One of the more popular herbal products in the last few years has been turmeric. Used as a spice in cooking, this herb has also been used for the usual wide range of unrelated conditions in traditional folk medicine, particularly in Ayurvedic and Chinese medicine. Turmeric is sometimes suggested for use in the treatment of cancers and inflammatory conditions, such as arthritis, in veterinary patients. A recent question from a reader prompted me to have a look at the evidence concerning the use of this herb.
What Is It?
Turmeric is a root cultivated as a spice and herbal medicine throughout Asia and parts of Africa. It contains a plethora of compounds, however the most studied in terms of medical applications are the curcuminoids.
What’s the Evidence?
There are abundant in vitro studies examining the chemical and biological properties of compounds found in turmeric. These studies suggest antioxidant, anti-inflammatory, and anti-cancer activity for curcumin and other constituents of turmeric. Such in vitro studies can never, of course, prove a clinical benefit for patients. Bleach kills cancer cells in a petri dish, but it is hardly a cure for cancer. However, these studies are important for identifying possible uses to be investigated and for building a plausible foundation for conducting clinical studies. The in vitro research certainly does suggest a number of potential medical uses for turmeric.
The actual clinical research, however, is sparse. As the National Center for Complementary an Alternative Medicine (NCCAM) puts it, “There is little reliable evidence to support the use of turmeric for any health condition because few clinical trials have been conducted.” Many of the studies that have been done in humans have focused on curcumin and have found that it is poorly absorbed when taken orally. Large quantities must be taken to achieve detectable levels of curcumin in the blood.
There has been one systematic review of the research concerning the use of turmeric for a wide range of conditions:
Ulbricht C, Basch E, Barrette EP, et al. Turmeric (Curcuma longa): An Evidence-Based Systematic Review by the Natural Standard Research Collaboration. Alternative and Complementary Therapies. August 2011, 17(4): 225-236.
The summary conclusions of the review have been posted here. All potential uses were given the evidence grade of C, meaning the evidence is unclear, conflicting, or insufficient to draw any conclusions. Overall, there is no compelling clinical evidence in humans supporting any use of curcumin or other turmeric compounds.
As usual, there is less evidence in companion animals. One study comparing a turmeric compound to placebo in dogs with arthritis found not significant effects in an objective measure of weight bearing or in subjective owner assessment, though there was a small difference according to the subjective assessment of investigators. There are no other controlled clinical trials. A few experimental studies have been done on potential topical applications for ringworm and bacterial infections, and one research group in Brazil has published several papers looking at specific physiologic effects of turmeric compounds in dogs intentionally injected with snake venom. These studies have little relevance to the clinical use of turmeric for treatment of arthritis, cancer, and other clinical problems.
Is It Safe?
As I emphasize frequently, any therapy that has meaningful benefits will also have potential side effects. The body is simply too complex to expect to tinker with one element and not have wide-ranging effects on other elements. Therefore, it is actually a bad sign when a treatment is promoted as having no side effects since it likely suggests that treatment doesn’t actually do anything.
Potential adverse effects have been reported for turemric, including gastrointestinal upset, possible effects on blood clotting, possible increase in the risk for some kinds of bladder and kidney stones, and interactions with other herbs and pharmaceuticals. The limited clinical research so far suggests these risks are small. However, there is far less research available than is typical for a new drug before it is put on the market, and it is not unusual for unanticipated side effects to show up after a medicine is used and studied in a much larger and more diverse population. Therefore, the best we can say about the safety of turmeric for medical use (which, of course, means doses dramatically greater than its use as a spice in cooking) is that there is no obvious evidence of great risk but that the safety profile is no more clearly established than the efficacy profile.
Turmeric contains a number of potentially useful chemical compounds, of which the most studied is curcumin. There is sufficient in vitro research to establish biological effects which might have clinical benefits, so the concept that these compounds could have therapeutic value is plausible. There is very little clinical research in humans, and there is not yet any convincing evidence to support the use of turmeric for any condition. There is virtually no clinical research in companion animals, and what there is does not support claims of benefit from turmeric compounds. Finally, the limited research to date suggests a few potential risks but the significance of these is unclear.