Essential fatty acids, DHA and human brain
http://www.100md.com
《美国医学杂志》
Child Care and Dental Health Center, Noida, UP, India
Abstract
Essential fatty acids cannot be synthesized in the body but they are required for maintenance of optimal health. There are two classes of polyunsaturated fatty acids (PUFAs)- omega-6 and omega-3. The parent omega-6 fatty acid, linoleic acid (LA) is desaturated in the body to form arachidonic acid while parent omega-3 fatty acid alpha- linolenic acid (ALA) is desaturated by microsomal enzyme system through a series of metabolic steps to form eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA). But there is a limited metabolic capability during early life to metabolize PUFAs to more active long-chain fatty acids. There is a critical role of EFAs and their metabolic products for maintenance of structural and functional integrity of central nervous system and retina. Most of the brain growth is completed by 5-6 years of age. At birth brain weight is 70% of an adult, 15% brain growth occurs during infancy and remaining brain growth is completed during preschool years. DHA is the predominant structural fatty acid in the central nervous system and retina and its availability is crucial for brain development. It is recommended that the pregnant and nursing woman should take at least 2.6g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her fetus and suckling infant. The follow-up studies have shown that infants of mothers supplemented with EFAs and DHA had higher mental processing scores, psychomotor development, eye-hand coordination and stereo acuity at 4 years of age. Intake of EFAs and DHA during preschool years may also have a beneficial role in the prevention of attention deficit hyperactivity disorder (ADHD) and enhancing learning capability and academic performance.
Keywords: Essential fatty acids; Omega-3 fatty acids; DHA; Brain growth; ADHD
Essential fatty acids (EFAs) are required for maintenance of optimal health but they cannot be synthesized in the body and must be obtained from dietary sources. They are also called polyunsaturated fatty acids (PUFAs). They remain in a liquid form even in cold weather unlike saturated oils which solidify. There are two classes of PUFAs, omega-6 and omega-3. The parent omega-6 fatty acid is linoleic acid (LA) and the parent omega-3 fatty acid is alpha-linolenic acid (ALA)[1],[2]. Till recently, deficiency of essential fatty acids was believed to cause crazy-pavement scaly dermatitis, alopecia, thrombocytopenia and failure to thrive.[3] But there is increasing evidence to suggest the critical role of EFAs and their active metabolic products for the maintenance of structural and functional integrity of central nervous system and retina.
Dietary sources
The main dietary sources of omega-6 fatty acids are vegetable oils like sunflower oil, safflower oil, sesame oil, palmolein oil and corn oil. About 10-15% of omega-6 fatty acids are obtained as an integral part of cereals, pulses, tubers, legumes and vegetables as 'invisible fat'. The rich dietary sources of omega-3 fatty acids are vegetable oils like flaxseed or linseed oil, rapeseed or canola oil, peanut oil, olive oil, soya oil, walnut oil, green leafy vegetables, fenugreek seeds, kidney beans, dry fruits, oily cold-water fish (mackerel, sardine, hilsa and salmon etc.) and fish oil.[4] Vegetarians specially vegans, who do not take even eggs and milk products, are likely to consume lower quantities of alpha linolenic acid (ALA) compared to linoleic acid (LA).[5]
Due to their greater availability and low cost, there is excessive consumption of omega-6 fatty acids in developing countries. Junk food is also loaded with n-6 fatty acids and transfatty acids. Most Indians consume omega-6 and omega-3 fatty acids in a ratio of 30-70:1 but the ideal ratio is 5-10:1 for optimal health benefits.[6] The Japanese are probably the only nation that consume EFAs in an ideal ratio of 2-4:1 by taking plenty of sea food.
