Health Benefits of Milk Thistle

You may have heard that milk thistle is good for your liver, or that is has cancer-fighting properties. And what about the rumor that it’s good for your skin? In this article we’ll dive deep into milk thistle, getting you the bottom line on each of its benefits.

Table of Contents

What is milk thistle?

Milk thistle is a thistle, a plant distinguished by having prickles on the leaves in order to deter herbivores from eating it. Unlike some thistles, milk thistle has prickles all over the stem and leaves, as well as on its bright purple flowers. Milk thistle can be found in many places in the world. Its seeds are used to create extracts that are associated with a range of health benefits.

Pedanius Dioscorides wrote about milk thistle over 2,000 years ago.
A 1500s translation of De Materia Medica by Discorides, containing the first written reference to milk thistle.

Where does milk thistle come from?

Milk thistle, or silybum marianum, has been used for thousands of years for its therapeutic properties. The earliest known reference to it dates back to roughly 2,000 years ago in the De Materia Medica, a text written by a Greek pharmacologist living in the first century AD, Pedanius Dioscorides. Dioscorides recommended eating the newly sprung up vegetable after boiling, with oil and salt. He also wrote that the juice of the root (along with a teaspoon of honey and water) can encourage vomiting. Other historic works also reference milk thistle, including those by Pliny the Elder (who called it sillybum) and Theophrastus, who called it pternix.

Dioscorides is attributed with giving it the name we still use for it today, silybum. The second part of its name, marianum, is allegedly attributed to Christian folklore. According to this legend, the white veins running through the leaves of the plant were caused by a drop of the Virgin Mary’s milk. As she sought a place to nurse her infant Jesus Christ, she found shelter under the thorny leaves of milk thistle. Thus, its historic use, which is now supported by academic research, is as a galactagogue, a plant that helps promote milk production in lactating mothers.

What are the active ingredients of milk thistle?

Its health-boosting characteristics are attributed to a range of compounds it contains. Most of the activity is attributed to its three classes of flavanolignans: silybin (sometimes called silibinin), silydianin, and silychristin. Flavanolignans are natural phenolics which are part flavanoid and part lignan, both of which are beneficial for health [Roleira 2018]. Silymarin refers to the constituent flavanolignans and to the plant derived flavonoid extracted from the plant. Since silymarin effectively refers to the plant derivative itself, we may use silymarin and milk thistle interchangeably in this article [Katiyar 2005].

Among the flavanolignans, silybin is considered to be the most important, and makes up 50-80% of silymarin. Although silymarin is found throughout the plant, its most concentrated in the fruit ands seeds, which is why the seeds are used to make the extract [Abenavoli 2010].

Milk thistle has many health benefits for the skin, as well as for the liver and as a way to boost breastmilk production.
Photo by Sandie Clarke on Unsplash

What are the benefits of milk thistle?

Milk thistle is one of the most well researched plants for the treatment of liver disease, but its benefits extend beyond this. Evidence indicates that milk thistle can help promote the production of breastmilk in lactating mothers, can be beneficial for skin health and in preventing or treating skin cancers.

Milk thistle for breastmilk production

Milk thistle may help increase breastmilk production in lactating mothers. Based on the evidence, the recommended dosage is 420mg/day of micronized milk thistle for 30 days.

One of the most compelling sources of evidence for milk thistle’s ability to enhance milk production comes from a double-blind study on 50 lactating women, half of whom were given 420 mg/day of micronized silymarin. Those given the the daily supplement had significantly higher milk production after 30 days than those given placebo. This advantage continued to persist after 60 days of treatment [Di Pierro 2008].

Why does milk thistle boost milk production? A study on rats indicates it increases levels of serum prolactin [Capasso 2014]. Prolactin is a hormone that helps stimulate milk production. In fact, boosting prolactin is the same mechanism by which other natural health remedies, like Shatavari, help promote breast milk production.

