Abstract
The present systematic literature review is a part of the 5th revision of the Nordic Nutrition Recommendations. The aim was to assess the health effects of different levels of protein intake in infancy and childhood in a Nordic setting. The initial literature search resulted in 435 abstracts, and 219 papers were identified as potentially relevant. Full paper selection resulted in 37 quality-assessed papers (4A, 30B, and 3C). A complementary search found four additional papers (all graded B). The evidence was classified as convincing, probable, limited-suggestive, and limited-inconclusive. Higher protein intake in infancy and early childhood is convincingly associated with increased growth and higher body mass index in childhood. The first 2 years of life is likely most sensitive to high protein intake. Protein intake between 15 E% and 20 E% in early childhood has been associated with an increased risk of being overweight later in life, but the exact level of protein intake above which there is an increased risk for being overweight later in life is yet to be established. Increased intake of animal protein in childhood is probably related to earlier puberty. There was limited-suggestive evidence that intake of animal protein, especially from dairy, has a stronger association with growth than vegetable protein. The evidence was limited-suggestive for a positive association between total protein intake and bone mineral content and/or other bone variables in childhood and adolescence. Regarding other outcomes, there were too few published studies to enable any conclusions. In conclusion, the intake of protein among children in the Nordic countries is high and may contribute to increased risk of later obesity. The upper level of a healthy intake is yet to be firmly established. In the meantime, we suggest a mean intake of 15 E% as an upper limit of recommended intake at 12 months, as a higher intake may contribute to increased risk for later obesity.
Highlights
MethodsSearch terms The main protein group in the NNR5-project managed the search and defined search terms in collaboration with the Infant and Young Child group and Hege Sletsjøe, librarian at the Norwegian Directorate of Health, Oslo, Norway
body mass indices (BMI), growth, body composition, and sIGF-I Tables 2Á3 show summaries of studies with outcome BMI, growth, body composition, and sIGF-I
Sixteen of those include outcomes on BMI/growth and these are briefly described in Table 2, in addition to the more detailed descriptions given in Table 3 and Appendix 3 for all the 23 studies
Summary
Search terms The main protein group in the NNR5-project managed the search and defined search terms in collaboration with the Infant and Young Child group and Hege Sletsjøe, librarian at the Norwegian Directorate of Health, Oslo, Norway. Inclusion and exclusion criteria The group focused on protein intake among healthy children. Inclusion criteria in the abstract screening process were the following: English or Nordic language, study population relevant to the Nordic countries. Papers were excluded if they focused on premature or sick children, if the study population was deemed too different from a Nordic population, if intake data was not measured in childhood, if the outcome did not match the research questions, or if the paper was a general overview rather than an SLR. Search results The search was run in January 2011, including all relevant population groups and clinical outcomes. Abstract screening was conducted in FebruaryÁMarch 2011 according to the guide for conducting SLRs for the 5th edition of the NNR (26)
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