Weaning practices in the United Kingdom and variations in anthropometric development

Optimal timing of introduction of complementary feeding: a systematic review and meta-analysis

CONTEXT

The timing of introducing complementary feeding (CF) is crucial because premature or delayed CF can be associated with adverse health outcomes in childhood and adulthood.

OBJECTIVE

This systematic review aims to evaluate the impact of the timing of CF introduction on health, nutrition, and developmental outcomes among normal-term infants.

DATA SOURCES

Electronic databases and trial registries were searched, along with the reference lists of the included studies and relevant systematic reviews.

DATA EXTRACTION

Two investigators independently extracted data from the included studies on a standardized data-extraction form.

DATA ANALYSIS

Data were meta-analyzed separately for randomized controlled trials (RCTs) and observational studies on the basis of early introduction of CF (< 3 months, < 4 months, < 6 months of age) or late introduction of CF (> 6 months, > 8 months of age). Evidence was summarized according to GRADE criteria. In total, 268 documents were included in the review, of which 7 were RCTs (from 24 articles) and 217 were observational studies (from 244 articles). Evidence from RCTs did not suggest an impact of early introduction, while low-certainty evidence from observational studies suggested that early introduction of CF (< 6 months) might increase body mass index (BMI) z score and overweight/obesity. Early introduction at < 3 months might increase BMI and odds of lower respiratory tract infection (LRTI), and early introduction at < 4 months might increase height, LRTI, and systolic and diastolic blood pressure (BP). For late introduction of CF, there was a lack of evidence from RCTs, but low-certainty evidence from observational studies suggests that late introduction of CF (> 6 months) might decrease height, BMI, and systolic and diastolic BP and might increase odds of intestinal helminth infection, while late introduction of CF (> 8 months) might increase height-for-age z score.

CONCLUSION

Insufficient evidence does suggest increased adiposity with early introduction of CF. Hence, the current recommendation of introduction of CF should stand, though more robust studies, especially from low- and middle-income settings, are needed.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42020218517.

Early Life Factors Influencing the Risk of Obesity

The obesity epidemic is a worldwide problem. Factors predisposing to obesity include genetics, race, socioeconomic conditions, birth by cesarean section, and perinatal antibiotic use. High protein (HP) content in infant formulas has been identified as a potential culprit predisposing to rapid weight gain in the first few months of life and leading to later obesity. In a large multicountry study the effects of lower protein (LP) formula (1.77 and 2.2 g protein/100 kcal, before and after the 5th month, respectively) were compared to those of higher protein (2.9 and 4.4 g protein/100 kcal, respectively). Results indicated that at 24 months, the weight-for-length z score of infants in the LP formula group was 0.20 (0.06, 0.34) lower than that of the HP group and was similar to that of the breastfed reference group. The authors concluded that a HP content of infant formula is associated with higher weight in the first 2 years of life but has no effect on length. LP intake in infancy might diminish the later risk of overweight and obesity. At 6 years of age HP children had a significantly higher body mass index (by 0.51; 95% confidence interval [CI], 0.13-0.90; p=0.009) and a 2.43 (95% CI, 1.12-5.27; p=0.024) fold greater risk of becoming obese than those who received the LP. In conclusion, several factors may influence development of metabolic syndrome and obesity. Breastfeeding should always be encouraged. An overall reduction of protein intake in formula non breastfed infants seems to be an additional way to prevent obesity.

Age at Weaning and Infant Growth: Primary Analysis and Systematic Review

OBJECTIVE

To test whether earlier age at weaning (age 3-6 months) may promote faster growth during infancy.

STUDY DESIGN

Weaning at age 3.0-7.0 months was reported by 571 mothers of term singletons in a prospective birth cohort study conducted in Cambridge, UK. Infant weight and length were measured at birth and at age 3 months and 12 months. Anthropometric values were transformed into age- and sex-adjusted z-scores. Three linear regression models were performed, including adjustment for confounders in a stepwise manner. Measurements at age 3 months, before weaning, were used to consider reverse causality.

RESULTS

Almost three-quarters (72.9%) of infants were weaned before age 6 months. Age at weaning of 3.0-7.0 months was inversely associated with weight and length (but not with body mass index) at 12 months (both P ≤ .01, adjusted for maternal and demographic factors). These associations were attenuated after adjustment for type of milk feeding and weight or length at age 3 months (before weaning). Rapid weight gain between 0 and 3 months predicted subsequent earlier age at weaning (P = .01). Our systematic review identified 2 trials, both reporting null effects of age at weaning on growth, and 15 observational studies, with 10 reporting an inverse association between age at weaning and infant growth and 4 reporting evidence of reverse causality.

