Tomatoes, especially when they're cooked with a little olive oil, may be good preventive medicine for the prostate.
A study published recently in the Journal of the National Cancer Institute found that men who ate a combined total of 10 servings per week of tomatoes, tomato sauce and pizza had lower risks of prostate cancer than men who averaged only 1.5 servings per week.
This particular study clarifies one prevention puzzle piece, critical because curing advanced-stage prostate cancer remains unlikely. In fact, 40,000 men will die from prostate cancer in the next five years unless prevention and/or cure rates improve.
Earlier studies have suggested that diets high in preformed vitamin A (from animal products like whole milk and liver) or high in animal fat of all kinds (from fatty meats like hamburger and sausage), might increase prostate cancer risks. Some studies show consuming more beta carotene (found in deep orange and dark green leafy vegetables) reduces prostate cancer risk, while other beta carotene studies have not shown this benefit.
So a fuzzy sort of prevention picture (eat less animal fat and more fruits and vegetables) is taking shape, but clear answers remain to be found.
In this six-year study, researchers set out to explore the relationship between prostate cancer and consumption of vegetables, fruits, preformed vitamin A, and various relatives of beta carotene. Of 46 fruits and vegetables evaluated, including the deep orange and dark green leafy ones, only the tomato products showed a measurable relationship to prostate cancer risk. For the 48,000 professional men in this study, as consumption of tomato products increased, risks for prostate cancer decreased.
Why tomatoes? The researchers think lycopene, a relative of beta carotene found in large quantities in tomatoes, is a big part of the answer.
Beta carotene, of course, has appeared in news stories, magazine articles and vitamin supplements because of its apparent power to reduce risks for numerous types of cancers. As an antioxidant, beta carotene "mops up" excess free radical oxygen before it can damage cells and create a foothold for cancer to begin.
Beta carotene has been widely explored because it's easy to find. Earlier, hundreds of studies showed eating lots of fruits and vegetables decreased cancer risks. As scientists looked for the responsible "ingredients," they found large quantities of beta carotene, so it was often promoted as the answer to everything. However, as research has become more refined, smaller but equally powerful beta carotene relatives have begun to appear. To date, more than 500 other carotenoids, including lycopene, have emerged, but their specific roles are still being defined.
What we know so far is that lycopene is the dominant carotenoid circulating in blood and present in body tissues, including the prostate gland. And when it comes to mopping up oxygen, it's the most efficient scavenger of all the carotenoids.
The picture became even clearer when this study showed that eating tomato products increased blood levels of lycopene. Researchers were even able to demonstrate that ethnic cuisine may be more important than genetics in predicting prostate cancer development. In this study, American men of southern-European ancestry ate the most tomato products and had the lowest prostate cancer risks. African-American men ate the fewest tomato products and had the highest risks. Family history, like having a father or sibling with prostate cancer, was not significant. But eating tomato products was.
Another interesting twist emerging from this study suggests cooking tomatoes in a small amount of olive oil (typical for tomato sauce, the No. 1 predictor of blood lycopene levels and reduced cancer risks in this study), actually makes the lycopene user-friendly. The lycopene from tomato juice was not absorbed and did not increase blood lycopene levels.
For pasta and pizza fans, this is good news. It means that the most flavorful tomato sauces, made with a little olive oil (rather than fat free), are the most prostate positive.
Other typical tomato sauce ingredients that may lend a helping hand in cancer prevention include garlic, onions and basil.
Colleen Pierre, a registered dietitian, is the nutrition consultant to the Union Memorial Sports Medicine Center and Vanderhorst & Associates in Baltimore.