Cutting Calories: Monkeys That Eat Less Live Longer
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This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty. And I'm Barbara Klein. This week, we tell about how thin monkeys live longer than fat ones, how aspirin can help colon cancer patients and some new information about Tyrannosaurus rex.
A study of monkeys over a twenty-year period suggests that eating less may extend life and prevent disease. American researchers said they believe their findings could apply to people as well. Their study was published in the journal Science.
Richard Weindruch of the University of Wisconsin in Madison and his team did the research. They tested the effects of calorie restriction in seventy-six rhesus monkeys over twenty years.
Half of the monkeys were permitted to eat as much as they wanted. The other half ate a controlled diet. They were fed two-thirds of the calories they would otherwise choose to eat. These monkeys were given vitamins and minerals to prevent malnutrition.
The researchers found that thirty-seven percent of the monkeys that ate as much as they wanted had died of causes related to aging after twenty years. In comparison, only thirteen percent of the monkeys on restricted diets had died.
On average, rhesus monkeys live about twenty-seven years in captivity, that is, when they live with humans and not in the wild. Mr. Weindruch says researchers do not know why reducing calories increases the length of life. But they believe there is a helpful change in the way the body processes energy in the monkeys that eat fewer calories.
Extended life was not the only observable difference between the two groups. The monkeys that ate less had half the amount of heart disease and cancer. They also had no cases of the disease diabetes. Richard Weindruch explains.
RICHARD WEINDRUCH: "Our data show that there is about a three-fold higher risk of developing a disease of aging in those animals fed the normal diet as opposed to those that have been on caloric restriction since they were adults."
Mr. Weindruch says not only is life extended in the monkeys that eat less, but their quality of life is also improved. He noted another surprising observation in the monkeys on a restricted diet. There was a delay in muscle loss and brain shrinkage that lead to mental problems linked to aging.
In addition, there is also a difference in the appearance of calorie-restricted monkeys and those on a normal diet. The monkeys that ate fewer calories look younger and healthier than fatter monkeys on an unrestricted diet.
The study was paid for by the United States National Institute on Aging. Some critics say more research is needed to prove that calorie restriction extends life in monkeys. Mr. Weindruch says his study is not complete and that his team will continue to observe the remaining monkeys throughout their lives.
Scientists first studied the effects of calorie restriction on aging in the nineteen thirties. Since then, similar studies have shown life-extending effects of reduced diets on rodents, yeast and worms. Scientists are currently studying the effects of restricted diets on people. However, this is more difficult because it is harder to control the diets of people and because they live longer than other animals.
People since ancient times have used aspirin-like medicines to fight pain and reduce high body temperature. Modern research has found other uses for aspirin. The drug acts as a blood thinner. It can help blood flow past a blockage in an artery. Blockages can cause heart attacks or strokes. As a result, patients at risk of blockages might be advised by their doctors to take a low-strength aspirin every day. And research continues. A new study has shown that aspirin can improve survival in colon cancer patients.
The study involved about one thousand three hundred patients with colorectal cancer. The cancer had not spread to other parts of the body yet. The study compared patients who took three hundred twenty-five milligrams of aspirin at least two times a week with those who did not use aspirin.
The study found that the aspirin users had an almost thirty percent lower risk of dying from their cancer. That was during an average of eleven years after the cancer was discovered.
Andrew Chan of Harvard Medical School and Massachusetts General Hospital led the study. Doctor Chan says the effects appeared especially strong among patients with tumors expressing an enzyme called COX-2. Two-thirds of colorectal cancers produce that chemical. Doctor Chan thinks the aspirin works by blocking it.
The study appeared in the Journal of the American Medical Association. It was an observational study. In a controlled study, some patients would have taken aspirin. Others would have received a placebo -- sugar pills -- for comparison.
Last year, Doctor Chan reported that a long-term study of almost fifty thousand men showed that aspirin can help prevent colon cancer. But the effects required at least six years of regular use. And the greatest risk reductions were in those who took more than fourteen aspirins per week.
But the researchers warned that the dangers from such large amounts of aspirin should be carefully considered. Aspirin is a kind of nonsteroidal anti-inflammatory drug, or NSAID. The earlier study found comparable reductions from the use of other NSAIDs, but not from the use of acetaminophen.
All of these drugs have their uses but they also have risks. Aspirin can cause bleeding in the stomach, the intestines and the brain. People who might want to consider taking aspirin as a preventative measure should first talk to a doctor.
There is new information about Tyrannosaurus rex, the most widely recognized dinosaur and a favorite among children. Many children's books show T.rex fighting bloody battles with other huge dinosaurs.
But now it seems that T.rex may not have been as fierce as scientists once believed.
"Tyrannosaurus" means "tyrant lizard" and "rex" is Latin for "king." The Tyrannosaurus lived in North America during the late Cretaceous Period. The huge animals died out about sixty-five million years ago.
T.rex was one of the largest meat-eating dinosaurs that ever lived. It stood four to six meters tall, was about twelve meters long, and weighed up to seven tons. Its huge head was one and a half meters long. It also had sharp, bone-crushing teeth. The animal was believed to be a fierce predator that ate other dinosaurs.
Scientists believed the Tyrannosaurus ate even larger plant-eating dinosaurs. And, they believed T.rex could eat up to two hundred thirty kilograms of meat in one bite. But new research suggests that the deadly dinos may not have been as fierce as earlier believed.
Oliver Rauhut is a paleontologist at Ludwig Maximilians University of Munich in Germany. David Hone is a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology of China in Beijing.
The two scientists have concluded from fossil records that giant meat-eating dinosaurs like the Tyrannosaurus rex mainly ate young dinosaurs. Fossil records of the stomach contents of the larger dinosaurs suggest they swallowed these young dinosaurs whole.
The scientists say this belief is further supported by the fact that past discoveries from dinosaur areas show they contained large numbers of dinosaur eggs. This should have resulted in a large number of baby dinosaurs. But Mr. Rauhut says fossil records show that this is not the case. He says young dinosaur fossils are extremely rare, a possible sign that many of them had been eaten by attackers.
Mr. Hone says the records suggest that Tyrannosaurus rex was like many other predators. It attacked young, old or sick animals that were not much of a threat.
There are some signs of conflict between T-rex and other large dinosaurs. But, Mr. Hone says the records seem to suggest that those were few. The scientists say they hope more fossils will be found that support their beliefs.
This SCIENCE IN THE NEWS was written by Caty Weaver, June Simms and Brianna Blake who was also the producer. I'm Bob Doughty. And I'm Barbara Klein. For transcripts, MP3s and podcasts of our shows, go to our Web site, voaspecialenglish.com. Listen again next week for more news about science in Special English on the Voice of America.