  In light of the known Higgs mass and the current constraints on the
quark-lepton Higgs coupling, we derive conditions for extracting upper limits
on the lepton-nucleon Higgs coupling from light atoms and ions, assuming the
availability of locally precise two- and three-body methods might be
beneficial. A recent work has proposed to extract these limits in heavy atoms
where the Higgs term is enhanced by $\approx 10^3 AZ$, due to both the large
coupling modifier and large $A$, $Z$, and assuming sufficiently precise
relativistic electron wave functions. We first revisit the old idea of using
the Lamb shift in light muonic ions where the coupling is enhanced by about
$201^3 AZ^3$ primarily due to the concentration of the muon wave function at
the origin, the muon coupling modifier already being close to 1. For the muonic
helium an experimental precision below 0.1 ppm is required to reach the
constraints on Higgs couplings. However, theoretical uncertainty is large due
to nuclear potential dependence of the finite size terms enhanced by the small
muon orbit, and their elimination by using several states is precluded due to
the Lamb shift being the only precisely measurable state. In normal
(electronic) light systems transitions between low-lying states lie near the
optical region allowing precise experiments, and extraction may be possible by
eliminating the finite-size, polarization and Zemach moment terms from a set of
transitions, e.g. $1S-2S$ and improved $2^3S-2^3P$ and $2^1S-2^3S$ in ${\rm
He}^+$, while isotope shifts could be used if additional transitions are
measured as precisely.
