How much protein is safe?
BACKGROUND
Since breastfeeding and human milk seem to prevent, while high dietary proteins in the first 2 y of life seem to promote, later overweight, questions have been raised on the safe levels of proteins in the early years. How much protein (as a percentage of total calorie intake) is safe?


METHODS
Revision of available data on the protein content of human milk, protein intake in the first 2 y of life and their association with body mass development.


RESULTS
We should move from the figure of 7-8% in the 4-month exclusively breastfed infants up to the maximum acceptable levels of 14% in 12-24-month-old infants. When protein supply represents less than 6% and energy is limited, fully breastfed infants are likely to enter a status of negative nutrient balance. Over the limit of 14% energy from proteins in the 6-24 months period, some mechanisms may begin to operate, leading young children towards an early adiposity rebound and overweight development, beyond any genetic predisposition. Preliminary data seem to indicate a causal role for whole cow's milk proteins.


CONCLUSIONS
We suggest maintaining breastfeeding as long as possible, and, in case human milk is insufficient, to introduce infant formulas, appropriate for age, up to 18-24 months, in order to keep protein intakes in the safe range of 8-12% within a diet adequate in energy and balanced as far as macronutrients.
Agostoni
C
C
Department of Pediatrics, San Paolo Hospital, University of Milan, Milan, Italy. carlo.agostoni@unimi.it
Scaglioni
S
S
Ghisleni
D
D
Verduci
E
E
Giovannini
M
M
Riva
E
E
D000818:Animals; D001942:Breast Feeding; D002417:Cattle; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D004734:Energy Metabolism; D006128:Growth / Q000502:physiology; D006801:Humans; D007223:Infant; D007225:Infant Food; D007227:Infant Nutritional Physiological Phenomena; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008894:Milk Proteins / Q000378:metabolism; D009765:Obesity / Q000209:etiology / Q000378:metabolism; D014886:Weaning
D004044:Dietary Proteins; D008894:Milk Proteins; D007334:Insulin-Like Growth Factor I