We present a new approach to parton distributions based on light-front holography and Veneziano duality. In this framework, parton distributions can be determined up to a universal reparametrization function $w(x)$, which is highly constrained by boundary conditions. The Regge behavior at small $x$ and the perturbative QCD counting rule at large $x$ are reproduced. Furthermore, unpolarized and polarized distributions are strictly related by the chirality separation from the holographic Lagrangian. It allows us to predict polarized distributions from unpolarized distributions without adding free parameters. The numerical results agree with existing experimental data and the perturbative QCD helicity retention prediction at $x\to1$ limit, and particularly, the down quark polarized distribution is predicted to change sign around $x\sim0.8$. This predictions bears minimal theoretical uncertainty and can be tested soon in future JLab experiments.