Epidemiological evidence suggests that a higher intake of sugar during pregnancy is associated with a higher risk of childhood asthma and atopy. However, randomised trial evidence supporting such a link is lacking. This study aimed to examine whether a low glycaemic index (GI) dietary intervention during pregnancy decreases the risk of childhood asthma and eczema. This is a secondary analysis of 514 children from the ROLO trial. Healthy women were randomised to receive an intervention of low GI dietary advice or routine care from early pregnancy. Mothers reported current doctor-diagnosed eczema in their children at 2 years (n 271) and current doctor-diagnosed asthma and eczema in their children at 5 (n 357) and 9–11 years (n 391) of age. Multivariable logistic regression models were used test the effect of the intervention on child outcomes overall and stratified by maternal education. There was a suggestion of a reduction in asthma at 5 years of age in children whose mothers received the low GI dietary intervention during pregnancy compared with usual care (adjusted OR 0·46 (95 % CI 0·19, 1·09); P = 0·08). In stratified adjusted analyses, the intervention was associated with a reduced risk of asthma at 5 years of age in children born to mothers with incomplete tertiary level education but not in those with complete tertiary level education (OR 0·14 (95 % CI 0·02, 0·69); P = 0·010 and OR 1·03 (95 % CI 0·34, 3·13); P = 0·94, respectively). A low GI diet in pregnancy may reduce the risk of developing asthma in childhood, particularly amongst children born to mothers with lower educational attainment.

Paternal exposures (and other non-maternal factors) around pregnancy could have important effects on offspring health. One challenge is that data on partners are usually from a subgroup of mothers with data, potentially introducing selection bias, limiting generalisability of findings. We aimed to investigate the potential for selection bias in studies using partner data.

We characterise availability of data on father/partner and mother health behaviours (smoking, alcohol, caffeine and physical activity) around pregnancy from three UK cohort studies: the Avon Longitudinal Study of Parents and Children (ALSPAC), Born in Bradford and the Millennium Cohort Study. We assess the extent of sample selection by comparing characteristics of families where fathers/partners do and do not participate. Using the association of parental smoking during pregnancy and child birthweight as an example, we perform simulations to investigate the extent to which missing father/partner data may induce bias in analyses conducted only in families with participating fathers/partners.

In all cohorts, father/partner data were less detailed and collected at fewer timepoints than mothers. Partners with a lower socio-economic position were less likely to participate. In simulations based on ALSPAC data, there was little evidence of selection bias in associations of maternal smoking with birthweight, and bias for father/partner smoking was relatively small. Missing partner data can induce selection bias. In our example analyses of the effect of parental smoking on offspring birthweight, the bias had a relatively small impact. In practice, the impact of selection bias will depend on both the analysis model and the selection mechanism.

This study examined the relationship between childhood diet quality and arterial stiffness and thickness during adolescence/early adulthood. Participants were from the Avon Longitudinal Study of Parents and Children (ALSPAC) with dietary data at ages 7, 10 and 13 years and pulse wave velocity (PWV) and carotid intima-media thickness (cIMT) at ages 17 and/or 24 years. Diet quality (DQ) was assessed using five scores: a children’s Mediterranean-style diet (C-rMED) Z-score, a children’s Dietary Inflammatory Z-score (C-DIS), a DASH diet Z-score, a children’s Eatwell Guide (C-EWG) Z-score reflecting UK dietary guidelines and a data-driven obesogenic Z-score. Adjusted regression models examined the associations between DQ scores at 7–13 years and PWV and cIMT at 17 and 24 years. In adjusted models, a high v. low Obesogenic Z-score at 7 and 10 years was associated with higher PWV at 17: β 0.07 (95 % CI 0.01, 0.13) and β 0.10 (95 % CI 0.04, 0.16), respectively. A high v. low C-rMED Z-score at 7 years was associated with lower PWV at 17 (β −0.07; 95 % CI −0.14, −0.01). A high (more anti-inflammatory) vs low C-DIS Z-score at 10 years was associated with a lower PWV at 17 years: β −0.06 (95 % CI −0.12, −0.01). No other associations were observed. In conclusion, an Obesogenic dietary pattern in childhood (7–10 years) was related to increased arterial stiffness, while Mediterranean-style and anti-inflammatory diets were related to decreased arterial stiffness in adolescence. This highlights the importance of establishing healthy dietary habits early in life to protect against vascular damage.

