Current calculations of nuclear shadowing for parton distributions are reviewed. The analysis of μA data is performed using exact QCD sum rules for the total momentum and baryon charge of nuclei. Evidence is found for an overall enhancement of Ga in nuclei (> 4% for A > 1). Combined with the calculation of nuclear shadowing at small χ ~ our analysis indicates an enhancement of valence quark and gluon fields in nuclei for χ ~ 0.1 of about 10 (20)% for A = 40 (A = ∞), as well as a suppression of the sea, at least for χ < 0.1 and of valence quarks at χ < 0.02. It is also pointed out that due to scaling violations the small shadowing observed in the Drell-Yan data at χ = 0.04 and 〈Q2〉 ~ 25 GeV2 corresponds to much larger shadowing for the sea in the Q2 range probed by NMC. Implications for disentangling the origin of nuclear forces are also discussed.