Methodology: A random blind clinical trial was performed in which full-term healthy newborns that are attended at the Universidad de La Sabana Clinic are included. The blind participants will be those persons measuring the results and analysing the data. The sample size is calculated for a type I error of 5%, a two tailed type II error of 20%, therefore estimating percentage losses of 30%; 150 infants were included per group. Randomization will be performed using permuted, size 6 blocks. Descriptive analysis will be conducted using central tendency and dispersion measurements. A bivariate analysis will be performed to determine which variables are associated with exclusive human lactation at 6 months. For continuous variables, the Student t- test will be used for independent samples or the Wilcoxon rank sum test, in case the assumptions of normality for the t-tests are not fulfilled. The assumption of normality will be evaluated with the Shapiro Wilk and Kolmogorov-Smirnov test. Categorical variables in contingency tables will be constructed, assessing independence between variables with the Chi-square test or Fisher's exact test when the assumption of the number of cases is not met by the cells in the contingency tables, times two. It will be calculated as a measurement of the effect of relative risk (RR) with confidence intervals; the adjusted measurements will be calculated using a multivaried regression Poisson model, variables with significant results will be used in the bivariate analysis and those with biological plausibility used for the adjustment. The analysis will be carried out for a two-tailed type I error level of 5%. The Stata 11 program will be used for the data analysis. An interim analysis will be performed upon submission of half of the expected events (106), setting limits for early termination of the trial according to the method proposed by Pampallona and Tsiatis (1994).