How do you counsel patients on multivitamin use during therapy?

I tell patients to stop intake of anti-oxidant multivitamins (A,C and E) at the time of consultation, and if they so wish, they can resume them no sooner than 6-8 weeks after course completion because "radiation continues to work after we're done." I simplify how radiation attacks/kills the cancer DNA, how we don’t want to neutralize (even in theory) the hard working ROS, etc, and most patients completely get it. I also use the opportunity to indoctrin-, ahem, educate them about some of the notable studies that showed no real benefit, and likely a detriment, to taking vitamins in general (assuming that, like most people, they get enough in food), and if they absolutely insist on taking them (those sensationalist headlines, infomercials, w...

Very important clinical question.

As to vitamin supplementation in my patients, and the discussion(s) I have with them/families, in this regard, I do these things:

1. Unless the patient appears cachectic, I often discourage supplement(s) in general. That is, a balanced diet will probably be more effective nutritionally for most patients, and is probably less expensive, too. Moreover, the effects of most free radical scavengers vitamins / supplements can affect the actions of the radiotherapy by scavenging the 'killer effects' (DNA stranded breaks) of the radiation by ridding the system of available free radicals per radiation induced, in the first place.

2. Most of my(our) patients are evaluated by our dieticians, who are MS RDs, once per wee...