Milk thistle and the liver: detox myth or real protection?
Detox sells well. Silibinin is an emergency medicine. Both come from the same plant. An honest look at what studies show and what they do not show.
Your liver is not waiting for a cure. It is detoxifying this very second, while you read this. The interesting question is not how you get it going. It is what you keep it busy with.
I bet you know that shelf. Between the vitamins and the slimming teas sit the boxes with the purple flower head. Liver cure. Detox. Cleanse. Fourteen days, and everything is fresh again.
Maybe you reach for one because the past few weeks have been exhausting. Too much wine, too little sleep, too much of everything. You feel heavy and somehow coated. And you would like the feeling of doing something about it.
I understand that impulse very well. It is honest. It is just that the box answers a question your body never asked.
Because here is the odd thing about this plant: advertising promises it something it does not have to deliver. And leaves out what it can actually do. Silibinin, the main active compound of milk thistle, stands ready in European emergency departments when someone has eaten a death cap mushroom. That is not a wellness story. That is intensive care medicine.
Both belong to the same plant. They are simply two completely different stories. Let us separate them.
Your liver has long been detoxifying. Without asking you.
May I ask you an uncomfortable question? If a cure boosts detoxification: what exactly is your liver doing during the other fifty weeks of the year?
The answer is unspectacular and reassuring at the same time. It works. Continuously. Around 1.5 litres of blood flow through it per minute, and everything floating in there gets sorted.
Do not picture the liver as a filter bag in which dirt collects that has to be knocked out. Picture it as a chemical conversion plant. It does not capture substances. It changes them until the body can get rid of them.
This happens in two steps, and this two step sequence is the real heart of any serious discussion about detoxification.
Phase I: convert
Cytochrome P450 enzymes attach a reactive group to fat soluble substances. A molecule the body cannot grasp becomes one with a handle.
The delicate intermediate step
Some of these intermediates are more reactive than the starting substance. This is exactly where the cell needs antioxidants, glutathione above all, to protect itself.
Phase II: package
A water soluble building block is coupled to the handle, for example glucuronic acid, sulfate, glycine or glutathione. Fat soluble becomes water soluble.
Phase III: move it out
Transport proteins move the finished package into the bile or into the blood. Exit: gut or kidney. Only here does the substance really leave the body.
Iyanagi summarised in 2007 how this system is built at the molecular level. The oxidative enzymes of phase I and the conjugating enzymes of phase II both sit in the same membrane inside the liver cell, the endoplasmic reticulum.
What was observed: both enzyme families have a deliberately unspecific active site. This allows them to accept a huge range of foreign molecules, including ones that never existed during evolution.
What this means for you: your detoxification system is not an emergency programme that would have to be switched on. It is a permanent installation with built in flexibility.
Iyanagi T. Int Rev Cytol. 2007;260:35-112. DOI: 10.1016/S0074-7696(06)60002-8And now comes the point where the detox narrative starts to wobble. If this system runs permanently, then a cure cannot start it. At most it could support it. That is a considerable difference in claim.
Klein and Kiat examined the available evidence on commercial detox programmes in 2015. They looked for clinical studies showing that such cures actually remove harmful substances from the body.
What was observed: a handful of clinical investigations were found. They did report effects on detoxification capacity and on the elimination of persistent organic pollutants, but they were all very small and methodologically weak. According to their search, not a single randomised controlled trial existed on the effectiveness of commercial detox diets in humans.
What this means for you: the detox industry is considerably larger than its data base. That does not mean none of it makes sense. It means the promises reach further than the evidence.
Klein AV, Kiat H. J Hum Nutr Diet. 2015;28(6):675-686. DOI: 10.1111/jhn.12286You may have thought: my liver is clogged and needs a rinse.
Turn that around for a moment. Your liver is a workshop with a full order book. It is not standing still. The question is not how you get it going, but how many orders you hand it every day and whether it has the material for the work.
And now you know why the word detoxification is used so readily in advertising. It sounds like an action you can trigger. Physiologically it describes a state that exists anyway.
What silymarin actually is
Before we talk about studies, a quick word on vocabulary. Because three terms are constantly mixed up, and that fog is part of the problem.
| Term | What is meant |
|---|---|
| Milk thistle | The plant, botanically Silybum marianum. A thistle with purple flower heads whose fruits are used. |
| Silymarin | The standardised extract from the fruits. A mixture of six flavonolignan isomers, not a single substance. |
| Silibinin | Also called silybin. The pharmacologically most active single component of the mixture. The one at the centre of emergency medicine and research. |
This is not hair splitting. It is the reason why studies on milk thistle turn out so differently. A tea, a capsule of powder, a standardised extract and an infusion solution with silibinin dihemisuccinate are pharmacologically four different things.
