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This is SCIENCE IN THE NEWS in VOA Special English.I'm Faith Lapidus.

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And I'm Bob Doughty.This week: the findings of a fifteen-year study of women's health.

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Results from the Women's Health Initiative, a huge project in the United States, seem to have created more questions than answers.Many doctors are now wondering what advice to give their patients, especially older women.And many patients are wondering what choices to make to improve their health.

The National Institutes of Health began the project in nineteen ninety-one.The goal was to learn more about how to prevent major causes of death and disability in older women.These are heart disease, breast and colorectal cancer and the bone-weakening disorder osteoporosis.

The studies involved more than one hundred sixty thousand women between the ages of fifty and seventy-nine.

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One of the major parts of the Women's Health Initiative was a clinical trial.This involved studies of diet, hormone therapy and treatment with calcium and vitamin D.In the end, doctors did not find much of what they had expected to find.

For example, doctors have urged people for years to eat a low-fat diet.Studies have suggested that a diet low in fats and high in fruits, vegetables and grains might lower the risk of heart disease.Yet the Women's Health Initiative found no such link.

About fifty thousand women were involved in the diet part of the study.Almost twenty thousand of them were put on a low-fat diet.The others continued with the foods they usually ate.

The goal for the women who changed their eating was to meet a daily target of twenty percent energy from fat.But most of them met only about seventy percent of the desired reduction.

Researchers followed the progress of the women for an average of eight years.The study used a controlled research design to test the findings of earlier studies.Those studies used observational research.That leaves a greater chance for influences other than diet to affect the results.

The results of the new study appeared earlier this month in the Journal of the American Medical Association.

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The researchers say the low-fat diet did not reduce the risk of heart disease.Almost seven percent of the low-fat group suffered heart disease.That compared to just over seven percent of the group without a restricted diet.The difference was small enough that scientists say it could be explained by chance.

But the researchers note that the study was not designed to compare the effects of different kinds of fats.Still, they say the findings pointed toward a reduction in heart disease risk in women who decreased their saturated and trans fats the most.

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Both groups in the diet study had similar rates of colorectal cancer.So the low-fat diet did not appear to reduce the risk.The scientists note that this form of cancer can take a long time to develop, so a five-year follow-up study is being done.

The women who changed their diet had a nine percent lower rate of breast cancer that those who followed their usual diet.The reduction is considered small enough that it could have resulted from chance.

Yet the scientists say there are reasons to think it might not be the result of chance alone.For example, women who started with a higher level of fat in their diet, and did more to lower it, had greater reductions in breast cancer risk.

The researchers say it is too soon to know if exercise had any effect on the women in the study.The findings are still being examined.And the study does not answers questions about what effects dietary changes might have on younger women.

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The findings from the tests of added calcium and vitamin D in the diet also surprised many people.The study found that these supplements offered only limited bone improvements.And there was no effect on the risk of colorectal cancer.

Eighteen thousand women took calcium and vitamin D; eighteen thousand others took a placebo, an inactive substance.None of the women knew which one they received.The New England Journal of Medicine published the results.

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The results suggest that calcium and vitamin D might reduce the risk of a broken hip in some women, especially those over the age of sixty.But there was no evidence that the supplements prevented other broken bones.

The study found that the group that took the calcium and vitamin D had a greater risk of kidney stones.The women had a seventeen percent increase in kidney stones compared to the other group.

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VOICE ONE:

You are listening to SCIENCE IN THE NEWS in VOA Special English from Washington.

When a woman experiences menopause, her reproductive ability ends.The body produces less and less estrogen and other female hormones.The ovaries no longer release eggs into the uterus and monthly bleeding stops.

As a result of these changes, women can experience sweating and intense feelings of heat as they enter menopause.They might also get angry or sad easily.Some women feel extremely tired.Others go through times when they cannot sleep peacefully.

To deal with these effects, doctors sometimes treat women with female hormones.This is called hormone replacement therapy.

But three years ago the Women's Health Initiative had some bad news for women who took a combination of progestin and estrogen.The study showed that the women who took these two hormones had an increased risk of breast cancer.Researchers halted that part of the study early as a result.

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But even the shortened study provided other findings as well -- and more bad news than good.Researchers say the combined hormone treatment also increased the risk of heart disease and loss of mental abilities from dementia.Yet the women who took progestin and estrogen did show a reduced risk of osteoporosis and colorectal cancer.

Another part of the hormone study examined the use of estrogen alone.Estrogen taken alone can cause cancer of the uterus.So the estrogen-alone study only involved women who in the past had to have their uterus removed.

About ten thousand women took part in the study.One group took estrogen; another received a placebo.

Doctors followed the progress of the women for almost seven years.Overall, the doctors found an increased risk of stroke and blood clots.But they say the estrogen appeared to reduce the risk of osteoporosis.They found no effect on rates of colon cancer.The researchers say the effects on breast cancer were not clear.

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Some researchers noted that younger women in the group that took estrogen appeared to gain some protection from heart disease.For example, they were found to have a lower rate of heart bypass operations than the older women in the group.

These findings are from what is called a subgroup.Researchers sometimes question the value of results based on a group within a group.They say the findings might not be as scientifically strong as those based on the full study.Subgroup findings can still be informative, however, and lead to further research.

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The United States government spent more than seven hundred million dollars on the Women's Health Initiative.

People hoping for some simple advice to follow will not find it in the reports.The results are complex.Not all of the women did what they were supposed to do during all of the years of the studies.And some scientists have criticisms of the way the research was designed.Big is not always better, they say.

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Jacques Rossouw, the project officer for the Women's Health Initiative, agrees that the findings are not very clear.Doctor Rossouw has said he shares concerns about how people will understand them.He says the results do not mean that a high-fat diet is fine or that calcium supplements are not useful.

People might not like it when studies conflict with widely held beliefs.Yet scientists would argue that testing widely held beliefs is the very nature of scientific study.After all, proof is often a moving target.

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SCIENCE IN THE NEWS was written by Caty Weaver and produced by Cynthia Kirk.I'm Bob Doughty.

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And I'm Faith Lapidus.Internet users can read and listen to our programs at WWW.51VOA.COM.Join us again next week for more news about science in Special English on the Voice of America.