METABOLISM OF EFAs
In humans, both EFAs (n-3 and n-6 are 18 carbon atoms fatty acids) are metabolized to long-chain fatty acids by desaturation and adding extra double bonds to the carboxyl group end of the molecule. Linoleic acid (LA) is metabolized to arachidonic acid (AA) while alpha-linolenic acid (ALA) is metabolized to eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA) as active metabolic end products table1.[7],[8]
During early life there is limited metabolic capability to convert ALA to DHA. Therefore, during fetal life, infancy and early childhood DHA should be consumed de novo.
Sources of dha
During pregnancy, the fetus depends completely on maternal sources of DHA from lipid stores, maternal diet and nutritional supplements. During fetal life, placenta selectively and substantially transports AA and DHA from the mother to the fetus. During third trimester of pregnancy, there is an avid accretion of DHA in the liver, brain and retina of the fetus at a rate of 4.13g of EFA per week i.e. 0.59 g/day.[9] Pregnancy leads to a progressive depletion of maternal plasma DHA, presumably due to the increased supply of this critical nutrient to the developing fetal nervous system.[10] After delivery maternal stores are replaced slowly or incompletely over a period of 5-6 months Figure1.[11] There is evidence to suggest that depletion of maternal DHA reserves during pregnancy is an important correlate of postpartum depression.
During infancy DHA needs of the baby are met through breast milk. DHA content of the human milk is atleast 30 times of the milk of other mammals and can be further improved by giving adequate dietary supplements to the nursing mother.[12] During preschool years, the DHA requirement are met by consumption of diet rich in n-3 fatty acids and DHA. Fish oil, sea food, marine algae and sea weed are eminently rich sources of EPA and DHA. Sea food is highly brain-friendly because apart from DHA, it is rich in iodine, taurine and zinc. The DHA content of the animal milk, meat, poultry and eggs can be increased by giving omega-3 fatty acid rich diet to the animals and chicken. Eggs of chicken fed with flax or microalgae have been shown to be loaded with DHA (100-150 mg DHA/egg).
Brain growth
Most of the brain growth occurs during fetal life. When a baby is born, the body weight is only 5% of an adult but the brain size is 70% of the adult brain.[1] After birth 15% of brain growth occurs during first year of life and the remaining 10% of brain growth occurs during pre-school years Figure2. Most of the brain growth is completed by 5-6 years of age.[9]
Structure of the brain
"From high fat to low fat with age, first to increase intelligence and then to increase life span"
- Kurt Widhalm
Brain is the fattiest organ of the body. Almost two-third of the weight of the human brain is accounted by phospholipids. DHA is the predominant structural fatty acid in the brain which is mostly distributed in the cerebral cortex, membranes of synaptic communication centers, mitochondria and photoreceptors of the retina.[13] It comprises approximately 40% of the PUFAs in the brain and 60% of PUFAs in the retina. Almost 50% weight of the neuronal membranes is accounted by DHA. Arachidonic acid, EPA and DHA along with other smart micronutrients like vitamin B complex, vitamin C, vitamin E, iodine, iron, zinc, copper, taurine and choline etc. are crucial for brain development and its integrity and functionality.[12]
PHYSIOLOGICAL EFFECTS OF EFAs
PUFAs are important source of energy in our diet. When omega-6 and omega-3 fatty acids are consumed in the recommended ratio of 5-10:1, they are essential for maintaining structural and functional integrity of central nervous system. Omega-6 fatty acids are pro-inflammatory and promote platelet aggregation while omega-3 fatty acids are anti-inflammatory and inhibit platelet aggregation. The metabolism of omega-6 fatty acids is associated with production of a number of eicosanoids like thromboxanes, leukotrienes and prostaglandins which are known to trigger inflammation in the blood vessels causing atherosclerosis.[14] Archidonic acid which is the metabolic end product of linoleic acid (n-6 PUFA) is the most potent inflammatory agent. It also stimulates the production of glutamate, a neurotransmitter which potentiates the destruction of neurons by over production of oxygen free radicals.
"The food that is good for the heart is likely to be good for the brain."