CONCLUSION

In high-income countries, weaning between 3 and 6 months appears to have a neutral effect on infant growth. Inverse associations are likely related to reverse causality.

Safety assessment and risk–benefit analysis of the use of azodicarbonamide in baby food jar closure technology: Putting trace levels of semicarbazide exposure into perspective – A review

The discovery of trace levels of semicarbazide (SEM) in bottled foods (especially baby foods) led to a consideration of the safety of this hydrazine compound by regulatory agencies worldwide. Azodicarbonamide, which is used in the jar-sealing technology known as Press On-Twist Off (or Push-Twist/PT) closures for the formation of a hermetic, plastisol seal, partially degrades with the heat of processing to form trace amounts of SEM. This review has evaluated the potential toxicological risks of resulting exposure to SEM and also the benefit of the PT technology (with azodicarbonamide) in the context of possible microbial contamination. It also considers the potential impact on infant nutrition if parents come to the conclusion that commercial baby foods are unsafe. SEM shows limited genotoxicity in vitro that is largely prevented by the presence of mammalian metabolic enzymes. Negative results were found in vivo in DNA alkaline elution, unscheduled DNA synthesis and micronucleus assays. This pattern is in contrast to the genotoxic hydrazines that also have been shown to cause tumours. Carcinogenicity studies of SEM are of limited quality, show a questionable weak effect in mice at high doses, which are not relevant to human exposure at trace levels, and show no effect in the rat. The IARC has assigned SEM as Group 3, 'Not classifiable as to its carcinogenicity to humans'. Based on estimates of exposure to infants consuming baby foods (with the assumption of SEM levels at the 95th percentile of 20 ng g(-1) in all of the consumed 'ready-to-eat' foods) compared with a no observed adverse effect level (NOAEL) in developmental toxicity studies, the margin of safety is more than 21 000. Since the risk of an adverse effect is negligible, it is clear that any theoretical risk is outweighed by the benefits of continuing use of the PT closure (with azodicarbonamide blowing agent) to ensure both the microbial integrity and availability of commercial baby foods as a valuable source of infant nutrition.

Efeito das práticas alimentares sobre o crescimento infantil

Vários fatores quer pré-natais como pós-natais podem influenciar o crescimento infantil. Nos primeiros meses de vida, a influência dos padrões alimentares é um aspecto importante para avaliar o padrão de crescimento infantil. O objetivo deste artigo é revisar os resultados divulgados na literatura e reunir informações que permitam elucidar questões referentes ao efeito das práticas alimentares sobre o crescimento infantil. É apresentada uma descrição sucinta dos determinantes do crescimento, dos estudos desenvolvidos para avaliar o efeito das práticas de alimentação sobre o crescimento infantil no primeiro ano de vida. Abordam-se ainda, uma descrição dos aspectos sobre a introdução da complementação alimentar. Os termos "breastfeeding practice", "infant growth" e "weight" foram determinados de acordo com os Medical Subjects Headings (MESH) e pesquisados na base MEDLINE. As divergências quanto ao momento de introduzir alimentos complementares e até que ponto a amamentação ao seio supre as necessidades de nutrientes no primeiro ano de vida levou a Organização Mundial da Saúde a alterar as recomendações sobre as práticas alimentares em 2001. Os estudos vêm demonstrando diferenças significativas no padrão de crescimento entre crianças amamentadas ao seio e aquelas que recebem fórmulas lácteas ou alimentos complementares.

Why are babies weaned early? Data from a prospective population based cohort study

BACKGROUND

The recommended age of introduction of solids food to the diet of infants (weaning) has recently been increased in the UK to 6 months, but most babies are still weaned before the age of 4 months.

AIMS

To examine what predicts the age of weaning and how this relates to weight gain and morbidity using data from a population based cohort.

METHODS

Parents of 923 term infants born in a defined geographical area and recruited shortly after birth were studied prospectively using postal questionnaires, weaning diaries, and routinely collected weights, of whom 707 (77%) returned data on weaning.

