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Deficiencies in iron and vitamin D

Body growth and brain development are faster in the early years of life than during any other period.   While an adequate intake of macronutrients (carbohydrate, protein and fat) and micronutrients (vitamins and minerals) is essential, there are certain key nutrients which deserve special attention, including iron and vitamin D.

The national pre-school nutrition survey

The National Pre-School Nutrition Survey (NPNS) investigated the eating habits of 500 young children in Ireland aged between one to four years (i.e. from the age of 12 months up to their fifth birthday)1. Four-day weighed food diaries were used to collect detailed food and beverage consumption data from these children.

Findings from the study showed that for the most part, Irish pre-school children are well nourished, and their diet meets dietary recommendations for most nutrients. However, from the survey 23% of one-year olds, 10% of two-year olds and 11% of three-year olds were not getting enough iron in their diets.   The RDA for iron for toddlers is 7mg per day.

The survey also indicated that a significant proportion of children may be at risk of vitamin D deficiency, particularly in winter. Overall daily vitamin D intakes were quite low with 70-84% of those aged between one and four consuming less than 5 µg (200 IU) per day1. The RDA for vitamin D for toddlers is 10 µg per day.

Iron

Babies and toddlers are at particular risk of iron deficiency due to high demands for iron during periods of rapid growth.  Relative to their size, toddlers need nearly five times more iron than a grown man2. A significant number of Irish toddlers may not be getting enough iron in their diets as detailed above.

There is a large body of research from over the past number of years, emphasising the importance of protecting the developing brain from iron deficiency. Iron deficiency in toddlers may have long lasting detrimental effects on neurodevelopment and behaviour.

Iron and brain development

The American Academy of Paediatrics published a clinical report in 2010 stressing the importance of minimising iron deficiency in toddlers given the potential long-lasting detrimental effects of iron deficiency on neurodevelopment and behaviour3.

Prolonged iron deficiency in early childhood – with or without anaemia – is associated with poorer cognitive, motor and behavioural outcomes, which can persist into adulthood4, 5.

Iron and energy metabolism

Iron plays a major role in the body’s use of oxygen. Toddlers have increased requirements for iron to support their expanding red cell mass and growing body tissues.

Iron in the diet

The Food Safety Authority of Ireland recently published Scientific Recommendations for Food-Based Dietary Guidelines for 1 to 5 year-olds in Ireland6.  This report includes the following recommendations:

  • Red meat is a rich bioavailable source of iron in the diet of 1–5 year-olds.  30g of red meat given approximately 3 times a week, helps ensure adequate iron intake.
  • Smaller children (i.e. 1–3  year olds growing at ≤25th percentile level) will require an additional 4 mg of iron/day.  This additional iron can be provided through the use of iron-fortified full-fat milks or formulae (containing at least 1 mg of iron/100ml).  Alternatively, a low-dose iron supplement providing the RDA for iron (7 mg) can be given 4 days a week.

Vitamin D

Toddlers have very rapid rates of bone growth. Peak bone mass accrual may not be achieved in children and adolescents with sub optimal Vitamin D levels7.  A large number of Irish toddlers are likely to be at risk of Vitamin D deficiency, particularly in winter. Results from the National Pre-School Nutrition Survey1 showed that 70 – 84% of 1–4 year olds were consuming less than 5 µg Vitamin D per day. The recommended daily allowance (RDA) for toddlers is 10 µg.

As well as being essential for bone health, it is possible that Vitamin D deficiency may be associated with a wide range of medical conditions including autoimmune disorders such as diabetes, multiple sclerosis, cancer and cardiovascular disease8. Research is ongoing in this area. Many cells and tissues in the body carry a Vitamin D receptor (VDR) and further research into the health effects of Vitamin D is ongoing.

Are children living in Ireland getting enough Vitamin D?

Data from the NPNS1 indicate that daily vitamin D intake in most Irish children is much less than 10 μg: mean daily intake of children aged 1–4 years was 3.5 μg, and 93% of children in this age group had intakes below 10 μg/day9.  Similarly, in 2-year-olds from the prospective Cork BASELINE Birth Cohort Study, the mean daily intake of vitamin D was 3.5 μg, and 96% had vitamin D intakes <10 μg/day10

This is supported by modelling undertaken for the FSAI Scientific Recommendations for Food-Based Dietary Guidelines for 1 to 5 year-olds in Ireland6 report, which shows that all children aged 1–5 years had inadequate intakes of vitamin D. 

Vitamin D in the diet

Studies in young children aged 1–5 years in Ireland show that the key food sources of vitamin D among consumers are vitamin D-fortified milks (particularly in 1–2 year-olds), fortified yogurts, nutritional supplements, fresh and processed meat, fortified breakfast cereals and eggs9.

During the summer, most young Irish children get enough vitamin D through diet and through the effect of sunlight on the skin.  Therefore in order to ameliorate seasonal decline in vitamin D status during the winter months, oral intake from fortified foodstuffs is advantageous.

Vitamin D supplementation – new recommedation in 2020

A low-dose vitamin D-only supplement (5 μg) is recommended for all 1–5year olds from Halloween to St Patrick’s Day (i.e. during the extended winter months)6,11.

  1. National Pre-School Nutrition Survey. Summary Report: Food and nutrient intakes, physical measurements and barriers to healthy eating. 2012.
  2. Food Safety Authority of Ireland (1999) Recommended Dietary Allowances for Ireland.
  3. Baker, Greer and the Committee on Nutrition of the American Academy of Pediatrics. Diagnosis and Prevention of Iron Deficiency and Iron Deficiency Anaemia in Infants and Young Children (0 – 3 Years of Age). Paediatrics 2010; 126: 1040.
  4. Lozoff B, Georgieff MK. Iron deficiency and brain development. Seminars in pediatric neurology.2006;13(3):158-65.
  5. Lozoff B, Smith JB, Kaciroti N, Clark KM, Guevara S, Jimenez E. Functional significance of early-life iron deficiency: outcomes at 25 years. J Pediatr. 2013;163(5):1260-6.
  6. Food Safety Authority of Ireland 2020.  Scientific Recommendations for Food-Based Dietary Guidelines for 1 to 5 Year Olds in Ireland.
  7. Institute of Medicine Committee to Review Dietary Reference Intakes for Vitamin D Calcium.
    Dietary Reference Intakes for Calcium and Vitamin D. In: Ross AC, Taylor CL, Yaktine AL, Del Valle.
  8. Winzenberg T, Powell S et al, Shaw KA, Jones G. Effects of vitamin D supplementation on bone density in healthy children: systematic review and meta analysis. BMJ 2011; 342:c7254.
  9. Hennessy A, Browne F, Kiely M, Walton J, Flynn A. The role of fortified foods and nutritional supplements in increasing vitamin D intake in Irish preschool children. European journal of nutrition. 2017;56(3):1219-31.
  10. Ni Chaoimh C, McCarthy EK, Hourihane JO, Kenny LC, Irvine AD, Murray DM, et al. Low vitamin D deficiency in Irish toddlers despite northerly latitude and a high prevalence of inadequate intakes. European journal of nutrition. 2016.
  11. HSE.  https://www2.hse.ie/wellbeing/child-health/vitamin-d-supplements-for-children-aged-1-to-4-years.html (Accessed on 16th October 2020).

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