Elaine K. McCarthy

Vitamin D and muscle strength throughout the life course: a review of epidemiological and intervention studies.

The putative role of vitamin D in muscle function and strength throughout the life course is of interest because muscle strength is required for engagement in physical activity at all ages. As vitamin D deficiency is widely reported in the population, especially in countries at high latitude, the potential importance of vitamin D in muscle function throughout life, and the potential impacts on growth and development, participation in physical activity, and effects on skeletal and cardio-metabolic health, comprise an important topic for discussion. This review provides an overview of muscle function and summarises the role of the vitamin D receptor and the proposed molecular mechanisms of action of vitamin D in muscle cells. In addition, the review provides a comprehensive assessment of the clinical evidence surrounding the association between vitamin D and muscle strength. Among adults, particularly older adults, cross-sectional and cohort studies reported a positive association between vitamin D status and muscle strength. These associations have been largely confirmed by intervention studies. Limited research has been carried out in adolescents and children; two cross-sectional studies in adolescents have suggested an association between serum 25-hydroxyvitamin D concentrations and muscle strength. However, the two intervention studies in adolescents have yielded conflicting results. Other than a single observational study, data in young children are very limited and further investigation in under 12-year-olds is warranted.

Eating behaviour and weight status at 2 years of age: data from the Cork BASELINE Birth Cohort Study

Background/Objectives:To conduct an analysis of associations between eating behaviours and weight status in 2-year-old children.Subjects/Methods:Data were collected prospectively in the maternal-infant dyad Cork BASELINE Birth Cohort Study. The weight status of children aged 2 years (n=1189) was assigned using the International Obesity Task Force BMI cutoffs using measured heights and weights. Eating behaviours were assessed using the Children’s Eating Behaviour Questionnaire (CEBQ).Results:Eighty percent of children were of normal weight, 14% were overweight or obese and 6% were underweight. From the CEBQ, food approach behaviours including Enjoyment of Food (odds ratio (OR)=1.90, 95% confidence interval (CI)=1.46–2.48) and Food Responsiveness (OR=1.73, 95% CI=1.47–2.03) were associated with overweight/obesity (all P<0.001). The food avoidant behaviours of Satiety Responsiveness (OR=2.03, 95% CI=1.38–2.98) and Slowness in Eating (OR=1.44, 95% CI=1.01–2.04) were associated with underweight at 2 years (all P<0.05).Conclusions:Eating behaviours are associated with weight status as early as 2 years of age.

Variation in iodine food composition data has a major impact on estimates of iodine intake in young children

Background/objectives:The reliability of an estimate of iodine intake is largely dependent on the quality of the food composition data. We aimed to assess the impact of variations in food composition data for iodine and season on the estimates of iodine intake in young children.Subjects/methods:Cross-sectional dietary intake study of Irish 2-year-olds participating in the Cork BASELINE Birth Cohort Study (n=468; 30% of the cohort at the 2-year follow-up) were used to assess the impact of variation in iodine food composition data on estimates of iodine intake, dietary adequacy and risk of exceeding the tolerable upper intake level (UL).Results:Mean (SD) iodine intakes calculated using UK (147 (71)) and Irish (177 (93)) food composition data were significantly different (P < 0.001) (mean difference (95% confidence interval) = 30 (26–33) µg/day) and largely adequate (7–14% below the estimated average requirement). Intakes at the 95th percentile were 138% and 173% of the UL using UK and Irish food composition data, respectively, of which milk accounted for 106% and 150% of the UL. This translated into 22% and 35% of toddlers exceeding the UL, using UK and Irish composition data, respectively. The mean (SD) daily intake of cow’s milk among the 91% of consumers was 309 (208) ml. Intakes of cow’s milk at the 75th and 95th percentiles were 452 and 706 ml, respectively. Using Irish composition data for iodine in cows’ milk, a daily intake of 450 ml could result in a toddler exceeding the UL from milk alone.Conclusions:Variability in food composition has a large impact on assessments of iodine intake, particularly among young children for whom milk contributes a large proportion of their daily nutrient intake. Although this is unlikely to result in long-term adverse effects, our study highlights the need for development of valid biomarkers of individual iodine status.

Impact of maternal, antenatal and birth-associated factors on iron stores at birth: data from a prospective maternal|[ndash]|infant birth cohort

