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Milk thistle is an herbal supplement sometimes recommended for certain health conditions. Commonly available in capsule, liquid extract and tincture form, milk thistle has a variety of estrogen-like properties that may worsen certain health conditions sensitive to estrogen, such as endometriosis. Although milk thistle may theoretically improve estrogen levels in the body, few studies have been performed on its effectiveness. Talk to your doctor before adding any milk thistle products to your daily routine.

Herbal Remedy

According to the University of Maryland Medical Center, milk thistle is a traditional herbal remedy that has been used for a variety of ailments, such as problems with the liver and gall bladder. Some studies have linked milk thistle compounds called silymarins with antioxidant and anti-inflammatory effects on the liver and other organs. These compounds, along with other flavonoids, may also inhibit cancer cells from dividing and reproducing.

Mimicing Estrogen

The MedlinePlus website links the consumption of milk thistle plant extract with enhanced effects of estrogen in the body. As you digest the milk thistle, certain plant compounds in it begin to mimic the physiological functions of estrogen. As a result, hormone-sensitive conditions such as breast cancer, uterine cancer, endometriosis or uterine fibroids may be worsened.

Milk Thistle Dosage

Healthy adults should limit their milk thistle dosage to 280 to 450 millgrams a day. Supplements containing extracts of the silymarin-phosphatidylcholine compound are generally limited to 200 to 400 milligrams a day, while herbal tinctures and liquid extracts of milk thistle often include recommended dosages on their labels according to the level of dilution. Because of its estrogen-stimulating properties, milk thistle is not recommended for individuals who have been diagnosed with certain estrogen-sensitive cancers, such as breast cancer.

Safety Concerns

Always talk to your doctor before taking any herbal supplement that could have an unbalancing effect on your hormone levels. Depending on individual factors, your estrogen levels may show either a noticeable or nondetectable increase. Keep your daily intake below the recommended 450 milligrams a day, and avoid milk thistle if you are pregnant or nursing.