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Men Benefit from Soy, Too
Gain added protection against prostate cancer by living a healthy lifestyle and by learning more about the causes of this common disease. According to research or other evidence, the following self-care steps may be helpful:
- Eat risk-reducing foods. Add plenty of tomato, soy, cruciferous vegetables (such as broccoli, kale, cauliflower, and Brussels sprouts), and fish to your meals.
- Supplement with selenium. Take 200 mg a day of this trace mineral to decrease your risks for developing the disease.
- Try vitamin E. 50 IU a day of this supplement may help lower prostate cancer risk.
- Take time for a checkup. See your healthcare professional once a year for a prostate exam that can help detect disease before it becomes advanced.
About prostate cancer
Prostate cancer is a malignancy of the prostate. It is characterized by unregulated replication of cells creating tumors, with the possibility of some of the cells spreading to other sites (metastasis).
Prostate cancer is the most common cancer among men in the United States. Although the cause is not known, most researchers believe that alterations in testosterone metabolism and/or bodily responses to testosterone are involved.
The incidence of potentially life-threatening prostate cancer varies greatly in different parts of the world. Researchers believe that some factors, possibly involving diet or lifestyle issues, determine the risk of having potentially life-threatening prostate cancer. American men are at high risk of being diagnosed with such prostate cancer, and African-American men are at particularly high risk, for reasons that are not completely clear. A family history of prostate cancer increases the risk to a limited extent. Farmers, mechanics, workers in tire and rubber manufacturing, sheet metal workers, and workers exposed to cadmium have also been reported to be at increased risk.
What are the symptoms?
Prostate cancer usually grows slowly, initially producing no symptoms. Later in the course of the disease, symptoms that overlap with symptoms of prostatic hyperplasia, a very common benign condition, may appear. Some of these symptoms include frequent urination (including having to urinate more frequently at night), pain on urination, a weak urinary stream, dribbling after urination, and a sensation of incomplete emptying. In addition, blood may appear in urine. None of these symptoms is specific to prostate cancer; the diagnosis of this disease requires the help of a doctor.
If prostate cancer spreads to a distant part of the body, it most often is found in bone, a condition that may cause bone pain. Late stages of the disease are associated with severe weight loss, untreatable fatigue-inducing anemia, and finally death.
Dietary changes that may be helpful
The following dietary changes have been studied in connection with prostate cancer.
Avoidance of alcohol
Although the effect of drinking alcohol on prostate cancer risk appears weak, some association between beer drinking and an increased risk may exist, according to an analysis of most published reports.
Tomatoes contain lycopene—an antioxidant similar in structure to beta-carotene. Most lycopene in our diet comes from tomatoes, though traces of lycopene exist in other foods. Lycopene has been reported to inhibit the proliferation of cancer cells in test tube research.
A review of published research found that higher intake of tomatoes or higher blood levels of lycopene correlated with a reduced risk of cancer in 57 of 72 studies. Findings in 35 of these studies were statistically significant. Evidence of a protective effect for tomato consumption was stronger for prostate cancer than for most other cancers.
Cabbage, Brussels sprouts, broccoli, and cauliflower belong to the Brassica family of vegetables, also known as "cruciferous" vegetables. In test tube and animal studies, these foods have shown to have anticancer activity, possibly due to several substances found in them, such as indole-3-carbinol, glucaric acid (calcium D-glucarate), and sulforaphane. A recent preliminary study of men newly diagnosed with prostate cancer showed a 41% decreased risk of prostate cancer among men eating three or more servings of cruciferous vegetables per week, compared with those eating less than one serving per week. Protective effects of cruciferous vegetables were thought to be due to their high concentration of the carotenoids lutein and zeaxanthin, as well as their stimulatory effects on the breakdown of environmental carcinogens associated with prostate cancer.
