Natural Antioxidant—Great for Liver Health

Milk Thistle and Cancer: Evidence of Potential Therapeutic Benefit

Milk thistle has cancer fighting benefits against a number of cancers and can relive side effects of chemotherapy, including for childhood leukemia.

Could milk thistle help prevent or treat cancer? Lab, animal, and clinical studies suggest compounds in milk thistle may indeed help fight cancer.(94146147)

Research shows that milk thistle extracts are nontoxic inhibitors to cancer cell cycles, effectively blocking cancer growth. In addition to its direct anticancer effects, milk thistle silymarin compounds may also reduce damage to the heart and liver from chemotherapy drugs.(94146-148)

In fact, integrative medicine doctors recommend taking milk thistle to alleviate common side effects of cancer treatment drugs.(149)

Lab and Animal Cancer Study Results Using Milk Thistle Compounds

Silymarin and silibinin flavonoid compounds from milk thistle seeds have anticancer properties. How do milk thistle compounds work against cancer? Besides milk thistle's antioxidant ability to fight damaging free radicals, preclinical studies show a number of anticancer activities:(94)

Milk Thistle Table 6: Effects on Different Cancer Types by Milk Thistle
Cancer Type Milk Thistle Compound & Study Type Study Results

Bladder cancer

Silybin (silibinin)(58)

Lab studies(58)

Effectiveness of photodynamic therapy on bladder cancer cell lines.(58)

Brain cancer

Silymarin and silibinin(88150)

Lab studies(88150)

Effectiveness of cancer drugs on treatment-resistant cells.(150)

Free radical damage.(88)

Proteins that protect brain cancer cells against TRAIL cancer treatment.(150)

Breast cancer

Silymarin and silibinin(60151)

Lab and animal studies(60151)

Cancer cell growth.(151)

Cancer cell viability.(151)

Cell migration and motility in breast cancer cells, alone and in combination with paclitaxel chemotherapy.(60)

Telomerase, an enzyme that is overexpressed in breast cancer cells and helps them survive.(152)

In lab studies, silibinin from milk thistle worked even better against breast cancer cells when combined with curcumin from turmeric.(152)

The combination of the milk thistle compound and chemotherapy significantly blocks metastasis of breast cancer to the lung. In animal research, milk thistle even works in a model for triple negative breast cancer, a type of breast cancer that is prone to spreading to other areas of the body.(60)

One of the side effects of tamoxifen, a chemotherapy drug commonly used to treat breast cancer, is non-alcoholic fatty liver disease. Animal studies suggest milk thistle extract may help prevent that damage.(153)

Cervical cancer

Silymarin and silymarin(151)

Lab studies(151)

Cancer cell growth.(151)

Cancer cell viability.(151)

Colon cancer

Silymarin and silibinin(154155)

Lab and animal studies(154155)

 Colon cancer cell cycle arrest.(154155)

Tumor suppressor proteins.(154)

Tumor cell proliferation.(154)

Combining milk thistle compounds with drugs or natural herbal compounds enhances milk thistle's ability to kill colon cancer cells:

  • Metformin, a pharmaceutical drug commonly used to treat diabetes.(156)
  • Curcumin, the bioactive pigment compound from the popular spice and herb turmeric.(157)

Preliminary clinical studies in patients with colon cancer show safe oral doses of silibinin reaches high levels in colorectal tissue.(158)

Kidney cancer

Silibinin(159)

Lab studies(159)

Metastatic potential of kidney cancer cells.(159)

Leukemia

Silymarin and silybin(160)

Lab studies(160)

Cancer cell cycle arrest.(160)

Leukemia cell death.(160)

Cancer cell growth.(160)

Exposure to low concentrations (50-400 μM) of silymarin, however, stimulated growth of leukemia cells in the first 24 hours. High doses (over 400 μM) and longer exposure (72 hours at 200 μM) showed anticancer effects.(160)

Liver cancer

Silymarin, silibinin, and oxidized silybin(82161162)

Lab and animal studies(82)(161)(162)