Causal inference from observational data is notoriously difficult, and relies upon many unverifiable assumptions, including no confounding or selection bias. Here, we demonstrate how to apply a range of sensitivity analyses to examine whether a causal interpretation from observational data may be justified. These methods include: testing different confounding structures (as the assumed confounding model may be incorrect), exploring potential residual confounding and assessing the impact of selection bias due to missing data. We aim to answer the causal question ‘Does religiosity promote cooperative behaviour?’ as a motivating example of how these methods can be applied. We use data from the parental generation of a large-scale (n = approximately 14,000) prospective UK birth cohort (the Avon Longitudinal Study of Parents and Children), which has detailed information on religiosity and potential confounding variables, while cooperation was measured via self-reported history of blood donation. In this study, there was no association between religious belief or affiliation and blood donation. Religious attendance was positively associated with blood donation, but could plausibly be explained by unmeasured confounding. In this population, evidence that religiosity causes blood donation is suggestive, but rather weak. These analyses illustrate how sensitivity analyses can aid causal inference from observational research.

Research into how alignment to UK dietary guidelines during childhood affects cardiometabolic health is limited. The association between adherence to UK dietary guidelines during childhood and overall cardiometabolic risk (CMR) in adolescence/early adulthood was explored using data from the Avon Longitudinal Study of Parents and Children (ALSPAC). ALSPAC children with diet diaries completed at 7, 10 and 13 years of age, and data on CMR markers at 17 years (n 1940) and 24 years (n 1957) were included. A children’s Eatwell Guide (C-EWG) score was created by comparing dietary intakes at each age to UK dietary guidelines for nine foods/nutrients. Cardiometabolic health at 17 and 24 years was assessed using a composite CMR score. Multivariable linear regression models examined associations between C-EWG scores at 7, 10 and 13 years and the CMR score at 17 and 24 years, adjusting for confounders. C-EWG scores were generally low. However, a higher score (adherence to more dietary guidelines) at 7 years old was associated with a lower CMR score at 17 and 24 years: β −0·13 (95 % CI −0·25, –0·01) and β −0·25 (95 % CI −0·38, –0·13) for a 1-point increase in C-EWG score, respectively. A higher C-EWG score at 10 years was also associated with a lower CMR z-score at 24 years. No clear associations were evident at other ages. Greater adherence to UK dietary guidelines during mid-childhood was associated with a better overall cardiometabolic profile, suggesting that encouraging children to eat in this way has long-term benefits to health.

Compliance to UK dietary recommendations was assessed in school-aged children from a population-based cohort: the Avon Longitudinal Study of Parents and Children (ALSPAC). A Children’s Eatwell Guide (C-EWG) score was developed to assess socio-demographic predictors of meeting dietary recommendations. ALSPAC children with plausible diet diary data at 7 years (n 5373), 10 years (n 4450) and 13 years (n 2223) were included in the study. Their dietary intakes (recorded between 1998 and 2006) were compared with dietary guidelines for total and saturated fats, free sugars, salt, fibre, protein, carbohydrates, fruit and vegetables, non-oily and oily fish and red/processed meat. The C-EWG score (0–9 points) indicated the number of recommendations met at each age. Cross-sectional associations between socio-demographic characteristics and C-EWG scores were assessed using multivariable regression. The lowest adherence to guidelines at 7 years was for sugar (0·1 % meeting recommendations), followed by fibre (7·7 %), oily fish (9·5 %), saturated fat (9·7 %) and fruit and vegetables (15·2 %). Highest adherence was for limiting red/processed meat (67·3 %) and meeting carbohydrate recommendations (77·3 %). At 7 years, 12·1 % of participants failed to meet any of the nine recommendations, 26·9 % met one and 28·2 % met two. Similar patterns were seen at 10 and 13 years. A lower social class and maternal educational attainment and higher maternal BMI were associated with meeting fewer recommendations. Most school-aged children in this cohort did not meet UK dietary recommendations, particularly children from lower socio-economic backgrounds. Additional public health initiatives are needed to improve the quality of UK children’s diets, particularly targeting lower socio-economic groups.

