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Tailored Food-based Strategies Can Increase the Intake and Absorption of Micronutrients among Young Children, Results of an IAEA Project Show.

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Vitamin and mineral-rich vegetables. (Photo: N. Mokhtar/IAEA)

Maternal and child nutrition during pregnancy and up to two years of age are critical for a child’s future. One important aspect of good nutrition in this period is the ability to supply adequate and highly absorbable essential vitamins and minerals, known as micronutrients, through the diet and breast milk. Yet micronutrient deficiencies remain a major public health problem, especially in the first 1000 days of life. For example, in 2016 alone, over 600 million women of reproductive age, 35 million of whom were pregnant, were affected by anaemia, a condition often associated with inadequate intake of iron from the diet.

For young children, micronutrient deficiencies are strongly related to sub-optimal breastfeeding practices. This is typically characterized by very low exclusive breastfeeding rates in the first six months, and the fact that foods used to complement breast milk after six months are predominantly plant-based. Paradoxically, these foods are also rich in chemical compounds such as phytic acid and polyphenols, which limit the absorption of key minerals such as iron and zinc. Complementary foods often contain negligible quantities of animal-origin food, a good source of highly absorbable iron and zinc, or fruit and vegetables, which are rich in ascorbic-acid and provitamin A carotenoids. This absence is often aggravated by the low concentration of certain key nutrients in human milk due to the mothers’ own poor nutritional status.

An IAEA Coordinated Research Project (CRPE43027) brought together researchers from Africa, Asia, Latin America and North America to consider a suite of stable isotope techniques to evaluate context-specific interventions to increase intake and absorption of iron and zinc from mainly plant-based diets. The overall goal was to contribute to the design of effective, feasible and sustainable interventions based on locally available foods that help prevent micronutrient deficiencies in infants and young children.

The researchers specifically aimed to:

  • Evaluate how the addition of foods of animal origin and other naturally nutrient-rich foods to local complementary foods influence bioavailability of iron and zinc and vitamin A status.
  • Evaluate how the absorption of iron and zinc from local complementary foods is influenced by adding foods of animal origin and vitamin C, both of which are known to aid absorption.
  • Evaluate the effect of feeding lactating mothers with provitamin A and vitamin A-rich foods on the vitamin A content in the human milk and their children’s vitamin A intake and status.

The CRP focused on the first 1000 days of a child’s life, from conception through age two, contributing new knowledge on dietary diversification and modification approaches that optimize trace element bioavailability and increase trace element and vitamin density to enhance the nutrient intake from plant-based local complementary foods and human milk. It showed that culturally acceptable, locally available, low cost food-based strategies in low- and middle-income-countries have the potential to reduce the burden of malnutrition, particularly in more vulnerable populations.

Preparing amaranth enriched tortillas in Guatemala. (Photo: J.T. Rodríguez)

A significant body of evidence was generated demonstrating that simple food-based strategies are very useful in enhancing infant and young child micronutrient intake from plant-based local foods and human milk, in low-resource settings. For instance, researchers in Guatemala found that although enriching traditional white maize tortillas with amaranth had no effect on the amount of total absorbed zinc, it did result in increased iron absorption. In Mexico, a whey-based supplement derived from dairy processing added to a plant-based diet increased the total amount of zinc absorbed by children. In Zimbabwe and Mexico respectively, investigators successfully used intrinsic labelling of beta-carotene rich kale and Moringa oleifera leaves with a stable isotope and found in both cases that the conversion of provitamin A to vitamin A improved when prepared and consumed as puree. The addition of peanut butter to kale greatly enhanced provitamin A to retinol conversion.

In India, plant-based sources, particularly green leafy vegetables are widely consumed and are the main source of beta-carotene, a precursor of vitamin A. The effect of a green leafy vegetable (coriander/curry/mint) powder on human milk vitamin A content was assessed when consumed for 4 months from approximately the 24th week of pregnancy until one month of lactation. The stable isotope method of deuterium oxide ‘dose-to-mother’ technique was used to assess human milk intake. This information in combination with measured concentration of vitamin A and beta-carotene in human milk, was used to calculate the child’s daily vitamin A intake. The intervention was found to be effective in increasing the vitamin A content in human milk and thus the intake by infants.

A total of 6 low-and-middle income countries (Bangladesh, Guatemala, India, Mexico, Zambia and Zimbabwe) participated in the CRP with technical support by participants from USA. The CRP fostered capacity building of human resources and technical skills in addition to building and enhancing collaboration between participating research entities. Overall, the CRP generated promising strategies that could be scaled-up in efficacy trials to confirm the positive impact on micronutrient nutrition in low-resource settings.

Participants interacted both on-line and face-to-face at the three coordination meetings held at the IAEA Headquarters in Vienna throughout the 5 years of the CRP from 2011 to 2016.

The Science: The IAEA supports the application of stable isotope techniques to assess diet quality and its impact on health with specific focus on the absorption and retention of provitamin A, iron and zinc from fortified foods, or biofortified foods or mixed diets.

To determine iron absorption, a baseline blood sample is collected and a test meal, containing a known amount of a stable isotope of iron (57Fe), is consumed. The ratios of stable iron isotopes before and after consumption of the test meals are used to determine the amount of iron absorbed from the meals and incorporated into the red blood cells, thus revealing the effect of enhancers or inhibitors present in the meal.

To determine vitamin A status, a dose of vitamin A labelled with a stable, non-radioactive, isotope of hydrogen (2H) or carbon (13C) is administered after a baseline blood sample has been collected. The labelled vitamin A mixes with the unlabelled vitamin A in the participant’s body. After a period of equilibration (usually 4 to 14 days), the ratio of labelled to unlabelled vitamin A in plasma is measured using mass spectrometry. The calculation of the total amount of vitamin A present in the participant’s body is based on the amount of labelled vitamin A that was administered and the ratio of labelled to unlabelled vitamin A in the blood.

For further information, please visit the CRP page.

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