Levels of natural antioxidants.(82)

Number of cancerous nodules.(82)

Enzymes that promote metastases.(161)

Pretreatment and post-treatment with dietary silymarin from milk thistle helps prevent the development and progression of liver cancer.(82)

Oxidized silybin actually works better than silybin or silymarin extract at stopping liver cancer growth.(82161)

Silibinin also enhances the effectiveness of chemotherapy drugs for liver cancer.(162)

Lung cancer

Water-soluble form of milk thistle silymarin, silibinin(83163164)

Lab and animal studies(83163164)

Natural antioxidants in lung cancer cell lines.(164)

Cell damage caused by exposure to paraquat herbicide.(164)

Tumor size and volume as well as chemotherapy drug gefitinib.(83)

Tumor regrowth.(83)

Lung damage from methotrexate, a drug used to treat cancer, rheumatoid arthritis, and psoriasis.(163)

Osteosarcoma

Silibinin(165)

Lab studies(165)

Enzymes that promote invasiveness and metastatic potential of bone cancer cells.(165)

Ovarian cancer

Silymarin(166)

Lab studies(166)

Cell cycle arrest in ovarian cancer cell lines.(166)

Tumor suppressor proteins.(166)

Death of ovarian cancer cells.(166)

Levels of proteins that help ovarian cancer cells survive.(166)

Prostate cancer

Silymarin and silibinin(94151)

Lab and animal studies(94151)

Effectiveness of chemotherapy drugs in arresting prostate tumor growth.(94)

Tumor suppressor proteins that get rid of damaged, potentially precancerous cells.(94)

Cell cycle progression and cell growth in prostate cancer cell lines.(94151)

Levels of proteins that help prostate cancer cells survive.(94)

Metastasis of prostate cancer.(167)

Production of inflammatory proteins, growth factors, and other markers linked to prostate cancer development, progression, and spread.(94)

Cancer cell viability.(151)

Tumor volume and weight by 29-64%, depending on dose and timing(167)

Skin cancer

Silymarin extract, applied to cancer cell lines and topically to animal skin(98168-172)

Dietary silibinin (1% dose)(171172)

Lab and animal studies(98168-172)

Tumor suppressor proteins that get rid of damaged, potentially precancerous cells.(171)

Excess enzyme receptor activity linked to skin cancer growth.(168)

Cell cycle progression and cell growth in skin cancer cell lines.(168)

Tumor incidence and volume.(98169)

Free radicals caused by chemical or UVA radiation exposure.(169170)

Sunburn.(98)

Production of inflammatory proteins, growth factors, and other markers linked to cancer development.(98172)

DNA damage.(170171)

In the animal studies, the skin cancer was induced by UVB radiation (one of 3 types of radiation from sunlight) or toxic chemicals. UVA and UVB are common causes of types of skin cancer.(98169171)

Milk Thistle for Cancer: Case and Clinical Studies

Preliminary research in cancer patients suggest echinacea may help by reducing the side effects of conventional cancer treatments. This includes reducing damage to kidneys caused by cisplatin.(173)

Milk Thistle Table 7: Clinical Studies Using Milk Thistle with Cancer Patients
Cancer Type Echinacea Species & Study Details Study Results

Acute lymphoblastic leukemia (childhood)

Randomized, double-blinded, placebo-controlled pilot study(174)

  • 50 children with leukemia experiencing toxic side effects in the liver from chemotherapy.(91)
  • 160-320 mg/day (depending on body weight) of milk thistle or placebo daily for 28 days.(91)

Leukemia patients who took milk thistle showed a significant trend toward reduced liver toxicity.(174)

Although not statistically significant, chemotherapy doses had to be reduced in fewer patients who took milk thistle compared to those who took placebo.(174)

Acute myelogenous and promyelocytic leukemia

Case studies

  • 2 adult patients with leukemia, reported separately.(175)
  • 560-800 mg/day of milk thistle (silymarin extract) supplements.(175)

