Concerns Over Curcumin Compounds in Turmeric

Food Safety Authorities Declare Curcumin is Non-Carcinogenic

The 1993 NTP report produced mostly positive results. In it, the U.S. scientists tested the safety of turmeric oleoresin, which contained 79-85% curcumin. This report was part of the evidence reviewed by European authorities when they were determining curcumin's safety. In fact, the European experts cited the results from the NTP report in support of their conclusion that curcumin is safe and not a carcinogen.

Their food safety scientists did make note of the few equivocal findings of cancer-causing activity mentioned in the NTP report. However, when these scientists reviewed the results, they determined the tumors found were actually benign, not malignant. There was no mention of this fact by the research team worried about curcumin.

The concern raised that turmeric's curcumin compound can damage DNA was based on results of certain lab studies. DNA damage can lead to the development of cancer. However, other scientists considered these lab results insufficient to reach the conclusion that the Seville group did.

Results from reportedly better-documented studies also contradict the findings that curcumin directly damages DNA. The results of these more rigorous studies, according to some scientists, suggest it would have been impossible for curcumin to cause the damage found in the earlier lab studies.

In addition, a clinical study involving patients with oral submucous fibrosis showed curcumin-containing turmeric actually reversed DNA damage. Oral submucous fibrosis is a precancerous condition in the mouth.

To date, the pro-oxidant effects of curcumin are found mostly in studies that demonstrated that curcumin generates free radicals to kill cancer cells with free radicals — not to kill normal, healthy cells. There have been lab experiments where high doses of curcumin caused normal cells to die. However, animal studies with the same high doses of curcumin demonstrated the opposite on the same types of tissue (e.g., liver cells).

How do scientists explain these apparently conflicting results? Those who conducted the lab and animal studies offered one explanation. In the body, curcumin stimulates the production of natural antioxidants that protect normal cells. In fact, even those concerned about curcumin's safety acknowledge it stimulates production of antioxidants and promotes antioxidant activity.

In 2008, one of those concerned about curcumin raised the fact that curcumin has poor bioavailability. This generally means the substance is poorly absorbed into the bloodstream, and that it doesn't stay in the body long enough to be effective.

Is Curcumin Ineffective and Safe? Or is Curcumin Effective but Unsafe?

The researcher stated that this made curcumin both ineffective as a cancer treatment and non-toxic. He predicted that because curcumin is so quickly broken down in the digestive system, it would not even work against cancer there. However, he did acknowledge evidence that showed curcumin's chemopreventive effects go beyond the gastrointestinal tract. But he does not explain how curcumin demonstrates effects that can prevent cancer without bioavailability. He also doesn't explain his apparently contradictory statements on curcumin's safety. How can curcumin be both non-toxic and potentially cause cancer?

In 2010, he and others concede that curcumin has benefits that could be developed into a pharmaceutical drug. However, they expected pure curcumin to fail to demonstrate any benefit in a Phase II pancreatic cancer clinical study. Their expectation of failure was because of curcumin's poor bioavailability.

Inaccurate Statements about Drug Treatment Standards

The “dark side” researchers concluded their 2010 article by commenting on the usual standard for determining a drug's effectiveness. They state that the accepted standard to measure effectiveness is a randomized, double blind, placebo-controlled clinical trial, and that no one had conducted any for curcumin. But they fail to mention that this type of clinical trial is actually not the standard for chemotherapy drugs — a fact noted by one of same researchers in 2008. Chemotherapy effectiveness is typically measured against that of other chemotherapy drugs, not against a placebo.

Failure to Disclose Study Results that Contradict their Conclusions

What is conspicuously not mentioned in the 2010 article is evidence that curcumin did show effectiveness as a cancer treatment for pancreatic cancer. The evidence came from results of a Phase II clinical trial published in 2008. Conducted at the University of Texas M.D. Anderson Cancer Center, the clinical trial involved patients in advanced stages of the lethal cancer. Two of the 21 patients available for evaluation showed clinical responses to curcumin. One patient had stabilized disease for about 2.5 years, and another had a brief but dramatic 73% reduction in pancreatic tumor size.

The two treatment drugs approved by the U.S. Food and Drug Administration to treat pancreatic cancer produce responses in less than 10% of patients. Given this, curcumin does appear to have value as an effective chemotherapy drug for this type of cancer. Not only was it safe and effective, the stage 4 pancreatic cancer patients tolerated curcumin well. They had none of the severe side effects often associated with chemotherapy drugs.