WEDNESDAY, April 9 (HealthDay News) -- A person who maintains aerobic fitness may delay biological aging by up to 12 years, a new analysis shows.

Jogging and other types of aerobic exercise improve the body's oxygen consumption and its use in generating energy (metabolism). However, a steady decline in maximal aerobic power begins in middle age, decreasing about 5 ml/ (kg. min) every decade, according to the information in the analysis.

When maximal aerobic power falls below about 18 ml in men and 15 ml in women, it becomes difficult to do any activity without experiencing major fatigue. A typical 60-year-old sedentary man has a maximal aerobic power of about 25 ml, nearly half of what it was at age 20.

But research shows that a long period of relatively high-intensity aerobic exercise can increase maximal aerobic power by 25 percent (about 6 ml), which equals 10 to 12 biological years.

The analysis was published online in the British Journal of Sports Medicine.

"There seems good evidence that the conservation of maximal oxygen intake increases the likelihood that the healthy elderly person will retain functional independence," said study author Dr. Roy Shephard, of the Faculty of Physical Education and Health and Department of Public Health Sciences, at the University of Toronto in Canada.

Aerobic exercise also reduces the risk of serious disease and promotes faster recovery after injury or illness. Additionally, it helps maintain muscle power, balance and coordination, which reduces the risk of falls.

More information

The U.S. Centers for Disease Control and Prevention has more about healthy aging for older adults.

TUESDAY, April 8 (HealthDay News) -- Caffeine, green tea and tart cherries may guard against multiple sclerosis, cancer and cardiovascular troubles, respectively, new research suggests.

All three findings, which confirm the healthy properties of these foods, were presented this week at the Experimental Biology 2008 meeting in San Diego.

Caffeine appears to help ward off multiple sclerosis, at least in a preliminary animal study. Mice given caffeine were 75 percent less likely to develop the animal model of MS than those not given it, said study senior author Dr. Margaret Bynoe, an assistant professor of microbiology and immunology at Cornell University School of Veterinary Medicine, in Ithaca, N.Y.

"The 25 percent who got it got mild cases," she said, although she noted the research is preliminary and the trials were in mice that had the animal model of MS.

MS is a debilitating autoimmune disease, and about 400,000 Americans are affected, according to the National Multiple Sclerosis Society. In MS, the immune system attacks the myelin, the fatty sheath that protects the nerve fibers in the central nervous system.

The myelin, as it is damaged, forms scar tissue that prevents or hinders nerve impulses from getting through, leading to a variety of symptoms such as numbness in the limbs or loss of vision. Treatments include medications, physical therapy and the use of assistive devices.

Why does caffeine help?

Caffeine is known to block a compound called adenosine. "Inhibiting adenosine prevents the infiltration of lymphocytes [a type of white blood cell involved in immune system response] into the central nervous system," Bynoe explained. "If the lymphocytes cannot get in, you cannot get the inflammation characteristic of MS. The inflammatory response is what causes the damage to the myelin covering the nerve cells."

Bynoe believes her team is the first to demonstrate this mechanism.

In the animals given caffeine, the equivalent of 6 to 8 cups of coffee a day for humans, "there was a reduction in the inflammation, the pathology, a reduction in the brain pathology," Bynoe said.

Adenosine plays a crucial role in many body processes, including energy transfer, the promotion of sleep and the suppression of arousal. On the cellular level, caffeine can bind to the same receptors as adenosine, preventing the adenosine from attaching to cells in the central nervous system.

The new finding is "certainly deserving of further study," said Dr. John Richert, executive vice president of research and clinical programs for the National Multiple Sclerosis Society.

But he had a caveat: "It's important to note that EAE [the animal model of MS] is not MS, and many potential treatments that have worked on EAE have not worked on MS."

In a second study, green tea extracts, already known for their antioxidant properties that help protect against cancer, had anticancer effects on cancer cell lines in the laboratory.

Scientists wanted to find out whether undigested extracts of black and green tea cancer-fighting compounds, known as catechins, would have more anticancer activity against the cancer cells than digested extracts, said study author Joshua Bomser, an associate professor of nutrition at Ohio State University.

"We set out to look at the effect of digestion, subjecting tea extracts to simulated digestion in the lab setting and looking for changes in biological activity between digested and undigested samples exposed to cancer cell lines," Bomser said.

In the laboratory study, they found that whether the extracts were digested or not and the type of tea affected the anticancer activity, as did the type of cancer cell.

"For the black tea, digestion didn't have much of an impact on colon cancer activity," he said. However, the anticancer effect of the green tea on the colon cancer cells was about 50 percent less when the extracts were digested. And the gastric cancer cells, overall, were less sensitive to the anticancer effects than were the colon cancer cells.

More study is needed, Bomser said, but, "If catechins [such as EGCG] are in fact the primary compounds responsible for anticancer activity rather than the breakdown products, you want to maintain and absorb as many catechins [as possible]," he said.

In a previous study, one researcher on the current team found that one way to protect the catechins from breaking down was to add lemon or vitamin C to tea.

The tea research is interesting, and the results not unexpected, said Tom Gasiewicz, chairman of the department of environmental medicine at the University of Rochester Medical Center, who has studied tea's health benefits extensively.

"To me, it's not unexpected that digestion would be accompanied by loss of [anticancer] activity," he said. "The bottom line is, we still don't know what concentrations are effective and have anticancer activity in other organs besides the GI tract."

