[fencepost]

I suspect that if you're the type to take a bunch of individual vitamin supplements then you know exactly what you're taking and how much, much more so than if you're taking a multivitamin every morning washed down with your coffee. There's also no reason to be lying about that to your doctor.

[saurik]

The issue isn't that the patient is lying or doesn't know; the issue is that the patient is taking supplements or not for a reason that is itself correlated with the other side of our analysis: someone who is taking vitamins might be more desperate, or might have more money (and so be living in very different conditions or have less stress), or might be more likely to be doing other random "maybe this will help?" things that are also random effects you aren't asking about, or might be better at doing anything at all on a routine (including other medical steps), or might be more able to get up and walk/drive to take/buy vitamins, or might be experiencing a different level of digestive effects from their chemotherapy. The reason why we use controlled randomized trials is because they just fully solve this correlation analysis issue.

[randycupertino]

Most oncology pts have so many meds they barely remember which ones they're taking when. Generally a spouse, family member or other caretaker organizes the med schedule and keeps track.

Working in the industry, the supplements we get the most questions about and that come up as conmeds for the main treatment is turmeric and biotin. The turmeric is getting popular as an antiinflamatory and biotin has good word of mouth to help prevent hair loss.

Biotin can really throw off lab values and for our infusion treatment patients we need to constantly monitor their labs, so that is really important to ensure they're not taking. Turmeric has some interactions as well, but not as severe as biotin.

[chiefalchemist]

Lying? No. Memory issues? Could be. Giving answers that you think are expected? Yup. Highly possible.

Someone or sonehow these humans were questioned. There are a number of reasons why that might not be accurate.