Preventing Prostate Cancer
You are what you eat! An old adage, yet true as far as the risk of developing certain cancers is concerned. Environmental factors are clearly involved in the development of both prostate and breast cancers and the risk is considerable.
In a recent review of the effects of evolution and diet on the development of species specific cancers in Urology, Donald S. Coffey of the Johns Hopkins Hospital, found a close relationship between the development of the Western-type diet with its increased fat intake, obesity, and burned food processing, and the development of hormonally sensitive cancers like prostate and breast.
Evolution indicates that the prostate and breast appeared about the same time, 65 million years ago, with the appearance of mammals. All mammals have a prostate, the gland which makes semen, but the presence of seminal vesicles, which store semen, is determined by diet. Species which eat meat do not have seminal vesicles, with the exception of man, but man's dietary changes occurred recently in evolutionary time.
Species Specificity of Prostate Cancer
There is no other aging animal at risk for prostate cancer except the dog. Man evolved about 150,000 years ago, but it was only in the last 10 to 15 thousand years ago that humans and dogs, which were domesticated, altered their diet and became more meat oriented. In contrast, the closest existing primate to humans, the pigmy chimpanzee (the bonobo) exists on a diet entirely of fruit and fresh vegetables. Current epidemiological evidence suggests that if we are to prevent prostate and breast cancers, we should return to the original diets of our ancestors.
The incidence and age adjusted mortality of both prostate and breast cancers is about 10x lower in Asian countries. When Asians move to this country their incidence of prostate and breast cancer slowly approaches the levels seen in the native population. This implicates environmental factors, most obvious of which is diet, but a detailed explanation is not yet available.
The risks factors for both prostate and breast cancers are similar including a lower risk associated with high intake of fruits, vegetables, fiber and soy products and a higher risk associated with increased intake of red meat, animal fats, dairy products, steroid exposure, and body mass.
Similarities Between Human Prostate and Breast Cancer
Many similarities exist between these two glands in their function, tumor incidence, and mortality rates, which correlate in more than one country. Both tumors require the presence of the reproductive glands for development and they are both sensitive to hormonal manipulation. Estrogen, androgen and progesterone receptors are found in both glands. The occurrence of prostate cancer correlates most significantly with the occurrence of breast cancers in many countries with cancer registries.
Androgens and estrogens play a critical role in breast and prostate growth. It is known that androgens suppress and estrogens induce breast formation in both males and females. It is well known that androgens are involved in the development and maintenance of male sex glands, like the prostate. Studies on the effects of hormones on the dog prostate at Johns Hopkins noted that estrogens amplify the effects of androgens on prostate growth about 4-fold. This effect is found with a specific metabolite of testosterone (dihydrotestosterone), but not with testosterone itself. It is believed that changing androgen and estrogen levels, which may occur with aging, may promote abnormal growth of the prostate.
Estrogens and Prostatitis
The role of estrogens on prostate growth is an exceedingly complex one. Early exposure in the neonatal period, called imprinting, can permanently reduce the size of the prostate and its ability to respond to androgens later in life. However, if estrogens are administered later in life, they have different effects ranging from inhibitory to stimulating prostate growth. They can also induce a marked inflammatory process of unknown origin. In the laboratory, the same kind of inflammation can be induced in rodents on long-term soy-free diets, and adding soy to the diet can reverse this trend. This could be related to the phytoestrogens in the soy that act as weak estrogens or antiestrogens. Soy also has an antioxidant effect.
Can diet affect the development of prostate cancer?
It is recognized that diet seems to have had an impact on the development of secondary sex characteristics in that mammals which eat meat have only a prostate gland, while mammals which are herbivores have both a prostate gland and seminal vesicles, which store the seminal fluid produced in the prostate. Humans appear to be an exception to this rule. However, this can be explained by the fact that humans evolved from a common ape ancestor (mostly herbivores) about 7 million years ago, and only in the last 10-15,000 years of human evolution has the focus of the diet changed towards meat with its higher caloric intake. Our closest relative, the pigmy chimpanzee has a diet of mostly fruits and vegetables. Humans evolved from a common ancestor to its present form in as little as 150,000 years, while the changes in the diet took place at a much higher rate, with which biological evolution could not keep pace. It is interesting to note that while prostate cancer is quite prevalent, seminal vesicle cancer is almost non-existent.
How does diet affect cancer development?
The relation of fat intake and cancer development has been proposed with compelling evidence. This is a complex issue due the variety of fats in the diet and the myriad of host related factors. Fats can alter hormonal status. Fat cells are a major source of estrogen precursors (primarily androgens), which then become metabolized into estrogens. This can alter the estrogen to androgen ratio often implicated in both abnormal prostate growth and as a risk factor in breast cancer development. It seems self-evident that the phytoestrogens that appear in our food sources have the ability to perturb the hormonal balance.
It seems that form an evolutionary point of view humans were not selected to eat the way Western diet has evolved to include meat, fat, dairy products, processed and cooked meats, along with low fruit, fiber intake, and a sedentary life-style. The suggestions of the National Cancer Institute and the American Cancer Society of how we might reduce our chance of getting prostate and breast cancer involve dietary changes resembling our earlier diet of more fruits and a variety of fresh vegetables; increased fiber and less sugar; decreased intake of red meat, animal fats and processed and cooked meats; substituting fish as a source of protein with its beneficial fish oils; decrease intake of dietary products as well as decreasing weight and increasing aerobic exercise.
It is easy to see how we are what we eat. It is often said that to live a healthy life we have to eat less. To live a long life we also have to pay attention to what we eat.
Reprinted with permission from Dialog Medical, dialogmedical.com.
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