WEDNESDAY, Jan. 23 (HealthDay News) -- Even a moderate amount of exercise can dramatically prolong a man's life, new research on middle-aged and elderly American veterans reveals.

The government-sponsored analysis -- the largest such study ever -- found that a regimen of brisk walking 30 minutes a day at least four to six days a week was enough to halve the risk of premature death from all causes.

"As you increase your ability to exercise -- increase your fitness -- you are decreasing in a step-wise fashion the risk of death," said study author Peter Kokkinos, director of the exercise testing and research lab in the cardiology department of the Veterans Affairs Medical Center in Washington, D.C.

That conclusion applies more or less equally to white and black men, regardless of their prior history of cardiovascular disease. According to Kokkinos, that may be because the veterans in the study all received the same level of care, regardless of income.

This evened the playing field, he said, giving him "great confidence" in the results, which will be published in the Feb. 5 issue of Circulation and were released online Jan. 22.

In the study, Kokkinos and his team reviewed information gathered by the VA from 15,660 black and white male patients treated either in Palo Alto, Calif., or in Washington, D.C.

The men ranged in age from 47 to 71 and had been referred to a VA medical facility for a clinically prescribed treadmill exercise test sometime between 1983 and 2006. All participants were asked to run until fatigued, at which point the researchers recorded the total amount of energy expended and oxygen consumed.

The numbers were then crunched into "metabolic equivalents," or METS. In turn, the researchers graded the fitness of each man according to his MET score, ranging from "low-fit" (below 5 METS) to "very-high fit" (above 10 METS).

By tracking fatalities through June 2007, Kokkinos and his colleagues found that for both black and white men it was their fitness level, rather than their age, blood pressure or body-mass index, that was most strongly linked to their future risk for death.

Every extra point in MET conferred a 14 percent reduction in the risk for death among black men, and a 12 percent reduction among whites. Among all participants, those categorized as "moderately fit" (5 to 7 METS) had about a 20 percent lower risk for death than "low-fit" men. "High-fit" men (7 to 10 METS) had a 50 percent lower risk, while the "very high fit" (10 METS or higher) cut their odds of an early death by 70 percent.

"The point is, it takes relatively little exercise to achieve the benefit we found," noted Kokkinos. "Approximately two to three hours per week of brisk walking per week. That's just 120 to 200 minutes per week. And this can be split up throughout the week, and throughout the day. So it's doable in the real world."

Alice H. Lichtenstein, director of the Cardiovascular Nutrition Lab at Tufts University's USDA Human Nutrition Research Center in Boston, agreed.

"What this finding demonstrates is that levels of physical activity that should be achievable by anyone can have a real benefit with respect to risk reduction," she said.

"What's really important to understand is that you don't need special clothes, special memberships, special equipment," added Lichtenstein, former chairwoman of the American Heart Association's nutrition committee. "It's something everyone can engage in. And although we don't know from this research that this applies to women as well, there's no reason to suspect that it wouldn't."

More information

There's more on physical fitness at the U.S. Centers for Disease Control and Prevention.

FRIDAY, Jan. 18 (HealthDay News) -- A mislabeled over-the-counter product described as a dietary supplement appears to have contributed to the development of aggressive prostate cancer in two men, researchers report.

"There were things on the label that were not in the product, and components in the product that were not on the label," said study author Dr. Shahrokh Shariat, chief resident in urology at the University of Texas Southwestern Medical Center.

The men developed rapidly advancing prostate cancer within months of using the dietary supplement, which was advertised as something that would increase stamina and muscle mass, and strengthen the heart, Shariat said. One of the men has died and the other "is in the final stages of the disease and probably will die within months," he said.

The findings were published in the current issue of Clinical Cancer Research.

The report did not name the product or its manufacturer, at the request of the journal editors who were fearful of "possible legal implications," Shariat said. The U.S. Food and Drug Administration, notified of the findings, issued a warning letter to the manufacturer, which led to removal of the product from the market, he said.

An analysis of the product found that it contained both testosterone and estradiol, a sex hormone, he said, and laboratory tests on human prostate cancer cells found it to be a more potent stimulator of cancer cell growth than testosterone alone.

"There are a lot of such products on the market in an unregulated fashion, because androgen supplements are the fastest-growing part of the supplement business," Shariat said. "There are dangerous ones out there, and people should be aware of it."

But Andrew Shao, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, which represents the supplement industry, said the study "hasn't established any causal link here. The findings are interesting, but don't draw us any closer to any conclusion because of work done in the test tube."

Acknowledging that "any time you put something in your body you want to be cautious about it," Shao maintained that "the overwhelming majority of dietary supplements are well-made and safe, the scientific evidence supports that."

At the same time, people should be aware that "dietary supplements are not drugs and they shouldn't look forever for weight loss or performance benefit or some magic bullet when they take them," he said.

Michael McGuffin, president of the American Herbal Products Association, criticized the decision not to identify the product. "The failure to identify the exact product means that consumers who still have it in their homes are at risk," he said.

It's also a mistake to call the product a dietary supplement, McGuffin said. "I'll tell you what the FDA calls these," he said. "They call them illegal drugs. The fact that someone found one of these should not implicate every herbal product and every vitamin product as somehow being adulterated with drugs or not containing what it should. That's just not true."

Andrew Vickers, a research methodologist in the epidemiology department at Memorial Sloan-Kettering Cancer Center in New York City, called the report "very well-written and very compelling."

Both men in the report originally had low levels of prostate-specific antigen, a signal for prostate cancer "and then suddenly presented with widespread cancer within six months, which is unusual," Vickers said. "Clearly, these are very unusual cases, and there is appropriate concern with this agent."

The substance taken by the men apparently was one of a number of products being advertised as improving male sexual health, Vickers said. "They are presumably very widely used, but we really don't know what they do," he said.

When you do self-diagnosis and self-treatment, you should be cautious in general and should be in contact with your health professional, Shao said.

More information

To learn more about prostate cancer, visit the U.S. National Cancer Institute.

MONDAY, Jan. 14 (HealthDay News) -- Low testosterone levels may boost the risk of fractures for men over 60, an Australian study finds.

The researchers tracked 609 men (average age 72.6) between 1989 and late 2005.

The University of Sydney researchers collected information about the men's bone mineral density, lifestyle habits, and blood levels of testosterone and estradiol (an estrogen).

During the study period, 113 men suffered low-trauma fractures (caused by a fall from standing height or lower). Of those men, 25 suffered multiple fractures.

There were a total of 149 fractures, including 55 vertebral, 27 hip, 28 rib, six wrist and 16 upper- and 17 lower-extremity fractures.

The risk of fracture was much higher among men with low testosterone levels, the team found.

Even after adjusting for a variety of potential risk factors, low blood levels of the two hormones "were associated with overall fracture risk," the study authors concluded. Fracture risk was associated "particularly with hip and non-vertebral fractures," they noted.

The findings are published in the Jan. 14 issue of the journal Archives of Internal Medicine.

"While testosterone may affect fracture risk via skeletal and non-skeletal mechanisms, the present findings suggest that measurement of [blood] testosterone provides additional clinical information for the assessment of fracture risk in elderly men," the researchers wrote.

More information

The U.S. National Institute on Aging has more about falls and fractures  .