Koltai and Fliegel described the composition more precisely in 2022. Silymarin consists of six flavonolignan isomers, of which silybin, silydianin and silychristin are the most important.
What was observed: silybin is functionally the most active of these substances. The described modes of action are antioxidant, they promote ribosomal synthesis and they stabilise mitochondrial membranes.
What this means for you: if a package only says milk thistle powder, without stating the silymarin content, you do not know how much of what the studies were about is actually in there.
Koltai T, Fliegel L. J Evid Based Integr Med. 2022;27:2515690X211068826. DOI: 10.1177/2515690X211068826On top of that comes a problem many plant compounds share: silymarin is poorly absorbed and quickly converted again. Interestingly, this does not seem to be the same in everyone.
Schrieber and a team investigated in 2011 how silymarin arrives in the blood in two different liver diseases. Groups of eight people each with fatty liver or with hepatitis C received 280 mg or 560 mg silymarin or placebo every eight hours for seven days.
What was observed: in fatty liver, concentrations of the free flavonolignans were higher, while the conjugated forms were lower than in hepatitis C. At 280 mg, the area under the curve for silybin B conjugates was 46 percent lower in fatty liver. Indications of an enterohepatic circulation were found exclusively in the fatty liver group.
What this means for you: the same capsule does not produce the same blood level in everyone. From this the authors suspected that an effect might be easier to observe in fatty liver than in hepatitis C. Exactly this pattern shows up again later in the clinical trials.
Schrieber SJ, Hawke RL, Wen Z et al. Drug Metab Dispos. 2011;39(12):2182-2190. DOI: 10.1124/dmd.111.040212And now you know why the question about milk thistle is not a simple yes or no question. It depends on which preparation, in which condition and in what amount.
The strongest evidence comes from the emergency department
Now it gets serious, in the literal sense.
The green death cap looks harmless. Worldwide, more than 90 percent of all fatal mushroom poisonings go back to amatoxin containing species, frequently after a mix up with edible mushrooms such as button or meadow mushrooms. The treacherous part: the first complaints appear at the earliest after about six to eight hours, sometimes only after half a day or later. Anyone who develops complaints the next morning often rules out the connection. By then the toxin has long reached the liver.
And here something happens that impresses me as a physician every single time. Amatoxins do not enter the liver cell on their own. They need a door.
Letschert and a team at the German Cancer Research Center in Heidelberg searched for exactly this door in 2006. They tested three transport proteins of the liver cell membrane in cell lines produced specifically for this purpose.
What was observed: only one of these proteins, OATP1B3, transported amanitin into the cell, with a Km value of 3.7 plus minus 0.6 micromol. The transport could be blocked by substances that occupy this transporter. Silibinin dihemisuccinate was among these blockers.
What this means for you: silibinin does not detoxify anything here. It positions itself in front of the door. The toxin stays outside and is excreted via the kidney instead of destroying the cell from within.
Letschert K, Faulstich H, Keller D, Keppler D. Toxicol Sci. 2006;91(1):140-149. DOI: 10.1093/toxsci/kfj141That is a wonderfully concrete mechanism. And it has clinical consequences that reach far beyond a food supplement.
Mengs, Pohl and Mitchell compiled in 2012 what was known from uncontrolled studies and case reports on intravenous silibinin. Controlled trials do not exist here for obvious ethical reasons, you cannot withhold treatment from a comparison group.
What was observed: in close to 1,500 documented cases, overall mortality under intravenous silibinin was below 10 percent. Under penicillin or under the combination of silibinin and penicillin it was above 20 percent.
What this means for you: this is not a wellness effect, it is a difference in survival. One important note on this source: the first author worked in research and development at the manufacturer of the infusion preparation. That does not devalue the figures, but it belongs in the picture. These are comparisons across time periods and centres, not randomised data, and they come from a review that was not compiled independently. It is not proof of causality in the strict sense.
Mengs U, Pohl RT, Mitchell T. Curr Pharm Biotechnol. 2012;13(10):1964-1970. DOI: 10.2174/138920112802273353Kieslichova and a team at the Institute for Clinical and Experimental Medicine in Prague evaluated 23 patients admitted between 2007 and 2016 after eating death cap mushrooms.
What was observed: treatment consisted of activated charcoal, fluids, high dose N-acetylcysteine and intravenous silibinin. Six people needed a liver transplant. All 16 who did not meet the King's College criteria for acute liver failure and were treated conservatively survived.
