I don't know if it's fine.
I've read a bunch of studies, and I didn't think any of them contained convincing evidence that I should not take it. On the other hand, it seems to have a lot of benefits. What I know for sure is that I feel better when I take it than when I don't.
Some sites warn against it when taking tamoxifen (
Komen,
Food for Breast Cancer, although the latter site highly recommends it for everyone else). There are just so many conflicting studies that no one seems equipped to sort them out. A more recent study (2013) says
curcumin induces cell death and restores tamoxifen sensitivity in certain anti-estrogen resistant cell lines.
I've cut out every other possible phytoestrogen from my diet and supplement regimen, but I'm not giving up curcumin. I would hesitate, though, to tell another tamoxifen user that it's safe to take.
If you're looking for something to enhance the tamoxifen, consider melatonin. The researchers who are studying it haven't managed to come up with an optimal dose, but there is speculation about a formulation that combines tamox and melatonin. It's that good. (I stopped taking it for a time, but I plan to restart it as soon as I can figure out how to remind myself to take it at a time of day that won't make me too tired in the evening or too groggy to wake up as early as I like. That's only an issue because I take 10-20 mg. A lower dose would not create the same problem.)