RESULTS

The median age of first weaning solids was 3.5 months, with 21% commencing before 3 months and only 6% after 4 months of age. Infants progressed quickly to regular solids with few reported difficulties, even when weaned early. Most parents did not perceive professional advice or written materials to be a major influence. The strongest independent predictors of earlier age at weaning were rapid weight gain to age 6 weeks, lower socioeconomic status, the parents' perception that their baby was hungry, and feeding mode. Weight gain after 6 weeks was unrelated to age of weaning. Babies weaned before 3 months, compared to after 4 months, had an increased risk of diarrhoea.

CONCLUSIONS

Social factors had some influence on when weaning solids were introduced, but the great majority of all infants were established on solids before the previously recommended age of 4 months, without difficulty. Earlier weaning was associated with an increased rate of minor morbidity.

Nutrition and the life cycle 2: infancy and weaning

The first article in this nutrition and the life cycle series discussed nutrition in pregnancy (Vol 9 (17): 1133-8). This second article will concentrate on infancy and weaning. Weaning infants is an area that causes concern for parents. Health professionals need to be well informed about this aspect of childcare, as practices have changed recently. Babies should usually begin weaning between 4 and 6 months of age. Infant diets need to be high in lipid for energy, and for essential long-chain fatty acids and fat-soluble vitamins. Their diets should also be rich in the micronutrients; infants are particularly at risk of deficiency for iron and zinc. Infants should be introduced to as many tastes and textures as reasonably possible, but foods likely to cause an allergic reaction should be avoided for as long as possible. Finally, all the family should enjoy mealtimes, and the pattern laid down for a life of healthy eating. The next article in this series will review nutrition in the school-age child.

Infant feeding practices in Ottawa-Carleton: the introduction of solid foods

Infant feeding guidelines regarding the introduction of solid foods are generally not well known in Canada. The guidelines recommend that solid foods be introduced between four to six months of age, depending on the developmental readiness of the infant. In order to understand the underlying factors and patterns which contribute to the introduction of solid foods in infants, data were analyzed from three cross-sectional surveys of parents of six-month-old infants from the Ottawa-Carleton region (n = 373, 1988; n = 330, 1992; n = 338, 1996) conducted by the Ottawa-Carleton Health Department. Multivariable analysis showed that mothers who: did not breastfeed, were younger, had lower education, smoked or had partners that smoked, and lacked support after birth, were more likely to introduce solid foods before four months of age. These data support the need for nutrition education programs to increase adherence to the new Nutrition for Healthy Term Infants guidelines.

An observational study of mothers with eating disorders and their infants

Two groups of primiparous mothers and their infants were observed at home during play and at a mealtime when the infants were 12-24 months old. The index group consisted of mothers who had experienced an eating disorder during the postnatal year while the control group had been free from such psychopathology. The main findings were that, when compared to controls, the index mothers were more intrusive with their infants during both mealtimes and play; and that they expressed more negative emotion towards their infants during mealtimes but not during play. There were, however, no differences between the groups in their positive expressed emotion. The index infants' emotional tone was generally more negative and their mealtimes more conflictual compared to controls. Furthermore, the index infants tended to be lighter than controls and infant weight was found to be independently and inversely related to both the amount of conflict during mealtimes and the extent of the mother's concern about her own body shape.

Extended breast-feeding and growth in rural China

The relationship between duration of breast-feeding and growth has been investigated in a cross-sectional study of children living in an economically disadvantaged rural area of Hubei province, People's Republic of China. Data were analyzed from 2148 initially breast-fed children aged 12-47 months. Children who were breast-fed for longer than 12 months had significantly higher mean Z scores for weight-for-age, height-for-age, and weight-for height than children breast-fed for shorter periods. The positive association between duration of breast-feeding remained after adjusting the data for 11 potentially confounding factors, including age, sex, father's occupation, mother's education, recent infections, age of introduction of solids, and the variety of the weaning diet at 1 year. These results support the contention that mothers in developing countries should be encouraged to breast-feed their children for the first 2 years of life with the addition of good quality weaning foods from about 4-6 months.

Infant weaning practices in Adelaide: the results of a shopping complex survey

The results are presented of a survey of infant weaning practices carried out in shopping complexes in the Adelaide metropolitan area. The types of foods and fluids currently being consumed by the sample of 258 healthy infants was documented, and a comparison made between the feeding practices of breast and artificially fed infants and with respect to socio-economic status. While the majority of weaning diets were compatible with the South Australian guidelines, 40% of infants under 4 months of age were having solid foods and a greater percentage of these infants were artificially fed. Iron intake may not be optimal after six months of age with the increasing use of cow's milk and non-fortified adult cereals. There is an increasing awareness of the inappropriateness of adding sugar and salt to infant foods; however, foods high in sugar and salt are still being used. The results suggest that parents may not always be aware of or understand the rationale behind recommendations for weaning and that dietary guidelines for adults and children may not always be appropriate for infants. Consistent guidelines for infants, modified to consider current food trends, would be useful for parents.

