FRIDAY, March 10 (HealthDay News) -- An extract from dried papaya slows the growth of cancer cells in the laboratory, researchers report.

It's not clear if it will have the same effect on cancer in people, however.

University of Florida researcher Dr. Nam Dang and Japanese colleagues report that the papaya extract appears to affect the regulation of the body's immune system and doesn't cause side effects by harming normal cells.

The findings reflect the use of papaya by indigenous people in Australia and Vietnam, Dang, a professor of medicine, said in a news release from the university.

"Based on what I have seen and heard in a clinical setting, nobody who takes this extract experiences demonstrable toxicity; it seems like you could take it for a long time -- as long as it is effective," he said.

The researchers report that four strengths of papaya leaf extract slowed the growth of 10 types of cancer cell cultures, including cancers of the cervix, breast, liver, lung and pancreas.

The study was published in a recent issue of Journal of Ethnopharmacology.

More information

The U.S. National Cancer Institute has more on the various types of cancer.

FRIDAY, March 12 (HealthDay News) -- Patients who get a total knee replacement are usually advised to avoid high-impact sports to preserve their new body part. But a new study suggests sport participation is not only safe -- it may even help people gain better knee function.

''Initially, we though high-impact sports were terrible for the prosthesis," said Dr. Sebastien Parratte, a research collaborator at the Mayo Clinic in Rochester, Minn., and an assistant professor at the Aix-Marseille University Center for Arthritis Surgery at Hospital Sainte-Marguerite in Marseille, France.

"Our eight-year results have shown it is not the case," he said.

He is the lead author of the study, scheduled for presentation Friday at the annual meeting of the American Academy of Orthopaedic Surgeons in New Orleans.

More than a half million total knee replacements are performed annually in the United States, according to the American Academy of Orthopaedic Surgeons. Parratte and his colleagues conducted the study knowing that patients routinely ignore their doctor's advice to take it easy after receiving a knee replacement. In fact, about one of six patients engage in high-impact activities post-implantation, experts say.

Parratte's team followed 535 patients in all. A total of 218 underwent knee replacement and then performed heavy manual labor or engaged in a non-recommended sport, such as high-impact aerobics, football, soccer, baseball, jogging or power lifting. The control group of 317 patients had knee replacement but did not engage in sports that were not recommended.

The researchers evaluated the patients clinically and with X-rays. About eight years after surgery, they found no significant radiological differences and no significant differences in the implant durability between groups.

In fact, the sport group had slightly higher knee function scores than the control group.

A first comparison found that the control group had a 20 percent higher need to repeat the operation because of mechanical failure of the knee (from wear, fracture or loosening) compared to the sport group. But when they took into account other health problems such as obesity or diabetes, the sport group had a 10 percent higher risk of mechanical failure compared to the control group, but the difference wasn't statistically significant.

''The control group was more likely to have high blood pressure, obesity and diabetes," Parratte added.

He said he doesn't know why the sport group's knees held up better.

Still, the study findings are no reason to tell patients with knee replacements to exercise in a high-impact way, said Dr. Christian Christensen, an orthopedic surgeon and head of adult reconstruction at the Lexington Clinic in Lexington, Ky.

"I think it's a good study and certainly a worthwhile one," he said. "Would it encourage me to tell my patients to play football? No way."

More research is needed to evaluate what's happening, he said. It's possible that the people with the best results may be the ones engaging in high-impact sports. "People with the knees that feel great, who have excellent results,'' are perhaps the ones who can engage in the high-impact sports without ill effect, he said.

Another possibility, he said, is that the follow-up may just not be long enough, that ill effects may show up later. Christensen said he'll continue to tell his knee-replacement patients to avoid high-impact sports. "Implants aren't meant to tolerate high-impact sports," he said.

Dr. Benjamin Bengs, another expert, called the new study findings promising. It shows these devices are long-lasting, can lead to lifelong pain relief and excellent functioning and activity in patients, said Bengs, an orthopedic surgeon at Santa Monica-University of California Medical Center and Orthopaedic Hospital.

But more time and study are needed before we completely release people to all high-impact activities, he said.

''One study is not enough to change the recommendations," Parratte agreed. He plans to study the topic further.

More information

To learn more about total knee replacement, visit the American Academy of Orthopaedic Surgeons  .

MONDAY, March 8 (HealthDay News) -- A good diet and regular exercise may help the mind function better, a new study suggests.

"It looks like exercise and diet improve the range of cognitive function," said Patrick Smith, an intern in clinical neuropsychology and a member of a Duke University team reporting the finding online in the March 8 issue of Hypertension. "It helps executive function, learning and psychomotor speed."

