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Docosahexaenoic Acid (DHA)
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| General Info | ||||||||||||||||||||
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Active Forms Docosahexaenoic acid Absorption DHA is absorbed from the intestinal tract, but since it is a fat, absorption is dependent on the amount of fat being consumed at that particular meal. One study reported that the absorption of EPA and DHA fish oils was increased three-fold when consumed with a high-fat meal.(1) Dietary Sources The richest dietary sources of DHA are the oils from cold water fish such as salmon, mackerel, herring, sardines, and other marine animals. |
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| Dosage Info | Back to Top | |||||||||||||||||||
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| Overview | Back to Top | |||||||||||||||||||
Although DHA can be consumed directly by eating certain kinds of fish, it can also be produced in the body. This process first requires the conversion of alpha linolenic acid (ALA), which is also known as omega-3, to EPA. In the next step of the metabolic process, EPA is converted into DHA. The metabolic processes that convert omega-3 to EPA accomplish this with desaturase and elongase enzymes. Desaturase enzymes produce additional double bonds, while elongase enzymes add carbon atoms to make a longer fatty acid chain. The parent or precursor omega-3 molecule, alpha linolenic acid, is a long-chain fatty acid that contains 18 carbon atoms with three double bonds. Under the influence of the desaturase and elongase enzymes, ALA is converted to eicosapentaenoic acid, which is a fatty acid that is 20 carbons long and contains five double bonds. EPA is then converted into DHA, which is a fatty acid that is 22 carbons long and contains six double bonds. Studies using omega-3 (ALA) labeled with radioisotopes indicate that many Americans, who normally ingest large quantities of omega-6 oils, probably convert less than 2% of their dietary alpha linolenic acid into (ALA) into docosahexaenoic acid (DHA).(4) Although fish are the best dietary source of DHA, monitoring by the Environmental Protection Agency reveals that commercially available fish may have unacceptably high levels of mercury.(5) Because this problem is of such concern, the EPA warns that pregnant or nursing women and small children should limit their intake of fish.(6) The above issues underscore the importance of taking DHA as a nutritional supplement. Individuals taking DHA supplementation must be warned about the importance of also taking adequate levels of antioxidants. |
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| Toxicities & Precautions | Back to Top | |||||||||||||||||||
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DHA is absorbed from the intestinal tract, but since it is a fat, absorption is dependent on the amount of fat being consumed at that particular meal. One study reported that the absorption of EPA and DHA fish oils was increased three-fold when consumed with a high-fat meal.(1) General Individuals who ingest supplemental DHA are advised to take additional antioxidants, especially vitamin E, to protect against free radical oxidation in the body. Side Effects Some people who take supplemental DHA in the form of fish oil complain of gastrointestinal burping and belching, which causes a “fishy” odor.(7) |
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| Functions in the Body | Back to Top | |||||||||||||||||||
Required for the development of the retina of the eye. Required for proper growth and development of the brain and nervous system.(8) |
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| Clinical Applications | Back to Top | |||||||||||||||||||
| ADHD Researchers report that children with ADHD have low plasma levels of DHA and exhibit symptoms indicative of essential fatty acid deficiency.(9) However, the results of a short 4-month trial reported that children who received 345 mg/day of DHA did not exhibit a decrease in the symptoms of ADHD.(10) |
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| Bipolar disorder Evidence suggests that long-chain omega-3 fatty acids contained in fish oils (EPA and DHA) exhibit mood-stabilizing properties in patients with bipolar disorder, which is also known as manic depressive illness. EPA and DHA seem to inhibit neuronal signal transduction pathways in a manner similar to lithium carbonate and valproate, which are medications frequently used to treat this disorder. In a four-month, double-blind, placebo-controlled trial, patients treated with the omega-3 fish oils exhibited a significantly longer period of remission, plus they scored better than the placebo group on virtually every outcome measure that was studied.(11) Researchers found that levels of DHA were lower in bipolar mood disorder patients than in controls and that supplementation of antioxidants and essential fatty acids may improve the patients' symptoms.(12) |
