The May 2 introduction to this column stated the purpose is to provide evidence-based assessments and recommendations to readers, and to inform them of the methods used in the clinical sciences with the goal of helping them make rational choices in their own health care decisions.

Today’s column and Part 2 to follow uses the example of a popular dietary supplement, curcumin, to achieve this goal.

Curcumin is the yellow substance in the spice turmeric. Supplements are sold online and in retail outlets. Proponents claim curcumin has “been widely utilized by Ayurvedic medicine since 1900 BC for its wide-reaching health and well-being benefits”.

More specific though less modest claims include helping to relieve joint and back pain, reduce inflammation and skin dryness, boost brain function and memory, improve digestion and blood circulation and enhance immune and nervous system. Also included are promoting healthy joints, eyes, skin, hair, heart and mood.

In stark contrast, Wikipedia accurately summarizes the prevailing scientific opinion, “Curcumin has no confirmed medical use in spite of efforts to find one via both laboratory and clinical research. It is difficult to study because it is both unstable and not bioavailable.”

What can explain such divergent statements?

Drug effects are studied both in vitro (in test tubes) and in vivo (animals and humans). To the consumer, in vivo human studies are the most relevant.

For example curcumin has multiple in vitro effects, including anti-inflammatory, anti-neoplastic and anti-oxidant properties. This suggests potential medical uses in humans, but also raises a number of important points.

First, desirable in vitro effects are meaningless and misleading if the drug cannot reach its target, such as inflamed joints or the brain.

Bioavailability is the term referring to the proportion of an oral dose that is absorbed from the gastrointestinal tract. Values range from no absorption to 100 percent or complete absorption. Many marketed preparations of curcumin have negligible bioavailability, and the claimed benefits from in vitro studies cannot be realized.

Second, some newer curcumin products are partially absorbed, a result of adding piperine (black pepper extract) or changing curcumin’s physical properties.

One product claims “27 times more bioavailable than the ordinary powder.” Another is “clinically proven to be 285 times more bioavailable than 95 percent standardized curcumin.”

For reasons beyond today’s column, these statements do not identify which of the two products has greatest absorption.

Third, no drug results in only beneficial effects. When one of the more bioavailable curcumin products is ingested, human cells, proteins and enzymes are exposed to a foreign molecule.

There is no reason to think the effects will only be beneficial. For example, curcumin and piperine inhibit the most important human drug metabolizing enzymes, raising the distinct possibility of undesirable drug-drug interactions.

Finally, curcumin products are advertised for human ailments. One product claims it is “backed by a human clinical study showing reduction in pain, a reduction in inflammation and increased mobility, as well as optimal cucuminoid absorption.”

Dietary supplements making such claims are also required by the 1994 Dietary Supplement Health and Education Act to advise “this product is not intended to diagnose, treat, cure or prevent any disease.” If you find this conflicting and confusing, you are not alone.

You should know. Drugs are often advertised to consumers using unfamiliar medical terms and misleading claims. Your health care providers, including your pharmacist, can help you make rational choices in your decisions.

The bottom line, however, is that only well-designed clinical trials can reveal the true safety and efficacy profile of a drug. That process will be the subject of Part 2.

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. The opinions expressed are those of the authors. The authors report no conflicts of interest.