Daily milk thistle supplements may reduce the risk of liver damage from chemotherapy. In both case reports, highly elevated liver enzymes caused by chemotherapy were significantly reduced by milk thistle.(175)

Brain cancer (metastatic tumors from lung cancer)

Case studies

  • 2 patients with brain tumors metastasized from non-small cell lung cancer (one smoker, one non-smoker).(176)
  • 3-5 oral Legasil®, containing up to 630 mg of silibinin daily for several months.(176)

Daily milk thistle supplements reduced size of brain tumors. Patients with brain metastasis have a median survival time of approximately 1 month. The 2 patients in these case studies were still alive well-past that marker.(176)

Breast cancer

Case report

  • 1 patient with breast cancer metastasized to the liver.(177)
  • Daily progressive doses of Legasil® (a combination of silibinin and vitamin E) daily along with chemotherapy.(177)

Fourth line chemotherapy treatment (carboplatin and gemcitabine) can have severe life-threatening effects in the liver.(177)

In this case, milk thistle extract and vitamin E supplements restored liver function. This allowed the patient to continue chemotherapy.(177)

Breast cancer

Clinical study

  • 12 patients with early-stage breast cancer.(178)
  • 2.8 mg/day of silybin phosphatidylcholine supplements for 4 weeks before surgery.(178)

After surgery, tests were conducted on tumor tissue and adjacent healthy tissue.(178)

Results showed that milk thistle extract accumulated in the cancer cells in higher concentrations than healthy cells. This makes silybin a promising biomarker for breast cancer prevention.(178)

Breast cancer

Randomized, double-blinded, placebo-controlled clinical trial

  • 47 premenopausal and 49 postmenopausal women randomly divided into 2 groups containing both pre- and post-menopausal women.(179)
  • Daily breast health supplement (containing lignans, 100 mg of milk thistle, vitamin D, and other herbs) or placebo.(179)

In combination with other beneficial compounds, milk thistle helped improve estrogen metabolite ratios. This could lower the risk of breast cancer.(179)

Head and neck cancer

Randomized, double-blinded, placebo-controlled clinical trial(91)

  • 27 patients with head and neck cancers.(91)
  • 420 mg/day of silymarin daily for 6 weeks during radiation therapy.(91)

Silymarin significantly delayed and reduced severe inflammation and sores caused by radiation cancer treatment.(91)

Liver cancer

Case reports

  • Patients with inoperable liver cancer.(3738)
  • 450 mg/day of silymarin daily for months.(3738)

Daily milk thistle supplements have been linked to 2 cases of spontaneous regression in liver cancer. Cases were reported separately.(3738)

Prostate cancer

Placebo-controlled, double blind clinical trial

  • 37 patients with prostate cancer.(180)
  • 570 mg of silymarin and 240 µg of selenium daily for 6 months (or placebo), 2-3 months after radical prostatectomy.(180)

The combination of selenium and milk thistle extracts showed the following benefits in prostate cancer patients:(180)

  • LDL and total cholesterol levels.
  • Selenium levels.

Elevated cholesterol and reduced selenium levels are both linked to prostate cancer progression. The selenium & milk thistle supplement also improved quality of life scores.(180)

Prostate cancer

Randomized, placebo-controlled, double blind, crossover clinical trial

  • 49 patients with prostate cancer and rising PSA levels following surgery or radiation.(181)
  • Multivitamin and herbal supplement containing 160 mg silymarin.(181)

Supplements containing milk thistle extracts, soy, lycopene, vitamin C, vitamin E, Co Q10, riboflavin, folic acid, selenium, zinc, and other beneficial compounds significantly reduced PSA levels.(181)

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Also referred to as silibin, silibinin is actually made of 2 compounds: silybin A and silybin B.(2094)
Silybin A and silybin B are collectively referred to as silibinin.(2094)
Also referred to as silibin, silybin has anti-leukemia effects in lab studies at high doses only.(2094160)
Silybin A and silybin B are collectively referred to as silibinin.(2094)
Silibinin meglumine.(83)