Brain development is a long term process, with different parts and functions of the brain developing at different time points in childhood.1 Especially during the first years of life, the brain is undergoing rapid development.2 During this phase, adequate dietary intake is of special importance for the developing brain, with nutrients like iron, iodine and omega-3 and omega-6 fatty acids playing a vital role.11-23
The importance of the first years
The brain reaches about 80% of its final weight at the age of two years,3 while the density of synapses (the meeting points between nerve cell and other cells) by the same age exceeds the adult mean.4 However, the formation of the outer layer of the nerve cell (myelination), of some parts of the brain continues also during adolescence, particularly of those nerve cells (neurons) that control higher cognitive functions.5
During the first years, toddlers acquire particular cognitive and motor skills. Their spoken vocabulary increases significantly, they gain greater motor coordination and they become able to concentrate on tasks for slightly longer periods.6 The development of these skills is the result of the interplay between genetic factors and a wide range of environmental determinants. Among those environmental determinants, visual and sound stimulation contribute importantly to the development of neural circuits.7,8 Also of great importance is the quality of dietary intake, which ensures that the brain receives all necessary nutrients for optimal development and proper function.9 Since the brain does not develop homogenously, the potential effect that a nutrient deficiency has on neurodevelopment depends on the severity, duration and timing of the deficiency.10
The role of nutrients
Understanding the role of some key nutrients involved in the brain neural development of toddlers, the European food safety authority EFSA has approved certain health claims related to those nutrients (Table 1). These nutrients and their role in neurodevelopment and growth are described below.
Iron plays an important role in the cognitive development of children, as it is necessary for basic neuronal processes such as myelination, neurotransmitter production and energy metabolism.11,12 Iron deficiency and iron deficiency anaemia are two of the most common and widespread nutritional disorders. Specifically, the World Health Organization (WHO) has reported that iron deficiency anaemia affects approximately 39% of children younger than 5 years in developing countries and 20% in industrialized countries based on blood haemoglobin concentration and that this disorder has adverse effects on cognitive development as well as on psychological and mental functions.13,14
Essential fatty acids
Alpha linolenic acid (ALA, an omega-3 fatty acid) and linoleic acid (LA, an omega-6 fatty acid) are essential fatty acids (EFAs) since they cannot be synthesized by the body. These fatty acids are needed for the normal growth and development of children16 as they play an important role in neuronal membrane structure, synaptogenesis and myelination.17 Furthermore, ALA is a precursor of docosahexaenoic acid (DHA), a longer chain omega-3 fatty acid which compromises 20% of the brain’s lipid content. The above highlights the need of adequate dietary omega-3 and omega-6 fatty acid supply in early childhood.18,19 For the age >6 months to 24 months an adequate daily intake of 100mg DHA has been set, whereas for older children there is a dietary advice regarding fish consumption (1 to 2 fatty fish meals per week).18 Nevertheless, some limited data in toddlers have reported low (below the recommended ranges) percentages of energy intake deriving from polyunsaturated fat.20,21
Iodine contributes to normal growth, since it is an essential component of the thyroid hormones.22 Thyroid hormones are necessary for the optimal brain development, while iodine deficiency disorders range from mild goitre to the very severe forms of cretinism (congenital, severe, irreversible mental and growth retardation) that arise from iodine deficiency during gestation or during the first months of life.20,23 While in several European countries insufficient iodine intake has been reported in school-aged children,23 there is limited data referring to toddlers.15
- Grossman, A.W., et al., Experience effects on brain development: possible contributions to psychopathology. J Child Psychol Psychiatry, 2003. 44(1): p. 33-63.
- Dobbing, J., Boyd Orr memorial lecture. Early nutrition and later achievement. Proc Nutr Soc, 1990. 49(2): p. 103-18.
- Dekaban, A.S., Changes in brain weights during the span of human life: relation of brain weights to body heights and body weights. Ann Neurol, 1978. 4(4): p. 345-56.
- Huttenlocher, P.R., Synaptic density in human frontal cortex – developmental changes and effects of aging. Brain Res, 1979. 163(2): p. 195-205.
- Toga, A.W., P.M. Thompson, and E.R. Sowell, Mapping brain maturation. Trends Neurosci, 2006. 29(3): p. 148-59.
- Sakai, K.L., Language acquisition and brain development. Science, 2005. 310(5749): p. 815-9.
- Greenough, W.T., J.E. Black, and C.S. Wallace, Experience and brain development. Child Dev, 1987. 58(3): p. 539-59.
- Tau, G.Z. and B.S. Peterson, Normal development of brain circuits. Neuropsychopharmacology, 2010. 35(1): p. 147-68.
- Rosales, F.J., J.S. Reznick, and S.H. Zeisel, Understanding the role of nutrition in the brain and behavioral development of toddlers and preschool children: identifying and addressing methodological barriers. Nutr Neurosci, 2009. 12(5): p. 190-202.
- Knudsen, E.I., Sensitive periods in the development of the brain and behavior. J Cogn Neurosci, 2004. 16(8): p. 1412-25.
- Scientific Opinion on the Substantiation of a health claim related to Iron and cognitive development of children pursuant to Article 14 of Regulation (EC) No 1924/2006; EFSA Journal 2009; 7(11):1360
- Beard, J.L. and J.R. Connor, Iron status and neural functioning. Annu Rev Nutr, 2003. 23: p. 41-58.
- Aggett, P.J., et al., Iron metabolism and requirements in early childhood: do we know enough?: a commentary by the ESPGHAN Committee on Nutrition. J Pediatr Gastroenterol Nutr, 2002. 34(4): p. 337-45.
- World Health Organization (2001) Iron deficiency anaemia: assessment, prevention, and control. A guide for programme managers. WHO/NHD/01.3.
- Mensink, G.B., et al., Mapping low intake of micronutrients across Europe. Br J Nutr, 2013: p. 1-19.
- ALA and LA and growth and development of children; Scientific substantiation of a health claim related to α-linolenic acid and linoleic acid and growth and development of children pursuant to Article 14 of Regulation (EC) No 1924/2006; The EFSA Journal (2008) 783, 1-9.
- Uauy, R. and A.D. Dangour, Nutrition in brain development and aging: role of essential fatty acids. Nutr Rev, 2006. 64(5 Pt 2): p. S24-33; discussion S72-91.
- Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol; EFSA Journal 2010; (3):1461.
- Trumbo, P., et al., Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids. J Am Diet Assoc, 2002. 102(11): p. 1621-30.
- Dutch National Food Consumption Survey- Young Children 2005/2006, RIVM Report 350070001/2008 available at: http://www.rivm.nl/dsresource?objectid=rivmp:13711&type=org&disposition=inline&ns_nc=1.
- Sioen, I., et al., n-6 and n-3 PUFA intakes of pre-school children in Flanders, Belgium. Br J Nutr, 2007. 98(4): p. 819-25.
- Scientific Opinion on the Substantiation of a health claim related to Iodine and the growth of children pursuant to Article 14 of Regulation (EC) No 1924/20061; EFSA Journal 2009; 7(11):1359.
- WHO (2007). Iodine deficiency in Europe. A continuing public health problem. Editors: Andersson, M., de Benoist, B., Darnton-Hill, I. published jointly with UNICEF/WHO. ISBN 9789241593960.http://www.who.int/nutrition/publications/VMNIS_Iodine_deficiency_in_Europe.pdf