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WEDNESDAY, Aug. 6 (HealthDay News) -- Short-duration stretching before exercise temporarily improves range of joint motion and doesn't weaken muscles, says new research that fuels the debate about whether stretching before exercise reduces muscle strength and performance.

In this study, moderately active, non-athlete participants did two, four and eight-minute sessions of lower leg and ankle stretching. The participants' exercise performance was assessed before and immediately after, and also 10, 20 and 30 minutes after stretching.

The stretching didn't cause any changes in muscle strength, but did improve range of motion of the ankle joint. The findings were published in the August issue of Medicine & Science in Sports & Exercise.

"In moderately active individuals, short durations of stretching seem to temporarily improve flexibility without the detrimental strength losses that have been previously reported," study author Eric Ryan said in an American College of Sports Medicine news release.

"Pre-competition stretching became controversial due to what has been reported as decreases in performance, however, future research still needs to determine how these stretching exercises may impact athletes," Ryan said.

"Durations of stretching at or less than eight minutes may not significantly alter lower-leg strength," study co-author Joel T. Cramer said in the news release. "Our findings, in conjunction with previous studies, suggest that for these muscles, there may be a 'threshold' of stretching between eight and 10 minutes that would be necessary to decrease muscle strength."

More information

The U.S. Centers for Disease Control and Prevention has more about physical fitness.

TUESDAY, Aug. 5 (HealthDay News) -- Fish may be brain food after all -- not making you smarter, as your grandmother said, but by lowering the risk of cognitive decline and stroke as you get older, according to a new study.

The benefit appears to come from fish rich in omega-3 fatty acids. In fact, eating fish such as tuna three times a week can reduce the risk of dementia or stroke by 26 percent, the study found.

"Older adults who consumed tuna or other baked or broiled fish had a lower risk of having abnormalities on brain MRIs," said study co-author Dr. David Siscovick, a professor of medicine and epidemiology at the University of Washington Cardiovascular Health Research Unit.

For the study, Siscovick and his colleagues looked for small vessel disease, which is known to lead to cognitive impairment, dementia and stroke. "This study looked at whether or not different types of fish intake were related to structural changes in the brain," he said.

The researchers collected data on 3,660 men and women 65 and older. They underwent brain scans to detect what doctors call silent brain infarcts, which are small lesions in the brain that are associated with the loss of thinking skills, dementia or stroke. These lesions are found in about 20 percent of otherwise healthy older people, and they're only detectable on brain scans, the researchers said.

Five years later, the researchers repeated the scans on 2,313 of the original study participants. In addition, the participants answered questions about the amount of fish in their diet.

Siscovick's team found that people who ate tuna that was broiled or baked, or other fish high in omega-3 fatty acids, three or more times a week, had almost a 26 percent lower risk of silent brain infarcts compared with people who didn't eat fish regularly. In fact, eating just one serving of fish a week reduced the risk by 13 percent.

What's more, people who ate fish regularly had fewer abnormal changes in their brain's white matter, the researchers found. Abnormal changes in white matter and small brain infarcts are signs of small vessel disease, Siscovick said.

But how the fish was cooked appeared to be important, according to the findings, which were published in the Aug. 5 issue of the journal Neurology.

"We didn't find any association with eating fried fish and having lower rates of these abnormalities," Siscovick said, adding that fish rich in omega-3 fatty acids aren't typically fried.

Besides tuna, fish rich in omega-3 fatty acids include salmon, mackerel, herring, sardines and anchovies.

"The message to the public is to eat more fish that has higher levels of omega-3 fatty acids, rather than eating more fried fish," Siscovick said.

Greg M. Cole, associate director of the Alzheimer's Disease Research Center at the UCLA David Geffen School of Medicine, said that fish consumption -- along with other components of a healthy diet -- may explain the study's findings.

The same people with higher fish intake also had other dietary differences, such as higher intake of fruits and vegetables, said Cole, who's also a neuroscientist at the Greater Los Angeles VA Healthcare System. "This may be related to the more than one factor, analogous to the Mediterranean diet that is also rich in fish and fruits and vegetables and has been frequently associated with less cardiovascular risk," he said.

Eating fatty fish has also been associated with reduced risk of Alzheimer's disease, Cole added.

More information

For more on the benefits of eating fish rich in omega-3 fatty acids, visit the American Heart Association  .

THURSDAY, July 3 (HealthDay News) -- A key compound in red wine known as resveratrol appears to protect against many of the health ravages associated with growing old, new animal research reveals.

"It's very hard to extrapolate from this finding to comment on the benefits of red wine directly, because red wine has many other compounds besides resveratrol, including ethanol, which have very active biological effects," noted study author Rafael de Cabo, unit chief of the laboratory of experimental gerontology at the National Institute on Aging in Baltimore.

"But red wine is a good source of resveratrol," he added. "And, in this mouse study, we have shown that this particular compound has very strong positive effects on preventing cardiovascular disease, reducing heart inflammation, keeping bone health in terms of structure and function, and maintaining loco-motor and balance activity. So, if these effects translate into humans, it will have a very good impact on the standard of human health."

De Cabo conducted the research with David A. Sinclair, of Harvard Medical School. Their team is publishing its findings in the July 3 online issue of Cell Metabolism.

Daily consumption of the compound -- also found in the skin of grapes and the crust of peanuts and walnuts -- broadly improved the long-term quality of life of middle-aged mice, although most mice did not end up living longer.

Nevertheless, the age-defying health benefits of resveratrol closely mimicked those previously associated with rigorous calorie-restricted diets -- raising hopes for simpler and easier means by which to help fight off age-related decline.

