MILK THISTLE: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews (2024)

Milk thistle (Silybum marianum) is a plant native to Europe that was brought to North America by early colonists. It seems to help lower blood sugar.

Milk thistle is now found throughout the eastern United States, California, South America, Africa, Australia, and Asia. Its seed might protect liver cells from toxic chemicals and drugs. It may also have antioxidant and anti-inflammatory effects.

People commonly take milk thistle by mouth for diabetes. It is also commonly used for liver disorders, including liver damage caused by alcohol, nonalcoholic fatty liver disease, cirrhosis of the liver, chronic hepatitis, and many other conditions, but there is no good scientific evidence to support many of these other uses.

Don't confuse milk thistle with blessed thistle (Cnicus benedictus).

How does it work ?

• Diabetes. Taking milk thistle extracts 210-600 mg daily seems to reduce blood sugar in people with diabetes. Taking milk thistle extract with tree turmeric extract also seems to reduce blood glucose levels in people with diabetes.

• Acne. Taking milk thistle might lessen acne severity. But the benefits, if any, are small.
• Liver disease in people who drink alcohol. There is conflicting evidence about the effectiveness of milk thistle for treating alcohol-related liver disease. Early research shows that taking milk thistle by mouth might improve liver function and reduce risk of death. However, other research shows no benefit.
• Mushroom poisoning. Early research shows that giving silibinin, a chemical found in milk thistle may lessen liver damage caused by Amanita phalloides mushroom (death cap mushroom) poisoning. However, it is hard to obtain silibinin in the US.
• A blood disorder that reduces levels of protein in the blood called hemoglobin (beta-thalassemia). Early research in children with this blood disorder shows that taking a specific milk thistle extract for 6-9 months, along with conventional medicine, might decrease iron levels better than conventional medicine alone.
• An adverse skin reaction caused by cancer drug treatment (chemotherapy-induced acral erythema). Early research shows that applying a gel containing milk thistle extract to the hands and feet beginning on the first day of chemotherapy and continuing for 9 weeks decreases the severity of this skin reaction caused by a cancer drug called capecitabine.
• Liver damage caused by cancer drugs. Early research shows that taking a specific milk thistle product containing the chemical silibinin beginning at the start of chemotherapy treatment does not significantly reduce liver toxicity caused by chemotherapy.
• Kidney damage caused by cancer drugs. Early research shows that taking milk thistle extract beginning 24-48 hours before starting therapy with cisplatin, and continuing until the end of the treatment course, does not prevent or decrease the rates of kidney injury.
• Liver scarring (cirrhosis). Early research shows that milk thistle extract might reduce the risk of death and improve liver function in people with cirrhosis. However, milk thistle extract does not seem to benefit all patients with liver disease.
• Kidney disease in people with diabetes (diabetic nephropathy). Early research shows that taking milk thistle extract together with conventional treatment might help treat kidney disease in people with diabetes.
• Hay fever. Some research shows that taking milk thistle extract by mouth along with the allergy medication cetirizine (Zyrtec) reduces seasonal allergies more than taking cetirizine alone.
• Swelling (inflammation) of the liver (hepatitis). Research on the effects of milk thistle in people with hepatitis is not consistent. Some research shows that taking milk thistle extract by mouth for 4 weeks reduces hepatitis symptoms, such as dark urine and jaundice, but does not improve liver function tests. But taking a product containing the milk thistle constituent silybin plus phosphatidylcholine by mouth for 2 weeks to 3 months might improve some liver function tests.
• Swelling (inflammation) of the liver caused by the hepatitis B virus (hepatitis B). Research on the effects of milk thistle in people with hepatitis B is not consistent. Early research shows that taking milk thistle extract by mouth for up to one year, or taking a product containing the milk thistle constituent silybin plus phosphatidylcholine by mouth for 1 week, improves liver function tests. But other research shows no benefit.
• Swelling (inflammation) of the liver caused by the hepatitis C virus (hepatitis C). Research on the effects of milk thistle in people with hepatitis C is inconsistent. Early research shows that taking milk thistle extract by mouth for up to one year, or taking a product containing the milk thistle constituent silybin plus phosphatidylcholine by mouth for 1 week, improves liver function tests. But other research shows no benefit.
• High levels of lipoproteins in the blood (hyperlipoproteinemia). Taking milk thistle doesn't seem to lower lipid levels in the blood in people with high levels due to liver disease.
• Liver damage caused by low oxygen levels. Early research shows that taking milk thistle extract might reduce liver damage caused by low levels of oxygen in the blood.
• Inability to become pregnant within a year of trying to conceive (infertility). Early research shows that taking milk thistle extract along with fertility hormones might provide some benefits for people undergoing in vitro fertilization due to male infertility.
• Breast feeding. Early research shows that taking milk thistle extract for 4 weeks does not increase milk production in mothers of premature infants.
• Symptoms of menopause. Early research suggests that milk thistle reduces menopausal symptoms such as hot flashes.
• Build-up of fat in the liver in people who drink little or no alcohol (nonalcoholic fatty liver disease or NAFLD). There is evidence that milk thistle extract improves markers of liver injury in people with NAFLD. But these markers aren't always linked with the NAFLD severity. Most experts recommend that people with NAFLD lose weight to reduce fat build-up in the liver and lower their cholesterol to reduce the risk of heart disease. Taking milk thistle does not seem to improve either of these outcomes.
• Swelling (inflammation) and build up of fat in the liver in people who drink little or no alcohol (nonalcoholic steatohepatitis or NASH). While taking milk thistle doesn't seem to improve the overall severity of NASH, it may reduce scarring of the liver.
• A type of anxiety marked by recurrent thoughts and repetitive behaviors (obsessive-compulsive disorder or OCD). Early research shows that taking milk thistle leaf extract by mouth three times daily for 8 weeks has a limited effect on OCD symptoms. It does not appear to more beneficial than conventional medication.
• Skin toxicity caused by radiation. Early research shows that applying a specific product containing milk thistle extract reduces the effect of radiation on the skin in people being treated for breast cancer.
• Inflammation and ulcers (mucositis) caused by radiation. Early research shows that taking milk thistle extract starting on the first day of radiation and continuing for 6 weeks thereafter decreases the severity of ulcers in the mouth and gut caused by radiation.
• Liver damage caused by chemicals. The effect of milk thistle on liver damage caused by chemicals is inconsistent. Taking milk thistle by mouth helps the liver to function in people who have been exposed to the chemicals toluene or xylene. It also seems to help the liver in people who take isotretinoin for acne or drugs for tuberculosis. But taking milk thistle extract by mouth does not seem to prevent liver damage associated with the drug tacrine (Cognex) in people with Alzheimer's disease.
• Hair pulling (trichotillomania). Early research shows that milk thistle taken for 6 weeks does not reduce the symptoms of hair pulling.
• A type of inflammatory bowel disease (ulcerative colitis). Early research shows that taking milk thistle extract by mouth for 6 months, in addition to standard medications, decreases the symptoms of ulcerative colitis and helps maintain remission.
• A skin disorder that causes white patches to develop on the skin (vitiligo). Early research shows that taking the milk thistle constituent silymarin along with phototherapy for 3 months is no better than phototherapy alone for improving vitiligo severity.
• Alzheimer disease.
• Enlarged prostate (benign prostatic hyperplasia or BPH).
• High cholesterol.
• Indigestion (dyspepsia).
• Kidney damage caused by contrast dyes (contrast induced nephropathy).
• Multiple sclerosis (MS).
• Parkinson disease.
• Prostate cancer.
• Other conditions.