- Hippocrates
On the other hand, omega-3 fatty acids and DHA are credited to reduce cellular and vascular inflammation in the brain, and ensure integrity of brain cell membranes to keep them soft and pliable. Fish oil and DHA are credited to reduce the level of thromboxane (TXA2) and increase prostacyclin (PGI2) level leading to enhanced tissue perfusion and oxygen delivery due to vasodilatation and decreased blood viscosity. Apart from its role in fabrication of synaptic communication centers, DHA is credited to increase the level of "feel good" neurotransmitter serotonin and "memory boosting" chemical acetylcholine. DHA is also credited to neutralize oxygen-free radicals.
HEALTH BENEFITS OF SUPPLEMENTS WITH EFAs AND DHA
The EFA status of the fetus depends upon the EFA content of the maternal diet. Pregnant women must take adequate amount of DHA in their diet or through nutritional supplements in order to optimize not only their own health but also the health and mental development of their offsprings. According to WHO and FAO the pregnant woman should take atleast 2.6g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her fetus.[15] The clinical studies have shown that the duration of gestation and birth weight are significantly increased when omega-3 rich food or DHA supplements are taken during last trimester of pregnancy.[11],[16],[17] Olsen et al[18] showed that risk of preterm delivery was 4 times less in mothers who received omega-3 food supplements during pregnancy. DHA is credited to reduce the levels of thromboxane (TXA2) and increase prostacyclin (PGI2) level leading to enhanced utero-placental perfusion and oxygen delivery, vasodilatation and thinning of blood. There is reduced risk of development of toxemia of pregnancy in mothers who received supplements of DHA. The follow-up studies have shown that infants born to mothers whose diet was supplemented with DHA, had higher mental processing scores and high degree of stereopsis and stereo acuity at 4 years of age .[19],[20]
The nutritional quality of breast milk depends upon the nutritional status and dietary supplements taken by the nursing mother. There is a linear correlation between the dietary intake of DHA by the nursing mother and the DHA content of her breast milk.[21],[22] It is recommended that nursing mother should take atleast 2.6g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her suckling infant. It has been shown that supplementation with 200 mg DHA/day is associated with increase in the concentration of her breast milk DHA content by 0.20-0.34 wt% i.e. 2-fold increase as compared to controls. There is a direct correlation between breast milk DHA levels with DHA content of baby's RBCs and neurodevelopment outcome at one year of age. Breast fed babies have been shown to have more DHA content in their brains with 8 points higher IQ compared to formula fed babies. The studies have shown that breast fed infants of mothers who were supplemented with DHA during lactation, had significantly better psychomotor development, eye-hand coordination and visual acuity at 2.5 years compared to breast fed infants of mothers who received a placebo.[23] Till recently, baby formulae available in the developed countries were not supplemented with DHA. But now many formulae available in the west are fortified with DHA to harness its benefits during the crucial phase of brain development during infancy.
The weaning foods and diets of preschool children should contain DHA because metabolic conversion of alpha-linolenic acid to DHA is limited to less than 0.2% in children. There is evidence to suggest that 40% of children with attention hyperactivity disorder (ADHD) have significantly low levels of plasma DHA.[24] It is believed that DHA may also have beneficial effects on the learning capabilities and academic performance of children. It is recommended that weaning foods should be rich in DHA (fish oil, sea food and dry fruits) or supplemented with nutritional supplements containing DHA.
References
1. Clandinin MT, Jumpsen J, Suh M. Relationship between fatty acid accretion, membrane composition and biologic functions. J Pediatr 1994; 125(5): S25-S32.
2. British Nutrition Foundation Task Force. Unsaturated fatty acids, nutritional and physiological significance. The report of BNF Task Force, London: British Nutrition Foundation, 1992
3. Behrman RE, Kliegman RM, Jenson HB. Nelson's Textbook of Pediatrics. Elsevier, New Delhi 2004: 2249.
4. Carper J. Your Miracle Brain. Harper Collins, New York 2000.
5. Davis BC, Kris-Etherton PK. Achieving optimal essential fatty acid status in vegetarians : current knowledge and practical implications. Am J Clin Nutr 2003; 78(suppl):640S-646S.