What this means for you: silibinin never stands alone here. It is one building block in a complete intensive care package. Anyone transferring that to a capsule has left the context behind.
Kieslichova E, Frankova S, Protus M et al. Transplant Proc. 2018;50(1):192-197. DOI: 10.1016/j.transproceed.2017.11.032Milk thistle does not have to prove itself as a detox cure. It already stands ready in European emergency departments, for the moment when a liver is fighting for its life. That is the more impressive story. It just sells less well.
And now you know why the sentence milk thistle protects the liver can be accurate and misleading at the same time. It depends on which liver, which toxin and which form of administration are meant.
How silymarin may act at the cell level
So if it is not detoxification, what is it? From the perspective of clinical psychoneuroimmunology it is worth looking through four lenses at once here. The liver is not an isolated organ but the hub between the immune system, metabolism and hormonal axes.
The four perspectives below are appraisals and hypotheses, not documented statements of effect.
Immune system
In fatty liver, activated immune cells sit in the tissue and release inflammatory messengers. In animal models silybin appears to dampen the NF-kappa-B signalling pathway, the central switch for this inflammatory response.
Metabolism
Between phase I and phase II, reactive intermediates arise. The Nrf2 pathway raises the cell's own antioxidant defence. In animal models silybin can activate this pathway and thereby increase the cell's self protection capacity.
Hormonal system
Insulin is the dominant hormone of the liver cell. It decides whether fat is stored or burned. In insulin resistance this control tips over, and the liver builds up fat even though plenty of energy is available.
Nervous system
The liver processes ammonia from the gut. In advanced liver disease this value can rise and show up as difficulty concentrating and severe tiredness. That is a late sign and not an explanation for everyday tiredness. Anyone who feels tired almost always has other reasons for it, from sleep to iron to the thyroid.
Ou and a team fed male C57BL/6 mice a diet without methionine and choline for eight weeks. This model reliably produces steatohepatitis. Part of the animals additionally received silybin by gavage.
What was observed: under silybin, steatosis, connective tissue proliferation and inflammation in the liver tissue were less pronounced. Genes of the Nrf2 pathway were read out more strongly, the activity of NF-kappa-B was dampened.
What this means for you: that is a plausible mechanism, but it is a mouse with an artificially produced fatty liver. Transfer to humans is a hypothesis, not a finding.
Ou Q, Weng Y, Wang S et al. Dig Dis Sci. 2018;63(12):3398-3408. DOI: 10.1007/s10620-018-5268-0The detox idea imagines silymarin as a cleaning crew that carries something out.
The study data suggest something else: it may be more like a safety helmet. It carries nothing out. It may make the cell more stable while it does its own work. That is less spectacular, but it fits the data.
And now you know why I prefer the word hepatoprotective to the word detoxifying. It describes more precisely what this is about: protection during the work, not the work itself.
Fatty liver: the evidence is densest here and still not clear cut
Now to the condition that most people actually reach for milk thistle because of, even if they often do not know it. Because the most common strain on the liver of our time is not a poisoning.
Younossi and a team evaluated population data from 1990 to 2019 in 2023, in total 92 studies with more than 9.3 million people.
What was observed: the worldwide prevalence of non-alcoholic fatty liver was 30.05 percent, with an interval of 27.88 to 32.32. Over time it rose by 50.4 percent, from 25.26 percent in the period 1990 to 2006 to 38.00 percent in the period 2016 to 2019. For Western Europe the value was 25.10 percent.
What this means for you: statistically, about one in four people in Western Europe has a fatty liver. The vast majority know nothing about it, because they feel nothing.
Younossi ZM, Golabi P, Paik JM et al. Hepatology. 2023;77(4):1335-1347. DOI: 10.1097/HEP.0000000000000004This is where the study data on silymarin are densest. And they are, honestly, mixed.
Li and colleagues pooled in 2023 all randomised trials on silymarin in fatty liver that they could find in six databases.
What was observed: under silymarin, liver values were lower, ALT with a standardised mean difference of minus 12.39 with an interval of minus 19.69 to minus 5.08, AST with minus 10.97 with an interval of minus 15.51 to minus 6.43. In the tissue sample, steatosis improved more frequently, odds ratio 3.25 with an interval of 1.80 to 5.87. Cholesterol and fasting insulin were also lower.
What this means for you: those are respectable figures. What belongs in the honest picture: for the insulin resistance index HOMA-IR the stated interval ran from minus 0.77 to plus 0.04 and thereby included zero. The authors themselves wrote that the effects would have to be confirmed in further research.