Intake and growth of breast-fed and formula-fed infants in relation to the timing of introduction of complementary foods: the DARLING study. Davis Area Research on Lactation, Infant Nutrition and Growth

We examined if the timing of introduction of solid foods was related to growth, intake, morbidity, activity or motor development among infants either breast fed or formula fed until > or = 12 months of age. Breast-fed infants given solids before 6 months of age (earlysol) consumed less breast milk at 6 and 9 months of age than those given solids > or = 6 months (latesol); thus total energy intake did not differ between groups. Z scores for weight, length and weight-for-length at 1-18 months did not differ between groups. Latesol infants gained less weight from 6 to 9 months but not during any other interval. Neither activity level nor morbidity differed between groups, but several developmental milestones occurred earlier in the earlysol versus the latesol group, probably due to reverse causation. Among formula-fed infants, timing of introduction of solid foods was not related to intake, growth, activity or morbidity. We conclude that solid foods given before 6 months of age generally replace the milk source among breast-fed but not formula-fed infants.

Breast feeding and the older infant

The possible benefits and disadvantages to the older infant of breast-feeding being continued after the introduction of solid foods are reviewed. The limited evidence from industrialised countries suggests that prolonged partial breast-feeding has little influence on child health and growth. In contrast, in poor areas of the developing world, the continuation of breast-feeding for 1-2 years after the introduction of other foods appears to have several major benefits. These include the supply of nutrients, the delivery of protective, digestive and trophic agents, and extending the period of infertility in the mother. Partial breast-feeding after 6 months is associated with reduced severity of infectious diseases particularly in severely malnourished individuals. There is no evidence that partial breast-feeding plays a causal role in poor growth performance. In poor areas of the developing world, breast-feeding, together with the provision of adequate amounts of other foods, should be encouraged for the first two years of life.

Modified fat diets: do they apply to infancy?

Almost no data exist to permit assessment of the optimal fat content in the diet of the 6- to 12-month-old infant. Human milk contains about 50% of energy as fat, a large portion of it saturated fat. Commercial infant formulas mimic this proportion but use vegetable sources; most of them also duplicate the saturated fat fraction. At present, only linoleic acid is known to be an essential fatty acid. However, if all but 2% to 3% of energy had to come from sources other than fat, the energy density of the feed would be low, perhaps too low to permit ingestion of adequate energy. On the other hand, if fat concentration were increased at the expense of carbohydrates, ketosis would result.

Identification of factors affecting infant growth in developing countries

The anthropometric progress of seven infants was followed throughout their first year of life. Weight, length, mid upper arm circumference, triceps and subscapular skinfold thicknesses were measured on a mean (SD) of 30 (6) occasions with weight alone being measured on a further 6 (2) occasions. The effects of infection and energy intake were identified and illustrated using both standard deviation (SD) score graphs for individual subjects, and more traditionally, regression analysis for the group. Diarrhoea and vomiting, pneumonia, and diarrhoea alone each resulted in significant reductions in growth velocity of 30 g/day. Multimeasurement SD score graphs showed the effects of all illnesses, and permitted simultaneous comparison of anthropometric measurements.

Infant feeding pattern and weaning practices in Kuwait

A survey was carried out to investigate infant feeding pattern and weaning practices in Kuwait. The study covered 2833 mothers of children less than three years old. The results showed that 60.6% of the infants were breast-fed, 14.0% were bottle-fed and 25.4% received mixed feeding. The mean duration of breast feeding was 5.8 months and varied from 9.5 to 4.3 months among illiterate and educated mothers respectively. The results also showed that older mothers were more likely to breast-feed their infants for a longer duration. On the contrary, mothers from high-income families were less likely to practise breast-feeding. In addition, the study revealed that 37.4% of the infants were weaned suddenly; the reasons for weaning were stated as: insufficient milk (30.7%), new pregnancy (14.7%), infant reaching weaning age (12.3%), mothers' sickness (12.0%), infant refusal (10.6%) and mothers' desire (6.6%).