6. WHO and FAO Joint Consultation : Fats and oils in human nutrition. Nutr Rev 1995, 53 : 202-205.
7. Pawlosky RJ, Hibbelin JR, Novotny JA, Salem N. Physiological compartmental analysis of linolenic acid metabolism in adult humans. J Lipid Res 2001; 42 : 1257-1265.
8. Mayers PA. Metabolism of unsaturated fatty acid and eicosanoids. In Murray RK, Granner DK, Mayers PA, Rodwell VW, eds. Harper's Biochemistry 24th edn. Prentice Hall, London 1996; 236-244.
9. Clandinin MT, Chappel JE, Leong S, Heim T, Swyer PR, Chance GW. Intrauterine fatty acid accretion in human brain : implications for fatty acid requirements. Early Hum Dev 1980, 4 : 121-129.
10. Uauy R, Mena P, Rojas C. Essential fatty acids in early life: Structural and functional role. Proceedings of the Nutrition Society 2000; 59:3-15.
11. Smuts CM, Huang M, Mundy D et al. A randomized trial of decosahexaenoic acid supplementation during the third trimester of pregnancy. Obstet Gynecol 2003; 101 (3): 469-479.
12. Singh M. Nutrition, brain and environment. How to have smarter babies Indian Pediatr 2003; 40 : 213-220.
13. Haag M. Essential fatty acids and the brain. Canad J Psychiatry 2003; 48 : 195-203.
14. Ghafoornissa SA. Requirements of dietary fats to meet nutritional needs and prevent risk of atherosclerosis : an Indian perspective. Indian J Med Res 1998; 108 : 191-202.
15. Simopoulos AP, Leaf A, Salem M. Workshop on the essentiality of and recommended dietary intakes of omega-6 and omega-3 fatty acids. Prostaglandins Leukot Essent Fatty Acids 2000; 63 : 119-121.
16. Yeh YY, Gehman MF, Yeh SM. Maternal dietary fish oil enriches decosahexaenoate levels in brain subcellular fractions of offspring. J Neurosc Res 1993; 35: 218-226.
17. Olsen SF, Secher NJ. Low consumption of sea food in early pregancy as a risk factor for preterm delivery: Prospective cohort study. BMJ 2002; 324: 447.
18. Olsen SF, Grandjean P, Weihe P, Weihe P, Videro T. Frequency of sea food intake in pregnancy as a determinant of birth weight : Evidence for a dose-dependant relationship. J Epidemiol Comm Hlth 1993; 47(6) : 436-440.
19. Helland IB, Smith L, Saarem K et al. Maternal supplementation with very-long chain n-3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age. Pediatrics 2003; 111 (1) : e 39-44.
20. Williams C, Birch EE, Emmett PM, Northstone K. Stereo acuity at age 3-5 years in children born full term is associated with pre-natal and post-natal dietary factors : a report from a population-based cohort study. Am J Clin Nutr 2001; 73 : 316-322.
21. Fidler N, Sauerwald T, Pohl A et al. Decosahexaenoic acid transfer into human milk after dietary supplementation : a randomized clinical trial. J Lipid Res 2000; 41 : 1376-1383.
22. Makrides M, Neumann MA, Gibson RA. Effects of maternal decosahexaenoic acid (DHA) supplementation on breast milk composition. Euro J Clin Nutr 1996; 50 : 352-357.
23. Jensen CL. Effects of maternal decosahexaenoic acid (DHA) supplementation on visual functions and neurodevelopment of breast fed infants. Pediatr Res 2001; 49 : 448A.
