Curcumin & Tamoxifen

Curcumin is the primary component of the Indian spice turmeric, and is responsible for
the bright yellow color of this popular spice. There is a significant amount of research
demonstrating curcumin’s anti-inflammatory and anti-cancer properties and, in fact, several
laboratory studies have found that this botanical enhances the effectiveness of chemotherapy
drugs in treating various types of tumors.

What’s really remarkable is that most of the
interactions are synergistic, meaning that curcumin actually multiplies the effectiveness of
several chemotherapy drugs. This has caused some to wonder if there is also the potential
for negative interactions, and whether curcumin could perhaps inhibit the effectiveness of
other chemotherapy drugs. Some of this concern has centered around tamoxifen. Specifically,
whether curcumin could inhibit tamoxifen’s activity.

It has been noted in a lab study that curcumin can inhibit an enzyme in the body (called
cytochrome p450 2D6), one of the enzymes that is involved in activation of tamoxifen. Some
antidepressant drugs also inhibit the same enzyme, and they can decrease the amount of
activated tamoxifen in the bloodstream. However, the lab study of curcumin found that there
was actually only a very minor inhibition of this enzyme. Curcumin had a stronger inhibition
on some other related cytochrome p450 enzymes in that lab study, for instance 3a4, the
enzyme involved in St John’s Wort interactions.

In the case of curcumin and tamoxifen, this
could have resulted in an increase in the level of tamoxifen in the blood. And in fact, when
curcumin was given along with tamoxifen to rats, the tamoxifen levels in the blood increased.
However, when this 3a4 interaction was tested in humans, it was of no clinical or statistical
significance.

Furthermore, other lab studies have shown curcumin to inhibit tamoxifen-induced
liver injury, to increase the toxicity of tamoxifen towards leukemia cells while protecting red
blood cells, and to sensitize breast cancer cells to tamoxifen treatment. It is thus extremely
unlikely that curcumin could have been inhibiting the activity of tamoxifen in this patient.