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| Breast Cancer There is an inverse relationship between the incidence of breast cancer and fish consumption, which suggests a role for DHA and EPA in the prevention of breast cancer. This may be due to the fact that the omega-3 fats competitively inhibit omega-6 fats, which are considered to promote breast cancer tumorigenesis and tumor cell proliferation.(13) |
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| Breast feeding (lactation) DHA is essential for the development of the brain and eyes in infants. Consequently, nursing mothers should be educated about the importance of obtaining optimal intakes of DHA. Infants receiving adequate DHA, either from supplementation or from well nourished mothers, exhibit increased cognitive function(14) and visual acuity(15) compared to controls. |
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| Cancer In an animal model, the addition of DHA/EPA to the diet resulted in a 35 to 46% reduction in tumor growth. Also, in cell culture studies, DHA resulted in a 46% decrease in cancer cell growth.(16) |
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| Chemotherapy The results of animal studies suggest that supplementation with DHA can make several types of chemotherapy both more effective and less toxic. In one study, mitomycin C was 10 times more effective in animals supplemented with DHA-containing menhaden oil.(17) In another study, after 2 months of treatment with cyclophosphamide, 50% of the animals on a 5% corn oil diet had died whereas none of the animals receiving the DHA/menhaden oil died.(18) |
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| Depression Studies indicate that people with major depression may have abnormal metabolism of the omega-3 polyunsaturated fatty acids. Thus, fatty acid analysis and appropriate supplementation may be an important aspect of treatment for patients suffering from major depression.(19) |
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| Dysmenorrhea Providing DHA along with EPA for two months to adolescents with dysmenorrhea resulted in a marked reduction in menstrual symptoms.(20) |
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| Elevated Triglycerides Patients who were given DHA (1.25 or 2.5 gm/day) for six weeks experienced approximately a 20 percent reduction in serum triglycerides.(21) Fish oil supplementation containing 1.0 g DHA and 1.5 g EPA significantly reduced plasma triacylglycerol levels.(22) |
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| Heart Disease Studies indicate that there is an inverse relationship between coronary heart disease risk and levels of docosahexaenoic acid.(23, 24) A study assessed the effect of omega-3 fatty acids on systemic arterial compliance (SAC). SAC is a measure of arterial elasticity and may serve as a marker for cardiovascular disease and related events. In this placebo controlled, randomized, double-blind trial, 38 individuals with dyslipidemias were randomly assigned to one of three groups: 3 g eicosapentaenoic acid (EPA) per day (n = 12), 3 g docosahexaenoic acid (DHA) per day (n = 12), or placebo (n = 14). Arterial functions, lipids and fatty acids were all measured prior to and following the treatment interventions. Compared to placebo the omega-3 fatty acids significantly increased the SAC. EPA increased SAC 36% and DHA increased SAC 27%. In addition, the omega-3 fatty acids significantly lowered the total and VLDL triacylgylcerol levels.(25) |
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| Infant Formulas Compared to controls, at 18 months of age, infants receiving supplemental DHA in their infant formulas scored significantly higher in mental development, as gauged by memory, problem solving, discrimination, and other related skills, and also showed "significant developmental age advantage" in motor and cognitive skills.(26) |
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| Premature Infants It has been reported that DHA is important for early development of the brain, nervous system, and retina of the eyes. Pre-term infants need to be supplemented with DHA since these infants are often incubated and not breast-fed.(27) In one study, pre-term infants supplemented with DHA developed higher visual acuity.(28) |
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| Schizophrenia Studies indicate that patients with schizophrenia have lower levels of the long-chain omega-3 fatty acids.(29) Supplementation led to a significant improvement in 20 schizophrenic symptoms.(30, 31) |
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| Sickle cell disease A group of patients suffering from sickle cell disease were administered menhaden fish oil (0.25 g/kg/d), which contained 12% EPA and 18% DHA. This treatment resulted in a substantial reduction of pain episodes requiring hospitalization from 7.8 hospitalizations the previous year down to 3.8 events/year. The authors suggest that the reduction in pain events requiring hospitalization were related to omega-3 fatty acid-dependent inhibition of thrombosis.(32) |