Li S, Duan F, Li S, Lu B. Ann Hepatol. 2024;29(2):101174. DOI: 10.1016/j.aohep.2023.101174Kalopitas and a team at the Aristotle University of Thessaloniki approached the same question more strictly in 2021. They included only placebo controlled randomised trials and systematically assessed the risks of bias.
What was observed: silymarin lowered transaminases more than placebo, and did so independently of whether participants lost weight. At the same time the authors explicitly pointed to possible quality shortcomings of the included trials.
What this means for you: the effect on liver values seems robust enough to be taken seriously. Whether a lower ALT value also means that the tissue recovers remains open in the authors' assessment.
Kalopitas G, Antza C, Doundoulakis I et al. Nutrition. 2021;83:111092. DOI: 10.1016/j.nut.2020.111092Exactly this open question was addressed by a research group in Kuala Lumpur. With tissue samples before and after. And the result is instructive, because it does not fit into a simple headline.
The research group around Wah Kheong at the University of Malaya treated people with biopsy confirmed steatohepatitis for 48 weeks with 700 mg silymarin three times daily or with placebo. Afterwards they were biopsied again.
What was observed: the primary endpoint, an improvement of the activity score by at least 30 percent, was missed. 32.7 percent in the silymarin group versus 26.0 percent under placebo, p equals 0.467. For connective tissue proliferation the picture was different: a regression by at least one point was shown by 22.4 percent under silymarin and 6.0 percent under placebo, p equals 0.023. In elastography, liver stiffness declined markedly in 24.2 percent versus 2.3 percent, p equals 0.002.
What this means for you: the main question was not confirmed. A secondary finding on fibrosis, by contrast, stood out. The authors phrased it cautiously: silymarin might influence fibrosis favourably, and a larger trial would first have to confirm that. I find this restraint exemplary.
Wah Kheong C, Nik Mustapha NR, Mahadeva S. Clin Gastroenterol Hepatol. 2017;15(12):1940-1949. DOI: 10.1016/j.cgh.2017.04.016Loguercio and a European study team tested a combination of silybin, phosphatidylcholine and vitamin E against placebo over twelve months in histologically confirmed fatty liver. 138 people could be evaluated per protocol.
What was observed: in the treatment group, liver values, insulin resistance index and tissue findings improved, in the placebo group they did not. In 15 percent of those treated, the body mass index fell into the reference range, under placebo in 2.1 percent. Serious side effects did not occur. Transient adverse effects were reported, among them diarrhoea, taste disturbance and pruritus.
What this means for you: the interesting part here is the formulation. Silybin was coupled to phosphatidylcholine to improve absorption, and combined with vitamin E. The effect therefore cannot be cleanly attributed to a single substance.
Loguercio C, Andreone P, Brisc C et al. Free Radic Biol Med. 2012;52(9):1658-1665. DOI: 10.1016/j.freeradbiomed.2012.02.008Where the signal is clearest
- Lower transaminases in fatty liver, in two independent meta-analyses
- Well tolerated in the trials, with the known limitations: gastrointestinal complaints, caution with Asteraceae allergy, no robust data in pregnancy and breastfeeding
- A clear transport mechanism in amatoxin poisoning
- First signals of metabolic effects, from small trials and, in the authors own appraisal, not yet sufficient for firm conclusions
Not yet shown
- Whether lower liver values also mean less tissue damage
- Whether fibrosis reliably regresses
- Whether hard endpoints such as mortality change
- Which preparation and which amount make sense
And now you know why I cannot deliver a headline on this topic. The honest answer is: there is a signal, it is not large, and it is not cleanly confirmed.
Where the evidence gets thin: hepatitis C and alcohol
An article that tells only the positive studies is advertising. So now I will tell you the two that did not work out.
First, because it matters: what follows is an appraisal of the study evidence and not a treatment recommendation. Viral hepatitis and alcohol related liver disease belong in medical care, and for both there are established therapies that a medicinal plant does not replace.
Fried and a team at four US centres studied people with chronic hepatitis C in whom interferon therapy had been unsuccessful and whose ALT value was at least 65 U/l. Over 24 weeks they received 420 mg silymarin, 700 mg silymarin or placebo three times daily. That is considerably more than the usual commercial amounts.
What was observed: exactly two people in each of the three groups reached the primary endpoint. The mean ALT decline did not differ meaningfully, p equals 0.75. Viral load and quality of life remained unchanged.
What this means for you: that is a methodologically clean trial with a clear negative result. Anyone recommending silymarin in hepatitis C has to argue around this work. I cannot do that.