Milk thistle for liver health

Milk thistle is one of the most studied plants for the treatment of liver disease. The evidence indicates that it promotes liver health and helps reduce liver damage through its antioxidant activity, as well as by promoting cell regeneration and blocking toxins. Studies are not yet conclusive as to dosage and treatment, although most tend to 420-800mg/daily of a well-standardized product.

The liver is a critical organ. It filters waste from the body, makes bile to help us digest food, stores sugars that we later use for energy and even makes protein. However, when put the liver into over-drive, it begins to struggle. In the case of excessive alcohol consumption, fats builds up in the liver cells, eventually leading to alcoholic fatty liver disease. Liver diseases are not limited to alcohol-induced ones, but because a significant portion of studies focus on alcohol-induced diseases we focus on that context here.

Several studies demonstrate the effectiveness of milk thistle in treating alcohol-induced liver disease. However, some results are conflicting and the evidence isn’t yet fully conclusive. Treatments are difficult to evaluate because the severity of the disease ranges between people and because of other variable factors, like asking patients to abstain from alcohol. For example, a study may ask participants to abstain from drinking, but cannot enforce this. Continued alcohol consumption worsens liver disease, and thus isn’t controlled for [Abenavoli 2010].

One study found that patients treated with 140mg of silymarin three times a day for about 41 months survived their cirrhosis longer than those in the placebo group. Cirrhosis is the final stage of liver disease, after the liver has suffered chronic damage, and eventually leads to liver failure. The results for this study were particularly compelling because the effects were even more pronounced for those with alcoholic cirrhosis [Ferenci 1989].

In a review of both double blind and non-blind studies evaluating the effectiveness of silymarin for liver disease and cirrhosis, silymarin was concluded to be an effective treatment in improving disease conditions. The total mortality rate was lower for those treated with silymarin, although the differences were not statistically significant in some studies. Overall, the consensus is that silymarin does appear to improve conditions and survival rates, although further research is necessary to identify the effective dose and outcomes. Most trials used 420-800mg/daily of a well-standardized product of silymarin. The extract and its purity are important factors because the bioavailability varies greatly between products [Saller 2012].

How does milk thistle help treat liver disease?

Milk thistle features several biological activities that support liver health, including its antioxidant and anti-inflammatory properties, as well as its ability to stimulate protein biosynthesis and block toxins.

Milk thistle has several modes of action that allow it to promote liver health, and to help treat liver disease [Abenavoli 2010]. One method is that it helps to regenerate liver cells, which is vital for recovery from acute or chronic liver disease. Studies conducted on the livers of rats show that silybin increases the synthesis of ribosomal RNA. Ribosomes, in turn, increase protein synthesis, which helps restore liver functions.

Milk thistle’s antioxidant activity also plays a role in improving liver health because free radicals are a component of liver disease. In vitro evidence using the cells of patients with alcoholic cirrhosis supports this idea. In vivo evidence on rats demonstrates that silymarin reduces free radical load. As a reminder, in vitro refers to studies done “in glass”, or in a lab setting using test tubes or the like, whereas in vivo refers to real-life experiments, where whole organisms are used to evaluate the idea. Both kinds of evidence are useful in concluding the effectiveness and the mode of operation of different treatments.

Another mode of operation is milk thistle’s ability to block toxins. It can prevent the absorption of toxins into liver cells by occupying the binding sites. This extends beyond alcohol and encapsulates poison from mushrooms [Abenavoli 2010]. In fact, silybin seems to be more effective than other treatments in treating fatal mushroom poisoning from death caps [Mengs 2012].

Milk thistle may applied topically for a range of skin conditions.
Photo by Nati Melnychuk on Unsplash

Milk thistle for skin health

Milk thistle is beneficial for skin health. Its potent antioxidant properties enable it to prevent and treat a range of skin conditions. Studies demonstrate its effectiveness in treating melasma and skin cancers, and in preventing radiation-induced conditions of the skin. Although further evidence is necessary to evaluate the efficacy in dosage in humans, the evidence (combined with the lack of side effects) indicates milk thistle may be a beneficial to promoting skin health.