24. Burgess JR, Stevens L, Zhang W, Peck L. Long-chain polyunsaturated fatty acids in children with attention deficit hyperactivity disorder. Am J Clin Nutr 2000; 71(1) : 327-330.(Singh Meharban)
Abstract
Essential fatty acids cannot be synthesized in the body but they are required for maintenance of optimal health. There are two classes of polyunsaturated fatty acids (PUFAs)- omega-6 and omega-3. The parent omega-6 fatty acid, linoleic acid (LA) is desaturated in the body to form arachidonic acid while parent omega-3 fatty acid alpha- linolenic acid (ALA) is desaturated by microsomal enzyme system through a series of metabolic steps to form eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA). But there is a limited metabolic capability during early life to metabolize PUFAs to more active long-chain fatty acids. There is a critical role of EFAs and their metabolic products for maintenance of structural and functional integrity of central nervous system and retina. Most of the brain growth is completed by 5-6 years of age. At birth brain weight is 70% of an adult, 15% brain growth occurs during infancy and remaining brain growth is completed during preschool years. DHA is the predominant structural fatty acid in the central nervous system and retina and its availability is crucial for brain development. It is recommended that the pregnant and nursing woman should take at least 2.6g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her fetus and suckling infant. The follow-up studies have shown that infants of mothers supplemented with EFAs and DHA had higher mental processing scores, psychomotor development, eye-hand coordination and stereo acuity at 4 years of age. Intake of EFAs and DHA during preschool years may also have a beneficial role in the prevention of attention deficit hyperactivity disorder (ADHD) and enhancing learning capability and academic performance.
Keywords: Essential fatty acids; Omega-3 fatty acids; DHA; Brain growth; ADHD
Essential fatty acids (EFAs) are required for maintenance of optimal health but they cannot be synthesized in the body and must be obtained from dietary sources. They are also called polyunsaturated fatty acids (PUFAs). They remain in a liquid form even in cold weather unlike saturated oils which solidify. There are two classes of PUFAs, omega-6 and omega-3. The parent omega-6 fatty acid is linoleic acid (LA) and the parent omega-3 fatty acid is alpha-linolenic acid (ALA)[1],[2]. Till recently, deficiency of essential fatty acids was believed to cause crazy-pavement scaly dermatitis, alopecia, thrombocytopenia and failure to thrive.[3] But there is increasing evidence to suggest the critical role of EFAs and their active metabolic products for the maintenance of structural and functional integrity of central nervous system and retina.
Dietary sources
The main dietary sources of omega-6 fatty acids are vegetable oils like sunflower oil, safflower oil, sesame oil, palmolein oil and corn oil. About 10-15% of omega-6 fatty acids are obtained as an integral part of cereals, pulses, tubers, legumes and vegetables as 'invisible fat'. The rich dietary sources of omega-3 fatty acids are vegetable oils like flaxseed or linseed oil, rapeseed or canola oil, peanut oil, olive oil, soya oil, walnut oil, green leafy vegetables, fenugreek seeds, kidney beans, dry fruits, oily cold-water fish (mackerel, sardine, hilsa and salmon etc.) and fish oil.[4] Vegetarians specially vegans, who do not take even eggs and milk products, are likely to consume lower quantities of alpha linolenic acid (ALA) compared to linoleic acid (LA).[5]
Due to their greater availability and low cost, there is excessive consumption of omega-6 fatty acids in developing countries. Junk food is also loaded with n-6 fatty acids and transfatty acids. Most Indians consume omega-6 and omega-3 fatty acids in a ratio of 30-70:1 but the ideal ratio is 5-10:1 for optimal health benefits.[6] The Japanese are probably the only nation that consume EFAs in an ideal ratio of 2-4:1 by taking plenty of sea food.
METABOLISM OF EFAs
In humans, both EFAs (n-3 and n-6 are 18 carbon atoms fatty acids) are metabolized to long-chain fatty acids by desaturation and adding extra double bonds to the carboxyl group end of the molecule. Linoleic acid (LA) is metabolized to arachidonic acid (AA) while alpha-linolenic acid (ALA) is metabolized to eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA) as active metabolic end products table1.[7],[8]
During early life there is limited metabolic capability to convert ALA to DHA. Therefore, during fetal life, infancy and early childhood DHA should be consumed de novo.