Fried MW, Navarro VJ, Afdhal N et al. JAMA. 2012;308(3):274-282. DOI: 10.1001/jama.2012.8265Rambaldi, Jacobs and Gluud of the Cochrane Hepato-Biliary Group in Copenhagen examined in 2007 all randomised trials on milk thistle in alcohol related or viral liver disease.
What was observed: no significant effect on all cause mortality was seen, relative risk 0.78 with an interval of 0.53 to 1.15. Liver related mortality was reduced across all trials, relative risk 0.50 with 0.29 to 0.88. Looking only at the methodologically high quality trials, this effect disappeared, relative risk 0.57 with 0.28 to 1.19. Only 28.6 percent of the trials met high quality criteria.
What this means for you: that is the classic pattern when an effect comes mainly from weaker studies. The authors explicitly questioned the benefit and called for better conducted trials.
Rambaldi A, Jacobs BP, Gluud C. Cochrane Database Syst Rev. 2007;(4):CD003620. DOI: 10.1002/14651858.CD003620.pub3Documented by randomised trials and meta-analyses: silymarin may lower transaminases in fatty liver and is well tolerated. In hepatitis C, the best trial showed no effect.
Mechanistically plausible, human data still thin: the antioxidant and inflammation dampening effects via Nrf2 and NF-kappa-B. These data so far come predominantly from cell culture and animal models.
Clinically I observe that people who start a liver cure also drink less, eat less sugar and sleep more during those same weeks. That is my observation, not a study statement. But it probably explains a large part of the perceived effect.
And now you know why I wrote this chapter at all. Placing a medicinal plant honestly means also telling the studies in which nothing happened.
The most common strain on the liver is not a poisoning. It is a metabolic problem.
Here we come to the point that matters most to me on this topic.
When a liver suffers today, it is mostly not because a toxin got into it. It is because too much energy flows in and metabolism has lost control. And the most striking single element in that is a sugar that almost nobody considers dangerous.
Fructose. Fruit sugar. It sounds like fruit, but it sits above all in table sugar, in soft drinks, in fruit juice concentrates and in countless convenience products.
The difference from glucose is decisive. Glucose is used by all body cells. Fructose is metabolised to a large extent in the liver, and part of it apparently already in the small intestine. The breakdown pathway in the liver cell bypasses an enzyme that otherwise serves as a brake. It can therefore run largely without feedback. In large amounts, new fat can arise from this in the liver cell, a process called de novo lipogenesis.
How important this pathway is was shown by a very elegant study that blocked exactly this enzyme.
Kazierad and a team tested an inhibitor of ketohexokinase, the first enzyme in fructose breakdown, over six weeks. Adults with more than six percent liver fat on magnetic resonance imaging were included.
What was observed: under the higher dose of 300 mg, liver fat content fell by 18.73 percent compared with placebo, p equals 0.04. Under 75 mg no significant difference was seen. Inflammatory markers improved. Serious side effects did not occur.
What this means for you: if blocking a single fructose enzyme can lower liver fat content by almost a fifth, then fructose metabolism could be an important switch. For context: it was a six week trial with 53 participants, funded by the manufacturer, and the compound is an investigational substance without approval. It shows a mechanism, not a finished therapy. And it did not change the diet, it blocked an enzyme.
Kazierad DJ, Chidsey K, Somayaji VR et al. Med. 2021;2(7):800-813. DOI: 10.1016/j.medj.2021.04.007Gutierrez and a team pursued the same question in an animal model. Rats received either a fructose rich diet with 30 percent of calories from fructose or a diet corresponding to the average American diet with 7.5 percent.
What was observed: even the everyday amount of 7.5 percent led to raised insulin and triglyceride values and to liver steatosis. Under the enzyme inhibitor these changes regressed, together with reduced new fat formation in the liver.
What this means for you: it does not take extreme amounts. This is an animal model, and transfer to humans remains an assumption. But it fits what the human study found.
Gutierrez JA, Liu W, Perez S et al. Mol Metab. 2021;48:101196. DOI: 10.1016/j.molmet.2021.101196And now the number that puts everything into proportion. Because there is one measure whose effect no preparation has shown in a comparable way so far.
Vilar-Gomez and a team followed people in Havana with biopsy confirmed steatohepatitis for one year with lifestyle modification. For 261 people, tissue samples from before and after the year were available.
What was observed: overall, steatohepatitis regressed in 25 percent. What mattered was the extent of weight loss. In everyone who lost at least ten percent of their body weight, the activity score fell. In 90 percent of them the steatohepatitis regressed, in 45 percent even the fibrosis.
