F&N Bulletin Vol 23 No 1b - United Nations University

Nuclear and isotopic techniques
the technical underpinnings to international efforts
for improving the quality of life [18]. To date, isotopic
strategies evolved through International Atomic
Energy Agency efforts to measure energy metabolism,
resistance to insulin, rate of synthesis of fat, changes
in protein synthesis, lactation performance, bone
mineral density, food composition, efficacy of nutrient
fortification, nutrient utilization, and prevalence of
infection are practiced in more than 50 of its member
states. A few examples are cited below.
The Regional Latin America (RLA/7/008) project,
with five participating countries (Argentina, Brazil,
Chile, Cuba, and Mexico), used isotopes to evaluate
nutrition-intervention programs. A technical cooperation
project in Chile completed a study on isotope
techniques to measure iron bioavailability in fortified
milk of the National Complementary Food Program
(PNAC), bioavailability of zinc and body composition
in children, and body composition and energy
expenditure in preschool children using doubly labeled
water. Similarly, the first phase of the Regional East
Asia and Pacific (RAS/7/010) study measuring the
effectiveness of multinutrient supplementation using
stable isotopic techniques to assess zinc and iron bioavailability
in seven participant countries (People’s
Republic of China, Indonesia, Malaysia, Pakistan, Philippines,
Thailand and Vietnam) has been completed.
A coordinated research project (People’s Republic
of China) on osteoporosis examined differences in
bone mineral density of young adults across a range of
races in 3,752 subjects recruited at 11 centers in nine
countries. There were highly significant differences
in mean weight, height, and bone mineral density
between countries (p < .001). After adjustment for age,
weight, and height, differences between centers in bone
mineral density persisted for both men and women.
Significant differences existed in young adult bone
mass, which, if persisting into old age, may contribute
to a two- to threefold difference in fracture risk.
A coordinated research project on the Reference
Asian Man with the participation of several Asian
countries (RAS project) generated reliable data sets
for dietary intake for all participating countries (and
in tissues by some) that will enhance their ability
to resolve national problems of radiological protection,
as well as facilitating the development of the
characteristics of a Reference Asian Man, the primary
goal of this Regional Project. Improved reference
values have been derived for a number of additional
elements and reference material matrices that will
also strengthen the capability to address issues of
nutritional interest.
Refined isotopic techniques resulting from a coordinated
research project on the isotopic evaluations
of maternal and child nutrition to help prevent stunting
have been extensively used in Latin America and
Pakistan in field studies and in an ongoing coordinated
research project on isotopic evaluations in infant
growth monitoring, in collaboration with the World
Health Organization (WHO) Growth Monitoring
Program.
According to 1993 statistics, persistent diarrhea
accounted for over 60% of infant diarrheal deaths
in Brazil, 47% in India, 36% in Senegal, and 26% in
Bangladesh [19]. Stable isotopic techniques have been
recognized as the best and cost-effective modes of
diagnosis of H. pylori infection through a simple breath
test using 13 C-enriched substrates and measurement
of labeled CO 2
. A number of countries in Africa,
Asia, and Latin America that joined a coordinated
research project on H. pylori infection and malnutrition,
particularly addressing public health problems in
the young population, have made significant progress
with fieldwork. Isotopic techniques using 13 C-labeled
substrate breath tests for bacterial colonization and
digestion and absorption of nutrients (lactose, amino
acids, and triglycerides), which are sensitive tools
to examine the significance of H. pylori and its consequences
for poor nutrient assimilation in young
children, have been successfully used for breath-sample
analyses in these countries.
To target malnutrition, the International Atomic
Energy Agency has been developing noninvasive isotopic
tracer techniques for measuring whole-body vitamin
A under conditions of supplementation (Ghana,
Peru), food fortification (Peru, Israel), and dietary
improvement (China, Thailand, Philippines, India) to
address problems of vitamin A nutrition in children
and pregnant or lactating women. Similarly, assessment
of iron absorption from diets to evaluate its
bioavailability is an important nutritional need.
Future prospects
A consultants’ meeting called by the International
Atomic Energy Agency in December 2000 [20] offered
insights into the future applications of stable isotopes
in nutrition research. Novel applications were identified
by improving existing techniques to extend the
usefulness of stable isotopic techniques in mineral and
trace element nutrition research and to allow their use
more routinely. Several examples are listed below:
» Recent investigations have shown that calcium in the
skeleton can be labeled with stable, long-lived radionuclide
calcium-41. This offers the unique opportunity
to look at calcium losses and balance in bone
directly via urinary excretion of the isotopic label.
» Based on the simultaneous excretion of an oral and
an intravenously administered label, the urinary
monitoring technique has been validated for determination
of true calcium absorption; attempts are
being made to validate this technique for urinary
monitoring of zinc and magnesium.
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