“What science allows is an increasing confidence in a hypothesis as the evidence accumulates, not a claim to infallibility on the first try.”
–– Steven Pinker, Enlightenment Now.
Using curcumin as an example, Part 1 of this column emphasized variability in curcumin absorption (bioavailability) and the resulting safety concerns. The more important question is this: Is curcumin likely effective and safe for the condition you wish to treat? Only clinical (human) trials can answer this.
Evidence Based Medicine provides a framework to guide medical decisions at the patient level, and for national guidelines like those from the U.S. Preventive Services Task Force (uspreventiveservicestaskforce.org). It emphasizes need for a high level of evidence to justify medical interventions.
The highest level of evidence comes from randomized clinical trials published in peer-reviewed journals. In these trials, participants are randomly assigned to receive a promising new treatment (like curcumin) verses a control such as placebo.
Ideally both participants and investigators are blinded. This strategy for evaluating efficacy and toxicity minimizes confounding influences, such as investigator and participant biases that could inadvertently affect study results.
If done properly, we conclude the study outcome was (probably) caused by the treatment.
Curcumin clinical studies are few and usually of low quality. This is not surprising. Clinical studies for dietary supplements are not required by FDA. Trials are expensive with low probability for return on investment.
Nevertheless, three clinical trials of curcumin for enhancement of cognition have recently been published. You can access these — and many clinical studies — via Google/Scholar/search term (for example, curcumin and cognition).
The highest quality study was published in the American Journal of Geriatric Psychiatry in March 2018. Investigators randomized 46 nondemented healthy adults, aged 51-84 years, to a bioavailable curcumin formulation (90 mg of Theracurmin, twice daily) or placebo.
Investigators and subjects were blinded. The primary measures of effectiveness included baseline tests of verbal memory (how many of 12 words can be recalled from memory) and visual memory (how many geometric forms can be redrawn).
Tests were repeated at 6, 12 and 18 months. Forty subjects completed the study; 21 received curcumin and 19 received placebo.
Curcumin recipients averaged 28 percent improvement in verbal memory at 18 months compared with 2.6 percent in placebo recipients. The difference in memory response between curcumin and placebo was statistically significant.
The authors concluded that “daily oral Theracurmin may lead to improved memory and attention in nondemented adults.”
What do we make of this?
First, this study received widespread attention because its design adheres to guidelines for the highest level of evidence and the findings have broad implications.
The difference in response between curcumin and placebo is unlikely due to chance (this is the meaning of “statistically significant”).
Second, should thousands of people begin taking curcumin based on results from 21 patients? The authors correctly state this was a pilot study and “not a claim to infallibility on the first try.”
Third, improved recall of 12 words on a memory test does not necessarily mean that practical memory functions of daily living will noticeably improve (for example, being less forgetful about where you put your car keys).
Fourth, only non-demented persons were studied. Results cannot be extrapolated to persons with dementia, such as Alzheimer’s disease.
Finally, if you use curcumin for its possible cognition benefits, you are advised to take the specific product and dosage studied. The estimated cost for 18 months is $540.
What you should know: The more you know about your drugs, including understanding the clinical science supporting their use, the more likely you will maximize benefit and minimize risk. The FDA provides this excellent guide for dietary supplements: bit.ly/1umyeN0.
Mountain Medicine is written by Ron Polk, Pharm.D., Emeritus Professor of Pharmacy and Medicine at Virginia Commonwealth University and a Lostine resident, in consultation with Kelsey Allen, D.O., a family medicine physician at Mountain View Medical Clinic in Enterprise.