I will present the tightest constraint on massive neutrinos that has been obtained recently using the Lyman-alpha forest, Baryon Acoustic Oscillations and CMB data. I will first describe the measurement of the power spectrum in the Lyman-alpha forest observed in quasars of the BOSS survey. I will then present the extensive suite of N-body/hydro simulations that has been developed specifically for the purpose of this study, and show how it can be used to place constraints on the sum of the neutrino masses at the level of 0.14 eV (95% confidence level). Finally, I will illustrate how these data and simulations can also constrain the effective number of neutrinos in the Universe.