Inacommentary,theresearchersdrawattentiontothefactthatthereasonwhythefirststudyproducedsuchdisappointingresultsmighthavetodowiththesmokersnotbeinggivencombinationsofvitaminsbutonlybetacarotene.

Please segment the words.
In a commentary, the researchers draw attention to the fact that the reason why the first study produced such disappointing results might have to do with the smokers not being given combinations of vitamins but only betacarotene.