Why do mothers mix milk feed their infants? Results from a systematic review.

CONTEXT: Combining or supplementing breastfeeding with formula feeding, also called mixed milk feeding (MMF), is a common infant feeding practice. However, there is no well-established MMF evidence-base for informing and guiding parents. A better understanding of the reasons why mothers practice MMF may facilitate identification of efficient strategies for supporting exclusive breastfeeding, and/or opportunities to prolong breastfeeding, at least partially. OBJECTIVE: An updated systematic literature review was undertaken with the primary aim of gaining a deeper understanding of the reasons why mothers choose MMF. DATA SOURCES: Six databases were searched for relevant articles published in English from January 2012 to January 2022. DATA EXTRACTION: Two reviewers independently performed the screenings and data extraction, and any differences were resolved by a third reviewer. Data from 138 articles were included, 90 of which contained data on MMF reasons/drivers, and 60 contained data on infant age and/or maternal demographic factors associated with MMF. DATA ANALYSIS: A total of 13 different unique MMF drivers/reasons were identified and categorized according to whether the drivers/reasons related to perceived choice, necessity, or pressure. Risk of bias was evaluated using the Quality Assessment Tool of Diverse Studies and the JBI Systematic Reviews tool. Several different terms were used to describe and classify MMF across the studies. The most commonly reported reasons for MMF were related to a perception of necessity (39% of drivers, eg, concerns about infant's hunger/perceived breast milk insufficiency or breastfeeding difficulties), followed by drivers associated with perceived choice (34%; eg, having more flexibility) and perceived pressure (25%; eg, returning to work or healthcare professionals' advice). This was particularly true for infants aged 3 months or younger. CONCLUSION: The key global drivers for MMF and their distribution across infant age and regions were identified and described, providing opportunities for the provision of optimal breastfeeding support. A unified definition of MMF is needed in order to enable more comparable and standardized research. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. CRD42022304253.

Mixed Milk Feeding: A New Approach to Describe Feeding Patterns in the First Year of Life Based on Individual Participant Data from Two Randomised Controlled Trials.

'Mixed Milk Feeding' (MMF), whereby infants are fed with both breastmilk and infant formula during the same period, is a common feeding practice. Despite its high prevalence, knowledge regarding MMF practices and their association with (health) outcomes is limited, potentially because MMF behaviours are highly variable and difficult to standardise longitudinally. In this paper, we applied a statistical clustering algorithm on individual infant feeding data collected over the first year of life from two clinical trials: 'TEMPO' (n = 855) and 'Venus' (n = 539); these studies were conducted in different years and world regions. In TEMPO, more than half of infants were MMF. Four distinct MMF clusters were identified: early exclusive formula feeding (32%), later exclusive formula feeding (25%), long-term MMF (21%), and mostly breastfeeding (22%). The same method applied to 'Venus' resulted in comparable clusters, building trust in the robustness of the cluster approach. These results demonstrate that distinct MMF patterns can be identified, which may be applicable to diverse populations. These insights could support the design of future research studying the impact of infant feeding patterns on health outcomes. To standardise this in future research, it is important to establish a unified definition of MMF.

Prevalence of Zinc Deficiency in Healthy 1-3-Year-Old Children from Three Western European Countries.

Zinc deficiency (ZnD) has adverse health consequences such as stunted growth. Since young children have an increased risk of developing ZnD, it is important to determine its prevalence and associated factors in this population. However, only a few studies have reported on ZnD prevalence in young children from Western high-income countries. This study evaluated ZnD prevalence and associated factors, including dietary Zn intake, in healthy 1-3-year-old children from Western European, high-income countries. ZnD was defined as serum Zn concentration <9.9 µmol/L. A total of 278 children were included with a median age of 1.7 years (Q1-Q3: 1.2-2.3). The median Zn concentration was 11.0 µmol/L (Q1-Q3: 9.0-12.2), and ZnD prevalence was 31.3%. No significant differences were observed in the socio-economic characteristics between children with and without ZnD. Dietary Zn intake was not associated with ZnD. ZnD is common in healthy 1-3-year-old children from Western European countries. However, the use of currently available cut-off values defining ZnD in young children has its limitations since these are largely based on reference values in older children. Moreover, these values were not evaluated in relation to health consequences, warranting further research.

Mixed milk feeding: a systematic review and meta-analysis of its prevalence and drivers.