Yet another team of researchers found in animal studies that tart cherries help reduce inflammation, in turn potentially reducing the risk of getting heart disease and type 2 diabetes. Inflammation is a normal process that fights infection or injury, but when it's chronic, it increases the risk for heart problems and diabetes.

The cherries contain antioxidants called anthocyanins, believed to give them their anti-inflammatory powers. The cherry study was funded by the Cherry Marketing Institute, but the institute had no other role in the study, conducted at the University of Michigan.

Compounds in the cherries, said Gasiewicz, may work in similar ways as the tea extracts.

More information

To learn more about multiple sclerosis, visit the National Multiple Sclerosis Society  .

THURSDAY, Feb. 28 (HealthDay News) -- A concentrated extract of freeze-dried broccoli sprouts reduced bladder tumor development by more than half in laboratory rats, according to a new study.

Researchers said the finding supports human epidemiologic studies indicating that eating broccoli and other cruciferous vegetables is associated with a lower risk of bladder cancer.

"Although this is an animal study, it provides potent evidence that eating vegetables is beneficial in bladder cancer prevention," senior investigator Dr. Yuesheng Zhang, a professor of oncology at Roswell Park Cancer Institute, said in a prepared statement.

It's believed that the protective effect of broccoli and other cruciferous vegetables -- such as cabbage, kale, and collard greens -- is at least partly due to isothyiocyanates (ITCs), a group of phytochemicals with anti-cancer properties.

"The bladder is particularly responsive to this group of natural chemicals," Zhang said.

He and his colleagues tested the freeze-dried broccoli sprout extract in rats given a chemical that induces bladder cancer. One group of rats did not receive the extract, while two other groups of rats were given either a low or high dose of the extract in their food, beginning two weeks before they received the cancer-causing chemical.

An average of about two tumors developed in 96 percent of the rats that didn't receive the extract, compared to an average of 1.39 tumors in 74 percent of the rats that received a low dose of the extract, and an average of .46 tumors in 38 percent of the rats that received a high dose of the extract.

The findings were published in the March 1 issue of the journal Cancer Research.

Broccoli sprouts have about 30 times more ITCs than mature broccoli, and the sprout extract used in this study has about 600 times as much. But Zhang said humans at risk for bladder cancer likely wouldn't have to eat large amounts of broccoli sprouts to achieve protective effects.

"Epidemiologic studies have shown that dietary ITCs and cruciferous vegetable intake are inversely associated with bladder cancer risk in humans. It is possible that ITC doses much lower than those given to the rats in this study may be adequate for bladder cancer prevention," he said.

More information

The American Urological Association has more about bladder cancer  .

THURSDAY, Jan. 10 (HealthDay News) -- Chewing too much sugar-free gum containing the artificial sweetener sorbitol can cause diarrhea leading to potentially dangerous weight loss, German physicians report.

The cases of a 21-year-old woman who suffered diarrhea that caused her to lose about 24 pounds and a 46-year-man who lost approximately 46 pounds because of diarrhea were mysteries until the doctors asked about their chewing habits.

Both were found to be consuming a lot of sorbitol, primarily from chewing gum, said Dr. Herbert Lochs, professor of internal medicine at Humboldt University in Berlin, and one author of the report.

The answer solved the mystery, since heavy consumption of sorbitol has long been associated with a risk of diarrhea, Lochs said.

"There have been case reports earlier, as far back as the 1980s," he said. "These were people who did not have malabsorbtion and malnutrition."

The risk is not as great for consumers in the United States, said Dr. Bret Lashner, a gastroenterologist who is professor of medicine at the Cleveland Clinic, since sorbitol is rarely used in chewing gum here. The preferred artificial sweetener for chewing gum and candy here is aspartame, sold as NutraSweet, Lashner said.

"NutraSweet and saccharin are safe," he said. "Sorbitol is not safe. People should look at the labels to see if they are getting something with sorbitol."

The new findings are published in the Jan. 12 issue of the British Medical Journal.

The two people seen by Lochs and Dr. Juergen Bauditz, a gastroenterologist at the University of Berlin, were consuming sorbitol-containing chewing gum with gusto -- 15 to 20 sticks a day, containing up to 20 grams of the sweetener, for the woman, and 20 sticks of gum and up to 200 grams a day of artificially sweetened candy for the man.

Both were visiting the bathroom 10 or more times a day, and both underwent extensive laboratory testing and physical examinations that left the cause unknown -- until the doctors asked about their chewing habits.

Mystery solved. After the woman stopped chewing gum, she was discharged from the hospital, with just one bowel movement per day. A year later, she had regained 15 pounds. It was the same story for the man -- one bowel movement a day and a weight gain of 11 pounds six months after the gum-chewing ended.

How much sorbitol is safe? It's hard to say, Lochs said. "We thought of trying in a group of healthy people to determine the limit in a majority of cases, but this has not been done yet," he said.

It's not a big issue for the majority of European gum-chewers, Lochs said. "If they don't have symptoms, they should not worry," he said. "If they have diarrhea, they should not chew gum for a while so that the cause can be diagnosed."

American gum-chewers who have diarrhea can mention the habit to their physicians, Lashner said. "Certainly, all doctors are aware of this," he said of the sorbitol connection.

The U.S. Food and Drug Administration says the danger of diarrhea is associated with consumption of more than 50 grams of sorbitol daily.

More information

The Calorie Control Council   describes the advantages and disadvantages of sorbitol.