Several studies demonstrate the skin protective activity of milk thistle, particularly with regards to skin cancer. The antioxidant nature of silymarin enables it to fight against free radical-generating agents like UV radiation and environmental pollutants, which contribute to oxidative stress and thus a variety of conditions including skin cancer [Katiyar 2005]. Its antioxidant activity is even several times greater than that of vitamin E [Altaei 2012].

Milk thistle for melasma

A compelling randomized trial demonstrated that milk thistle effectively treated melasma, or discoloration of the face, over 4 weeks of twice daily topical application.

Milk thistle has been demonstrated to effectively treat melasma in humans. Melasma is a skin condition characterized by grey-brown patches of discoloration on the face, generally a result of sun exposure. Among the 96 adult participants in this double-blind randomized trial, those who uses a topical silymarin cream (either 7mg/ml or 14mg/ml concentration) experienced significant improvements in the condition and a return to typical skin pigmentation. Those using the cream were instructed to apply it to the affected areas twice daily for 4 weeks, to avoid sun exposure, and to use sunscreen of at least SPF 15. There were two experimental groups, one use a cream with 7mg silymarin/ml concentration and the other at 14mg silymarin/ml. Both showed dramatic improvements compared to the placebo group [Altaei 2012].

Milk thistle is particularly effective against melasma because it inhibits the expression of tyrosinase proteins. Tyrosinase enzymes are directly linked to the biosynthesis of melanin, and melanin is what pigments the skin, thus too much causes melasma [Bae-Harboe 2012].

Milk thistle for hand-foot syndrome

Milk thistle effectively slowed the progression and incidence of hand-foot syndrome (a skin condition on the palms and feet) for patients undergoing chemotherapy.

Hand-foot syndrome (HFS) is a common side effect of chemotherapy. It ranges in severity but includes welling and painful or burning sensations of the palms and soles, eventually leading to blistering or shedding of the skin.

One randomized, double-blind trial, recruited patients with gastric or colorectal cancer who would be administered chemotherapy. Those in the treatment group had a silymarin cream applied twice daily to the palms and soles throughout the 9-week treatment. The cream was a 1% silymarin gel from an Iranian pharmaceutical company (Goldaru Pharmaceutical Company, Isfahan, Iran), with 80% active ingredients of silymarin flavonolignans. Throughout the trial, silymarin effectively slowed the progression of HFS. By the end of the trial, those who used the cream had a lower rate and lower severity of HFS than those in the placebo group [Elyasi 2017].

Milk thistle for dermatitis from radiotherapy

Milk thistle effectively reduced the rate at which dermatitis occurred on the breasts as a result of radiotherapy.

If breast cancer is caught early, the mode of treatment used is referred to as breast-conserving therapy, which includes surgery followed by a postoperative radiation treatment to kill any remaining traces of cancer. The majority of patients undergoing this radiotherapy develop dermatitis, which may feature itching, pain, or burning sensations.

Patients with silymarin cream applied daily (and at least 2 hours before radiation) had a dramatic reduction in the rate of dermatitis versus those without any intervention. The cream significantly prolonged the time before which patients developed signs of toxicity as a result of the radiotherapy. It even prevented a significant portion of patients from ever getting skin reactions. Without any cream, only 2% of patients experienced no skin issues, but with the cream, 23.5% of patients went through the entire radiation process without any signs of dermatitis.

The cream used in this study was Leviaderm, which is considered to be a silymarin-based cream, because it contains 0.25% silymarin, in addition to about a dozen other therapeutic ingredients [Becker-Schiebe 2011].

Milk thistle may help protect against UV radiation, in addition to sunscreen.
Photo by Rajiv Bajaj on Unsplash

Milk thistle for skin cancer

Animal studies conclude that milk thistle may be a promising treatment, to use in conjunction with other treatments, for UV-induced skin cancer. Studies on rodents show that topically applied silymarin (and even ingested silymarin) reduce cancer presence.

