N05049: The influence of diet in infancy on early growth, and bone health and cognitive function at four years of age

Study Duration: January 2004 to June 2007

Contractor: University of Southampton, MRC Environmental Epidemiology Unit

Poor growth in infancy is associated with a greater risk of developing coronary heart disease and osteoporosis in adult life. It is also associated with impaired development of cognitive function. Nutrition is a major influence on infant growth, but its role in western populations is poorly understood and its effects may depend on the trajectory of growth established before birth. The Southampton Women's Survey provides a unique opportunity to study a general population sample of 1,875 infants whose prenatal growth was measured by serial ultrasound and whose diets were assessed at 6 and 12 months of age. The objectives of this proposal are (1) to describe diet in infancy in a contemporary sample of infants; (2) to relate different patterns of early diet to infant growth; (3) in a sub-sample of 500 infants whose bone mass was measured immediately after birth, to assess how early diet affects bone mass and cognitive function at 4 years of age.

Infants grow rapidly so that by the age of 1 year they have added another 50% to their birth length and have more than doubled their weight. An estimated 23% of their energy intake is used for growth, which is sensitive to environmental influences such as nutrition and illness. Surprisingly little is known about the environmental influences that determine growth in contemporary British infants. The quantity and quality of infant diet has a major effect, but postnatal growth is also influenced by the intrauterine environment. In order to understand the effects of dietary intakes during infancy it is therefore necessary to study infants whose intrauterine growth was measured by serial ultrasound. The Southampton Women's Survey includes infants characterised in this way.

In the Southampton Women's Survey 12,000 women aged 20 to 34 years were characterised before pregnancy between 1998 and 2002. They are representative of the British population in terms of ethnicity, and have a similar range of Townsend Index Scores, a measure of area deprivation. On recruitment their body composition, diet and lifestyles were recorded at home interview. Those who subsequently became pregnant had ultrasound measurements of fetal and placental growth at 11, 19 and 34 weeks of gestation, together with detailed neonatal anthropometry. By December 2003, an estimated 2,017 babies will have been born. The babies' growth and diets are documented at 6 and 12 months during home visits by research nurses; growth is recorded again at 2 and 3 years. Allowing for a current follow-up rate of 93% at 12 months, this would represent a study population of 1,875 infants. This extensive dataset will allow examination of the effects of dietary intakes and patterns of feeding in infancy (1) on growth in infancy; (2) in a sub-sample of 500, on bone mineral content (BMC), bone mineral density (BMD) and cognitive function at 4 years of age. The 500 babies in the sub-sample had dual energy x-ray absorptiometry (DXA) scans in the neonatal period. At 4 years repeat measurements will be made of lumbar spine, proximal femur and total body BMC, bone area and BMD as well as total and regional lean and fat mass. Their cognitive functions will be measured using the Wechsler Pre-school and Primary Scale of Intelligence.

This project aims (1) to analyse the dietary and growth data collected at 6 and 12 months, and (2) to collect and analyse data at 4 years in the sub-sample. The Southampton Women's Survey provides the only group of contemporary infants in the UK whose trajectory of pre-natal growth was measured by serial ultrasound, which is essential for an understanding of the effects of environmental influences on early post-natal growth. The 500 children in the sub-sample are unique in that, having had DXA examinations as newborns, the effects of post-natal influences on change in bone mass can be measured. The results of this study will inform the Agency about the patterns of diet among contemporary infants and the way these patterns relate to growth, and hence the development of cardiovascular disease and type 2 diabetes in later life. It will also allow an examination of how bone mass and cognition at 4 years is influenced by infant diet