Sources of dha
During pregnancy, the fetus depends completely on maternal sources of DHA from lipid stores, maternal diet and nutritional supplements. During fetal life, placenta selectively and substantially transports AA and DHA from the mother to the fetus. During third trimester of pregnancy, there is an avid accretion of DHA in the liver, brain and retina of the fetus at a rate of 4.13g of EFA per week i.e. 0.59 g/day.[9] Pregnancy leads to a progressive depletion of maternal plasma DHA, presumably due to the increased supply of this critical nutrient to the developing fetal nervous system.[10] After delivery maternal stores are replaced slowly or incompletely over a period of 5-6 months Figure1.[11] There is evidence to suggest that depletion of maternal DHA reserves during pregnancy is an important correlate of postpartum depression.
During infancy DHA needs of the baby are met through breast milk. DHA content of the human milk is atleast 30 times of the milk of other mammals and can be further improved by giving adequate dietary supplements to the nursing mother.[12] During preschool years, the DHA requirement are met by consumption of diet rich in n-3 fatty acids and DHA. Fish oil, sea food, marine algae and sea weed are eminently rich sources of EPA and DHA. Sea food is highly brain-friendly because apart from DHA, it is rich in iodine, taurine and zinc. The DHA content of the animal milk, meat, poultry and eggs can be increased by giving omega-3 fatty acid rich diet to the animals and chicken. Eggs of chicken fed with flax or microalgae have been shown to be loaded with DHA (100-150 mg DHA/egg).
Brain growth
Most of the brain growth occurs during fetal life. When a baby is born, the body weight is only 5% of an adult but the brain size is 70% of the adult brain.[1] After birth 15% of brain growth occurs during first year of life and the remaining 10% of brain growth occurs during pre-school years Figure2. Most of the brain growth is completed by 5-6 years of age.[9]
Structure of the brain
"From high fat to low fat with age, first to increase intelligence and then to increase life span"
- Kurt Widhalm
Brain is the fattiest organ of the body. Almost two-third of the weight of the human brain is accounted by phospholipids. DHA is the predominant structural fatty acid in the brain which is mostly distributed in the cerebral cortex, membranes of synaptic communication centers, mitochondria and photoreceptors of the retina.[13] It comprises approximately 40% of the PUFAs in the brain and 60% of PUFAs in the retina. Almost 50% weight of the neuronal membranes is accounted by DHA. Arachidonic acid, EPA and DHA along with other smart micronutrients like vitamin B complex, vitamin C, vitamin E, iodine, iron, zinc, copper, taurine and choline etc. are crucial for brain development and its integrity and functionality.[12]
PHYSIOLOGICAL EFFECTS OF EFAs
PUFAs are important source of energy in our diet. When omega-6 and omega-3 fatty acids are consumed in the recommended ratio of 5-10:1, they are essential for maintaining structural and functional integrity of central nervous system. Omega-6 fatty acids are pro-inflammatory and promote platelet aggregation while omega-3 fatty acids are anti-inflammatory and inhibit platelet aggregation. The metabolism of omega-6 fatty acids is associated with production of a number of eicosanoids like thromboxanes, leukotrienes and prostaglandins which are known to trigger inflammation in the blood vessels causing atherosclerosis.[14] Archidonic acid which is the metabolic end product of linoleic acid (n-6 PUFA) is the most potent inflammatory agent. It also stimulates the production of glutamate, a neurotransmitter which potentiates the destruction of neurons by over production of oxygen free radicals.
"The food that is good for the heart is likely to be good for the brain."
