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This is SCIENCE IN THE NEWS, in VOA Special English. I'm SarahLong.

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And I'm Bob Doughty. On ourprogram this week: we look at a dispute over a proposed nuclearenergy project and how too much of something considered good for youmay increase your risk of dying early.

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But first, a blood treatment offers hope to adults fighting thedisease leukemia.

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Two new studies show that tissue connecting an unborn child toits mother may help some adults with leukemia. At birth, blood fromthe umbilical cord of a baby contains stem cells. Researchscientists say such cells can rebuild the natural defense system ofan adult with the blood disorder.

The defense system protects the body against disease. However,some treatments for leukemia can destroy this system. Theresearchers say their studies show that cord blood can restore thenatural defenses. They say cord blood can be used when a more provenmethod of treatment is not possible.

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Umbilical cord stem cells are already used for children fightingleukemia. Until now, many researchers believed that cord blood couldonly help children or small adults. The two studies suggest that isno longer a problem.

Cord blood is not as rich in stem cells as bone marrow. Bonemarrow is the connective tissue that fills bones. Marrow producesmuch of a person's blood supply. Bone marrow currently is thesubstance most used to restore a person's natural defenses againstdisease.

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For years, many doctors have chosen to replace destroyed adultbone marrow with healthy marrow. This process is called a bonemarrow transplant. It can happen only under limited conditions. Thepatient's body must accept bone marrow from another person. Theperson providing healthy marrow is called the donor. For thetransplant process to be successful, the patient and the donorusually must have similar tissues.

But it is difficult to find a donor whose marrow the patient canuse. Each year, doctors say most leukemia patients with a destroyednatural defense system die before the right donor can be found.

Stem cells are unformed. They exist in the blood and withintissues that make blood. They grow inside a patient. They direct theproduction of all kinds of blood cells. That is how stem cells canrebuild a person's natural defense system.

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The New England Journal of Medicine published both new studiesabout cord blood stem cells. One study was performed in Europe. Theother was in the United States. Both involved hundreds of patients.

Most patients in the studies were very sick. Many died over twoor three years. But the European study showed that cord blood workedequally effectively as the best kind of marrow transplants. Both hada survival rate of about thirty-three percent. In the Americanstudy, the percentage of survivors helped by cord blood was almostas hopeful.

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Mary Laughlin of the Case Western Reserve University School ofMedicine led the American study. She says all the survivors wouldhave died without treatment. Cancer experts not involved in theeither study expressed hope over the results. They noted thedifficulty of leukemia patients in finding a donor similar enoughfor a bone marrow transplant to be successful.

One blood expert, Pablo Rubenstein, noted another reason toconsider cord blood treatment. He said stem cells in cord blood areless likely than adult bone marrow to cause a sickness calledgrant-versus-host disease. It strikes when the stem cells of thedonor attack the patient's tissues and organs.

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The Institute of Medicine is a federal agency in Washington, D.C.It says patients may be able to find useful cord blood more easilythan donor marrow. The Institute is studying ways to establish anational center for the supply of cord blood.

About four million babies are born in the United States eachyear. After each birth, medical workers block off and cut theumbilical cord. Most cords are thrown away. Taking blood from themis safe and painless for mother and child.

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The European Union says it is set to move forward with plans fora nuclear fusion reactor. E.U. officials agreed last month tocontinue seeking Japanese support to build the reactor in France.They also said the European Union is prepared to build it withoutJapan if negotiations fail. Later, Japanese officials criticized theEuropean Union for talking about acting on its own. They urged theEuropeans to continue talks with other countries involved in theproject. The others are Japan, China, Russia, South Korea and theUnited States.

The project is called the International ThermonuclearExperimental Reactor, or ITER (EE-tur). It is expected to cost aboutthirteen thousand million dollars over the next thirty years. TheEuropean Union plans to pay for forty percent of the project.

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For years, scientists have said nuclear fusion could produceunlimited amounts of energy. Nuclear fusion is a natural process. Itis the process that makes the sun and other stars shine. Nuclearfusion involves the central parts of small atoms such as hydrogen.

Deep inside the sun, extreme heat and pressure cause the atoms tojoin together. This fusion of two hydrogen atoms forms a differentelement: helium. It also releases a large burst of energy. This isthe heat and light produced by the sun. Nuclear fusion is differentfrom the process used in nuclear power centers. That process iscalled nuclear fission. Fusion is the opposite of fission.

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Fusion creates energy by joining atoms together. Fission createsenergy by splitting atoms apart. Fusion produces only a small amountof radioactive waste. Fission produces large amounts of highlyradioactive waste that must be kept in containers for thousands ofyears.

Supporters of the nuclear fusion process say it is safer thanfission. They say a fusion reaction can be stopped easily. There isanother reason people are excited about nuclear fusion. The processuses a fuel supply that is huge and low in cost.

The fuel is a heavy form of hydrogen called deuterium. Deuteriumis found in all the world's oceans. It can be taken from the watereasily and in almost endless amounts. Experts say about one-halfkilogram of fusion fuel could produce as much energy as three andone-half million liters of oil.

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Many people take vitamin supplements to improve their health. Inthe United States, pills containing Vitamin E are among the mostpopular. Americans spent seven hundred ten million dollars onVitamin E last year.

Recently, American researchers reported that Vitamin Esupplements might do more harm than good. They said people who takelarge amounts of Vitamin E could be increasing their risk of dyingearly.

Edgar Miller of Johns Hopkins University led the study. Hepresented the findings at a meeting of the American HeartAssociation in New Orleans, Louisiana.

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Doctor Miller and his team combined and examined the results ofnineteen studies on the effects of Vitamin E. The studies involvedalmost one hundred thirty-six thousand people in North America,Europe and China.

The researchers found no increased health risk from taking smallamounts of Vitamin E. About thirty international units of Vitamin Eare present in a single multivitamin pill.

However, the team found an increased risk of dying among peoplewho took four hundred international units a day or more. Their deathrate was thirty-nine for every ten thousand persons in the combinedstudies.

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A supplement trade group, the Council for Responsible Nutrition,criticized the findings. It said the study greatly overstated theirimportance.

Earlier studies had suggested that Vitamin E blocks the harmfuleffects of oxygen. That is why so many Americans take vitaminsupplements to reduce their risk of heart disease and otherdisorders.

Doctor Miller says his team believes there is no need for peopleto take large amounts of Vitamin E. He reportedly said people shouldget enough Vitamin E from the foods they eat. You can get up to teninternational units of it from seeds, vegetable oils, olives,spinach and other green vegetables.

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This program was written by Jerilyn Watson and Brian Kim. CynthiaKirk was our producer. Our engineer was Dwayne Collins. I'm SarahLong.

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And I'm Bob Doughty. Join us again next week for SCIENCE IN THENEWS in VOA Special English.