silymarin
Meaning of silymarin: A widely sold liver supplement whose one genuinely established use has little to do with the bottle on the shelf.
Definition of silymarin
Silymarin is an extract of milk thistle seeds, a mixture of related plant compounds of which silybin is the most abundant and the most studied. It is sold worldwide as a supplement for liver complaints. A purified intravenous form of silybin is used in several countries as an antidote for poisoning by the death cap mushroom.
What is in the extract?
Not a single chemical. Silymarin is a mixture of flavonolignans, compounds built from a flavonoid unit joined to a lignan unit, and the proportions vary between products made from different seed batches by different methods. Silybin makes up the largest share and carries most of the activity credited to the whole. Because the mixture itself is variable, findings from one preparation do not transfer cleanly to another, which is part of why the published research is so hard to reconcile.
What is it thought to do?
Traditional use for complaints of the liver and gall bladder runs back centuries. Laboratory work shows the extract steadying cell membranes, mopping up reactive molecules, and competing with certain toxins for the transporter that carries them into liver cells. That last mechanism is the basis of the mushroom antidote: blocking uptake of the toxin gives liver cells a chance to survive the poisoning while the rest of the treatment proceeds.
Does the evidence support the supplement?
| Use | State of the evidence |
|---|---|
| Death cap poisoning | Intravenous silybin used as an antidote in several countries |
| Alcohol related liver disease | Trials inconsistent, with no clear effect on survival |
| Viral hepatitis | Enzyme levels may fall without any change in the virus |
| Protecting the liver during chemotherapy | Studied, but not established practice |
The gap between antidote and capsule is one of dose and route. The antidote is a purified compound delivered into a vein at high concentration under supervision. A capsule delivers a variable mixture that is absorbed poorly and cleared quickly. No trial has shown that taking it prevents liver cancer, and the two situations share little beyond a common plant.
What is known about safety?
It is generally well tolerated, with loose stools and mild digestive upset the usual complaints, and allergic reaction possible in people sensitive to plants of the daisy family. Interaction is the more relevant issue. Extracts can affect enzymes and transporters that clear other drugs, so a supplement taken alongside prescribed treatment is not a neutral addition. Describing silymarin only as an agent under study against damage from cancer therapy understates how often it is taken without medical involvement, and how rarely it reaches a medication list.
Also known as
Used in a sentence
The medication list included a milk thistle supplement containing silymarin.
Good to know
The intravenous silybin given as a mushroom poisoning antidote is a purified compound at high concentration, and its use does not support the claims made for oral silymarin capsules.