I'm about to start it after radiation, per my oncological naturopath. I have a double-check email out to make sure it doesn't interact with tamoxifen. I'll follow-up here.

A lot of reputable sources point out that phytoestrogens aren't the same as animal estrogens. They may even have beneficial effects for reducing breast cancer (newer studies on dietary soy show benefits to Caucasian women--previous studies were initially done in Asia, which makes sense given the prevalence of soy in East Asian diets). My MO suggested that a few servings of dietary soy every week would be fine, and her only question about curcumin is whether it interacts with tamoxifen. I'll post when I here back. My naturopath is empirically driven.

ETA: Here's an animal study: http://www.ncbi.nlm.nih.gov/pubmed/22512082

Effects of curcumin on the pharmacokinetics of tamoxifen and its active metabolite, 4-hydroxytamoxifen, in rats: possible role of CYP3A4 and P-glycoprotein inhibition by curcumin

Abstract

The effects of curcumin, a natural anti-cancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its metabolite, 4-hydroxytamoxifen, were investigated in rats. Tamoxifen and curcumin interact with cytochrom P450 (CYP) enzymes and P-glycoprotein, and the increase in the use of health supplements may result in curcumin being taken concomitantly with tamoxifen as a combination therapy to treat or prevent cancer. A single dose of tamoxifen was administered orally (9 mg x kg(-1)) with or without curcumin (0.5, 2.5 and 10 mg x kg(-1)) and intravenously (2mg x kg(-1)) with or without curcumin (2.5 and 10 mg x kg(-1)) to rats. The effects of curcumin on P-glycoprotein (P-gp) and CYP3A4 activity were also evaluated. Curcumin inhibited CYP3A4 activity with 50% inhibition concentration (IC50) values of 2.7 microM. In addition, curcumin significantly (P < 0.01 at 10 microM) enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp in a concentration-dependent manner. This result suggested that curcumin significantly inhibited P-gp activity. Compared to the oral control group (given tamoxifen alone), the area under the plasma concentration-time curve (AUC(0-infinity)) and the peak plasma concentration (C(max)) of tamoxifen were significantly (P < 0.05 for 2.5 mg x kg(-1); P < 0.01 for 10 mg x kg(-1)) increased by 33.1-64.0% and 38.9-70.6%, respectively, by curcumin. Consequently, the absolute bioavailability of tamoxifen in the presence of curcumin (2.5 and 10 mg x kg(-1)) was 27.2-33.5%, which was significantly enhanced (P < 0.05 for 2.5 mg x kg(-1); P < 0.01 for 10 mg x kg(-1)) compared to that in the oral control group (20.4%). Moreover, the relative bioavailability of tamoxifen was 1.12- to 1.64-fold greater than that in the control group. Furthermore, concurrent use of curcumin significantly decreased (P < 0.05 for 10 mg x kg(-1)) the metabolite-parent AUC ratio (MR), implying that curcumin may inhibit the CYP-mediated metabolism of tamoxifen to its active metabolite, 4-hydroxytamoxifen. The enhanced bioavailability of tamoxifen by curcumin may be mainly due to inhibition of the CYP3A4-mediated metabolism of tamoxifen in the small intestine and/or in the liver and to inhibition of the P-gp efflux transporter in the small intestine rather than to reduction of renal elimination of tamoxifen, suggesting that curcumin may reduce the first-pass metabolism of tamoxifen in the small intestine and/or in the liver by inhibition of P-gp or CYP3A4 subfamily.

(Emphasis mine.)

Sure. I'm not disagreeing. Katy, in that study it appears to help by slowing the body's metabolism of tamoxifen (therefore making more available for a longer time).

I don't think curcumin is that different from dietary turmeric--it's one of its active components. Here's what Andrew Weil says:

Other studies of turmeric and curcumin have shown the following benefits:

• Turmeric extract worked as well as a non-steroidal anti-inflammatory drug for treatment of osteoarthritis of the knee in a study published in the August 2009 issue of the Journal of Alternative and Complementary Medicine.
• Laboratory studies suggest that curcumin acts as a weak phytoestrogen and seems to have cancer protective effects.
• Lab studies have also shown that curcumin induces programmed death of colon cancer cells, and clinical trials are investigating the use of curcumin in treatment of colon cancer.
• Curcumin suppresses microinflammation in the GI tract associated with inflammatory bowel disease.

I frequently recommend turmeric supplements, and I believe whole turmeric is more effective than isolated curcumin for inflammatory disorders, including arthritis, tendonitis, and autoimmune conditions. Take 400 to 600 milligrams of turmeric extracts (available in tablets or capsules) three times per day or as directed on the product label. Look for products standardized for 95% curcuminoids. Neither curcumin nor turmeric taken orally is well absorbed unless taken with black pepper or piperine, a constituent of black pepper responsible for its pungency. When shopping for supplements, make sure that the one you choose contains black pepper extract or piperine. (If you're cooking with turmeric, be sure to add some black pepper to the food.). Be patient when taking turmeric supplements: the full benefits may not be apparent for eight weeks.

Don't use turmeric if you have gallstones or bile duct dysfunction. Pregnant women shouldn't use it without their doctors' approval. In rare cases, extended use can cause stomach upset or heartburn. (Note that piperine can slow the elimination of some prescription drugs including phenytoin [Dilantin], propranolol [Inderal], and theophylline. Some evidence also suggests that curcumin can interfere with a chemotherapy agent used to treat breast cancer, so if you're being treated for this disease, be sure to discuss the advisability of taking curcumin with your physician.