What this means for you: ten percent weight loss is a lot and not easy for everyone. Important for context: these 90 percent apply only to the small group that actually reached those ten percent. In the trial that was a minority. Across the whole group, steatohepatitis regressed in a quarter. Even so, these figures show where the biggest lever might sit. It is a cohort study without a control group, it is not proof of causality.
Vilar-Gomez E, Martinez-Perez Y, Calzadilla-Bertot L et al. Gastroenterology. 2015;149(2):367-378. DOI: 10.1053/j.gastro.2015.04.005Hadi and a team pooled in 2018 the randomised trials on silymarin in type 2 diabetes. Eight publications from seven studies were included.
What was observed: under silymarin, fasting blood glucose, HbA1c, insulin, LDL cholesterol and the oxidation marker malondialdehyde were lower, HDL cholesterol higher. On total cholesterol and triglycerides no meaningful effect was seen.
What this means for you: that is the most interesting point of contact. If silymarin can achieve something in fatty liver, then possibly less via detoxification and more via sugar metabolism. The authors themselves called the evidence still insufficient for firm conclusions.
Hadi A, Pourmasoumi M, Mohammadi H et al. Complement Ther Med. 2018;41:311-319. DOI: 10.1016/j.ctim.2018.08.010Your liver does not have a cleaning problem. In most cases it has a quantity problem.
Detox logic says: there is something in there, it has to come out.
Metabolic logic says: too much is coming in, and the control is out of rhythm. That changes the action completely. No longer adding, but putting less in. Not flushing, but unburdening.
And this is no longer about a lab result. A liver that does not constantly have to work against an oversupply gives you back something you notice in everyday life: energy that carries you through the whole day. That is not a lab value. That is quality of life.
And now you know why, with people who have raised liver values, I rarely talk about plants before we have talked about fructose, alcohol, sleep and movement.
Safety, interactions and what I would clarify first
That leaves the practical side. Because the fact that something is herbal says nothing about its safety. The death cap is also herbal, in the broadest sense.
With silymarin, the balance in the trials does look benign. In the Cochrane review the risk of adverse events was at a relative risk of 0.83 with an interval of 0.46 to 1.50, so not increased compared with placebo. In the trial from Kuala Lumpur, side effects likewise did not differ between the two groups, and none of the events was attributed to silymarin. That does not mean free of side effects. Reported were gastrointestinal complaints, loose stools, diarrhoea, taste disturbance and pruritus, and with Asteraceae allergy, allergic reactions up to anaphylaxis have been described.
For a long time the biggest concern was interactions. In cell experiments, silymarin markedly inhibited various drug metabolising enzymes. That would be relevant, because many people with liver disease take several medications.
Kawaguchi-Suzuki and a team gave nine healthy volunteers a standardised milk thistle extract three times daily for 14 days. Before and afterwards they measured the activity of the main drug metabolising enzymes with four probe substances at once, among them caffeine and midazolam.
What was observed: the activity of CYP1A2, CYP2C9, CYP2D6 and CYP3A4/5 remained unaffected. The inhibition feared on the basis of cell experiments was not confirmed in humans.
What this means for you: this is a small study in healthy people, not an all clear for every situation. But it is a good example of why cell culture results must not be transferred to everyday life unchecked.
Kawaguchi-Suzuki M, Frye RF, Zhu HJ et al. Drug Metab Dispos. 2014;42(10):1611-1616. DOI: 10.1124/dmd.114.057232However, only four of these enzymes were tested, in nine healthy volunteers. What was not tested are the transport proteins of the liver cell and glucuronidation. And those are exactly the interesting ones here. Earlier in this article stands the finding that silibinin can block OATP1B3. Statins among others enter the liver cell by that route. Whether this matters in everyday use is open. As long as that is open: if you take medication long term, especially cholesterol lowering drugs, medication for diabetes or immunosuppressants, discuss every supplement with your doctor.
Why I rarely start with the plant
When someone comes to me with raised liver values, milk thistle is not my first thought. Not because I think little of it, but because the order matters.
First I want to know why the values are raised. Then we look together at the things that act on the liver every day: alcohol, fructose, lack of sleep, medications, movement, waist circumference. Only once this level has been worked on does the question of a herbal supplement become meaningful at all.
That is my reasoned position, not the final word of science. Other colleagues set different priorities, and the conventional medical work up of raised liver values is and remains the foundation of everything that comes after.
