CNRC Researchers Publish Stable Isotope “Bible”

Nutrition scientists finally have a ‘cookbook' to refer to when conducting high-tech studies using stable-isotope tracers, courtesy of two CNRC researchers who are renowned experts in the field.

“Because stable isotopes are safe and relatively easy to use, their use in nutrition research has grown tremendously over the past 20 years,” said Dr. William Wong, a professor of pediatrics at Baylor College of Medicine. “However, until this handbook, scientists had to search through published research papers to find information on each type of study they wished to conduct.”

Wong co-authored the handbook, Stable Isotopes in Human Nutrition, with fellow CNRC scientist, Dr. Steven Abrams. The book provides information on the production of stable isotopes as well as their use in mineral-, protein-, glucose-, cholesterol-, and fat-metabolism studies, and studies of nutrient bioavailability and energy utilization. Written for nutrition researchers and graduate students, the handbook is available from CABI Publishing.

“Stable isotopes readily give us important information about the body's metabolic workings that might otherwise be expensive and cumbersome, if not impossible, to obtain,” Wong said.

For example, the doubly labeled water method, which Wong helped perfect, is the only method available for capturing how many calories people burn during normal, everyday life.

"The doubly labeled water method requires only that study volunteers drink a small amount of stable-isotope labeled water and collect a sample of their saliva each day for about a week. It is so simple, yet, we get very accurate information about how much energy they routinely expend as they go about their normal, everyday routines,” Wong said.

Because differences in calories burned over time is closely tied to physical activity levels, the doubly labeled water method has become an important research tool in the battle against obesity.

"Metabolic studies using stable isotopes are among the most effective tools we have for understanding how dietary compentns affect the development and treatment of health problems like obesity, diabetes, osteoporosis, and cardiovascular disease," Wong said. “And now with this handbook, the information needed to conduct these studies can be at a researcher's fingertips."

Wong became an expert on the use of stable isotopes as an environmental scientist and oceanographer in the early 1970s. He joined the CNRC in the early 1980s to establish the centers stable isotope lab, turning his research interests toward the use of stable isotopes in the study of energy utilization and body composition. Abrams, a pediatrician and professor of pediatrics at Baylor, uses stable isotopes to study calcium, iron, magnesium, and zinc metabolism. His calcium stable-isotope research laid the foundation for the revised calcium recommendations for children released in 1999. His current studies use stable isotopes to help improve the iron, zinc and vitamin A status of children in developing countries.

Wong and Abrams tapped CNRC scientists Dr. Morey Haymond and Dr. Agneta Sunehag, both pediatricians, to contribute a chapte rin the book on the use of stable isotopes to study glucose metabolism. They are currently studying how diet composition and exercise affects glucose metabolism and insulin production in overweight versus normal weight children using stable isotope techniques. Dr. Farook Jahoor, also a CNRC researcher, contributed a chapter on the use of stable isotope techniques in the study of protein metabolism. He uses stable isotopes to understand the metabolic basis of complications associated with muscle-wasting conditions like malnutrition and HIV-infection and to develop nutritional interventions for these conditions.