Alleviating Micronutrient Deficiency:
Isotopes in Action
Around the world, approaches to improve the intake of micronutrients include nutritional supplementation programmes, fortification of staple foods, modification of traditional diets, and control of parasites and infections.
In supplementation programmes, those at risk of deficiency are given the nutrients in capsule or syrup forms.
Fortification programmes add micronutrients to staple foods, such as flour or oil, as a means of providing them to people on a large scale.
Promoting the diversification of foods in the diet may also improve the absorption of essential micronutrients.
Controlling parasites, particularly worms, can also help prevent deficiencies
Information about the nutritional status of individuals and populations is essential in order to initiate any intervention. This information comes from evaluating measurements of nutrient requirements and studies of the uptake and bioavailability of vitamins and minerals. Over the last 20 years, developments in nuclear science have provided new techniques and methods that are today being used to gather such information.
There are two forms of isotopic tracers: stable and radioactive. Radioactive isotopic tracers can be measured by the radiation they emit. While these types of tracers are often used in environmental studies or medical diagnosis, stable isotopes are usually used in nutritional studies, especially those involving infants and young children.
Stable isotopes do not emit radiation. In nature, most elements occur as a mixture of two or more stable isotopes, which differ only in the number of neutrons present in their nuclei.
Stable isotopes can be given orally in water, food, or a capsule. Depending on the rate of absorption, these stable isotopes will be incorporated into metabolic products, such as body water, urea, or carbon dioxide that the body produces. By measuring these metabolic products in saliva, breast milk, urine, breath, or stool, the ratio of minor to major isotopes can be determined.
Specialized equipment is used to measure stable isotopes in samples
Mass spectrometers are used to quantify the number of atoms or molecules present in a sample, by “weighing” the atoms present using their mass-to-charge ratio.
Infrared absorption spectroscopy is used to identify and measure organic and organometallic molecules in samples by detecting how they react with specific wavelengths of infrared light.
Atomic emission spectroscopy is used to determine the concentration of compounds in a sample by measuring how the atoms present in the sample react when energy is applied.
The uptake and metabolism of micronutrients labelled with stable isotopes can be traced in vivo (a Latin term meaning “in life” and is used to describe a test in a living being rather than a test tube). Because stable isotopes have virtually no health risk in their use, they can be used in measured amounts to trace how the micronutrients are metabolized by the body. This technique is considered the “gold standard” for iron and other nutrient bioavailability studies in humans. It is being widely used to measure the effectiveness of fortification and supplementation programmes in several developing countries.
The Agency’s Initiative
The IAEA is funding projects worldwide aimed at developing effective strategies to combat micronutrient malnutrition in developing countries using isotopic and nuclear techniques. These techniques are effective in both evaluating the source of deficiency and the effectiveness of the intervention as illustrated in this diagram.
An estimated 50 per cent of preschool children in Indonesia are deficient in iron and zinc. In response, the government has decided to fortify wheat flour with iron and zinc.
Through a TC regional project isotopic techniques are being used to study the bioavailability of iron and to assess the interaction between zinc and iron added to the flour.
The results: iron sulfate from fortified flour is well absorbed (15 per cent), but when zinc sulfate is also added to the flour, the interaction reduces the bioavailability of iron sulfate. In contrast, zinc oxide does not affect the bioavailability of iron.
Anaemia is prevalent among women and children in China. Through the TC regional Asia project, the iron status of school children consuming iron-fortified sauce was evaluated over a three-month period. The results: fortification was successful in restoring the iron level of the anaemic children to normal levels.
Despite considerable progress to address malnutrition in Thailand in recent
years, pockets of malnutrition and micronutrient deficiencies still persist.
As part of the regional project, the Institute of Nutrition in Mahidol
University, Bangkok has been investigating the fortification of fish sauce.
The next phase
will use isotopic techniques to study the bioavailability of iron in women
of childbearing age who are given the different formulations of the fortified
Healthier Lives in Latin America
“ About 80 million rural and urban people in Latin America are covered to some degree by national nutrition programmes, costing billions of dollars,” noted Dr. R. Uauy, former Director of the Institute of Nutrition and Food Technology in Chile. “Without careful measurements of the body’s intake and use of vitamins and minerals, the programmes cannot be as effective”.
The IAEA project is providing such measurements in Brazil, Chile, Cuba, and Mexico using stable isotopes. The data being acquired through the use of these techniques are — for the first time — being used to set nutrition guidelines tailored to local conditions and needs. In Chile, for example, the data resulted in the government’s decision to modify its pre-school nutrition intervention programme. The result: within one year, anaemia prevalence was reduced by 20 per cent.
Vitamin A Assessment
To address the problem of adequate vitamin A in children and pregnant or nursing women, the IAEA has provided support to use isotopic techniques to measure the whole body vitamin A of those participating in: supplementation programmes in Ghana and Peru; diet improvement programmes in China, India, the Philippines, and Thailand; and food fortification programmes in Israel and the Philippines.
In Peru, evaluation of the plasma vitamin A levels using isotopic techniques has shown the positive effect of the supplementation programme. In the Philippines, isotope measurement of vitamin A found that there is an improvement in the amount of vitamin A stored in the liver of those participating in the fortification programme.