- Hippocrates
On the other hand, omega-3 fatty acids and DHA are credited to reduce cellular and vascular inflammation in the brain, and ensure integrity of brain cell membranes to keep them soft and pliable. Fish oil and DHA are credited to reduce the level of thromboxane (TXA2) and increase prostacyclin (PGI2) level leading to enhanced tissue perfusion and oxygen delivery due to vasodilatation and decreased blood viscosity. Apart from its role in fabrication of synaptic communication centers, DHA is credited to increase the level of "feel good" neurotransmitter serotonin and "memory boosting" chemical acetylcholine. DHA is also credited to neutralize oxygen-free radicals.
HEALTH BENEFITS OF SUPPLEMENTS WITH EFAs AND DHA
The EFA status of the fetus depends upon the EFA content of the maternal diet. Pregnant women must take adequate amount of DHA in their diet or through nutritional supplements in order to optimize not only their own health but also the health and mental development of their offsprings. According to WHO and FAO the pregnant woman should take atleast 2.6g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her fetus.[15] The clinical studies have shown that the duration of gestation and birth weight are significantly increased when omega-3 rich food or DHA supplements are taken during last trimester of pregnancy.[11],[16],[17] Olsen et al[18] showed that risk of preterm delivery was 4 times less in mothers who received omega-3 food supplements during pregnancy. DHA is credited to reduce the levels of thromboxane (TXA2) and increase prostacyclin (PGI2) level leading to enhanced utero-placental perfusion and oxygen delivery, vasodilatation and thinning of blood. There is reduced risk of development of toxemia of pregnancy in mothers who received supplements of DHA. The follow-up studies have shown that infants born to mothers whose diet was supplemented with DHA, had higher mental processing scores and high degree of stereopsis and stereo acuity at 4 years of age .[19],[20]
The nutritional quality of breast milk depends upon the nutritional status and dietary supplements taken by the nursing mother. There is a linear correlation between the dietary intake of DHA by the nursing mother and the DHA content of her breast milk.[21],[22] It is recommended that nursing mother should take atleast 2.6g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her suckling infant. It has been shown that supplementation with 200 mg DHA/day is associated with increase in the concentration of her breast milk DHA content by 0.20-0.34 wt% i.e. 2-fold increase as compared to controls. There is a direct correlation between breast milk DHA levels with DHA content of baby's RBCs and neurodevelopment outcome at one year of age. Breast fed babies have been shown to have more DHA content in their brains with 8 points higher IQ compared to formula fed babies. The studies have shown that breast fed infants of mothers who were supplemented with DHA during lactation, had significantly better psychomotor development, eye-hand coordination and visual acuity at 2.5 years compared to breast fed infants of mothers who received a placebo.[23] Till recently, baby formulae available in the developed countries were not supplemented with DHA. But now many formulae available in the west are fortified with DHA to harness its benefits during the crucial phase of brain development during infancy.
The weaning foods and diets of preschool children should contain DHA because metabolic conversion of alpha-linolenic acid to DHA is limited to less than 0.2% in children. There is evidence to suggest that 40% of children with attention hyperactivity disorder (ADHD) have significantly low levels of plasma DHA.[24] It is believed that DHA may also have beneficial effects on the learning capabilities and academic performance of children. It is recommended that weaning foods should be rich in DHA (fish oil, sea food and dry fruits) or supplemented with nutritional supplements containing DHA.
References
1. Clandinin MT, Jumpsen J, Suh M. Relationship between fatty acid accretion, membrane composition and biologic functions. J Pediatr 1994; 125(5): S25-S32.
2. British Nutrition Foundation Task Force. Unsaturated fatty acids, nutritional and physiological significance. The report of BNF Task Force, London: British Nutrition Foundation, 1992
3. Behrman RE, Kliegman RM, Jenson HB. Nelson's Textbook of Pediatrics. Elsevier, New Delhi 2004: 2249.
4. Carper J. Your Miracle Brain. Harper Collins, New York 2000.
5. Davis BC, Kris-Etherton PK. Achieving optimal essential fatty acid status in vegetarians : current knowledge and practical implications. Am J Clin Nutr 2003; 78(suppl):640S-646S.
