 13 studies investigating leptin report negative associations between breast milk leptin and the infant growth outcomes, BMI z-score [3], weight-for-length z-score [4], infant weight [5], and weight gain [6], indicating a satiety effect of human milk leptin. However, the growth outcomes in the different studies varies, which makes comparison challenging as other factors might influence the associations. The findings on leptin are supported by two recently published studies; the study by Enstad [7] reports that human milk (HM) leptin at 4 months was negatively associated with infant fat mass percentage, and Larson-Meyer [8] found that HM leptin measured at 1 month was negatively associated with infant weight-for-age z-score at both 6 and 12 months. Although Mazzocchi and colleagues conclude contradictive findings in their systematic review, these new publications contribute to the understanding of leptin as an appetite-regulating hormone. A major limitation is the method of milk sample collection, which differs between the studies and makes comparison problematic. Human milk composition changes during lactation, throughout the day and throughout the feed. Especially
hind milk has been shown to contain higher levels of fat compared to foremilk [8], and total fat content is suggested to be higher during the day and evening compared to morning and night [9], which might also influence concentrations of leptin in the milk. To our knowledge, there is no golden standard for milk sample collection yet, and a validated method needs to be established in order to compare future studies.
A general concern when investigating the influence of bioactive compounds on infant growth is whether the compounds are absorbed in the infant gut. Only a few
studies have explored the association between the concentrations of hormones in HM with the concentrations found in the infant’s circulation, which might support the associations. A better understanding of how HM composition is related to weight gain, linear growth, and body composition is a fascinating research area, which is
likely to provide a better understanding of mechanisms behind growth, growth faltering, and overweight. More longitudinal studies are needed to strengthen the understanding of the associations between milk composition and growth. Two ongoing large multicenter studies, also including low and middle-income countries, are likely to provide interesting and relevant results on this topic (MILQ: www.clinicaltrials.gov/ct2/show/NCT03254329 and IMiC: www.milcresearch.com/imic.html).
Subclinical mastitis in a European multicenter cohort: Prevalence, impact on human milk (HM) composition, and association with infant HM intake and growth
Comments: Subclinical mastitis (SCM) is a local inflammation in the mammary glands typically caused by milk stasis or infection. The condition causes increased permeability of the tight junctions, which allows larger substances to pass from plasma to the milk. This could change the milk composition and possibly influence infant growth. This large cohort study called ATLAS was conducted in seven European countries and aimed to assess HM composition and maternal diet as well as other clinical maternal and infant parameters for the mother and infant. In this present study, the authors investigated HM composition, infant growth, and HM intake in mothers with SCM (Na:K ratio >0.6) compared to mothers without SCM. They collected milk samples on day 2, 17, 30, 60, 90, and 120 after birth, which were analyzed for macronutrients, minerals, and trace elements. Infant growth parameters were measured at the same time points, and milk intake was assessed using a modified test weighing method on a subset of participants close to a study visit. The authors found a prevalence of SCM of 35.4%, mainly occurring during the early time period, which is in line with previous literature [10]. In addition, they found large differences in SCM prevalence among countries with high prevalence for Romania (67%) and low prevalence for Norway (0%) and Italy (7%), although some countries have low sample size. Besides low sample size, an explanation could be difference in breastfeeding practice among countries as SCM often occur due to milk stasis. The authors also report significantly lower gestational age at delivery and higher rates of caesarean mode of delivery for mothers with SCM. Although they found no difference in total energy in the milk, milk from mothers with SCM had higher levels of protein and lower levels of lactose. Additionally, they reported higher levels of iron, selenium, manganese, zinc and copper, and lower levels of calcium and phosphorous in the milk from mothers with SCM. The mechanism behind these altered HM levels of macro- and micronutrients was suggested to be higher permeability caused by SCM. As the highest prevalence of SCM was seen at day 2 postpartum (39.6%), when colostrum is still dominant, it could be discussed whether these results reflect HM composition in colostrum and a higher permeability partly due to early milk stasis. Thus, SCM defined by a Na:K ratio of 0.6 reflecting high permeability could be a physiological condition in very early breastfeeding. The study reports no significant differences in infant growth parameters between mothers with SCM and without SCM, although they found lower birth weight and smaller head circumference, which can be explained by the significantly lower gestational age at birth. Their findings are most likely influenced by the low frequency of SCM at the later time points, which are included in their statistical analysis.
