Dietary Isoflavones (Plant Estrogen) Containing Soy Foods: for The Treatment or Prevention of Prostate Cancer
Prostate cancer has become the most commonly diagnosed cancer among men in the US. It usually grows slowly. Men who have it often die from other causes before the cancer kills them. Still, prostate cancer is one of the most common causes of cancer death in American men. The prostate cancer death rate is especially high among African American men.
For many men a diagnosis of prostate cancer can be frightening, not only because of the threat to their lives, but because of the threat to their sexuality. In fact, the possible consequences of treatment for prostate cancer — which include bladder control problems and erectile dysfunction (ED) or impotence — can be a great concern for some men.
The prostate is normally about 3 cm long (slightly more than 1 inch) and lies at the neck of the bladder and in front of the rectum.The prostate surrounds the urethra, which is a tubular structure that carries sperm and urine out of the penis.It produces a thin, milky fluid that is added to the sperm at the time of ejaculation.Older men often have an enlarged prostate, which is a noncancerous condition called benign prostatic hypertrophy (BPH) that causes urinary symptoms.
Prostate cancer can be aggressive, which means it grows quickly and spreads to other parts of the body. (When cancer spreads, doctors say the cancer has "metastasized.") Patients with slow-growing cancer can expect to live as long as men who do not have cancer. Most patients with slow-growing cancer will never have symptoms. Three out of four cases of prostate cancer are of the slow-growing type that is relatively harmless.
There is no known prevention. Following a vegetarian, low-fat diet or one similar to the traditional Japanese diet may lower risk. Early identification (as opposed to prevention) is now possible by yearly screening of men over 40 or 50 years old through digital rectal examination (DRE) and PSA blood test.
Making moderate changes in lifestyles can result in considerable gains. For example, a reduction in saturated fat intake of 1% - 3% can reduce the risk of coronary heart disease by 25%. Regular physical activity reduces the risk of breast and colon cancer and possibly that of endometrial and prostate cancer.This is partly due to a diet characterized by low salt, soy beans, fish, seaweed and green vegetables.
High-fat diets have been linked to prostate cancer. Therefore, limiting your intake of high-fat foods and emphasizing fruits, vegetables and whole fibers may help you reduce your risk. Foods rich in lycopenes, an antioxidant, also may help lower your prostate cancer risk. These foods include raw or cooked tomatoes, tomato products, grapefruit and watermelon. Garlic and cruciferous vegetables such as arugula, bok choy, broccoli, brussels sprouts, cabbage and cauliflower also may help fight cancer.Eating certain foods that contain substances called antioxidants (vitamins C and E and beta carotene) may be protective.
Soy products contain isoflavones that seem to keep testosterone in check. Because prostate cancer feeds off testosterone, isoflavones may reduce the risk and progression of the disease.
Consumption of the estrogen-like "isoflavone" substances found in soy may reduce the risk of developing early prostate cancer, but isoflavones appear to be associated with advanced disease if prostate cancer does occur, Japanese researchers report.
Plant oestrogens or phytoestrogens are plant compounds which belong to a group called phytochemicals. They are naturally occurring substances found in all plants in varying amounts, in the seeds, stems, roots and flowers. In leguminous plants (peas and beans) phytoestrogens function as signals from the roots to attract nitrogen fixing bacteria and as part of the plant’s defence mechanism against microorganisms. They also act as natural fungicides and protect the plants from the action of ultraviolet radiation.
There are three main classes of phytoestrogens based on the structure of the compounds: lignans, coumestans and isoflavones.This classification is based on the structure of the compounds. The lignans and isoflavones are the most studied of the three, as they are found in a
wide array of foods and make the largest contribution of phytoestrogens to our diets.Coumestrol is the most common form of coumestan.
Isoflavones are especially well documented as they are abundant in soy beans.
Isoflavones found in traditional foods that Japanese eat throughout life may be protective against prostate cancer, Dr. Norie Kurahashi told Reuters Health, but we can not recommend isoflavones from supplements to those who don't consume them regularly, "because isoflavones may increase the risk of advanced prostate cancer."
Kurahashi and associates from the National Cancer Center, Tokyo, investigated the association between dietary isoflavones and risk of prostate cancer in a study of Japanese men, who generally consume large amounts of soy products and have a low rate of prostate cancer.
The study, which is reported in Cancer Epidemiology, Biomarkers & Prevention, involved some 43,500 men followed from 1995 through 2004. During that time, 307 of them were diagnosed with prostate cancer.
Consumption of isoflavones (principally genistein, but also daidzein and soy foods) was associated with a decreased risk of early prostate cancer, the authors report. Genistein and daidzein, however, were associated with an increased risk of advanced prostate cancer, the results indicate.
The protective effect of isoflavones for early prostate cancer was clearest among men over 60 years old, the researchers note, as was the association of isoflavone with an increased risk of advanced prostate cancer.
"We suggest that isoflavones delay the progression from latent cancer to clinically significant prostate cancer in Japanese who consume isoflavones regularly throughout life," Kurahashi said. "However, we do not know when or how isoflavones affect latent or (early) prostate cancer development and whether isoflavones can be used in the treatment or...prevention of this cancer."
More studies are needed "to clarify what period in life soy consumption exerts an effect against prostate cancer and what type of prostate cancer it can prevent," Kurahashi concluded.