Milk Thistle and Cancer: Evidence of Potential Therapeutic Benefit

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

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

Prevented free radical damage.⁽⁸⁸⁾

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

Suppressed cancer cell growth.⁽¹⁵¹⁾

Reduced cancer cell viability.⁽¹⁵¹⁾

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

Decreased levels of 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⁾

Blocked cancer cell growth.⁽¹⁵¹⁾

Decreased cancer cell viability.⁽¹⁵¹⁾

Induced colon cancer cell cycle arrest.^(154, 155)

Boosted levels of tumor suppressor proteins.⁽¹⁵⁴⁾

Blocked 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⁾

Decreased metastatic potential of kidney cancer cells.⁽¹⁵⁹⁾

Increased cancer cell cycle arrest.⁽¹⁶⁰⁾

Induced leukemia cell death.⁽¹⁶⁰⁾

Blocked 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⁾

Boosted levels of natural antioxidants.⁽⁸²⁾

Reduced number of cancerous nodules.⁽⁸²⁾

Decreased 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.^(82, 161)

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

Promoted natural antioxidants in lung cancer cell lines.⁽¹⁶⁴⁾

Prevented cell damage caused by exposure to paraquat herbicide.⁽¹⁶⁴⁾

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

Blocked tumor regrowth.⁽⁸³⁾

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

Blocked damage in the oral cavity caused by Swedish smokeless tobacco.⁽²³⁶⁾

Decreased levels of enzymes that promote invasiveness and metastatic potential of bone cancer cells.⁽¹⁶⁵⁾

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

Boosted tumor suppressor proteins.⁽¹⁶⁶⁾

Induced death of ovarian cancer cells.⁽¹⁶⁶⁾

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

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

Boosted levels of tumor suppressor proteins that get rid of damaged, potentially precancerous cells.⁽⁹⁴⁾

Blocked cell cycle progression and cell growth in prostate cancer cell lines.^(94, 151)

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

Helped prevent metastasis of prostate cancer.⁽¹⁶⁷⁾

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

Decreased cancer cell viability.⁽¹⁵¹⁾

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

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

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

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

Decreased tumor incidence and volume.^(98, 169)

Blocked free radicals caused by chemical or UVA radiation exposure.^(169, 170)

Prevented sunburn.⁽⁹⁸⁾

Down-regulated production of inflammatory proteins, growth factors, and other markers linked to cancer development.^(98, 172)

Reduced DNA damage.^(170, 171)

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.^{(98, 169, 171)}

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⁾

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⁾

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⁾

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⁾

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⁾

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

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

Daily milk thistle supplements have been linked to 2 cases of spontaneous regression in liver cancer. Cases were reported separately.^(37, 38)

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⁾

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⁾