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An Isotopic Technique to Get Vitamin A Programmes Right

Orange-fleshed fruits like mangoes, leafy green vegetables and supplement tablets are all sources of vitamin A.

Orange-fleshed fruits and vegetables like mangoes, pumpkins and carrots as well as green leafy vegetables contain carotenes, which can be converted to vitamin A in the body. Many countries also administer high-dose vitamin A supplements with immunization services. (Photo: J. Brandwayn, N. Dumlao, M. Blackwell)

“You are what you eat,” the old saying goes, and those getting a limited variety of nutrients in their diet can expect poor health. For decades, governments and NGOs around the world have been battling this problem by promoting supplements and foods fortified with nutrients including vitamin A. Concerns, however, are now being raised about whether uncoordinated, overlapping schemes are causing too much of a good thing — that is, a bad thing — and harming people’s health.

A recent IAEA technical meeting explored these concerns, bringing to the forefront a technique using stable isotopes that can with great accuracy help nutritionists and public health professionals better understand the vitamin A status in populations exposed to several programmes addressing vitamin A deficiency (See Using isotopes to measure Vitamin A status).

Vitamin A is an organic compound that’s important for growth and development. It helps maintain your immune system and is essential for good vision. Getting enough vitamin A isn’t within reach for everyone, since the biologically active form occurs only in a few animal products such as eggs, dairy products and liver. More accessible foods such as orange-fleshed fruits and vegetables like mangoes, pumpkins and carrots as well as green leafy vegetables contain carotenes, which can be converted to vitamin A in the body.

Unlike vitamin C, or other water-soluble nutrients, vitamin A is fat soluble. That means once ingested it does not leave the body quickly and accumulates in the liver — potentially damaging it and causing symptoms similar to those of alcoholism, like yellowing of the white part of the eyes.

The World Health Organization (WHO) classifies vitamin A deficiency as a public health problem and estimates that, globally, 190 million children under the age of five are affected. Their data suggests 800,000 deaths can be attributed annually to vitamin A deficiency. Many countries have therefore been administering high-dose vitamin A supplements with immunization services, but this does come with some risks if other vitamin A programmes are in place. Studies in South Africa, Philippines and Guatemala suggest that some population groups may be getting too much of vitamin A due to overlapping supplementation and fortification programmes coupled with improved diets.

Too much of a good thing

“Historically, vitamin A excess has been rare and seen amongst people that eat the livers of large carnivores, like polar bears,” said Pernille Kaestel, an IAEA nutrition specialist. “Today, also excess vitamin A intake is a risk. Understanding who is getting too little and too much vitamin A is a priority to make sure nutrition programmes are doing the right thing.”

Addressing this problem begins with measuring vitamin A status in populations. Public health professionals and nutritionists have a host of different measuring techniques at their disposal, but they are often only effective at identifying when a person has low levels of vitamin A.

The IAEA’s Virtual Technical Meeting on ‘Optimizing Nuclear Techniques to Assess Vitamin A Status’, held last month, gathered 20 experts from around the world to discuss how the retinol isotope dilution test (RID), a nuclear technique that can measure vitamin A levels in the body in all scenarios, can be optimized for use in nutrition programmes.

As part of the IAEA’s meeting, a panel discussion with international stakeholders from organisations concerned about the global vitamin A situation was organised. The World Health Organization (WHO), the Bill and Melinda Gates Foundation, the Global Alliance on Vitamin A and Helen Keller International were represented.

Panellists agreed that results from programmes using RID can assist countries in deciding when to discontinue or change supplement practices — in the best case, continuation may be a waste of resources, in the worst case it may put some population groups at risk of high vitamin A intake.

Dialogue in the panel further helped guide discussion for the remaining days of the technical meeting. Participants pinned down research priorities for addressing open methodological questions on RID and identified ways to make the technique fit for use at larger scale. Outcomes from the meeting will now be addressed in an upcoming IAEA coordinated research project planned to begin later this year.

RID has been around since the 1990s, but because it’s an isotopic technique that requires specialised equipment and knowledge to perform accurately, it has not been routinely applied beyond research settings. Experts at the meeting, however, confirmed the potential for it in wider contexts where it can complement the shortcomings of other techniques.

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