Researchers have shown that a compound derived from broccoli linked to reducing the risk and progression of prostate cancer accumulates in prostate tissue, providing evidence for how the protection may work.
Scientists and clinicians from the Quadram institute and Norfolk and Norwich University Hospital (NNUH) made the finding after carrying out a clinical trial involving patients from Norfolk with known or suspected prostate cancer who volunteered to take supplements ahead of their routine prostate biopsies.
The results answer a key question about how dietary compounds may exert their influence on normal and cancerous tissue in the prostate, by demonstrating that they accumulate to significant levels in the prostate gland itself. This provides more supportive evidence that dietary interventions that provide these compounds could benefit patients with prostate cancer.
Diets rich in cruciferous vegetables such as broccoli, and alliaceous vegetables such as garlic, have been correlated with a reduction in the risk of developing aggressive prostate cancer, and its progression. The protective activity of these foods is thought to be due to the activity of the foods’ breakdown compounds. These compounds are broken down by plant enzymes or our gut bacteria into other biologically active compounds that protect against prostate cancer in studies on cells or in animals.
Measurements show that the levels of the compounds circulating in the blood are lower than that typically used in experimental systems, and barely detectable after 24 hours. So, to exert an effect, could these compounds be accumulating in the prostate?
A trial recruited 40 men who were due to undergo prostate biopsies for suspected prostate cancer, or those with known prostate cancer who were under a programme of active surveillance. This means that they have been diagnosed with early, localised, slow growing prostate cancer, and are being regularly monitored to ensure the cancer hasn’t become more aggressive or advanced.
For the ADaPT Trial, the men were asked to take supplements for four weeks before their routine prostate biopsy. The supplements contained either glucoraphanin from broccoli, or alliin from garlic – two compounds associated with protecting against prostate cancer – or a placebo. Neither the patients nor the researchers knew which supplement combination they received.
The analysis found that consuming the glucoraphanin supplement significantly increased the concentration of its active compound, sulforaphane, in all zones of the prostate sampled. This supports the theory that it can exert a local effect on cancer cells in the prostate in the same way seen in lab experiments.
Tracey Livingstone, Urology registrar and Principal Investigator of the ADaPt trial: “There is a wealth of evidence suggesting that dietary compounds found in cruciferous and alliaceous vegetables reduce the risk, or progression of prostate cancer. However, the way in which the prostate gland becomes exposed to these active compounds, was until now largely unknown.”
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