A 30-week study demonstrated that topical application of silymarin inhibited tumor promotion and tumor incidence for hairless mice who had cancer induced by UVB radiation. Here, 9 mg silymarin was applied topically per day [Katiyar 1997].

The use of milk thistle for skin health is not limited to topical application. One study on mice found that adding silybin to the diet improved outcomes for cancers induced by UV radiation. There were less tumors which multiplied less for those mice who had 1% of their diet as silybin, compared to those who did not [Mallikarjuna 2004].

Although silybin is one of the most heavily examined components of milk thistle, other components also appear to have photo-protective properties. One in vitro study found that one component, 2,3-dehydrosilybin (DHSB), had the highest UVA protection factor and the highest ability in scavenging a particular kind of free radical, compared to the flavonolignans [Vostálová 2019].

Thus, milk thistle shows to be a promising treatment and preventative measure for a range of skin conditions including sunburn, DNA damage, non-melanoma skin cancer and immune suppression. Its especially important to note that sunscreen alone is not fully effective in preventing these conditions. Thus, a combination of silybum and UV protection may be advantageous. Of course, we still need more research to determine its correct usage and effectiveness, but researchers argue that “supplementation of skin care products or sunscreens with silymarin is likely to lead to further improvement in the photo-protective efficacy in human system” [Katiyar 2005].

Milk thistle is safe to take, even in therapeutic doses. It is safe to use topically as a cream or by ingesting capsules.
Photo by Matt Seymour on Unsplash

Is milk thistle safe to take?

Milk thistle is safe to take, even in therapeutic doses. Clinical trials on humans prescribe upwards of 800mg/daily for treatment.

There is no known acute toxicity for sylimarin or silybin. From a review of over 40 human studies, ranging in dosage and duration, the majority reported no adverse effects. Some did report side effects, although these are rare, and difficult to distinguish if they are due to the treatment. Silymarin is safe even at high, therapeutic doses of over 2,000mg/day for 6 months [Soleimani 2019].

There are no known complications or concerns about taking milk thistle during pregnancy, although we lack studies definitely proving its safety. The closest study is one that administered two doses of 70mg after the pregnancy terminated, with no adverse effects reported [Baghbahadorani 2017].

Typical doses observed (often in patients with hepatitis) are 140mg two or three times daily or 5-20mg/kg/daily.

Does milk thistle have any side effects?

In some studies, milk thistle is associated with some adverse effects, the most common of which is gastrointestinal discomfort. The majority of studies evaluating milk thistle do not report side effects.

Some studies administering silymarin report adverse effects, including: gastrointestinal discomfort, nausea, diarrhea, heating sensation (particularly from intravenous administration), headaches, and vomiting. Given the length of the clinical trials, it is often difficult to determine if the side effects are a direct result of the treatment or some other circumstance. Some of the studies reporting side effects take place over 6 or 12 month periods, thus many other variables are not accounted for. Researchers conclude that silymarin is safe to take in therapeutic doses.

Studies using topical applications report no adverse effects [Soleimani 2019] [Elyasi 2017] [Altaei 2012].

The bottom line

Milk thistle is a potent, therapeutic herb, and its derivatives may be used topically or orally for different health reasons. Many of its benefits may be attributed to its potent antioxidant activity. These benefits and the lack of corresponding side effects makes milk thistle an appealing treatment for a range of conditions.

Applied topically, milk thistle is beneficial for skin health. Its been demonstrated to protect the skin from damage resulting from radiation (whether from radiotherapy or from the sun). Although we as of yet lack studies verifying the necessary dosage for general usage, studies indicate that a 1% concentrated cream may be effective in treating and preventing different skin conditions.

Milk thistle also appears to be a promising area of research for the treatment of liver disease, although thus far studies are not entirely conclusive to what dosage and application provides the best results.

Lastly, breastfeeding mothers may turn to milk thistle to help boost their milk production.

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