What We Know About Milk Thistle And Prostate Cancer Prevention

As men get older, their risk of prostate cancer significantly increases. Prostate cancer is the second most common type of cancer among men, affecting 1 in 8, according to the American Cancer Society. More than half of prostate cancer diagnoses occur in men over 65.

Although you can't control the risk factor of age, a healthy lifestyle including a balanced diet and regular exercise can improve your overall health (try these three foods to help prevent prostate cancer). Some men might also choose to take prostate health supplements such as milk thistle to reduce their risk of prostate cancer. Dr. Justin Houman, a top urologist and the leading urological surgeon in Los Angeles, told Health Digest that there isn't enough evidence to confirm that milk thistle prevents prostate cancer.

"While some laboratory studies have shown that silymarin may have anti-cancer properties, we don't have strong clinical data supporting its use as a preventive measure in humans," Houman said. That doesn't mean milk thistle can't help men with prostate cancer, however. Houman says there is promising research showing that milk thistle can supplement prostate cancer treatments.

For more than two centuries, people have been using the fruit and seeds from the milk thistle plant to treat conditions of the liver (per National Cancer Institute). Its powerful ingredient is silymarin, which Houman says has anti-inflammatory and antioxidant properties. Milk thistle might boost the effectiveness of chemotherapy and reduce its side effects.

"In simple terms, it may help protect healthy cells from damage during chemotherapy while potentially making cancer cells more vulnerable to treatment," Houman said. "It's also thought to potentially slow the growth and spread of cancer cells. However, the exact mechanisms are not fully understood and are still being researched."

Milk thistle might also support prostate health in people with prostate cancer, according to a 2022 review in the Iranian Journal of Basic Medical Sciences. Because high cholesterol is linked to prostate cancer progression, taking silymarin for six months following prostate surgery can lower cholesterol. Men are often screened for prostate cancer through a prostate-specific antigen (PSA) test, where high PSA levels could indicate prostate cancer. A daily supplement of silymarin for six months has been shown to reduce PSA levels.

Although the Food & Drug Administration hasn't approved the herb to treat any cancers, milk thistle might have some health benefits. As an ancient treatment for the liver, milk thistle might reduce free radical damage in your liver. Silymarin's antioxidant properties might also protect your brain cells from oxidative stress to prevent cognitive decline, although milk thistle's neuroprotective effects haven't been tested on humans (per Healthline).

Houman says that milk thistle is generally safe, but it might interact with some of the medications you're taking. Specifically, Drugs.com says if you're already taking simeprevir to treat hepatitis C, milk thistle increases the level of simeprevir in your system which could increase side effects. Milk thistle can also interact with deferiprone, indinavir, and raloxifene. 

Milk thistle alone might have mild side effects such as gastrointestinal issues, particularly among people with liver disorders. "As with any supplement, patients should always consult with their healthcare provider before incorporating milk thistle into their regimen, especially if they're undergoing cancer treatment," Houman said.

If you're looking to maintain your prostate health, Houman advises his patients to eat a healthy diet, exercise regularly, quit smoking, and follow prostate cancer screening guidelines. "While we continue to research potential complementary therapies like milk thistle, they should not replace standard medical care for prostate cancer prevention or treatment," he said.