A new study suggests that men who get moderate amounts of exercise regularly may reduce their risk of prostate cancer, including the type consisting of aggressive, fast-growing tumors.

The study, published in the November 2009 issue of Journal of Urology, showed prostate cancer was less likely to be diagnosed in men who got exercise regularly than those who led a sedentary lifestyle.

Dr. Stephen J. Freedland and a team of his colleagues of the Duke University Prostate Center and the VA Medical Center in Durham, North Carolina analyzed data from 190 men who underwent biopsies for suspected prostate cancer and found the association.

They found that those patients who exercised moderately, or those who engaged in three to six hours of walking each week, were two-thirds less likely to be diagnosed with prostate cancer than their sedentary counterparts.

Of 111 men who followed a sedentary lifestyle in the study, about 50 percent were diagnosed with the disease compared to 27 percent of those who exercised to a degree equivalent to three to six hours of walking each week.

The researchers also found that men who got the amount of exercise equivalent to one to three hours of walking each week were 86 percent less likely to develop an aggressive form of the cancer.

Of the men diagnosed with prostate cancer, aggressive cancer was found in 51 percent of those who lived a sedentary life and only 22 percent in those who were physically active - getting the equivalent of one to three hours of walking every week.

The study found an association between exercise and reduced risk of prostate cancer. But the results do not prove that exercise is the cause for the reduction in the male reproductive cancer; however, the possibility cannot be excluded either.

Exercise or being physically active has been linked to a reduced risk of cancer in general, not just prostate cancer. One possibility is that those who exercise may follow a healthy lifestyle including a healthy diet.

However, exercise by itself may potentially have a protective effect against prostate cancer and possibly other types of cancer as well.

To say the least, it has been known that exercise lowers blood levels of sexual hormones like testosterone and others that are known to promote prostate cancer growth. Exercise can also boost immunity and the body's anti-oxidation mechanisms, which may help reduce odds for men to acquire prostate cancer.

A recent study published on Oct 27, 2009 in the online British Journal of Cancer, also suggests that being physically active may help reduce risk of prostate cancer.

The study, led by N. Orsini from Karolinska Institutet in Stockholm, Sweden and colleagues found an inverse association between physical activity, such as walking or bicycling, and reduced risk of prostate cancer.

Orsini and colleagues analyzed data from a cohort of 45,887 men aged 45 - 79 years; the researchers followed them between January 1998 and December 2007, checking for prostate cancer incidence. They also tested the patients between 1998 and December 2006 for its subtypes and for fatal prostate cancer.

During the follow-ups, 2735 cases of prostate cancer and 190 cases of fatal prostate cancer were recorded.

The researchers observed prostate cancer incidence in the top quartile of lifetime total physical activity was decreased by 16%, compared with that in the bottom quartile. A similar inverse association was also found between average lifetime work or occupational activity and walking or bicycling duration and the risk of prostate cancer.

Compared with those who were required to sit for the most of their workday, men who sit only half of the time experienced a 20% reduced risk.

For every 30 minutes per day increment of lifetime walking or bicycling in the range of 30 to 120 minutes per day, the risk for total prostate cancer decreased by 7 percent; for localized prostate cancer by 8 percent and for advanced prostate cancer by 12 percent.

An estimated 192,280 men in the United States will be diagnosed with prostate cancer in 2009. The disease is expected to kill 27,360 men in the country this year, according to the National Cancer Institute.