Supplements now cause about one in five cases of drug-related liver injury in the US

Herbal and dietary supplements, widely assumed to be gentle because they are "natural" and sold without a prescription, are now a leading cause of drug-related liver injury: they account for roughly 20% of hepatotoxicity cases in the United States, according to research data reviewed by liver specialists [s1]. The products most often implicated are not obscure — bodybuilding steroids, green tea extract and multi-ingredient nutritional blends lead the list [s1].

What the evidence base is

The figures come from a review published in Hepatology, the journal of the American Association for the Study of Liver Diseases, summarising a two-day research symposium that the association ran jointly with the National Institutes of Health on supplement-induced liver injury [s1]. The review draws on clinical research into real cases of hepatotoxicity — people who developed liver injury and were worked up to identify the cause — rather than on marketing claims or adverse-event tip lines. Its central number is that herbal and dietary supplement injury now accounts for 20% of hepatotoxicity cases in the US, a share that has risen in proportion to how much people use these products [s1].

That reframes the risk. A prescription drug carries a label listing hepatotoxicity as a known effect and a physician who monitors for it. A supplement bought off a shelf carries neither, and the assumption that a botanical or "nutritional" product cannot damage the liver is precisely the assumption the case data contradict.

The products that keep appearing

The review sorts the main offenders into recognisable groups, each with its own pattern of injury [s1]. Anabolic steroids marketed as bodybuilding supplements typically cause a prolonged cholestatic injury — one that blocks bile flow — which is ultimately self-limiting but has a distinctive biochemical and tissue signature [s1]. Green tea extract, by contrast, and many other products tend to cause an acute hepatitis-like injury, the pattern seen with a sudden inflammatory insult to liver cells [s1]. The distinction matters because it shows there is no single "supplement liver injury" — different products injure the liver in different ways, which is part of why they are hard to recognise and easy to miss.

The hardest category is the largest. The review states that the majority of supplement-associated liver injury cases are now due to multi-ingredient nutritional supplements, and that the specific component responsible for the toxicity is usually unknown or can only be suspected [s1]. A product with a dozen botanical extracts on the label offers no way to know which one — or which contaminant, or which undisclosed addition — caused the harm. That opacity is a regulatory problem as much as a medical one, and the review calls explicitly for improved oversight of non-prescription products to guarantee their contents and ensure purity and safety [s1].

Why "natural" is not the safety signal it seems

Even substances with a long record of apparently safe use can injure the liver, and a comparison makes the point. Acetaminophen — paracetamol — is one of the most-used drugs in the world and, at ordinary doses, is generally well tolerated; yet the NIH's LiverTox resource notes that even at therapeutic doses it can cause transient elevations in liver enzymes, and in overdose it is a major cause of acute liver failure [s2]. If a single, well-characterised, tightly regulated molecule can do that, an unregulated blend of botanical extracts of uncertain identity and dose is not obviously safer for being plant-derived. The relevant safety question is not whether a product is natural but whether its contents are known, consistent and tested — and for many supplements, the review's answer is that they are not [s1].

What a person cannot easily do

The uncomfortable practical implication is that a consumer often cannot self-diagnose the risk. Supplement liver injury can appear weeks into use, its symptoms (fatigue, nausea, dark urine, yellowing of the skin or eyes) are non-specific, and tracing it back to a product — especially a multi-ingredient one — can defeat even specialists, who describe identifying the injurious ingredient as a research challenge requiring chemists and toxicologists, not just clinicians [s1]. This is one reason liver doctors ask specifically about supplements when investigating unexplained liver-test abnormalities, and why an honest account of the evidence stops short of a simple "avoid X" list: for the biggest category, the culprit ingredient is frequently unidentified [s1].

What this leaves a reader with

The "natural equals safe" assumption does not hold for the liver: supplements cause about a fifth of US drug-related liver injury, with bodybuilding steroids, green tea extract and multi-ingredient blends most often involved, and the responsible ingredient in the largest category typically unknown [s1] [s2]. Anyone taking supplements alongside symptoms of liver trouble, or facing an unexplained abnormal liver test, has a specific and useful thing to raise with a clinician — the full list of what they are taking, prescription and non-prescription alike.

This article is informational and is not medical advice.

Sources

• Liver injury from herbal and dietary supplements — Hepatology (AASLD), 2016-11-17
• Acetaminophen (LiverTox: Clinical and Research Information on Drug-Induced Liver Injury) — National Institute of Diabetes and Digestive and Kidney Diseases (NIH)