The first thing to say about this is that the data are mixed: Some studies find an effect of giving beta blockers such as propranolol, and other studies do not find this.
The latest part of the study, which involved about 4, 000 participants, also looked at the effect of replacing beta-carotene in the supplements formulation with lutein and zeaxanthin because of studies that found former smokers who take beta-carotene have a higher incidence of lung cancer.