Meat and how it is cooked
Meat contains high amounts of arachidonic acid. Some by-products of arachidonic acid have promoted prostate cancer in animals. Preliminary reports have suggested that frequently eating well-done steak or cured meats may also increase the risk of prostate cancer in men, though the association between prostate cancer and other meats has not been consistently reported.
Fish eaters have been reported to have low risk for prostate cancer. The omega-3 fatty acids found in fish are thought by some researchers to be the components of fish responsible for protection against cancer.
Low-fat diet and prevention
When combined with a low-fiber diet, men consuming a high-fat diet have been reported to have higher levels of testosterone, which might increase their risk of prostate cancer. The risk of prostate cancer correlates with dietary fat from country to country, a finding supported in some, but not all, preliminary trials. In one study, prostate cancer patients consuming the most saturated fat (from meat and dairy), and followed for over five years, had over three times the risk of dying from prostate cancer compared with men consuming the least amount of saturated fat.
Genistein is an isoflavone found in soybeans and many soy foods, such as tofu, soy milk, and some soy protein powders. Except for soy sauce and soy protein concentrates processed with alcohol, most soy-based foods contain significant amounts of isoflavones, such as genistein. Genistein inhibits growth of prostate cancer cells, helps kill these cells, and has other known anticancer actions, according to test tube research findings.
In preliminary research, men who consumed soy milk more than once per day were reported to have a significantly lower risk of prostate cancer compared with other men. Some researchers are now saying that genistein may eventually be shown to have the potential to treat prostate cancer, while others say only that enough evidence exists to recommend that future genistein research be devoted to the subject of prostate cancer prevention.
Vitamins that may be helpful
Selenium has been reported to have diverse anticancer actions. Selenium inhibits cancer in animals. Low soil levels of selenium (probably associated with low dietary intake), have been associated with increased cancer incidence in humans. Blood levels of selenium have been reported to be low in patients with prostate cancer. In preliminary reports, people with the lowest blood levels of selenium had between 3.8 and 5.8 times the risk of dying from cancer compared with those who had the highest selenium levels.
The strongest evidence supporting the anti-cancer effects of selenium supplementation comes from a double-blind trial of 1,312 Americans with a history of skin cancer who were treated with 200 mcg of yeast-based selenium per day or placebo for 4.5 years and then followed for an additional two years. Although no decrease in skin cancers occurred, a dramatic 50% reduction in overall cancer deaths and a 37% reduction in total cancer incidence were observed. A statistically significant 63% decrease in prostate cancer incidence was reported. In another trial, 5,141 men were randomly assigned to receive a placebo or a daily supplement containing 100 mcg of selenium, 120 mg of vitamin C, 30 IU of vitamin E, 6 mg of beta-carotene, and 20 mg of zinc 20 for eight years. Among men with a normal PSA level at the start of the study, there was a statistically significant 48% reduction in the incidence of prostate cancer. Among men with an initially elevated PSA level, the supplemented group had an increased incidence of prostate cancer that was not statistically significant.
Relatively high blood levels of vitamin E have been associated with relatively low levels of hormones linked to prostate cancer. While a relationship between higher blood levels of vitamin E and a reduced risk of prostate cancer has been reported only inconsistently, supplemental use of vitamin E has been associated with a reduced risk of prostate cancer in smokers. In a double-blind trial studying smokers, vitamin E supplementation (50 IU of vitamin E per day for an average of six years) led to a 32% decrease in prostate cancer incidence and a 41% decrease in prostate cancer deaths. Both findings were statistically significant. The effects of vitamin E have yet to be studied in men already diagnosed with prostate cancer.
Herbs that may be helpful
In a double-blind trial, men with precancerous changes in the prostate received a green tea extract providing 600 mg of catechins per day or a placebo for one year. After one year, prostate cancer had developed in 3.3% of the men receiving the green tea extract and in 30% of those given the placebo, a statistically significant difference. These results suggest that drinking green tea or taking green tea catechins may help prevent prostate cancer in men at high risk of developing the disease.
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