The Recommended Dose of Milk Thistle

Milk thistle’s role in traditional medicine began 2,000 years ago when it was used to treat liver disorders. Today it’s still used for the same purpose, but studies of its effectiveness have been inconsistent. Some yield positive results, and others show no benefits from milk thistle. Its active ingredients can interfere with some drugs, so talk to your health care provider before taking milk thistle if you’re on prescription medications.

Milk thistle’s reddish-purple flowers top stems that can grow up to 8 feet high. Thanks to its tendency to take over and kill surrounding plants, it’s classified as a noxious weed, yet milk thistle is edible. The stems, leaves, flowers and even the seeds were used in English cuisine, notes New York University. Milk thistle contains flavonoids that have antioxidant and anti-inflammatory properties. The active ingredient -- silymarin -- includes several flavonoids extracted from the seeds, according to the University of Colorado.

Taking silymarin together with an antihistamine may improve symptoms from allergies better than the antihistamine alone, according to Medline Plus. Studies in animals indicate that milk thistle may protect the liver from toxins, but in human studies the results show conflicting evidence, according to a review of the research on New York University's Langone Medical Center website. The most promising benefit is for treating alcoholic hepatitis and reducing the death rate from cirrhosis, but more studies are needed to verify milk thistle’s role. Silymarin had a moderate anti-inflammatory effect in patients with chronic hepatitis C, reported a study in the July 2013 issue of the “Journal of Viral Hepatitis.”

If you want to use milk thistle for allergies, you should take 140 milligrams of silymarin three times daily according to MedlinePlus. The standard dose is 200 milligrams taken two to three times daily, according to New York University. Your body absorbs milk thistle better if the extract is bound with phosphatidylcholine. If your supplements contain this extra ingredient, then the dosage is 100 to 200 milligrams twice a day. The U.S. Food and Drug Administration does not regulate supplements, so look for the “USP Verified” mark. It indicates the supplements were tested by the U.S. Pharmacopeial Convention, and they’re verified to contain the type and amount of ingredients stated on the label.

Consult your physician before taking milk thistle extracts if you’re pregnant or have hormone-sensitive conditions, including breast cancer, ovarian cancer, endometriosis and uterine fibroids. Milk thistle belongs to the same family as daisies, ragweed and marigolds. Even though it's generally safe, you may experience side-effects if you’re allergic to these plants. Milk thistle may interfere with the way your liver metabolizes a variety of medications. If you take any prescription medications, consult your doctor before taking milk thistle.