A recently published study by Li et al. [10] investigating whether SCM, HM cytokines, and intake of minerals and trace elements were associated with infant growth found
presence of SCM negatively associated with weight-for-length Z-score (WLZ) during early lactation. Further, they found that IL-1β was negatively associated with LAZ and
positively associated with linear growth velocity, although IL-1β was unaffected by SCM. They also reported higher prevalence of SCM in early (30%) compared to established (10%) breastfeeding, which supports the findings by Samuel et al. (reviewed herewith). Furthermore, it supports the hypothesis that SCM in early lactation defined by a Na:K ratio of 0.6 might be a naturally occurring condition. Levels of interleukin(IL)-6, IL-8, and TNF-α were elevated in milk from mothers with SCM and were positively correlated with the Na:K ratio during early lactation reflecting the inflammatory state. Lastly, they report higher levels of selenium, which is in line with the finding by Samuel et al. Li et al. suggest that the altered levels of micronutrients in milk from mothers with SCM can result in inadequate intake for the infants and/or cause microbial dysbiosis, and thereby influence infant growth. Until now, SCM has primarily been investigated in animal studies, so human studies exploring SCM and the influence on HM micronutrient composition, milk intake, inflammation markers, and infant growth are needed. It is especially interesting in future studies to investigate to what degree early SCM is related to altered levels of inflammation markers or if it is rather caused by increased permeability.
Breastfeeding Duration and Growth
Early infant feeding and BMI trajectories in the first 5 years of life
Comments: This paper is commented together with the following two papers below (Bjertnaes et al. and Wu et al.).
No significant associations between breastfeeding practices and overweight in 8-year-old children
Comments: This paper is commented together with the following paper below (Wu et al.).
Exclusive breastfeeding can attenuate body-mass-index increase among genetically susceptible children: A longitudinal study from the ALSPAC cohort
Comments: The protective effect of breastfeeding on later overweight and obesity is still a subject of discussion, and conflicting results have been reported [11–14]. This is also reflected in the three papers we have chosen, which are discussed below. In the study by Zheng et al., associations between both duration of breastfeeding (≥6 vs. <6 months) and time of introduction of complementary feeding (before vs. after 6 months) and constructed BMI z-score (BMIz) trajectories from birth to 5 years were
investigated in a cohort of 542 Australian infants.
The study adds to the other studies examining growth trajectories and breastfeeding, investigating the associations at several time points during infancy and early childhood. The authors found a consistent lower BMIz from 3 months of age and up to 5 years for infants breastfed for at least 6 months compared to infants breastfed less than 6 months. The difference persisted after adjustments for potential confounding factors such as child birth weight, maternal education, and pre pregnancy BMI. At the age of 5 years, the adjusted mean difference in BMIz was –0.23. It is interesting that they found the association of duration of breastfeeding and timing of introduction of solid foods with BMIz trajectories to be independent of each other. Children introduced to solids before 6 months had a higher BMIz at 42 months in unadjusted models, but the difference disappeared at 5 years. Thus, the timing of complementary feeding seems to be less important for later BMI compared to duration of breastfeeding. A shortcoming of the study is that information on duration of exclusive breastfeeding was not included and that both breastfeeding and introduction of solids were only analyzed as binary variables. Duration of breastfeeding and age of introduction of solids should be included in future studies to explore the possible dose-response relations and differences between breastfeeding groups.
Information on duration of exclusive and partial breastfeeding was available in the Norwegian study by Bjertnæs et al., which included 951 children. However, the authors found no associations in adjusted analyses between BMIz at 8 years of age and duration of exclusive or partial breastfeeding indicating no significant dose-response relationship. Besides birth weight, parental education, and current parental BMI, they also adjusted for lifestyle factors such as dietary habits and physical activity in this study. This is relevant and a strength of the study as they might be potential confounders or mediators. Another difference between the studies is the time point for BMI measurement, where the Norwegian study measured BMI 3 years later in childhood (5 vs. 8 years). This could be important as the effect of breastfeeding might diminish over time. Zheng et al. collected data on duration of breastfeeding prospectively during infancy, while information regarding breastfeeding in the Norwegian study was collected when the children started pre-school, thus increasing the risk of recall bias. Furthermore, the high prevalence and duration of breastfeeding in the Norwegian study could result in a type II error not showing an effect as mentioned by the authors. Only 9.7% of the infants were never breastfed, and the mean duration of
exclusive breastfeeding and partial breastfeeding was 4.6 and 10.7 months, respectively. Though both studies were observational studies from high-income countries, the findings were inconsistent. These studies contribute to the understanding of the role of breastfeeding on later obesity. They show that the effect is not clear, and differences in methodology, settings, and the observational nature of studies may contribute to the discrepancy.