An adequate intake of PUFA plays a vital role in human health. Therefore, it is important to assess PUFA intakes in different populations and validate them with biomarkers, but only a few small studies are in paediatric populations. We calculated the dietary intake of PUFA and their main food sources in children and assessed associations between PUFA intakes and plasma proportions. Dietary intakes of 7-year-old children (n 8242) enrolled in the Avon Longitudinal Study of Parents and Children were calculated from the parental-completed FFQ. Plasma PUFA were measured in 5571 children 8 months later, and 4380 children had complete dietary and plasma data. The association between dietary and plasma PUFA proportions was estimated using Spearman’s correlation coefficients, quintile cross-classification and Cohen’s κ coefficients. Mean total PUFA intake was 13·2 g/d (sd 4·2), contributing 6·5 % of total energy intake; n-6 PUFA contributed 5·2 % and n-3 PUFA 0·7 %. The n-6:n-3 ratio was 7·9:1. Mean intakes of EPA and DHA were 35·7 mg/d and 49·7 mg/d, respectively. Most n-3 and n-6 PUFA intakes were weakly correlated with their respective plasma lipids (0·07 ≤ r ≤ 0·16, P < 0·001). The correlation between dietary and plasma DHA was stronger though (r = 0·34, P < 0·001), supported by a modest level of agreement between quintiles (k = 0·32). The results indicate that the FFQ was able to reasonably rank the long-chain (LC) PUFA, DHA, in this paediatric population. Public health initiatives need to address the suboptimal ratio of n-6:n-3 PUFA and very low n-3 LC-PUFA intakes in school-age children in the UK.

Picky eating is a common behaviour in early childhood. There is neither a universally accepted definition of picky eating, nor is there agreement on the best tool to identify it. Causes of picky eating include early feeding difficulties, late introduction of lumpy foods at weaning, pressure to eat and early choosiness, especially if the mother is worried by this; protective factors include the provision of fresh foods and eating the same meal as the child. The consequences for the child's diet include poor dietary variety and a possible distortion of nutrient intakes, with low intakes of iron and zinc (associated with low intakes of meat, and fruit and vegetables) being of particular concern. Low intakes of dietary fibre, as a result of low intakes of fruit and vegetables, are associated with constipation in picky eaters. There may be developmental difficulties in some children with persistent picky eating. There is little evidence, however, for a consistent effect of being a picky eater on growth trajectories. There may be a small subgroup of children in whom picky eating does not resolve who might be at risk of thinness during adolescence, or of developing an eating disorder or adult picky eating: these children need to be identified at an early age to enable support, monitoring and advice to be offered to parents. Strategies for avoiding or ameliorating picky eating include repeated exposures to unfamiliar foods, parental modelling of eating fruit and vegetables and unfamiliar foods, and the creation of positive social experiences around mealtimes.

n-3 Highly unsaturated fatty acids (HUFA), are essential components of neuronal membranes and mediate a range of complex bioactive properties including gene expression, myelination, cell-signalling and dopaminergic function. Deficits in n-3 HUFA have been linked to increased risks for addictive disorders, thus we posited that lower fish consumption would be associated with greater risks for perinatal smoking among 9640 mothers enroled in the Avon Longitudinal Study of Parents and Children. We used univariable and multivariable regression models to examine relationships between self-reported prenatal dietary intakes of n-3 HUFA-rich foods (fish and shellfish) and maternal smoking; outcomes included cessation and the number of cigarettes smoked per d. Both before and during pregnancy, there was consistent evidence (P<0·001) of protective fish intake–smoking associations; relative to mothers reporting no fish consumption, those who reported some fish consumption (<340 g/week) and high fish consumption (340 g+/week) at 32 weeks of gestation showed lower likelihoods of smoking (adjusted P values <0·001). Respective OR for these relationships were 0·87 (95% CI 0·77, 0·97) and 0·73 (95% CI 0·61, 0·86). Although the prevalence of smoking diminished, from a high of 31·6% (pre-pregnancy) to a low of 18·7% (second trimester), the magnitude of fish intake–smoking associations remained stable following adjustment for confounders. These observations suggest that greater fish or n-3 HUFA consumption should be evaluated as an intervention to reduce or prevent smoking in randomised clinical trials.

