Doctor: Aurore Camier

Title: Infant diet and growth during childhood

Supervisor: Blandine de Lauzon-Guillain

Doctoral school: ED 393 Epidemiology and Biomedical Information Sciences, Université Paris Cité

Date of thesis defense: 17/01/2022

Jury: Sylvie Issanchou, Rémi Béranger

Thesis summary:

The protective effect of breastfeeding on obesity risk is highlighted by numerous studies. However, few of these studies have considered other aspects of early nutrition such as complementary food introduction. Thus, the main objective of this thesis was to characterize infant feeding practices, entirely, and then to study the associations with the growth of the child. In the first part, to characterize infant diet, besides breastfeeding duration or age at complementary feeding, it appeared relevant to consider the age at introduction of particular food groups, especially sweet drinks and cow’s milk, or the introduction of the food pieces. In addition, recommended infant feeding practices such as breastfeeding or complementary food introduction in the recommended period are strongly associated with each other. Analyses of related family characteristics indicated that an older maternal age and higher level of education are associated with breastfeeding duration and complementary feeding practices in line with the guidelines. Moreover, migration and low income are associated with longer breastfeeding and that the presence of older children in the household is associated with both longer breastfeeding and early introduction of cow’s milk. A second part focused on the links between infant feeding practices and early growth, through BMI up to 5 years or the peak and the rebound of adiposity. We highlighted that the child’s sex was a moderating factor in the associations between infant feeding practices and growth, with, for instance a stronger effect of breastfeeding in girls. Longer breastfeeding was associated with lower early growth, while the associations with later growth are not in favour of a protective effect of breastfeeding on overweight. Early complementary feeding was associated with a higher BMI between 1 and 5 years. Children with longer breastfeeding and later initiation to complementary feeding had lower growth parameters in the first year, but this trend was not systematically confirmed for later growth parameters. Finally, in a third part, the influence of the protein content of infant formulas on early growth was studied. This analysis is part of an exploration of mechanisms explaining the links between early diet, including breastfeeding, and growth. High protein intake in the first year of life appeared associated with higher growth. This latest analysis confirmed a positive gradient between protein content of infant formulas on the market and early growth: the higher the protein content of the infant formula consumed at 4 months was, the higher the growth parameters between 6 and 18 months were (weight-, height- and BMI-for-age z-scores). Together, these analyses showed the effect of early feeding practices on childhood growth. Early complementary food introduction and high protein content in infant formula are associated with higher early growth. The associations between breastfeeding and growth are more heterogeneous and are not systematically in favour of a protective effect of breastfeeding on the risk of overweight.

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