Fighting Prostate Cancer: Eat Your Way to Victory
If you could reduce your risk of prostate cancer by adjusting your diet, would you do it? If you knew that 186,320 new cases of prostate cancer would be diagnosed this year, and that 28,660 men would die, would you reconsider your answer? There is mounting evidence that diet is strongly linked to prostate cancer—the second most common cause of cancer-related death in American men.
Though the statistics sound gloomy, the good news is that the diet you eat today may actually delay or prevent the development of prostate cancer down the road. In Asia, for example, the percentage of men who develop prostate cancer is far less than that of the United States, and the prostate cancer that develops in Asian men is more curable. Researchers have long speculated that certain aspects of the Asian diet may be protective against prostate cancer. And in certain Mediterranean countries, such as Greece and Italy, the rate of prostate cancer is also low; some researchers speculate that diet is a factor there, as well.
Compounds called isoflavones, found mainly in soybeans, are present in the Asian diet, but are virtually absent in the typical American diet. Asians eat the whole soybean or minimally processed by-products of the soybean, such as tofu and soymilk.
It is estimated that Japanese men consume up to 200 mg of isoflavones per day while other Asian men consume 25-45 mg. American men, however, typically consume less than 5 mg of isoflavones per day.
Isoflavones may exert anti-tumor properties in a variety of ways. They might play a role in prohibiting the formation of new blood vessels that are necessary to feed a growing cancer. Since prostate cancer is a hormone-dependent cancer, the isoflavones may lower the hormones that contribute to the development of prostate cancer, theoretically lessening the likelihood of the cancer growing.
Good sources of isoflavones include:
- Tofu—available in most refrigerated produce or dairy sections of your local supermarket. You can make a healthy shake by blending together ½ cup of tofu with a banana, orange juice, and other fruit.
- Soy nuts—yields 60 mg of isoflavones per ¼ cup
- Tempeh (cake of fermented soybeans)—yields 60 mg
- Soy flour—yields 44 mg
- Flavored soymilk—yields about 40 mg per 1 cup
- Roasted soybeans—packs the highest amount of isoflavone per serving—about 167 mg for a 3.5 ounce serving (or 7 tablespoons); these are available at healthfood stores and also online.
Green tea contains cancer-preventing compounds called flavonoids, which act as antioxidants and also have anti-inflammatory properties. Several studies performed in animals suggest that one particular flavonoid, epigallocatechin gallate (EGCG), may have the ability to stop tumors from spreading by preventing new blood vessel growth in tumors.
Japanese researchers have noted that cancer onset in patients consuming 10 cups of green tea per day seems to be 3-8 years later when compared with people who consume three or less cups of green tea. (The typical Asian consumes an average of five cups of green tea per day.) It is important to remember, however, that these studies are preliminary and more research is needed.
According to Dr. Douglas Balentine of the Lipton Tea company, if green tea is steeped for only one minute, the average flavonoid content is 208 mg. If it is steeped for four minutes, the flavonoid content increases to 300 mg.
Red Fruits and Vegetables
Lycopene is part of a group of compounds called carotenoids that are known for their antioxidant properties, which may include the ability to inhibit cancer. Where can you find lycopene? Watermelon and pink grapefruit contain lycopene, but tomato-based foods contain the most. When tomato-based foods are heated and mixed with a small amount of oil, the lycopene absorption is maximized. That makes cooked tomato products excellent sources of lycopene.
In one study, Dr. Edward Giovannucci of the Harvard Medical School examined the diets of more than 47,000 males over a six-year period. He noted a correlation between prostate cancer and a marginal intake of tomato-based foods, which contain large amounts of lycopene. Men who ate ten or more servings per week of tomato-based foods had a 45% lower likelihood of developing prostate cancer.
"The jury is still out on lycopene," says Colleen Doyle, MS, RD, nutrition and physical activity director for the American Cancer Society (ACS). "Earlier studies have not consistently shown that men who consume more lycopene are at a reduced risk of developing prostate cancer."
However, Doyle points out that tomatoes are still an important part of a healthy diet. "Everyone should eat at least five servings of a wide variety of fruits and vegetables every day and tomatoes are a great way to get in your five daily vegetable servings," she says.
A recent study from the Fred Hutchinson Center in Seattle confirms that all vegetables may help reduce the risk of prostate cancer. According to Dr. Alan Kristal, "Eating a lot of vegetables can cut your risk of prostate cancer by about 45%. And if those vegetables are from the cruciferous family, like cabbage and broccoli, you may reduce your risk even further."
This study—which examined the risks for prostate cancer in younger men (ages 40 to 64)—looked at the associations between overall fruit and vegetable consumption as well as specific fruits and vegetables and prostate cancer risk.
In the study, men who ate three or more servings per day of vegetables had a 48% lower risk of prostate cancer, compared with men who ate less than one serving per day. This association was independent of other dietary factors (such as fat intake) and a history of prostate cancer in a father or a brother. The strongest correlation was noted with the cruciferous vegetables—broccoli, cauliflower, cabbage, and Brussels sprouts.
It has been speculated that the typical high fat intake in the Western diet may accelerate prostate cancer. A study at Sloan Kettering Institute for Cancer Research noted that the antioxidant effects of vitamin E seem to halt prostate tumor growth in mice, which was initially triggered by a high-fat diet.
In the US and Canada, the daily requirement is 15 mg of vitamin E. The best food sources are polyunsaturated vegetable oils, seeds, nuts, and whole grains.
Prostate cancer is a hormone-dependent cancer. Any aspect of the diet that binds hormones could have a positive effect on prostate health. Dietary fiber, for instance, may remove hormones from the system. It has been found that men who eat more fruits, vegetables, and whole grains—all excellent sources of fiber—have lower circulating levels of male hormones. The National Cancer Institute recommends consuming at least 25 grams of fiber per day. A ½ cup serving of fruit or vegetables contains about 2 grams of fiber, a slice of whole grain bread 5 grams, and a ½ cup serving of high fiber cereal a whopping 14 grams.
The Bottom Line
No one food or supplement can protect you from prostate cancer. A diet that is lower in fat, contains at least five servings per day of fruits and vegetables, and includes soy-based products may go a long way in protecting your prostate.
Prostate Cancer Foundation
US Soyfoods Directory
Canada's Food Guide
Canadian Cancer Society
Green tea. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/thisTopic.php?marketID=15topicID=114. Updated June 2008. Accessed September 4, 2008.
How many men get prostate cancer? American Cancer Society website. Available at: http://www.cancer.org/. Updated June 2007. Accessed September 4, 2008.
Isoflavones. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/thisTopic.php?marketID=15topicID=114. Updated July 2008. Accessed September 4, 2008.
Lycopene. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/thisTopic.php?marketID=15topicID=114. Updated January 2008. Accessed September 4, 2008.
Vitamin E. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/thisTopic.php?marketID=15topicID=114. Updated March 2008. Accessed September 4, 2008.
Last reviewed September 2008 by Adrienne Carmack, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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