Many people were hoping the long-awaited results of two major cancer prevention studies would deliver important news about stopping the spread of prostate cancer. But to the health community’s dismay, researchers delivered a “no effect” verdict in December 2008 when the data were published in the online edition of the Journal of the American Medical Association.
In light of National Cancer Prevention Month, it seems like an especially good time to take stock of where we are in the fight against this widespread disease. SELECT (Selenium and Vitamin E Cancer Prevention Trial) was a large clinical trial that provided supplements of the mineral selenium (200 micrograms (mcg) daily) and vitamin E (400 International Units (IU)) to more than 35,000 men aged 50 and older.
Researchers hoped that people taking one or both of these supplements would show lower risk of prostate cancer compared to those receiving a placebo pill. Unfortunately, when the supplements showed no signs of reducing prostate cancer and raised some concerns about possible health risks, the trial was stopped early.
The Physicians’ Health Study II is another trial that looked at factors affecting prostate and total cancer risk. Researchers watched more than 14,000 men age 50-plus for about eight years to see if supplements of vitamin E (400 IU every other day) or vitamin C (500 milligrams (mg) daily) could provide protection. In the end, neither supplement had any effect on prostate or total cancer risk.
While these results are disappointing, it won’t end research on these supplements. Scientists are asking questions about whether changing the chemical form of the nutrients, the dose, or the age at which supplementation begins could bring about different results.
Meanwhile, although evidence is far from certain, emerging research suggests that some vegetables may help lower prostate cancer risk. Broccoli and other cruciferous vegetables yield natural compounds called isothiocyanates that stimulate enzymes that detoxify carcinogens. Research now shows that these compounds also support tumor suppressor genes that help our body catch and eliminate damaged cells that could become cancerous.
Tomatoes supply a compound called lycopene, a cousin to beta-carotene and a powerful antioxidant. Research now suggests that this compound may promote control of cell growth and stimulate self-destruction of abnormal cells. Although lycopene is available in a variety of supplements, these sources may not be as effective as when we get it from food. Part of that difference may reflect interaction of lycopene with other compounds in tomatoes and in other foods such as broccoli and soy.
Garlic is also identified as a food that may play a possible role in reducing prostate cancer risk according to Food and Drug Administration (FDA) review. Several compounds in garlic offer antioxidant, anti-inflammatory and specific anti-cancer- effects. Laboratory studies show that these compounds can slow later stages of prostate cancer development, too. But we need more human data.
Other foods might help prevent prostate cancer, too, including green tea, flaxseed, soy and perhaps other beans. These are nutritious foods, but the link to lower prostate cancer risk is not established. And avoiding excessive amounts of milk or high doses of calcium (more than 1500 mg daily) is suggested because of possible links to increased prostate cancer risk.
As a result of the recent findings, some experts believe that efforts to identify specific nutrients or compounds for supplementation may be better spent elsewhere, focusing on healthy dietary patterns and lifestyle habits for example.