How much protein is safe?

Abstract

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. CONCLUSION: 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. On the whole, we could define these observations as the 'early origins' hypothesis of adult disease. Breastfeeding is the ideal way of feeding infants born at term, since it provides adequate nutrients to support optimal growth and development of infants together with antiinfective protection, thus forming a unique biological and emotional basis for the health and well-being of both mother and child. 4,5 Breastfeeding is fundamental also in premature babies (34-27 weeks of gestational age), where the capability of suckling is present, and even in extremely premature babies (28-32 weeks of gestational age) the use of expressed and/or banked human milk (adequately fortified) may have favorable short-and long-term effects. 6The American Academy of Pediatrics (AAP) recommends breastfeeding for the first 6 months of life.7 After that date, a combination of solid foods and breast milk should be given in order to complement nutrients that are insufficient if supplied only with human milk (particularly energy, protein, iron, zinc and fat-soluble vitamins). The process is called weaning, and represents the progressive introduction of solid foods into children's diets in order to fulfill their changing nutritional needs. Breastfeeding, human milk and overweight/obesity preventionSeveral studies have suggested a protective role of breastfeeding vs formula-feeding on the development of overweight and obesity in later childhood and adolescence. Protective effects were seen in a large retrospective crosssectional study on almost 10 000 children at the age of 5 y in Bavaria, 9 in a survey of 15 000 adolescents whose mothers participated in the Nurses' Hea...

The effects of whole milk and infant formula on growth and IGF-I in late infancy

“…The risk of obesity may be relevant, according to the protein-adiposity hypothesis, which postulates that a high protein intake during infancy and early childhood increases the risk of obesity (RollandCachera et al, 1995;Agostoni et al, 2005;Michaelsen et al, 2007). Some studies have supported this hypothesis (Rolland-Cachera et al, 1995;Scaglioni et al, 2000) but some have not (Vobecky et al, 1983;Dorosty et al, 2000;Hoppe et al, 2004b).…”

The aetiology of childhood obesity: a review

“…It might also be a factor of the amount of protein in the diet, with bottle-feeding and early weaning increasing protein intake (breast milk provides a relatively high amount of energy from fat), which may reduce the age of adiposity rebound and increase the risk of subsequent obesity 112 . Feeding style may also be important to the infant's risk of obesity.…”

Scientific Opinion on nutrient requirements and dietary intakes of infants and young children in the European Union

“…Given an energy content of 272 to 280 kJ/100 mL (65 to 67/100 mL) of human milk, an RI of around 40 to 45 % E% as carbohydrates can be derived and considered adequate for the majority of infants in the first six months of life (Jensen, 1995 Panel, 2010f, 2012aPanel, 2010f, , 2013b and 15 E% as the maximum acceptable limit (Agostoni et al, 2005), an intake of carbohydrates between 45 E% and 55 E% can be considered adequate for the majority of infants in the second half of the first year of life.…”