Seafood intake in pregnancy has been positively associated with childhood cognitive outcomes which could potentially relate to the high vitamin D content of oily fish. However, whether higher maternal vitamin D status (serum 25-hydroxyvitamin D (25(OH)D)) in pregnancy is associated with a reduced risk of offspring suboptimal neurodevelopmental outcomes is unclear. A total of 7065 mother–child pairs were studied from the Avon Longitudinal Study of Parents and Children cohort who had data for both serum total 25(OH)D concentration in pregnancy and at least one measure of offspring neurodevelopment (pre-school development at 6–42 months; ‘Strengths and Difficulties Questionnaire’ scores at 7 years; intelligence quotient (IQ) at 8 years; reading ability at 9 years). After adjustment for confounders, children of vitamin D-deficient mothers (<50·0 nmol/l) were more likely to have scores in the lowest quartile for gross-motor development at 30 months (OR 1·20; 95 % CI 1·03, 1·40), fine-motor development at 30 months (OR 1·23; 95 % CI 1·05, 1·44) and social development at 42 months (OR 1·20; 95 % CI 1·01, 1·41) than vitamin D-sufficient mothers (≥50·0 nmol/l). No associations were found with neurodevelopmental outcomes, including IQ, measured at older ages. However, our results suggest that deficient maternal vitamin D status in pregnancy may have adverse effects on some measures of motor and social development in children under 4 years. Prevention of vitamin D deficiency may be important for preventing suboptimal development in the first 4 years of life.

This study aims to examine repeatability of reduced rank regression (RRR) methods in calculating dietary patterns (DP) and cross-sectional associations with overweight (OW)/obesity across European and Australian samples of adolescents. Data from two cross-sectional surveys in Europe (2006/2007 Healthy Lifestyle in Europe by Nutrition in Adolescence study, including 1954 adolescents, 12–17 years) and Australia (2007 National Children’s Nutrition and Physical Activity Survey, including 1498 adolescents, 12–16 years) were used. Dietary intake was measured using two non-consecutive, 24-h recalls. RRR was used to identify DP using dietary energy density, fibre density and percentage of energy intake from fat as the intermediate variables. Associations between DP scores and body mass/fat were examined using multivariable linear and logistic regression as appropriate, stratified by sex. The first DP extracted (labelled ‘energy dense, high fat, low fibre’) explained 47 and 31 % of the response variation in Australian and European adolescents, respectively. It was similar for European and Australian adolescents and characterised by higher consumption of biscuits/cakes, chocolate/confectionery, crisps/savoury snacks, sugar-sweetened beverages, and lower consumption of yogurt, high-fibre bread, vegetables and fresh fruit. DP scores were inversely associated with BMI z-scores in Australian adolescent boys and borderline inverse in European adolescent boys (so as with %BF). Similarly, a lower likelihood for OW in boys was observed with higher DP scores in both surveys. No such relationships were observed in adolescent girls. In conclusion, the DP identified in this cross-country study was comparable for European and Australian adolescents, demonstrating robustness of the RRR method in calculating DP among populations. However, longitudinal designs are more relevant when studying diet–obesity associations, to prevent reverse causality.

The aim of this study was to assess the economic benefits of improved cognitive development related to being breast-fed. Breast-feeding rates were assessed in the Avon Longitudinal Study of Parents and Children. Educational attainment was assessed at age 16 years with higher attainment defined as gaining five General Certificate of Secondary Education (GCSE) passes at a high grade. The economic benefit of being breast-fed was calculated in a decision model using a child’s educational attainment and the corresponding expected value of average income in later life. There was a positive association between being breast-fed and achieving higher educational attainment, which remained significant, after adjustment for possible confounders: being breast-fed <6 months yielded an OR of 1·30 (95 % CI 1·13, 1·51) and for ≥6 months yielded an OR of 1·72 (95 % CI 1·46, 2·05), compared with never breast-fed children. On the basis of UK income statistics, the present value of lifetime gross income was calculated to be £67 500 higher for children achieving 5 high-grade GCSE passes compared with not achieving this. Therefore, the economic benefit of being breast-fed <6 months would be £4208 and that for ≥6 months would be £8799/child. The model shows that the increased educational attainment associated with being breast-fed has a positive economic benefit for society, even from small improvements in breast-feeding rates. Within a total UK birth cohort of 800 000/year an increase by 1 % in breast-feeding rates would be worth >£33·6 million over the working life of the cohort. Therefore, breast-feeding promotion is likely to be highly cost-effective and policymakers should take this into consideration.