Grape seed extract, a natural supplement made from the seeds of wine grapes, is already known for its benefits in lowering cholesterol and blood pressure.
But now, scientists are exploring whether it might also help slow down prostate cancer growth in men who have already been treated for the disease.
Dr. Paul Maroni from the University of Colorado Cancer Center recently led a study to test this idea. He presented the results of this Phase II trial at a major cancer research meeting, and the findings will soon be published in the journal Cancer Research.
Prostate cancer is the second most common cancer among men in the United States, just behind skin cancer. It affects the prostate, a small gland below the bladder that helps produce semen. In 2024 alone, about 314,000 American men are expected to be diagnosed with the disease, and around 35,800 will die from it.
Though prostate cancer is usually treatable—especially if found early—it’s still a leading cause of cancer-related deaths in men due to the large number of cases.
Doctors often treat early-stage prostate cancer with surgery or radiation. But for men whose cancer comes back after treatment, doctors usually turn to hormone therapy, known as androgen deprivation therapy (ADT).
ADT lowers male hormones to slow cancer growth, but it can cause side effects like hot flashes, weight gain, fatigue, and increased risk of heart problems.
In some cases, when the cancer is not spreading quickly or hasn’t reached other parts of the body, doctors may hold off on starting ADT. This waiting period gives patients time to try lower-impact treatments or supplements. That’s where grape seed extract comes in.
Dr. Maroni teamed up with Dr. Rajesh Agarwal, who has studied the cancer-fighting potential of grape seed extract for years. Grape seed extract contains antioxidants called proanthocyanidins, which are believed to help fight cancer.
In the new trial, researchers gave 41 men—whose prostate cancer had returned but wasn’t spreading—150 mg of grape seed extract twice a day for up to 12 months.
The goal was to see if the supplement could slow the rise in PSA levels. PSA, or prostate-specific antigen, is a protein in the blood that increases when prostate cancer is active. Researchers measured how long it took for each man’s PSA level to double—a marker of how quickly the cancer might be growing.
Before taking the supplement, the average PSA doubling time was 5.71 months. After taking the extract, that time increased to 6.86 months, meaning the cancer was growing more slowly. About 78% of the men had a longer PSA doubling time, and 37% had a significant improvement—at least 30% slower growth.
Interestingly, the supplement seemed to work best for men who started with higher PSA levels and higher testosterone levels. Just as importantly, the grape seed extract caused very few side effects, suggesting it’s safe for most patients.
While these results are promising, Dr. Maroni warns that this supplement is not a cure or guaranteed treatment. He stresses the need for more research and larger studies before grape seed extract can be recommended as a standard option for managing prostate cancer.
For now, men interested in trying grape seed extract should talk to their doctors first. Supplements can interact with other medications or may not be suitable for everyone. It’s important not to rely on supplements alone to treat serious diseases like cancer.
In summary, this study suggests that grape seed extract might help slow the growth of prostate cancer in some men, especially those with higher PSA levels.
The supplement appears to be safe and may delay the need for more aggressive treatments like hormone therapy. However, more research is needed to confirm these findings and understand who might benefit the most.
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The study is published in Cancer Research.
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