One reason that the effect of breastfeeding on later risk of obesity is conflicting and still discussed could be that the effect depends on the genetic risk of developing obesity. This was examined in the third paper we selected on this topic by Wu and colleagues. It is based on data from the large longitudinal British ALSPAC cohort study. In this sub-study, which included 5,266 children, BMI was measured from birth to 18 years. They constructed an obesity-specific risk score (GRS) from genome-wide significant genetic variants. In the upper GRS quartile with the highest risk of developing obesity, exclusive breastfeeding for 5 months reduced BMI at the age of 18 years by 1.14 kg/m2 in boys and by 1.53 kg/m2 in girls. These differences are remarkable and likely to be of clinical relevance at population level. This study might explain the conflicting results in many studies examining the potential protective effect of breastfeeding on risk of developing overweight and obesity. The genetic risk score might
differ between studies and could be included in future studies with a high sample size examining the additional effect of the genetic score. The results also support the recommendations about breastfeeding, as it seems like children with the highest genetic risk of developing overweight and obesity appear to have a reduced risk if they
are breastfed exclusively for 6 months.
Protein Content of Infant Formula and Growth
A modified low-protein infant formula supports adequate growth in healthy, term infants: A randomized, double-blind, equivalence trial
Comments: The impact of formulas on risk of later obesity has been widely investigated during recent years [15]. According to the “early protein hypothesis”, high protein intake in early life can stimulate growth, especially fat tissue, which can lead to increased risk of later obesity [16]. Therefore, new formulas with reduced protein content simulating the composition of human milk and growth patterns equivalent to breastfed infants are warranted. In this study, the safety of a low-protein infant formula was investigated. Growth was compared between infants receiving the low-protein formula, infants receiving a control formula with higher protein content, and a reference group of breastfed infants. Growth assessment was comprehensive, including weight, length, head circumference, and body composition. Besides changing the protein quantity, the authors optimized protein quality by adding free amino acids (30%). The protein content was 1.7 g/100 kcal in the low protein formula and 2.1 g/100 kcal in the control formula. To obtain the same relative content of free amino acids in both formulas, free amino acids were also added to the control formula. At 17 weeks and 6 months, there was no difference in growth or body composition between the two formulas, but compared to the breastfeeding reference group, both formula groups
showed higher weight and length gain. The authors conclude that low-protein formula is safe as the growth is adequate and within the WHO growth standards. In contrast, other studies have found different growth patterns for formulas with low versus high (standard) protein content, e.g. The EU Childhood Obesity Programme (CHOP)
[17, 18] and the Early Protein and Obesity in Childhood study (EPOC) [19]. However, in these studies the difference in protein content was larger compared to the study by Kouwenhoven et al. In the CHOP study, the protein content in the formula used for the first 4 months was 1.77 versus 2.9 g/100 kcal and 2.2 versus 4.4 for the formula
used after 4 months [17]. In the EPOC study, the protein content in the compared formulas was 1.8 versus 2.7 g/100 kcal used for the first 4 months. Furthermore, in the
study by Kouwenhoven et al., the mean age at enrollment was around 1 month, and the infants were allowed to breastfeed once a day, which might have affected the
growth. The findings of the study suggest that even lower protein content may be safe and advantageous for obtaining growth similar to that of breastfed infants. The
study furthermore emphasizes that not only protein quantity but also the amino acid profile should be optimized. As mentioned in the editorial by Liotto [20], discussing the paper by Kouwenkoven et al., a limitation is that the infants were only followed up to 6 months, and there was no information on milk intake volume [20]. Some free
amino acids seem to have an effect on milk intake volume. Especially the free glutamate content has been reported to influence volume intake [21]. In the paper by Kouwenkoven et al., there was a difference in total glutamate content between the two formulas, but the amount of free glutamate and other free amino acids in the two formulas was not included.
