  We discuss the impact of different solar neutrino data on the
spin-flavor-precession (SFP) mechanism of neutrino conversion. We find that,
although detailed solar rates and spectra allow the SFP solution as a
sub-leading effect, the recent KamLAND constraint on the solar antineutrino
flux places stronger constraints to this mechanism. Moreover, we show that for
the case of random magnetic fields inside the Sun, one obtains a more stringent
constraint on the neutrino magnetic moment down to the level of \mu_\nu \lsim
few \times 10^{-12}\mu_B, similar to bounds obtained from star cooling.
