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DHA In Children : Introduction |
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DHA Introduction : Docosahexaenoic acid (DHA) is an omega-3 fatty acid which is an essential fatty acid. Essential fatty acids cannot be synthesized in the body. They are also called polyunsaturated fatty acid (PUFA). These PUFA must be obtained from dietary food. There are 2 types of PUFA - omega 6 and omega 3. Omega 3 fatty acids are also known as Long Chain polyunsaturated fatty acids (LC PUFA's). The most important omega 6 (n-6) fatty acid is arachidonic acid (ARA) that is formed from linoleic acid (LA) while most important omega 3 (n-3) fatty acid is DHA which is formed from alpha - linolenic acid (ALA ) (1).
Throughout most of life, there is a very limited metabolic capacity to convert ALA to DHA (2). Essential fatty acids are structural components of all tissues and are indispensable for cell membrane synthesis; the brain, retina and others neural tissues are particularly rich in long chain PUFA. These fatty acids serve as specific precursors for eicosanoids, which regulate numerous cell and organ functions (3). The most abundant brain PUFA are DHA (n-3); arachidonic acid (n-6) and adrenic acid (n-6) (4) and DHA is most abundant in the outer rod photoreceptors in the eye.
DHA: DHA is an omega 3 PUFA which has very limited synthesis in the body. In the human body, DHA is derived from eicosapentaenoic acid (EPA) via docosapentaenoic acid (DPA) as an intermediate by desaturase enzyme and beta oxidation in peroxisomes (5). During early life, there is limited metabolic capacity to convert ALA to DHA. Thus in fetal life, infancy and early childhood, DHA should be acquired from dietary sources to maintain optimal health (6).
Sources of DHA: Fish oils are rich in DHA. Most of the DHA in fish and other organisms originate from microalgae. ALA is present in vegetable oils such as flaxseed or linseed oil, rapeseed or canola oil, peanut oil, olive oil, soya oil, walnut oil, green leafy vegetables, fenugreek seeds, kidney beans and dry fruits (7). DHA is also manufactured from microalgae in vegetarian form (1) for commercial use.
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Body stores of DHA: Over the first 6 months of life, DHA accumulates at about 10 mg/d in the whole body of breast-fed infants with 48% of that amount appearing in the brain. To achieve that rate of accumulation, breast-fed infants need to consume a minimum of 20 mg DHA/d. Virtually all breast milk provides a DHA intake of at least 60 mg/d though it may be variable. Thus a store of about 1050 mg of DHA in body fat at term birth is present (8).
DHA (food) concentrations in breast milk range from 0.07% - >1.0% of total fatty acids with a mean of 0.34% depending on maternal DHA intake (1). A working group from the ISSFAL (International Society for the study of Fatty Acids & Lipids) has recommended 300 mg/day of DHA for pregnant and lactating women to achieve good fetal DHA stores (9) as during pregnancy, fetus depends completely on maternal sources of DHA. During infancy DHA needs of the baby are met through breast milk. During early childhood, DHA requirement are met by consumption of DHA rich food. However it has been found that DHA in average diet is very little due to westernization of diet as well poor intake of fish in diet, vegetarians who do not take even eggs or milk products, can only obtain DHA through the very limited conversion of dietary ALA. (10). In Canadian children between 4-7 year of age and not living near a marine environment, dietary intakes of DHA & AA are relatively low. Retinal and neuronal development continues throughout childhood, therefore it is conceivable that low intake a AA and DHA may have negative impact (11). Most Indians consume omega-6 and omega-3 fatty acids in ratio of 30-70:1 but ideal ratio is 5-10:1 for optimal health benefits (12).
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Brain : DHA is one of the major building structure of membrane phospholipids of brain. Epidemiological studies have linked low maternal DHA to increased risk of poor child neural development and intervention studies have shown decrease in risk of poor neural development (13). Neurodevelopment and cognitive abilities are enhanced by n-3 PUFA through breast milk or DHA-fortified food (14). Furthermore, there is increasing evidence that increased intake of DHA may confer benefits in a variety of psychiatric and neurological disorders and in particular neurodegenerative conditions. In addition, it may also have significant neuroprotective potential in acute neurological injury (15).
Vision : Light sensitivity of retinal rod photoreceptors is significantly reduced in newborns with DHA deficiency and DHA supplements significantly enhance visual acuity maturation (3).
