One of the most common questions I get in response to my article on reversing fatty liver disease is: Should you take milk thistle for your liver health? It's a popular supplement, and many recommend it for the treatment of fatty liver, insulin resistance, and diabetes.
In this article, I'll give you all the information you need to determine if milk thistle is right for you, breaking down the latest evidence supporting its use. I'll also go over the best way to take it, and at the end, cover important safety parameters and its toxicity profile.
Hi, I'm Dr. Leonid Kim, and I share the most up-to-date, evidence-based information on weight loss, metabolic health, and longevity. Let's get into it.
What Is Milk Thistle?
Milk thistle has been used medicinally in Europe for centuries, historically for the treatment of liver, gallbladder, spleen, and kidney diseases, and there are even records of its use for snake bites.
The active ingredient in milk thistle is silymarin, extracted from the dried seeds and fruits of Silybum marianum, a plant native to southern Europe and the Mediterranean region. Silymarin contains a mixture of flavonoids and polyphenols.
compounds known for their antioxidant properties, which is how some speculate it helps restore liver health. In addition to its antioxidant properties, silymarin is also antifibrotic, which helps with liver cell regeneration. It also modulates the immune system and helps prevent the inflammation that drives much of the damage seen in fatty liver disease.
What the Clinical Evidence Shows
This all sounds convincing in theory, but the clinical evidence, especially from human trials, is a bit muddier and less clear.
Alcohol-Related Liver Disease
Years ago, milk thistle was investigated in many clinical studies involving patients with alcohol-related liver disease, and the findings were mixed. A pooled analysis of five studies, published in 2001, showed a significant reduction in liver-related mortality in patients treated with silymarin compared to placebo, with a mortality rate of 4.9% per year in the treatment group versus 99.3% per year in the placebo group.
A follow-up Cochrane review that examined 18 randomized controlled trials involving patients with alcohol-related or viral liver disease found that, compared with placebo, milk thistle significantly reduced liver-related mortality when all trials were pooled, but not when the analysis was limited to high-quality trials.
This means larger-scale studies are needed to confirm whether the mortality benefit actually holds up. Some speculate that in the studies where milk thistle didn't show a mortality benefit, too many patients had severe, end-stage, irreversible liver disease, making it difficult to demonstrate any benefit on mortality in that population.
If you look at studies focused on liver function itself, milk thistle has more consistently demonstrated a reduction in liver enzyme levels, like ALT, compared with a placebo. An older, double-blind, randomized study of 97 patients with mild alcoholic liver disease showed that treatment with silymarin for four weeks resulted in significantly greater improvement in liver function compared with placebo.
Another 12-month randomized controlled study looked at 60 people with alcoholic cirrhosis and diabetes and found that treatment with silymarin at 600 mg per day significantly reduced hemoglobin A1c levels, as well as exogenous insulin requirements, in the treatment group.
Non-Alcoholic Fatty Liver Disease
When it comes to non-alcoholic fatty liver disease, small studies show that treatment with silymarin reduces transaminase (liver function) levels and significantly improves biometric parameters, such as abdominal circumference and BMI. The treatment group also showed improvement in liver health as measured by ultrasound.
There's also a study looking specifically at a population with NASH (non-alcoholic steatohepatitis), a more advanced stage of fatty liver disease. This 48-week, double-masked, randomized, placebo-controlled trial showed that treatment with silymarin at 2,100 mg per day resulted in a statistically significant reduction in fibrosis. However, the study did not reach statistical significance for its primary endpoint, a 30% improvement from baseline in the NAFLD activity score, a tool used to grade the severity of fatty liver disease.
Overall Picture
Looking at all of the studies together, there seems to be a small benefit to using milk thistle in mild liver disease or the early stages of fatty liver disease. However, there doesn't seem to be strong evidence to suggest any benefit in more advanced stages of liver disease, like NASH or cirrhosis.
Safety Profile
When it comes to safety, milk thistle seems to be well tolerated, with only minor adverse events reported, mostly headaches, diarrhea, and nausea. In clinical trials, milk thistle was well tolerated at doses of up to 420 mg per day for up to 4 years, and in one study, at doses of up to 2,100 mg per day for up to 48 weeks. As always, please talk to your doctor before taking this or any other supplement to make sure it's safe for your individual situation.
My Take
So where do I stand on recommending milk thistle to my patients? Based on the totality of the available evidence, I don't believe we have sufficient data to recommend it broadly to patients with fatty liver or other liver diseases. That said, the small studies we do have show a trend toward improved liver function, especially when treatment is started in the early stages of liver disease. Milk thistle also seems relatively safe for most people, so even though I don't routinely recommend it, I wouldn't tell most patients to stop taking it unless I'm concerned about an interaction with other medications.
Conclusion
Milk thistle has a long history of traditional use for liver health, and modern research offers some genuine, if modest, support, particularly for improving liver enzyme levels and function in early-stage or alcohol-related liver disease. The evidence is much weaker for more advanced conditions like NASH or cirrhosis, and larger, high-quality trials are still needed to confirm a true mortality benefit. On the safety side, milk thistle appears well-tolerated even at higher doses over extended periods. Overall, it's a reasonable, low-risk option to discuss with your doctor, especially for those in the earlier stages of liver disease. However, it shouldn't be viewed as a proven treatment for more advanced liver conditions.
FAQ
What is the active ingredient in milk thistle?
The active ingredient is silymarin, a mixture of flavonoids and polyphenols extracted from the seeds and fruit of the Silybum marianum plant. It has antioxidant, antifibrotic, and immune-modulating properties.
Does milk thistle actually help liver disease?
The evidence is mixed but somewhat encouraging for early-stage or mild liver disease, particularly alcohol-related liver disease, where it has shown improvements in liver enzyme levels and function. Evidence for more advanced conditions like NASH or cirrhosis is weaker.
Can milk thistle help with fatty liver disease specifically?
Small studies suggest that silymarin can reduce liver enzyme levels and improve certain biometric markers, such as abdominal circumference and BMI, in non-alcoholic fatty liver disease. However, studies in more advanced fatty liver disease (NASH) have not consistently met their primary treatment goals.
Is milk thistle safe to take?
Yes, generally. Clinical trials have shown milk thistle to be well tolerated at doses up to 420 mg per day for up to 4 years, and up to 2,100 mg per day for up to 48 weeks in some studies. Minor side effects can include headaches, diarrhea, and nausea.
Should I take milk thistle for my liver health?
There isn't yet enough strong evidence to broadly recommend milk thistle for fatty liver or other liver diseases. However, given its relatively good safety profile and some evidence of benefit in early-stage disease, it may be reasonable to discuss with your doctor, particularly if you're in the earlier stages of liver disease.
Does milk thistle interact with other medications?
This review doesn't detail specific drug interactions. Still, as with any supplement, it's important to talk to your doctor before starting milk thistle, especially if you're on other medications, to rule out potential interactions.