The authors noted that prior research has touted the healthy benefits associated with daily caloric restriction of between 30 percent and 50 percent below average, as well as with fasting every other day. Such diets have been linked to a reduction in the risk for age-associated disease and stress, alongside a slowing of age-related functional decline.

"But we can't have half of America going permanently on a diet," said de Cabo. "We just can't do it. It's not practical, and it's not going to happen."

Alternatively, he and his colleagues began to explore the potential of resveratrol -- a compound that has already been shown to extend the lives of yeast, worms, flies and fish.

In initial studies, the team found that consuming the compound did improve the health and survival of obese mice -- despite consuming a high-calorie diet.

To follow up, the researchers now compared the health and life spans of middle-age mice given either a standard diet or a calorie-restricted diet, with or without high or low daily dosages of resveratrol.

De Cabo and his colleagues found that resveratrol had the same positive impact on mouse livers, muscles, hearts and bones as calorie restriction alone.

Regardless of dietary protocol, the general health and vigor of mice on a long-term regimen (approximately one year) of resveratrol improved overall, without apparent side effects. However, only mice consuming resveratrol alongside a high-calorie diet were found to actually live longer.

"This certainly is consistent with previous studies," noted Dr. Edward A. Fisher, a professor of cardiovascular medicine and cell biology at the New York University School of Medicine in New York City. "So, I'm not surprised by the finding."

"But by looking at specific outcomes in specific tissues, this work is certainly more detailed and rigorous," he added. "And it further supports the hypothesis that this compound staves off the effects of aging."

On another food front, researchers out of Athens Medical School in Greece have published a new study in the current issue of the European Journal of Cardiovascular Prevention and Rehabilitation suggesting that drinking green tea is good for the heart.

Consuming green tea, the authors noted, appeared to quickly improve the function of cells that line the circulatory system, known as endothelial cells. Because endothelial cell damage is a key contributor to the onset of atherosclerosis, boosting the performance of such cells could help stave off heart disease.

More information

For additional information on health benefits associated with red wine and resveratrol, visit the Mayo Clinic  .

THURSDAY, June 5 (HealthDay News) -- "You are what you eat" is a frustrating truism familiar to the diet-conscious choosing between carrots and carrot cake. But new research suggests that weight control isn't just a matter of what you put in your mouth, but also how the nervous system is genetically predisposed to process fat.

The theory is based on research with worms that suggests that the brain chemical serotonin -- long known for its appetite control properties -- relies on independent but coordinated nerve pathways to drive not only hunger, but also fat metabolism.

"I want to be clear that there is absolutely nothing in our study that says that good nutrition and activity is not important or not good for you," said study lead author Kaveh Ashrafi, an assistant professor in the department of physiology and the Diabetes Center at the University of California, San Francisco. "But that said, I think that it is important to realize that there is a major contributing factor to body weight that is genetic."

The new findings, based on research with so-called C. elegans worms, is published in the June issue of the journal Cell Metabolism.

Ashrafi and his colleagues noted that, while the worms are obviously smaller and simpler organisms than humans, they are molecularly very close, having about 20,000 genes to a human's 25,000 genes. And both humans and worms have genetically evolved to protect and conserve energy depending on food availability, the researchers said.

Because of such similarities, the researchers attempted to partially deconstruct the worm's nervous system by tracking cell receptors that serotonin connects with when prompting feeding in worms. Then they tracked only those pathways that serotonin activates when regulating fat control.

The researchers were surprised to find that serotonin-directed feeding and fat-burning pathways are, in fact, two separate channels, each operating in a complementary but "molecularly disassociated" fashion.

Also, the worms' feeding behavior appeared to be dependent on their nervous system's shifting gauge -- both genetically and environmentally triggered -- as to how much food was available for consumption. When food was scarce, fat reserves piled up as the worms' metabolic rate adjusted to conserve energy and save fat for a rainy day.

Comparisons to humans are obviously limited by appreciable systemic differences. For example, the authors noted that high levels of serotonin appear to lead to fat loss in the worms, as is the case with humans. But, while in worms, serotonin boosts lead to increased eating and fat loss, in humans, serotonin bumps are known to prompt less eating, which in turn leads to a decrease in fat tissue.

Nevertheless, Ashrafi and his team concluded that their analysis of worms offers clear cross-species indications that whether one is fat or thin is not a pure calculation of caloric intake but rather a complex result of multiple nervous system calculations based on both genetic and environmental factors.

"We don't know the real answer yet," Ashrafi said. "We are just beginning to scratch the surface. But I think chances are pretty good that this is something likely to be operating in most organisms. And, the fact is that the consumption of food is a very dynamic process, with a strong genetic component that clearly goes beyond the question of diet."

Alice H. Lichtenstein, director of the Cardiovascular Nutrition Lab at Tufts University's USDA Human Nutrition Research Center in Boston, cautioned that attributing weight and fat gain to environmental or genetic sources can be tricky and complicated.

"We clearly know that the nervous system will impact on food intake, and the exploration of genetic predispositions toward weight gain and obesity is not new," she said. "In fact, there has been an immense amount of effort over a long period of time devoted toward sorting this out."

"This study probably adds a new dimension to the ongoing work," added Lichtenstein, immediate past chair of the American Heart Association's nutrition committee. "But the issue is really very, very complex. So, while I think it's important to bring up all the different possibilities of what can impact on weight, it's certainly going to take a long time to sort it all out."

More information

To learn more about the causes of obesity, visit the U.S. Centers for Disease Control and Prevention.