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Indian Pediatr 2019;56: 547-548 |
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Ironing out the Iron Requirements of Children
and Adolescents
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Raghu Pullakhandam, Bharati Kulkarni and Hemalatha
Rajkumar
National Institute of Nutrition, Hyderabad, India
Correspondence to: Dr Bharati Kulkarni, Clinical
Division, National Institute of Nutrition, Hyderabad, India.
Email:
[email protected]
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I ron deficiency is one of the most prevalent and
important micronutrient deficiencies worldwide, and iron deficiency
anemia adversely impacts human capital in developing countries.
Although, there is recent evidence suggesting that dietary iron intake
and anemia may not be strongly related [1], iron fortification of
staples has been one of the major strategies to tackle iron deficiency
anemia worldwide. Supplemental iron, however, is a double-edged sword as
iron intake exceeding requirement is known to cause multiple adverse
effects, including oxidative stress, inflammation and modulation of gut
microbiota [2,3]. Careful estimation of iron requirements in different
physiological groups using rigorous methods is, therefore, extremely
important.
Optimal growth during childhood and adolescence, and
sustained health throughout life require multiple nutrients at specific
levels; and these requirements vary across the life stages.
Nutritionally demanding physiological states such as growth during
childhood and adolescence, pregnancy and lactation impose additional
requirements. Moreover, the nutrient absorption and metabolism in
different population vary due to multiple reasons, including differences
in the diet quality and bioavailability, body composition, and genetic
makeup [4]. Estimating the nutrient requirements of population subgroups
using population-specific data to the extent possible is of paramount
importance.
The dietary recommendations serve as an important
tool while formulating public health policies as these recommendations
are used for evaluating the inadequacy of dietary intakes and help
regulatory recommendations for fortification programs. The current
nutrient requirements (RDA 2010) by Indian Council of Medical Research
(ICMR) [5] provide a single value as the recommended dietary allowance
(RDA) for each nutrient, which is more relevant for assessment of
dietary adequacy for individuals rather than for population as a whole.
Further, international framework of dietary reference intakes (DRIs)
requires defining estimated average requirements (EAR) and RDAs of
nutrients. The study published in this issue of Indian Pediatrics
by Ghosh, et al. [6] provides estimates of the iron requirements
of children and adolescents (1-17 years) under the framework of global
DRIs (United Nations University’s Food and Nutrition Program, in
collaboration FAO, WHO and UNICEF) [7], and makes an important
contribution to knowledge in the area of iron nutrition.
Computation of dietary requirements in children and
adolescents is especially complicated because, apart from the basal or
obligatory requirements, additional growth related requirements (which
vary as per the rate of growth in different age groups) need to be
considered. Basal requirements are estimated based on the norm that if
the absorption of a nutrient from diet equals its obligatory losses, an
individual is able to maintain the nutrient balance. Therefore, the sum
of nutrient losses (basal losses and additional menstrual losses in case
of adolescent girls) plus additional growth related requirements, when
adjusted for bioavailability, provides a realistic estimate of nutrient
requirements. This is often referred to as factorial approach. Ideally,
the data on these variables measured in the same population should be
used for deriving the nutrient requirement estimates but such data are
often not available. The authors of this study [6] have, therefore, used
relevant published data to estimate basal iron losses, including
menstrual losses in adolescent girls and additional growth related
requirements (due to blood volume expansion, tissue iron and storage
pool). The values have been adjusted for age-specific bioavailability,
and all these factors and their respective variances have been summed
using appropriate statistical tools for computing EAR and RDA (RDA
defined as the 97.5 th
percentile of the distribution of requirements) for children from
different age groups. The reference body weights of children and
adolescents were based on the WHO Child Growth Standards (directly or
derived) unlike the 95th
percentile value from the National Nutrition Monitoring Bureau (NNMB)
data as used by the ICMR RDA. Due to methodological differences, the EAR
and RDA values calculated by the authors are lower than the ICMR RDA in
all age groups, except the RDA values for adolescent girls that are
higher than the ICMR RDA. The EAR value (18.5 mg/d) in adolescent girls
suggested for fortification by authors is lower than the ICMR RDA (27
mg/d) currently being used for fortification programs.
This work is significant in many ways. First, it
attempts to harmonize the iron requirement recommendations with
international framework of DRIs. Second, the EAR-based dietary
inadequacy assessment suggested by the authors is more realistic from
population perspective, and would provide much lower estimate of
inadequacy compared to the current practice of using RDA-based
cut-point. Third, since food fortification standards are anchored on
requirements of adolescent girls, the EAR metric derived for adolescent
girls in the present study has implications in revising the
fortification standards in the country. This is especially important
when adolescents are likely to receive supplemental iron from multiple
sources, including weekly iron for late supplementation program as well
as from multiple iron-fortified foods; and there is a plausible risk of
total iron take crossing the tolerable upper limit (40 mg/day in
children below 14 years and 45 mg/day above 14 years age) [8]. Moreover,
due to high prevalence of undernutrition in the country, majority of the
children and adolescents are likely to have body weights far lower than
the reference weights, which further increases the risk of excessive
iron intakes.
It is, however, important to note that these nutrient
requirement calculations involve complex analyses, and the estimates
rely on a number of assumptions that are imperfect. The problem is
further compounded by lack of data on iron losses as well as body iron
stores that are representative of Indian population.
Important knowledge gaps exist as the basal iron
losses, including menstrual iron loss and body iron stores, are based on
extremely limited number of studies carried out in western populations.
Further refinement of the DRIs, therefore, needs focused research to
evaluate the basal losses as well as body stores of iron during growth
in representative Indian participants, which requires methodological
advances. Moreover, studies estimating iron absorption with different
meals, especially composite meals, in different age groups are needed as
the bioavailability was found to be major contributing factor to the
higher EARs of iron for Indians compared to Western population.
Funding: None; Competing interest: None
stated.
References
1. Swaminathan S, Ghosh S, Varghese JS, Sachdev HS,
Kurpad AV, Thomas T. Dietary iron intake and anemia are weakly
associated, limiting effective iron fortification strategies in India J
Nutr. 2019;149:831-39.
2. Moen IW, Bergholdt HKM, Mandrup-Poulsen T,
Nordestgaard BG, Ellervik C. Increased plasma ferritin concentration and
low-grade inflammation — a Mendelian randomization study. Clin Chem.
2018;64:374-85.
3. Paganini D, Zimmermann MB. The effects of iron
fortification and supplementation on the gut microbiome and diarrhea in
infants and children: A review. Am J Clin Nutr. 2017;106:1688s-93s.
4. Reddy VS, Palika R, Ismail A, Pullakhandam R,
Reddy GB. Nutrigenomics: opportunities and challenges for public health
nutrition. Indian J Med Res. 2018;148: 632-41.
5. Indian Council of Medical Research. Nutrient
Requirements and Recommended Dietary Allowances for Indians. A Report of
the Expert Group of the Indian Council of Medical Research. Hyderabad:
National Institute of Nutrition, 2010.
6. Ghosh S, Sinha S, Shivakumar N, Thomas T, Sachdev
HP, Kurpad AV. Daily iron requirements in healthy Indian children and
adolescents. Indian Pediatr. 2019;56:551-5.
7. King JC, Garza C. Harmonization of nutrient intake
values. Food Nutr Bull. 2007;28:S3-12.
8. Institute of Medicine (US) Panel on
Micronutrients. Dietary Reference Intakes for Vitamin A, Vitamin K,
Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum,
Nickel, Silicon, Vanadium, and Zinc. Washington (DC): National Academies
Press (US); 2001.
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