6. WHO and FAO Joint Consultation : Fats and oils in human nutrition. Nutr Rev 1995, 53 : 202-205.
7. Pawlosky RJ, Hibbelin JR, Novotny JA, Salem N. Physiological compartmental analysis of linolenic acid metabolism in adult humans. J Lipid Res 2001; 42 : 1257-1265.
8. Mayers PA. Metabolism of unsaturated fatty acid and eicosanoids. In Murray RK, Granner DK, Mayers PA, Rodwell VW, eds. Harper's Biochemistry 24th edn. Prentice Hall, London 1996; 236-244.
9. Clandinin MT, Chappel JE, Leong S, Heim T, Swyer PR, Chance GW. Intrauterine fatty acid accretion in human brain : implications for fatty acid requirements. Early Hum Dev 1980, 4 : 121-129.
10. Uauy R, Mena P, Rojas C. Essential fatty acids in early life: Structural and functional role. Proceedings of the Nutrition Society 2000; 59:3-15.
11. Smuts CM, Huang M, Mundy D et al. A randomized trial of decosahexaenoic acid supplementation during the third trimester of pregnancy. Obstet Gynecol 2003; 101 (3): 469-479.
12. Singh M. Nutrition, brain and environment. How to have smarter babies Indian Pediatr 2003; 40 : 213-220.
13. Haag M. Essential fatty acids and the brain. Canad J Psychiatry 2003; 48 : 195-203.
14. Ghafoornissa SA. Requirements of dietary fats to meet nutritional needs and prevent risk of atherosclerosis : an Indian perspective. Indian J Med Res 1998; 108 : 191-202.
15. Simopoulos AP, Leaf A, Salem M. Workshop on the essentiality of and recommended dietary intakes of omega-6 and omega-3 fatty acids. Prostaglandins Leukot Essent Fatty Acids 2000; 63 : 119-121.
16. Yeh YY, Gehman MF, Yeh SM. Maternal dietary fish oil enriches decosahexaenoate levels in brain subcellular fractions of offspring. J Neurosc Res 1993; 35: 218-226.
17. Olsen SF, Secher NJ. Low consumption of sea food in early pregancy as a risk factor for preterm delivery: Prospective cohort study. BMJ 2002; 324: 447.
18. Olsen SF, Grandjean P, Weihe P, Weihe P, Videro T. Frequency of sea food intake in pregnancy as a determinant of birth weight : Evidence for a dose-dependant relationship. J Epidemiol Comm Hlth 1993; 47(6) : 436-440.
19. Helland IB, Smith L, Saarem K et al. Maternal supplementation with very-long chain n-3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age. Pediatrics 2003; 111 (1) : e 39-44.
20. Williams C, Birch EE, Emmett PM, Northstone K. Stereo acuity at age 3-5 years in children born full term is associated with pre-natal and post-natal dietary factors : a report from a population-based cohort study. Am J Clin Nutr 2001; 73 : 316-322.
21. Fidler N, Sauerwald T, Pohl A et al. Decosahexaenoic acid transfer into human milk after dietary supplementation : a randomized clinical trial. J Lipid Res 2000; 41 : 1376-1383.
22. Makrides M, Neumann MA, Gibson RA. Effects of maternal decosahexaenoic acid (DHA) supplementation on breast milk composition. Euro J Clin Nutr 1996; 50 : 352-357.
23. Jensen CL. Effects of maternal decosahexaenoic acid (DHA) supplementation on visual functions and neurodevelopment of breast fed infants. Pediatr Res 2001; 49 : 448A.
24. Burgess JR, Stevens L, Zhang W, Peck L. Long-chain polyunsaturated fatty acids in children with attention deficit hyperactivity disorder. Am J Clin Nutr 2000; 71(1) : 327-330.(Singh Meharban)