Milk thistle's therapeutic uses

• PRINCIPAL PROPOSED USES: Alcoholic hepatitis, liver cirrhosis, mushroom poisoning (special intravenous form only), protection from liver-toxic medications, rosacea, viral hepatitis

• OTHER PROPOSED USES: Diabetes, obsessive-compulsive disorder

DEFINITION: Natural plant product used to treat specific health conditions

Overview

The milk thistle plant commonly grows from two to seven feet in height, with spiny leaves and reddish-purple, thistle-shaped flowers. It has also been called wild artichoke, holy thistle, and Mary thistle. Native to Europe, milk thistle has a long history of use as both a food and a medicine. At the turn of the twentieth century, English gardeners grew milk thistle to use its leaves like lettuce after cutting off the spines, the stalks like asparagus, the roasted seeds like coffee, and the roots soaked overnight like oyster plant. The seeds and leaves of milk thistle were used for medicinal purposes as well, such as treating jaundice and increasing breast milk production.

German researchers in the 1960s were sufficiently impressed with the history and clinical effectiveness of milk thistle to begin examining it for active constituents. In 1986, Germany’s Commission E approved an oral extract of milk thistle as a treatment for liver disease. Later studies have found that the survival rate of patients with liver disease was higher if they supplemented their treatment with milk thistle.

Therapeutic Dosages

Milk thistle products are made from seeds of the milk thistle plant, usually containing 70 to 80 percent silymarin. These supplements are available in capsules containing 120 to 140 milligrams (mg) of silymarin, as well as a liquid extract.

The standard dosage of milk thistle is 200 mg one to three times a day of an extract standardized to contain 70 percent silymarin. There is some evidence that silymarin bound to phosphatidylcholine may be better absorbed. This form should be taken at a dosage of 100 to 200 mg twice a day. Considering the severe nature of liver disease, a doctor’s supervision is essential. Also, milk thistle preparations designed for oral use should not be injected. Milk thistle extract has been taken safely for up to one year, but research does not support longer use.

Therapeutic Uses

Based on the extensive folk use of milk thistle in cases of jaundice, European medical researchers began to investigate its medicinal effects. It is used to treat alcoholic hepatitis, liver cirrhosis, liver poisoning, and viral hepatitis, as well as to protect the liver in general from the effects of liver-toxic medications. However, despite this wide usage, there is no definitive evidence that it is effective.

Standardized milk thistle extract contains the active ingredient known as silymarin. Silymarin is a mixture of the flavonoids silibinin, silidianin, and silicristin. Silibinin is also a mixture of the related substances silibinin A and silibinin B. Silibinin functions by displacing toxins that might bind to the liver, as well as by causing the liver to regenerate more quickly. It may also act as an antioxidant and also stabilize liver cell membranes. When injected intravenously, silibinin is thought to act as an antidote to poisoning by the death cap mushroom (Amanita phalloides). Animal studies suggest that milk thistle extracts can also protect against many other poisonous substances, from toluene to the drug acetaminophen. One animal study suggests that milk thistle can also protect against fetal damage caused by alcohol.

In Europe, milk thistle is often added as extra protection when patients are given medications known to cause liver problems. However, milk thistle failed to prove effective in preventing liver inflammation caused by the Alzheimer’s drug Cognex (tacrine hydrochloride).

Milk thistle is also used in a vague condition known as minor hepatic insufficiency or sluggish liver. This term is mostly used by European physicians and American naturopathic practitioners, though conventional physicians in the United States do not recognize it. Symptoms are supposed to include aching under the ribs, fatigue, unhealthy skin appearance, general malaise, constipation, premenstrual syndrome, chemical sensitivities, and allergies.

One small but apparently well-conducted, double-blind trial found evidence that milk thistle might improve blood sugar control in type 2 diabetes. Milk thistle may also offer some protection to the kidney. Highly preliminary evidence hints that milk thistle might help reduce breast cancer risk. Milk thistle is sometimes recommended for gallstones and psoriasis, but there is little evidence that it helps these conditions.

In one small, placebo-controlled trial, the topical application of milk thistle with methylsulfonylmethane (MSM) for one month appeared to be effective in the treatment of forty-six subjects with the skin condition rosacea.

A small preliminary study investigated whether milk thistle can help relieve obsessive-compulsive disorder (OCD). Thirty-five adults with OCD were randomized to receive milk thistle at 600 mg per day, or the commonly used OCD medication fluoxetine (Prozac) at 30 mg per day. At the end of the eight-week trial, no significant differences emerged between the two groups. However, further study is needed because milk thistle has been shown to increase serotonin and modulate neurotransmitters.

