Early childhood nutrition can have a lasting impact on health, a new study suggests. Researchers say that nutrition during the first days or weeks of life can program a person’s metabolism and health for the future.  This phenomenon is called the metabolic programming effect. In a study, researchers compared growth, body composition and blood pressure in three groups of healthy, full-term newborns.  One group received only breast milk for the first four months of life while the two other groups were randomized to receive either a low-protein formula or a high-protein formula. After four months, the formula-fed infants continued to receive the same formula, and the breastfed infants were assigned to the low-protein formula, if needed. Three years later, the researchers observed that children who had been breastfed exclusively during the first weeks of life showed a specific pattern of growth and a specific metabolic profile, which appeared to differ in formula-fed infants. During the course of the study, various differences arose, including differences in blood insulin levels (which were lower in breastfed infants) and growth patterns.  Over the course of the three years, however, these differences disappeared.  However, others persisted. Specifically, after three years, diastolic and mean blood pressures were higher in the infants who had been fed the high-protein formula compared to the breastfed infants. However, these levels were still within the normal range. Study author Guy Putet, MD, believes the protein content in infant formula may be a key factor in inducing these differences. "It appears that formula feeding induces differences in some hormonal profiles as well as in patterns of growth compared with breastfeeding," Dr. Putet said. "The long-term consequences of such changes are not well-understood in humans and may play a role in later health. Well-designed studies with long-term follow-up are needed." Dr. Putet recommended that if breastfeeding was not possible, infants should be fed formulas that allow a growth pattern and a metabolic profile similar to that of breastfed infants.