  We estimate the values of Yukawa couplings of a light pseudoscalar A with a
mass of about 17 MeV, which would explain the $^8Be$ anomaly observed in the
Atomki pair spectrometer experiment. The resulting couplings of A to up and
down type quarks are about 0.3 times the coupling of the standard Higgs boson.
Then constraints from K and B decays require that loop contributions to flavour
changing vertices cancel at least at the 10% level. Constraints from beam dump
experiments require the coupling of A to electrons to be larger than about 4
times the coupling of the standard Higgs boson, leading to a short enough A
life time consistent with an explanation of the anomaly.