The researchers followed 124 men and women with high blood pressure who were 52 and a minimum of 15 pounds overweight, on average.

Led by James Blumenthal, a professor of psychology and neuroscience at Duke, the study was designed primarily to determine the effect of diet and exercise on blood pressure and included people with mild to moderate high blood pressure.

The mental studies were included because "some previous data linked exercise and diet to better cognitive function," Smith said. The new results verified those findings, he noted.

A third of the participants went about eating and exercising as they usually did. Another third followed the DASH -- Dietary Approaches to Stop Hypertension -- diet, which emphasizes low-fat dairy products, fruits and vegetables, in combination with regular exercise. The final third were in a program that combined the DASH diet with a weight-management program and aerobic exercise.

Two strategies were used in the weight-management program: One centered on reducing portion size and changing habits, such as snacking. The other used an approach called appetite awareness training, which provides guidelines on how much to eat, not just what to eat.

Smith said the exercise part of the program wasn't drastic -- "workouts of 30 minutes three to four times a week, enough to put the heart up to 75 to 80 percent of its maximum rate."

To assess the effects on mental function, the participants were asked to do certain paper-and-pencil tests, such as crossing off specific digits on a page of numbers as quickly as possible.

The group that ate well and exercised regularly had an overall 30 percent improvement in mental function by the end of the four-month period, the researchers noted.

Physical activity does seem to have a direct effect on brain cells, Smith said. "There are neurochemical changes that happen with exercise, he said. There is increased production of brain-derived neurotrophic factor, which stimulates connection with other brain cells, he said, but also there is some evidence that it helps grow new brain cells."

And the combination of good eating and exercise also produced the expected physical advances. Diet-and-exercise participants lost an average of 19 pounds and lowered systolic blood pressure (the higher of the 120/80 reading) by 16 points and diastolic pressure by 10 points by the end of the four-month program.

Some experts believe the study has shortcomings, however. It's a well-done study, but one that has flaws, said Dr. Donald LaVan, a clinical associate professor of medicine at the University of Pennsylvania and a spokesman for the American Heart Association.

"Its entirely too small," LaVan said. "I would call it a keyhole study, suggestive but nothing definitive. Also, it did not have a control group to look at the effect of exercise alone. We need a bigger study with a longer duration and a control group for exercise alone."

Nothing in the study should deter anyone from exercising for the sake of the mind as well as the body, LaVan said.

"Exercise is great," he said. "But how much exercise itself contributes to mental function is not clear."

More information

Advice on physical activity is given by the American Heart Association  .

TUESDAY, March 2 (HealthDay News) -- Workplace wellness programs help employees lose weight and reduce their risk of heart disease, a new study shows.

U.S. researchers followed 757 hospital workers who took part in a voluntary 12-week, team-based wellness program that focused on diet and exercise. Data on the participants' weight, lifestyle behavior and heart disease risk factors were collected at the start of the study, at the end of the wellness program and a year after the program ended.

At the start of the study, 33 percent of participants were overweight (body mass index, or BMI, of 25 to 29.9) and 30 percent were obese (BMI of 30 or more).

The researchers found that obese participants lost the most weight -- 3 percent at 12 weeks and 0.9 percent at one year -- and were most likely to reduce their intake of dietary sugar. Overweight participants did almost as well, with an average weight loss of 2.7 percent at 12 weeks and 0.4 percent at one year.

All participants had similar improvements in levels of physical activity, along with lower cholesterol and blood pressure levels, and reduced waist circumferences at program end and at one year, the findings showed.

"Voluntary wellness programs can successfully address weight loss and lifestyle behaviors for employees in all weight categories, but more work is needed to improve long-term changes," the Massachusetts General Hospital researchers concluded.

The study was to be presented Tuesday at the American Heart Association's Nutrition, Physical Activity and Metabolism Conference in San Francisco.

Other research to be released Tuesday at the meeting found that aerobic exercise reduces levels of inflammatory markers in men with heart disease.

The Polish study included 100 men, average age 55, who'd had coronary artery bypass surgery about two months previously to treat angina pectoris -- chest pain experienced during physical activity.

The men were randomly selected to be in a control group or a group that did six weeks of exercise training, three times a week, at 60 percent to 80 percent of maximum heart rate. At the start of the study, at the end of the training period and after one year, all of the men underwent an exercise stress test and their blood was tested for levels of inflammatory markers such as C-reactive protein.

At the end of their program, the men in the training group showed significant improvement in exercise capacity and a significant decrease in inflammatory markers. This did not occur in the control group. One year later, levels of inflammatory markers among men in the training group were still significantly lower than they had been at the start of the study.

More information

The U.S. National Heart, Lung, and Blood Institute offers tips on how to prevent and control heart disease.