The numbers are small, but the headlines linking dietary supplements to liver damage are big--- big enough to generate yet another round of medical and regulatory hand-wringing about the problem of “uncontrolled” supplements.
The study in question, headed by Victor Navarro, MD, of the Einstein Medical Center, Philadelphia, and published in late September in the journal, Hepatology, claims that 20% of all cases of chemical-induced hepatotoxicity –that’s one in five—are traceable to herbal products and dietary supplements.
That’s up from one in ten cases a decade ago.
Drawing from a national registry of drug-induced liver injuries, Dr. Navarro and colleagues identified 130 cases with a clear link to supplements over a period of eight years. That’s roughly 16 cases per year.
One third of these were due to anabolic steroids in muscle-building or performance-enhancing “supplements.” Steroids are known to cause cholestatic liver damage, though in most cases this is reversible.
The remaining 85 cases were tied to a wide range of herbal and nutraceutical products. The investigators named six products from a company called Slimquick, four from Herbalife, four from Hydroxycut, and two each from MoveFree and Airborne.
But they note that many of the products in question contain multiple ingredients, and might also contain undisclosed compounds or contaminants, making it difficult in most cases to peg the liver problems to any specific vitamins, minerals or bioactive substances. They indicate that Chinese, Korean and Indian/Ayurvedic multi-herb formulations are particularly problematic.
One specific ingredient did stand out in several cases: green tea extract, which can cause acute hepatitis-like damage in some rare cases.
Under-Reported but Over-Inflated
Dr. Navarro believes supplement related hepatotoxicity is greatly under-reported. This is because: A) the onset is slow and non-dramatic, often taking months or years to develop; B) people seldom report potential adverse reactions on their own, and they’re are not always forthright with healthcare practitioners (or do not have the time during standard office visits); and C) busy practitioners often fail to ask about supplement use or fail to report potential adverse events.
That said, the authors acknowledge that fortunately, “liver injury from supplements is rare.”
And indeed, it is.
There are approximately 324 million adults in the US. According to a recent federal estimate just published in the Journal of the American Medical Association, 52% of all Americans take supplements, meaning there are about 166 million supplement users in the country.
Using that figure, and Dr. Navarro’s 16 hepatotoxicity cases per year, the incidence of supplement induced hepatotoxicity would calculate out to roughly 0.000009% per year.
Let’s assume Navarro is correct and the problem is grossly under-reported. Even if it were a thousand times more common than these current data indicate, the incidence would still be 0.009%!
But that didn’t stop Hepatology, a major gastroenterology journal, from spotlighting the study. Nor did it stop Reuters newswire service from running a generalized and alarmist headline stating, “Herbal and Dietary Supplements Tied to Liver Damage.”
There’s no question that there are holes in the regulatory process, that some supplement products get to market containing potentially hazardous compounds, that adverse effects do occur, and that they likely go unreported.
But studies like this, and the news reports that follow--which make sweeping judgments based on very small numbers—smell more of sensationalism than science.