Scientific Evidence

As noted above, there is considerable evidence from studies in animals that milk thistle can protect the liver from numerous toxins. However, human studies of people suffering from various liver diseases have often yielded mixed results. A 2007 review of published and unpublished studies on milk thistle as a treatment for liver disease caused by alcohol or viral hepatitis concluded that benefits were seen only in low-quality trials, and even in those, milk thistle did not show more than a slight benefit. However, a study published in 2020 in Advances in Therapy on patients with liver disease showed that over a period of at least twenty-four months, a placebo group had a significantly higher death rate than those who supplemented their treatment with milk thistle.

Acute viral hepatitis. A twenty-one-day, double-blind, placebo-controlled study of fifty-seven people with acute viral hepatitis found significant improvements in the group receiving milk thistle. In another study, 105 people with acute hepatitis receiving milk thistle at a dose of 140 mg three times daily showed modest improvement in some symptoms compared with those taking a placebo for four weeks. On the other hand, a thirty-five-day study of 151 individuals thought to have acute hepatitis found no benefit with milk thistle, but this study has been criticized for failing to document that the participants actually had acute hepatitis.

Chronic viral hepatitis. Inconsistent evidence exists regarding whether milk thistle is helpful for chronic viral hepatitis B or C. The herb does not appear to affect levels of virus in the body, but it might help protect the liver from damage and improve some symptoms.

Alcoholic hepatitis. A double-blind, placebo-controlled study performed in 1981 followed 106 Finnish soldiers with alcoholic liver disease for four weeks. The treated group showed a significant decrease in elevated liver enzymes and improvement in liver histology, as evaluated by biopsy in twenty-nine subjects.

Two similar studies provided essentially equivalent results. However, a three-month, randomized, double-blind study of 116 people showed little to no additional benefit, perhaps because most participants reduced their alcohol consumption and almost half stopped drinking entirely. Another study found no benefit in seventy-two patients followed for fifteen months. It is more effective for people with an addiction to alcohol to quit drinking than to continue drinking and take milk thistle.

Liver cirrhosis. A double-blind, placebo-controlled study of 170 people with alcoholic or nonalcoholic cirrhosis found that in the group treated with milk thistle, the four-year survival rate was 58 percent compared with only 38 percent in the placebo group. This difference was statistically significant.

A double-blind, placebo-controlled trial that enrolled 172 people with cirrhosis for four years also found reductions in mortality, but it just missed the conventional cutoff for statistical significance. A two-year, double-blind, placebo-controlled study of 200 individuals with alcoholic cirrhosis found no reduction in mortality attributable to the use of milk thistle. However, in an analysis of nineteen randomized trials, researchers concluded that milk thistle was significantly more effective at reducing mortality from liver cirrhosismostly alcohol-relatedcompared with a placebo but was no more effective at reducing mortality from any cause.

Other double-blind studies of people with various forms of cirrhosis have looked at changes in tests of liver function rather than mortality. Some found benefit, while others did not.

Protection from medications that damage the liver. Numerous medications can injure or inflame the liver. Preliminary evidence suggests that milk thistle might protect against liver toxicity caused by drugs such as acetaminophen, alcohol, phenothiazines, and phenytoin (Dilantin). However, according to a twelve-week, double-blind study of 222 people, milk thistle does not seem to prevent the liver inflammation caused by the Alzheimer’s drug tacrine (Cognex).

Studies in the early 2020s found that milk thistle’s use as an aid in cancer treatment may warrant further study. Several laboratory and animal studies found that silymarin exhibits anti-cancer, anti-tumor, and protective properties over cells being treated with certain chemotherapies. If these properties can be better understood and harnessed, milk thistle may provide a meaningful and low-risk way to limit chemotherapy-induced cytotoxicity and improve its efficacy.

Safety Issues

Milk thistle is believed to possess very little toxicity. Animal studies have not shown any negative effects, even when high doses were administered over a long period. A study of 2,637 participants reported in 1992 showed a low incidence of side effects, limited mainly to mild gastrointestinal disturbance. However, on rare occasions, severe abdominal discomfort may occur.

On the basis of its extensive use as a food, milk thistle is believed to be safe for pregnant or nursing women, and researchers have enrolled pregnant women in studies. However, safety in young children, pregnant or nursing women, and individuals with severe renal disease has not been formally established.

Important Interactions

Milk thistle might have a protective function in persons taking medications that could damage the liver, such as acetaminophen, phenytoin (Dilantin), alcohol, and phenothiazines. One report noted that silibinin inhibits the bacterial enzyme called beta-glucuronidase. This may cause some medications, like oral contraceptives, to be less effective, but interactions vary by medication type and individual conditions.

Bibliography

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Wang, Yin, et al. “Silymarin in Cancer Therapy: Mechanisms of Action, Protective Roles in Chemotherapy-Induced Toxicity, and Nanoformulations.” Journal of Functional Foods, vol. 100. doi:10.1016/j.jff.2022.105384.

West, Helen. "7 Science-Based Benefits of Milk Thistle." Healthline, 16 Aug. 2024, www.healthline.com/nutrition/milk-thistle-benefits. Accessed 20 Sept. 2024.