CONTEXT: Extensive literature is available on exclusive breastfeeding and formula-feeding practices and health effects. In contrast, limited and unstructured literature exists on mixed milk feeding (MMF), here defined as the combination of breastfeeding and formula feeding during the same period in term infants > 72 hours old (inclusion criterion). OBJECTIVE: A systematic review and meta-analysis were performed, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, on the global prevalence of MMF (primary outcome) and related drivers and practices (secondary outcomes). DATA SOURCES: The search of MMF in generally healthy populations was conducted across 6 databases, restricted to publications from January 2000 to August 2018 in English, Spanish, French, and Mandarin. DATA EXTRACTION: Two reviewers independently performed screenings and data extraction according to a priori inclusion and exclusion criteria. DATA ANALYSIS: Of the 2931 abstracts identified, 151 full-text publications were included for data extraction and 96 of those were included for data synthesis (the majority of those were cross-sectional and cohort studies). The authors summarized data across 5 different categories (feeding intention prenatally, and 4 age intervals between > 72 hours and > 6-23 months) and 5 regional subgroups. The overall prevalence of MMF across different age intervals and regions varied between 23% and 32%; the highest rate was found for the age group 4-6 months (32%; 95% confidence interval, 27%-38%); regional comparisons indicated highest MMF rates in Asia (34%), North and South America (33%), and Middle East and Africa together (36%), using a random effects meta-analysis model for proportions. Some drivers and practices for MMF were identified. CONCLUSION: MMF is a widespread feeding reality. A shared and aligned definition of MMF will help shed light on this feeding practice and evaluate its influence on the duration of total breastfeeding, as well as on infants' nutrition status, growth, development, and health status in the short and long terms. PROSPERO registration number CRD42018105337.

Iron status of young children in Europe.

Iron deficiency (ID) is common in young children aged 6-36 mo. Although the hazards associated with iron deficiency anemia (IDA) are well known, concerns about risks associated with excess iron intake in young children are emerging. To characterize iron status in Europe, we describe the prevalence of ID, IDA, iron repletion, and excess stores with the use of published data from a systematic review on iron intake and deficiency rates, combined with other selected iron status data in young European children. Various definitions for ID and IDA were applied across studies. ID prevalence varied depending on socioeconomic status and type of milk fed (i.e., human or cow milk or formula). Without regard to these factors, ID was reported in 3-48% of children aged ≥12 mo across the countries. For 6- to 12-mo-old infants, based on studies that did not differentiate these factors, ID prevalence was 4-18%. IDA was <5% in most studies in Northern and Western Europe but was considerably higher in Eastern Europe (9-50%). According to current iron status data from a sample of healthy Western European children aged 12-36 mo, 69% were iron replete, and the 97.5th percentile for serum ferritin (SF) was 64.3 µg/L. In another sample, 79% of 24-mo-old children were iron replete, and the 97.5th percentile for SF was 57.3 µg/L. Average iron intake in most countries studied was close to or below the UK's Recommended Dietary Allowance. In conclusion, even in healthy European children aged 6-36 mo, ID is still common. In Western European populations for whom data were available, approximately three-quarters of children were found to be iron replete, and excess iron stores (SF >100 µg/L) did not appear to be a concern. Consensus on the definitions of iron repletion and excess stores, as well as on ID and IDA, is needed.

Long-chain PUFA supplementation in rural African infants: a randomized controlled trial of effects on gut integrity, growth, and cognitive development.

BACKGROUND: Intestinal damage and malabsorption caused by chronic environmental enteropathy are associated with growth faltering seen in infants in less-developed countries. Evidence has suggested that supplementary omega-3 (n-3) long-chain PUFAs (LC-PUFAs) might ameliorate this damage by reducing gastrointestinal inflammation. LC-PUFA supplementation may also benefit cognitive development. OBJECTIVE: We tested whether early n-3 LC-PUFA supplementation improves infant intestinal integrity, growth, and cognitive function. DESIGN: A randomized, double-blind, controlled trial [200 mg DHA and 300 mg EPA or 2 mL olive oil/d for 6 mo] was conducted in a population of 172 rural Gambian infants aged 3-9 mo. The primary endpoints were anthropometric measures and gut integrity [assessed by using urinary lactulose:mannitol ratios (LMRs)]. Plasma fatty acid status, intestinal mucosal inflammation (fecal calprotectin), daily morbidity, and cognitive development (2-step means-end test and an attention assessment) were secondary endpoints. RESULTS: PUFA supplementation resulted in a significant increase in plasma n-3 LC-PUFA concentrations (P < 0.001 for both DHA and EPA) and midupper arm circumference (MUAC) (effect size: 0.31 z scores; 95% CI: 0.06, 0.56; P = 0.017) at 9 mo of age. At 12 mo, MUAC remained greater in the intervention group, and we observed significant increases in skinfold thicknesses (P ≤ 0.022 for all). No other significant differences between treatment groups were detected for growth or LMRs at 9 mo or for secondary outcomes. CONCLUSIONS: Fish-oil supplementation successfully increased plasma n-3 fatty acid status. However, in young, breastfed Gambian infants, the intervention failed to improve linear growth, intestinal integrity, morbidity, or selected measures of cognitive development. The trial was registered at www.isrctn.org as ISRCTN66645725.