Report on Milk Thistle Side Effects and Usage

Milk Thistle

Natural health supplements sometimes have unexpected side effects or interactions with medication that can lead to adverse reactions that are sometimes life threatening. The following is a list of cautions that you should be aware of before using Milk Thistle (Silbum marianum). These are referred to as drug/herb interactions.

Warning 1 – Contraindications: Women who have breast, uterine, or ovarian cancer, fibroid tumors, endometriosis, or are breastfeeding or pregnant should not take milk thistle.

Warning 2 – Drug/herb interactions: Because milk thistle affects a specific enzyme (cylochrome p450 or CYP450) that metabolizes drugs it should not be used with certain medications.
If you are taking any prescription drug talk to your doctor before using milk thistle. To see if this applies to your medication, do a search on the name of your drug+cyp450 or drug+p450. Valium is one of these drugs.

Warning 3 – Mineral interaction: Taking higher amounts of milk thistle will in time decrease manganese and iron stores, which can be an advantage for those with hemochromatosis (excess iron storage disease).

Used as a natural health remedy: milk thistle is used internally for the following benefits:

  • Anti-inflammatory (See other herbs for inflammation)
  • Detox or cleanse the system of marijuana (THC)
  • Reduce liver stress caused by menopause (See other herbs for menopause)
  • Improve liver function
  • Reduce toxin-induced liver damage from Amanita phalloides (“death cap” mushroom poisoning and other toxins
  • Improve insulin resistance
  • May lower cholesterol levels
  • May reduce insulin resistance in people with type 2 diabetes who also have cirrhosis
  • May improve liver function in active hepatitis patients
  • May reduce the effects of a hangover
  • May reduce liver damaging effects of drugs used in chemotherapy
  • May improve diabetic nephropathy
  • May reduce the growth of cancer cells in breast, cervical, and prostate cancers
  • May improve gallbladder function

The main active ingredient in milk thistle is silymarin, which is both an anti-inflammatory and an antioxidant.

Side Effects of Milk Thistle

While milk thistle usually causes few, if any, side effects. In a small percentage of people it may cause:

  1. mild diarrhea
  2. nausea
  3. gas
  4. bloating
  5. upset stomach

This herb has been found safe in studies for up to 41 months.

If you are allergic to ragweed, you should avoid milk thistle as it may cause a rash or lead to a severe allergic reaction.

Other side effects may also occur when using Milk Thistle. (See form below)

As with any herb, a serious allergic reaction is possible. Seek immediate medical attention if you notice any symptoms of a serious allergic reaction. These may include a rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, or trouble breathing.

Return to the Herb List.

For questions and answers about the side effects of herbs see the Herb Forum

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