Three levers that already count today
What you can take into your own hands
- Liquid fructose first. Soft drinks, fruit juices and smoothies deliver fructose without fibre and without satiety. Whole fruit is something different, it comes with fibre and in limited amounts. If you start at a single point, start here.
- Alcohol free days as a fixed feature. Not meant as abstinence, but as a recovery window. The liver needs time windows without a task in order to work on its own repairs.
- Movement that challenges the muscle. Muscles take up sugar even without much insulin. That lowers the pressure on the liver, quite independently of whether anything happens on the scales.
If you are interested in a preparation anyway
First of all: milk thistle preparations are usually food supplements. They are not a treatment for liver disease and do not replace a diagnostic work up.
- Make sure the silymarin content is stated. Pure milk thistle powder without standardisation says little.
- Clarify the cause of your liver values first. A preparation cannot replace a diagnostic work up.
- Discuss taking it with your doctor, especially if you take medication long term, and most of all with diabetes medication or cholesterol lowering drugs.
- The amounts named in this article, for example three times 700 mg or three times 420 mg, are figures from studies. They are explicitly not a dosing recommendation from me.
- Do not expect a noticeable change within a few days. The studies ran over weeks to months.
And now you know why the most honest answer to the question about milk thistle is neither an enthusiastic yes nor a dismissive no. It is: it depends, and the order decides.
Frequently asked questions about milk thistle and the liver
Can milk thistle detoxify the liver?
The liver detoxifies anyway, around the clock, through two enzyme stages.
In phase I, cytochrome P450 enzymes convert fat soluble substances, and in phase II these intermediates are conjugated and thereby made water soluble, so that they can leave the body via bile and kidney. A plant does not start this process, it runs permanently.
A critical review by Klein and Kiat found not a single randomised controlled trial in humans on commercial detox programmes. The more useful question is therefore whether your liver has enough building blocks and enough rest for its own work.
What is the difference between milk thistle, silymarin and silibinin?
Milk thistle is the plant, botanically Silybum marianum. Silymarin is the standardised extract from its fruits, a mixture of six flavonolignan isomers. Silibinin, also called silybin, is the pharmacologically most active component of that mixture.
When studies report strong effects, they almost always concern silibinin or standardised silymarin extracts, not milk thistle tea.
These three terms are constantly blurred in advertising. In research they are clearly separated, and that is precisely why study results cannot be transferred unchecked to every product on the shelf.
Can milk thistle help with fatty liver?
This is where the data are densest, but not conclusive.
A meta-analysis by Li and colleagues pooled 26 randomised trials with 2,375 participants and found lower ALT and AST values under silymarin as well as more frequent improvement of steatosis in the tissue sample, odds ratio 3.25 with an interval of 1.80 to 5.87.
A randomised trial from Kuala Lumpur in 99 people with confirmed steatohepatitis, by contrast, missed its primary endpoint, 32.7 percent versus 26.0 percent under placebo. What stood out there was only a secondary finding on connective tissue proliferation.
For the insulin resistance index HOMA-IR, the same meta-analysis showed no confirmed effect, and the authors themselves write that the results would have to be confirmed in further research.
So silymarin may influence liver values favourably. It is not a substitute for treating the cause. In Germany, milk thistle preparations are predominantly food supplements and not a treatment for liver disease.
How quickly can milk thistle work?
There is no serious number for this.
In the fatty liver trials, treatment periods typically ran over weeks up to twelve months, and even then the results were inconsistent. A preparation that makes a noticeable difference after three days would be biologically hard to explain with this mode of action.
A quick sense of lightness during a liver cure comes more from the accompanying circumstances: less alcohol, less sugar, more water, more sleep. That is not a criticism of this feeling. It is simply an honest attribution of who deserves the credit.
Does milk thistle make sense in hepatitis C?
According to the best available trial, rather not.
Fried and a team at four US centres studied 154 people with chronic hepatitis C in whom interferon therapy had been unsuccessful. Over 24 weeks they received 420 mg or 700 mg silymarin three times daily or placebo, considerably more than commercially usual amounts.
Exactly two people in each group reached the primary endpoint. Viral load and quality of life did not differ either. That is a cleanly conducted negative result, and I consider it important to say so openly rather than pass over it.
Does milk thistle protect the liver from alcohol?
It is certainly not a free pass.
A Cochrane review by Rambaldi and colleagues evaluated 18 randomised trials with 1,088 participants, predominantly with alcohol related or viral liver disease. No significant effect on all cause mortality was seen, relative risk 0.78 with an interval of 0.53 to 1.15.
Liver related mortality was reduced across all trials. In the methodologically high quality trials it no longer was. Only 28.6 percent of the included trials met high quality criteria.
