preventing prostate cancer

columnist: Paul Sieber, MD

The diagnosis and treatment of prostate cancer changed dramatically when the blood test known as PSA (prostate specific antigen) became available as a screening tool. As a result, we can now detect prostate cancer at an earlier stage; but wouldn't it be even better if we could prevent prostate cancer altogether?

Japanese men die of prostate cancer at one-tenth the rate of Americans. In addition, within one generation of moving to North America, their risk of dying of prostate cancer is equal to that of their American counterparts. Obviously, diet plays some role in this phenomenon but studies to verify which item or group of items is responsible for such changes are very complex. Actually, picking out and studying any single dietary item that might be cancer preventive is probably too simplistic an approach and we should all exercise care in using this kind of thinking.

For an example of this reasoning:

I read that Japanese diets are very rich in soy; therefore, if I eat soy products, I am protected against prostate cancer.

Many factors in the Japanese diet appear to protect men from prostate cancer:

Soy and Lignans
The Japanese diet is rich in soy. Soy acts as a phytoestrogen, which is a naturally occurring plant substance that affects the body similarly to the natural estrogen found in humans. Other foods with similar properties, such as flaxseeds and lentil beans, are rich sources of lignans, another class of plant estrogens. Laboratory studies have suggested numerous ways these natural estrogens may inhibit prostate cancer.
Tea consumption is high.
Green tea, in particular, is rich in substances known as polyphenols. All teas contain polyphenols; but green tea, which is consumed in large amounts in Japan, is particularly rich in these compounds. Medical science is currently intrigued enough by the preventive potential of green tea that it warranted an entire chapter in the 2002 Urologic Clinics of North America’s feature on Complementary Medicine.
Fat consumption is low.
A high fat diet is associated with an increased rate of prostate cancer but also with increases in colon and breast cancers. The American Cancer Society, in its last update on Cancer and Diet, highlighted the risks associated with a high fat diet and emphasized the importance of exercise in addition to dietary considerations for cancer prevention.

The above list clearly shows that numerous variables in the Japanese diet affect prostate cancer rates, and that no single factor is the whole answer to prevention.

What is my take on all this?

Exercise more
Eat a Low-fat diet
Increase consumption of fresh fruits and vegetables
Drink more green Tea
Take Extra vitamins and minerals (any good vitamin with minerals will do).

Use the letters in bold to remember this on a daily basis (ELITE.) It would also be good to read Mark Moyad's book, The ABC's of Nutrition & Supplements for Prostate Cancer. This is an excellent overview by a recognized expert in the field and I highly recommend it.

In addition to the studies underway on dietary changes that may be helpful, a variety of studies is ongoing in the field of chemoprevention of prostate cancer. Chemoprevention means taking medicines to prevent cancer. At least four large trials are now underway:

The Select Trial involves the use of vitamin E and selenium as preventives. It is well accepted among medical experts that men with low blood levels of selenium are at higher risk. Can we prevent prostate cancer with this simple supplement?
The second trial focuses on the use of a drug that blocks the conversion of testosterone to dihydrotestosterone. This is similar to the effect that soy and other phytoestrogens exert over this conversion.
The third study involves the use of a COX 2 inhibitor to prevent prostate cancer. It has been suggested for some time that men who regularly take aspirin or ibuprofen have less colon and prostate cancer. This study is designed to test the science behind this observation.
A fourth study is looking at the use of a selective estrogen receptor modulator to see if it can reverse High Grade PIN (prostatic intraepithelial neoplasia, a pre-malignant prostate condition.)

In summary, a number of ongoing trials look very promising in the realm of cancer prevention. The results of these studies plus our greater awareness of preventive dietary factors may put prostate cancer prevention within our grasp in the near future.

References:

CA Cancer J Clin 2002 Mar-Apr; 52(2): 92-119.

Moyad, Mark, The ABC's of Nutrition & Supplements for Prostate Cancer: Sleeping Bear Press, 2000.

Urologic Clinics of North America, Feb 2002 29.

January 2003