  Energy levels of hydrogen are calculated as one-loop matrix elements of the
QED energy-momentum tensor trace in the external field approximation. An
explicit connection established between the one-loop trace diagrams and the
standard Lamb shift one-loop diagrams. Our calculations provide an argument
against inclusion of the anomalous trace contribution in the decomposition of
the QED quantum field Hamiltonian and serve as an illustration how the trace
anomaly is realized in the bound state QED.