Background/Objectives:Low serum ferritin concentrations at birth, which reflect neonatal iron stores, track through to early childhood and have been associated with poorer neurodevelopmental outcomes. We aimed to identify maternal, antenatal and birth-associated factors that influence iron stores at birth in a prospective maternal–infant birth cohort.Subjects/Methods:In a population-based, longitudinal, birth cohort in Ireland, 413 maternal–infant dyads with prospectively collected lifestyle and clinical data from 15 weeks’ gestation had umbilical cord serum ferritin concentrations measured. Regression models were developed to identify independent factors associated with cord ferritin concentrations.Results:Median (IQR) cord ferritin concentrations were 185.7 (131.7, 385.5) μg/l, and 8% (n=33) of infants had low iron stores (ferritin <76 μg/l) at birth. Maternal obesity (BMI ⩾30 kg/m2) at 15 weeks’ gestation (adj. estimate (95% confidence interval (CI)): −66.4 (−106.9, −25.9) μg/l, P<0.0001) and delivery by caesarean section (−38.8 (−70.2, −7.4) μg/l, P=0.016) were inversely associated with cord ferritin concentrations. In addition, maternal smoking at 15 weeks’ gestation (adj. odds ratio (95% CI): 2.9 (1.2, 7), P=0.020) and being born small-for-gestational age (3.4 (1.3, 8.9), P=0.012) were associated with an increased risk of low iron stores (ferritin <76 μg/l) at birth.Conclusions:We have identified a number of potentially modifiable lifestyle factors that influence iron stores at birth, with the important role of overall maternal health and lifestyle during pregnancy highlighted. Public health policies targeting women of child-bearing age to improve nutrition and health outcomes should be prioritised for the health of the next generation.

Microcytosis is associated with low cognitive outcomes in healthy 2-year-olds in a high-resource setting

Fe deficiency in early childhood is associated with long-term consequences for cognitive, motor and behavioural development; however explorations in healthy children from low risk, high-resource settings have been limited. We aimed to explore associations between Fe status and neurodevelopmental outcomes in low risk, healthy 2-year-olds. This study was a secondary analysis of a nested case-control subgroup from the prospective, maternal-infant Cork Babies after Screening for Pregnancy Endpoints: Evaluating the Longitudinal Impact using Neurological and Nutritional Endpoints (BASELINE) Birth Cohort Study. At 2 years, serum ferritin, Hb and mean corpuscular volume (MCV) were measured and neurodevelopment was assessed using the Bayley Scales of Infant and Toddler Development (n 87). Five children had Fe deficiency (ferritin <12 µg/l) and no child had Fe deficiency anaemia (Hb<110 g/l+ferritin<12 µg/l). Children with microcytosis (MCV<74 fl, n 13) had significantly lower mean cognitive composite scores (88·5 (sd 13·3) v. 97·0 (sd 7·8), P=0·04, Cohens d effect size=0·8) than those without microcytosis. The ferritin concentration which best predicted microcytosis was calculated as 18·4 µg/l (AUC=0·87 (95% CI 0·75, 0·98), P<0·0001, sensitivity 92 %, specificity 75 %). Using 18·5 µg/l as a threshold, children with concentrations <18·5 µg/l had significantly lower mean cognitive composite scores (92·3 (sd 10·5) v. 97·8 (sd 8·1), P=0·012, Cohens d effect size=0·6) compared with those with ferritin ≥18·5 µg/l. All associations were robust after adjustment for potential confounding factors. Despite a low prevalence of Fe deficiency using current diagnostic criteria in this healthy cohort, microcytosis was associated with lower cognitive outcomes at 2 years. This exploratory study emphasises the need for re-evaluation of the diagnostic criteria for Fe deficiency in young children, with further research in adequately powered studies warranted.

Iron intakes and dietary sources in two year olds from the Cork BASELINE Birth Cohort Study

E. K. McCarthy, C. Ní Chaoimh, D.M. Murray, L. C. Kenny, J. O’B. Hourihane and M. Kiely Maternal and Infant Nutrition Research Group, School of Food and Nutritional Sciences, University College Cork, Department of Paediatrics and Child Health, University College Cork and The Irish Centre for Fetal and Neonatal Translational Research, Department of Obstetrics and Gynaecology, University College Cork

Dietary patterns of 24-month old children and associated nutrient intakes and body weight status

Dietary pattern analysis is a useful method to describe the whole diet and evaluate associations with health outcomes and can complement traditional methodologies which use individual foods or nutrients. There are few dietary pattern studies in young children. We aimed to identify the dietary patterns of young children living in Ireland, and investigate associations with body weight status and nutrient intakes and status. Cross-sectional food consumption data of 24-month old children participating in the Cork BASELINE Birth Cohort Study were collected using a 2-day weighed food record (n = 468). K-means clustering was conducted to identify predominant dietary patterns on the basis of the % contribution of food groups to total energy intake (%TE). Body weight status, adequacy of nutrient intake and biomarkers of vitamin D and iron status were compared across the dietary pattern groups. Four dietary pattern clusters were derived from this analysis, two of which differed principally by the type and volume of milk a child consumed, namely “Cows’ milk” [median (IQR): 495 (178) ml/d; 32 %TE] and “Formula” [median (IQR): 368 (193) ml/d; 23 % TE]. A “Traditional” pattern, characterised by higher intakes of wholemeal breads, butter and fat spreads, fresh meat and fruit, with lower intakes of processed meat, and a “Convenience” pattern, characterised by higher intakes of sweets, confectionary and cakes (15 %TE), processed meat, convenience foods (pizza, spaghetti hoops, instant noodles) and lower intakes of fresh meat, were identified. Overall, 7 % of children were classified as obese (>98 centile); however, no significant associations between dietary patterns and body weight (p= 0·121), height (p= 0·327) or body weight status (>98 centile: p= 0·328; BMI z-score: p= 0·170) at 24 months were observed.