Should drug trials routinely screen for alternative medicines?

As a citizen member of the research management committee for a health research funding organization, I sometimes review research applications for drug trials.  We look at how the researchers recruit participants by excluding those taking other drugs not explicitly allowed in the trial or those having conditions that would distort the trial or cause health issues for the person participating. This type of screening is generally the norm.

But then I got to thinking...

And I asked the question of the committee -- Shouldn't researchers be screening participants for the use of alternative medicines and treatments as well?  There was a pause.

If there is no screening for these -- 

• How would the researchers know if it is the drug that is effective or if the participant in the trial is happily ingesting St. John's Wort, or doing acupuncture, or something else, or combinations of things --  and that is what is yielding the positive result? 

• How would they know if combining an alternative medicine with their drug provides additional benefit to the taking of the drug alone? Or worse, what if the combination produces reactions harmful to the patient?

Is it possible that being deeply immersed in a professional world distances researchers from the world of the regular person?  

Is it possible we are screening so carefully for medicines and conditions that we don't look at people's profiles, choices and behaviour that might impact the efficacy of a drug? 

What can we do better to consider the whole person in the process of drug testing so that the outcomes are valid for real people?