Animal Source Food Intake and Early Growth
The effect of eggs on early child growth in rural Malawi: The Mazira Project randomized controlled trial
Comments: This paper is commented together with the paper below (Ianotti et al.).
Egg intervention effect on linear growth no longer present after two years
Comments: Stunted growth is associated with increased risk of morbidity, mortality, and delayed cognitive development in childhood as well as reduced working capacity and economic productivity later in life [22]. It seems to start in utero and aggravate in early childhood [22]. Especially during complementary feeding, poor diet with low energy density and inadequate nutrients may contribute to growth faltering [23]. Intake of animal source foods, including eggs, dairy, meat, and fish, may increase linear growth [24–26]. Many studies have focused on the effects of dairy intake on linear growth and lean mass accretion [27, 28]. However, recently, eggs have gained increasing interest. In 2015, the Lulun project was conducted in Ecuador among 163 6- to 9-month-old infants [29]. The randomized controlled trial showed that intake of one egg per day for 6 months reduced the prevalence of stunting by 47% and increased length-forage Z-score (LAZ) by 0.63 [29]. The results were very promising, and a larger parallel study, published recently and discussed here, was set up to examine if a similar effect could be seen in 660 infants from rural Malawi. One egg per day was provided to 6- to 9-month-old infants during a period of 6 months. Anthropometry was measured at baseline and at 6 months follow-up. Unfortunately, Stewart et al. did not find any effect of the egg intervention on LAZ, weight-for-age Z-score, weight-for-length Z-increased by 0.18 (95% CI: 0.01–0.34) in the egg intervention group. The authors suggested that lack of effect could be due to a lower stunting prevalence at baseline (14% in Malawi vs. 38% in Ecuador) and higher intake of other animal source foods in the Malawian trial. The trial was conducted in communities close to a lake and around 2/3 of the children had consumed fish the previous 24 h at the 6-month visit. There was an interaction between maternal education and LAZ (p = 0.02). A significant effect of eggs on LAZ was observed in children whose mothers had completed primary school or higher (0.23, 95% CI: 0.04–0.42). The compliance with egg intake did not differ with maternal education; however, higher education was associated with, e.g. better housing, less illness, less fish, but more dairy intake. All these differences may have contributed to a higher response to the egg intervention. The education level of caregivers and the sanitary conditions in Ecuadorian households were better than they were in the Malawian study. It was speculated that this could perhaps also contribute to a larger effect of eggs on stunting in the Ecuadorian trial.
The other publication we have selected is a follow-up of the Lulun study. Approximately 2 years after the Ecuadorian Lulun project, more than 90% of the children that completed the trial were followed up in a Lulun II study to evaluate the possible long term effects of the egg intervention. However, there was no effect of the egg intervention on height-for-age Z-score (HAZ) after 2 years. In addition, children in both groups had declined in HAZ between termination of the first Lulun trial and conduct of the Lulun II follow-up study. HAZ decreased more among children in the egg than the control group (–1.4 to –2.1 HAZ vs. –1.7 to –2.0 HAZ). Predictors of the reduction in HAZ were analyzed, and intake of any eggs in the past 24 hours was associated with reduced growth faltering between termination of Lulun and Lulun II. This indicates that continued intake of animal source food is needed throughout complementary feeding and early childhood to support healthy growth. A limitation of the Lulun studies may be a risk of regression to the mean due to lack of equivalence of LAZ in the two groups at baseline of the first Lulun trial and the longitudinal study design. However, the RCT design should in principle minimize this risk.
Together, the two studies indicate that eggs may have an effect on linear growth; however, the effect may be small and may disappear if other animal source foods are
consumed. The effect of eggs on growth may also depend on the level of stunting, and perhaps the level of water, hygiene, and sanitation (WASH). Three highly profiled trials in Kenya, Bangladesh, and Zimbabwe investigating the separate and combined effects of WASH and nutrition interventions all found limited effects of nutrition interventions (0.13–0.25 LAZ) and no effects of WASH interventions on stunting [30–32]. In a joint article, the investigators recommended that future research in WASH should aim at radically more effective WASH interventions [33].