The most reliable liver protection with alcohol remains less alcohol. That is uncomfortable, but it is the statement with the best data base. Alcohol related liver disease belongs in medical care, and this is an appraisal of the study evidence, not a treatment recommendation.
If your alcohol consumption worries you, in Germany: Sucht und Drogen Hotline 01806 313031, BZgA addiction prevention information line 0221 892031.
Does milk thistle have side effects?
In the trials, silymarin was mostly well tolerated, with the known limitations. That does not mean free of side effects.
In the Cochrane review, the risk of adverse events was not increased compared with placebo, relative risk 0.83 with an interval of 0.46 to 1.50. In the trial from Kuala Lumpur, the number of side effects likewise did not differ between silymarin and placebo, and none of the events was attributed to the preparation.
Most frequently reported are loose stools and mild gastrointestinal complaints, and in one of the trials also diarrhoea, taste disturbance and pruritus. Anyone allergic to Asteraceae such as mugwort, chamomile or ragweed should avoid it: allergic reactions up to anaphylaxis have been described.
In pregnancy and breastfeeding, and in children and adolescents, robust data are lacking, so restraint applies there. And if you take medication for diabetes, especially insulin, sulfonylureas or glinides, clarify any additional intake with your doctor beforehand. An additional lowering of blood glucose could in theory favour hypoglycaemia.
Are there interactions with medications?
According to the clinical data available so far, interactions via the classic liver enzymes are smaller than long feared.
Kawaguchi-Suzuki and a team gave nine healthy volunteers a standardised milk thistle extract three times daily for 14 days and measured the activity of the main drug metabolising enzymes with four probe substances. CYP1A2, CYP2C9, CYP2D6 and CYP3A4/5 remained unaffected.
Cell experiments had previously suggested marked inhibition. In humans this was not confirmed. That is a nice example of the fact that in vitro data do not automatically apply to everyday life.
However, only four of these enzymes were tested, in nine healthy volunteers. What was not tested are the transport proteins of the liver cell and glucuronidation. Silibinin can block OATP1B3, and statins among others enter the liver cell by that route. Whether this matters in everyday use is open.
As long as that is open: if you take medication long term, especially cholesterol lowering drugs or medication for diabetes, discuss every supplement with your doctor.
Why is silibinin given as an infusion in death cap poisoning?
Because a very concrete mechanism applies there and because a capsule is not sufficient for it.
Amatoxins do not enter the liver cell on their own, they need a transport protein. Letschert and a team at the German Cancer Research Center identified OATP1B3 as this transporter, with a Km value of 3.7 micromol. Silibinin dihemisuccinate was among the substances that blocked this transport.
In practical terms this means: the toxin is intercepted at the door and excreted via the kidney instead. That requires high blood levels over many hours, which only intravenous administration achieves. In the review by Mengs and colleagues, mortality under intravenous silibinin in close to 1,500 documented cases was below 10 percent. The first author of that review worked at the manufacturer of the infusion preparation, and that belongs in the picture.
This infusion solution is a prescription only medicine, is given exclusively in hospital under intensive care monitoring and can itself cause adverse effects, among them hypersensitivity reactions. For everyday use it is not an option.
What does the liver more good than a liver cure?
For the most common strain on the liver of all, fatty liver, it is weight and sugar load.
Vilar-Gomez and a team followed 293 people with biopsy confirmed steatohepatitis over 52 weeks with lifestyle modification. In everyone who lost at least ten percent of body weight, the activity score fell. In 90 percent of them the steatohepatitis regressed, in 45 percent even the fibrosis. Important for context: these 90 percent apply only to the small group that actually reached those ten percent. Across the whole group it was a quarter. No preparation has shown such figures in a comparable way so far.
The fructose research fits with this. In a six week phase 2 trial with 53 participants, liver fat content fell by 18.73 percent compared with placebo under an inhibitor of fructose breakdown. The compound is an investigational substance without approval, the trial was funded by the manufacturer, and it shows a mechanism, not a finished therapy. Less liquid fructose, less alcohol, more movement and enough sleep are unspectacular. But they address the cause.
Further reading in the Medicinal Plants Guide
Related posts from this cluster
- Turmeric against inflammation: what curcumin can do and where the hype overshoots
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- All posts in the Medicinal Plants Guide
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Related topics
Medicinal plants
What extracts can do and where advertising overshoots
This articleDetoxification
Phase I, phase II and what detox reflects of it
Nutrition
Fructose, sugar and the load on the liver
Weight loss
Weight, insulin resistance and liver fat
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