More evidence is needed to rate the effectiveness of milk thistle for these uses.

When taken by mouth: Milk thistle extract is LIKELY SAFE for most people when taken by mouth. In some people, taking milk thistle extract can cause diarrhea, nausea, intestinal gas, fullness, loss of appetite, and possibly headache.

When applied to the skin: Milk thistle extract is POSSIBLY SAFE when applied directly to the skin for short periods of time.

When taken by mouth: Milk thistle extract is LIKELY SAFE for most people when taken by mouth. In some people, taking milk thistle extract can cause diarrhea, nausea, intestinal gas, fullness, loss of appetite, and possibly headache.

When applied to the skin: Milk thistle extract is POSSIBLY SAFE when applied directly to the skin for short periods of time.

Pregnancy and breast-feeding: There isn't enough reliable information to know if milk thistle is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Milk thistle is POSSIBLY SAFE when taken by mouth, appropriately, for up to 9 months in children 1 year of age and older.

Allergy to ragweed and related plants: Milk thistle may cause an allergic reaction in people who are sensitive to the Asteraceae/Compositae plant family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many others. If you have allergies, be sure to check with your healthcare provider before taking milk thistle.

Hormone-sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Milk thistle extracts might act like estrogen. If you have any condition that might be made worse by exposure to estrogen, don't use these extracts.

The following doses have been studied in scientific research:

ADULTS
BY MOUTH:

• For diabetes: Milk thistle extract 210-600 mg has been used daily for up to 6 months. 200 mg of milk thistle extract has been taken once daily or three times daily for 4 months to one year. A specific product (Berberol, PharmExtracta) containing 210 mg of milk thistle extract and 1176 mg of tree turmeric extract has been taken daily for 3-12 months.