Hyperlipidemia in children : Recent research shows that DHA supplementation restores endothelial - dependant flow - mediated dilatation in hyperlipidemic children and has potential for preventing progression of early coronary heart disease in high risk children (16).
Other effects : Though DHA has been tried for behavioral alteration in children with autism its role still remains undefined (17). DHA had been found to inhibit growth of human colon carcinoma cells but its role in treatment of cancer remains undefined (18).
Conclusion : DHA is an omega 3 essential fatty acid indispensable for functions of brain and retina. In infants and children, better mental processing scores, psychomotor development and stereo acuity are associated with DHA intake (6). Diet being poor in DHA in pre-schoolers and non-breast led infants, DHA fortified food helps to maintain plasma phospholipids DHA content in children.
References :
1. |
Docosahexaenoic acid - Wikipedia. Available at URL http://en.wikipedia.org. Accessed on 25th November 2009.
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2. |
ISSFAL: 2009, January, ISSFAL Official Statement Number 5 "α-Linolenic Acid Supplementation and Conversion to n-3 Long Chain Polyunsaturated Fatty Acids in Humans. |
3. |
Uauy R, Hoffman DR, Peirano P, Birch DG, Birch EE. Essential fatty acids in visual and brain development. Lipids. 2001; 36: 885-895
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4. |
Martinez M. Tissue levels of polyunsaturated fatty acids during early human development. J Pediatr. 1992; 120: S129-S138
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5. |
Voss A, Reinhart M, Sankarappa S, Sprecher H. The metabolism of 7,10,13,16,19-docosapentaenoic acid to 4,7,10,13,16,19-docosahexaenoic acid in rat liver is independent of a 4-desaturase. J Biol Chem. 1991; 266: 19995-20000
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6. |
Singh M. Essential fatty acids, DHA and human brain. Indian J Pediatr. 2005; 72: 239-242
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7. |
Carper J. Your miracle brain, Harper collins, New York, 2000.
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8. |
Cunnane SC, Francescutti V, Brenna JT, Crawford MA. Breast-fed infants achieve a higher rate of brain and whole body docosahexaenoate accumulation than formula-fed infants not consuming dietary docosahexaenoate. Lipids. 2000; 35: 105-111.
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9. |
Denomme J, Stark KD, Holub BJ. Directly quantitated dietary (n-3) fatty acid intakes of pregnant Canadian women are lower than current dietary recommendations. J Nutr. 2005; 135: 206-211
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10. |
Davis BC, Kris-Etherton PM. Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. Am J Clin Nutr. 2003; 78 (3 Suppl): 640S-646S
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11. |
Lien VW, Clandinin MT. Dietary assessment of arachidonic acid and docosahexaenoic acid intake in 4-7 year-old children. J Am Coll Nutr. 2009; 28: 7-15
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12. |
WHO and FAO joint consultation: fats and oils in human nutrition. Nutr Rev. 1995; 53: 202-205
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13. |
Innis SM. Dietary omega 3 fatty acids and the developing brain. Brain Res. 2008; 1237: 35-43
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14. |
Dangour AD, Uauy R. N-3 long-chain polyunsaturated fatty acids for optimal function during brain development and ageing. Asia Pac J Clin Nutr. 2008; 17 Suppl 1: 185-188
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15. |
Dyall SC, Michael-Titus AT. Neurological benefits of omega-3 fatty acids. Neuromolecular Med. 2008; 10: 219-235
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16. |
Engler MM, Engler MB, Malloy M, Chiu E, Besio D, Paul S, et al. Docosahexaenoic acid restores endothelial function in children with hyperlipidemia: results from the EARLY study. Int J Clin Pharmacol Ther. 2004; 42: 672-679.
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17. |
Politi P, Cena H, Comelli M, Marrone G, Allegri C, Emanuele E, Ucelli di Nemi S. Behavioral effects of omega-3 fatty acid supplementation in young adults with severe autism: an open label study. Arch Med Res. 2008 ; 39: 682-685
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18. |
Kato T, Hancock RL, Mohammadpour H, McGregor B, Manalo P, Khaiboullina S, et al. Influence of omega-3 fatty acids on the growth of human colon carcinoma in nude mice. Cancer Lett. 2002; 187: 169-177
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