What they have found is that almost immediately after it is donated, human blood starts to lose a key gas that functions to open up blood vessels and help the transfer of oxygen from red blood cells to oxygen-starved tissues. The Duke findings appear in two separate papers published Oct. 9 in the Proceedings of the National Academy of Sciences.
The gas is nitric oxide and it is crucial in red blood cells for the delivery of oxygen to human tissue. The two studies demonstrated, however, that nitric oxide in red blood cells begins to break down almost at the moment red blood cells leave the body.
"It doesn't matter how much oxygen is being carried by red blood cells, it cannot get to the tissues that need it without nitric oxide," said Dr. Jonathan Stamler, senior author of one of the PNAS papers. It was Stamler's group at Duke whose group originally discovered the role of red blood cell nitric oxide in oxygen delivery.
"Nitric oxide opens up the tiny blood vessels, allowing red blood cells to pass and deliver oxygen," Stamler said. "If the blood vessels cannot open, the red blood cells back up in the vessel and tissues go without oxygen. The result can be a heart attack or even death."
What this means is that for decades millions of patients worldwide have apparently received, and are continuing to receive, transfusions with blood that is impaired in its ability to deliver oxygen. It is estimated that each year in the United States alone close to 14 million units of red blood cells are administered to about 4.8 million patients.
"The issue of transfused blood being potentially harmful to patients is one of the biggest problems facing American medicine," said Stamler, who is a professor of cardiovascular and pulmonary medicine. "Most people do not appreciate that blood has the intrinsic capacity to open blood vessels, thereby enabling oxygen to get to tissues. Banked blood cannot do this properly."
In procedures conducted on laboratory animals, researchers found that reintroducing nitric oxide into stored blood before transfusion appears to restore red blood cells' all-important ability to transfer oxygen to tissues.
These studies go a long way toward answering a major problem that many physicians are beginning to appreciate - blood transfusions with banked human blood might do more harm than good for a majority of patients, the Duke researchers say.
Yet transfusions are still critically important, Stamler insists
"Banked blood is truly a national treasure that needs to be protected," Stamler said. "Blood can be life-saving, only it is not helping the way we had hoped and in many cases it may be making things worse. In principle, we now have a solution to the nitric-oxide problem - we can put it back - but it needs to be proven in a clinical trial."
DAIRY DEFICIT
Recent research at Pennsylvania State University indicates that U.S. children are failing to drink enough milk to build strong bones. Making matters worse, the milk products they do consume are high in fat and might be contributing to America's childhood obesity epidemic.
"There is a strong correlation between dairy consumption and calcium," said Sibylle Kranz, assistant professor of nutritional sciences at Penn State. "While there is calcium in fortified orange juice, for example, it is not as bioavailable as that found in milk."
Kranz points out that children and adults need to consume calcium with vitamin D and some protein for optimal use in the body. Milk produced in the United States is usually fortified with vitamin D.
Kranz and her colleagues investigated children's average daily dairy consumption and compared it with that recommended by the U.S. Department of Agriculture's My Pyramid dairy recommendations for children between the ages of 2 and 18.
As reported in the Journal of Pediatrics, the Penn State researchers found that only children age 2 and 3 met the My Pyramid dairy recommendations. The also found that the dairy products most consumed by children were those with the highest fat content, such as high-fat cheeses, yogurt, ice cream and dairy-based whipped toppings.
The Penn State researcher say these additional calories can add up and might contribute to nationwide increases in childhood obesity.
Daily dairy consumption guidelines for 1- to 3-year-old children recommend the consumption of 2 cups of milk per day; 4- to 8-year-olds is two to three cups of milk; and 9- to 18-year-olds is three to four cups.
Kranz and colleagues found by comparison that only the youngest age group met these requirements. Among 4- to 8-year-olds and 9- to 13-year-olds, consumption averaged less than two cups a day. For teens between 14 and 18 it was even less.
"Although the recommendations are all for low-fat dairy," says Kranz. "People are still consuming great amounts of whole-fat dairy products."
Kranz's team discovered that between 43 percent and 51 percent of the dairy consumed by younger children was from whole-fat sources with only 5 percent to 11 percent from nonfat dairy. Older children consumed about 35 percent to 36 percent from whole-fat dairy and 11 percent to 13 percent from non-fat dairy sources.
"A glass of fat-free milk has 80 calories, while whole milk has 150 calories," says Kranz. "That is a difference per glass of 70 calories or 210 to 280 calories a day for individuals consuming three to four servings of dairy."
E-mail Ven Griva at ven.griva@copleynews.com or write to P.O. Box 120190, San Diego, CA 92112.