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| X-linked retinitis pigmentosa It has been discovered that individuals with this condition have a metabolic defect in the activity of their delta-5 desaturase enzyme activity, which inhibits their ability to biosynthesize DHA.(33) Another study provided evidence that DHA could be beneficial to patients with X-linked retinitis pigmentosa (XLRP).(34) There were not any identifiable safety risks associated with long-term docosahexaenoic acid supplementation to XLRP patients. Plasma antioxidant capacity, platelet aggregation, liver function enzyme activity, or plasma lipoprotein lipid content were not compromised by DHA supplementation.(35) |
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| Zellweger syndrome Individuals with this genetic peroxisomal disorder have low levels of DHA.(36) Patients treated with DHA exhibit improved vision and muscle as well as MRI-documented improvements in myelination. Treatment has been most successful when initiated before 6 months of age.(37) |
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| Symptoms & Causes of Deficiency | ||||||||||||||||||||
A deficiency of DHA has become increasingly common for the following reasons:
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| Footnotes | Back to Top | |||||||||||||||||||
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1 Lawson LD, et al. Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal. Biochem Biophys Res Commun. Oct1988;156(2):960-3. View Abstract 2 Helland IB, 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. Jan2003;111(1):e39-44. View Abstract 3 Colombo J, Kannass KN, Jill Shaddy D, et al. Maternal DHA and the Development of Attention in Infancy and Toddlerhood. Child Dev. Jul2004;75(4):1254-67. View Abstract 4 Gerster H. Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)? Int J Vitam Nutr Res. 1998;68(3):159-73. View Abstract 5 EPA Fact Sheet. Mercury Update: Impact on Fish Advisories, EPA-823-F-01-011. Jun2001. 6 EPA-Office of Water: Consumption Advisories. Available at: http://www.epa.gov/ost/fishadvice/advice.html. Accessed: Jul2001. 7 Healy DA, et al. Effect of low-to-moderate amounts of dietary fish oil on neutrophil lipid composition and function. Lipids. Jul2000;35(7):763-8. View Abstract 8 Khedr EM, Farghaly WM, Amry Sel-D, Osman AA. Neural maturation of breastfed and formula-fed infants. Acta Paediatr. Jun2004;93(6):734-8. View Abstract 9 Burgess JR, et al. Long-chain polyunsaturated fatty acids in children with attention-deficit hyperactivity disorder. Am J Clin Nutr. Jan2000;71(1 Suppl):327S-30S. View Abstract 10 Voigt RG, Llorente AM, Jensen CL, et al. A randomized, double-blind, placebo-controlled trial of docosahexaenoic acid supplementation in children with attention-deficit/hyperactivity disorder. J Pediatr. Aug2001;139(2):189-96. View Abstract 11 Stoll AL, et al. Omega 3 fatty acids in bipolar disorder; A preliminary double-blind, placebo-controlled trial. Archives of General Psychiatry. May1999;66:407-412. View Abstract 12 Ranjekar PK, Hinge A, Hegde MV, et al. Decreased antioxidant enzymes and membrane essential polyunsaturated fatty acids in schizophrenic and bipolar mood disorder patients. Psychiatry Res. Dec2003;121(2):109-22. View Abstract 13 Noguchi M. The Role of Fatty Acids and Eicosanoid Synthesis Inhibitors in Breast Cancer. Oncology. 1995;52:265- 271. View Abstract 14 Willatts P, Forsyth JS, DiModugno MK, et al. Effect of long-chain polyunsaturated fatty acids in infant formula on problem solving at 10 months of age. Lancet. Aug1998;352(9129):688-91. View Abstract 15 Jorgensen MH, Hernell O, Hughes E, Michaelsen KF. Is there a relation between docosahexaenoic acid concentration in mothers' milk and visual development in term infants? J Pediatr Gastroenterol Nutr. Mar2001;32(3):293-6. View Abstract 16 Colquhoun A, Ramos KL, Schumacher RI. Eicosapentaenoic acid and docosahexaenoic acid effects on tumour mitochondrial metabolism, acyl CoA metabolism and cell proliferation. Cell Biochem Funct. Jun2001;19(2):97-105. View Abstract 17 Shao Y, Pardini L, Pardini RS. Dietary menhaden oil enhances mitomycin C antitumor activity toward human mammary carcinoma MX-1. Lipids. Nov1995;30(11):1035-45. View Abstract 18 Shao Y, Pardini L, Pardini RS. Intervention of transplantable human mammary carcinoma MX-1 chemotherapy with dietary menhaden oil in athymic mice: increased therapeutic effects and decreased toxicity of cyclophosphamide. Nutr Cancer. 1997;28(1):63-73. View Abstract 19 Edwards R, Peet M, Shay J. Depletion of docosahexanoic acid in red blood cell membranes of depressive patients. Biochem Soc Trans. May1998;26(2):S142. 20 Harel Z, et al. Supplementation With Omega-3 Polyunsaturated Fatty Acids in the Management of Dysmenorrhea in Adolescents. American Journal of Obstetrics and Gynecology. Apr1996;174(4):1335-8. View Abstract 21 Davidson M, et al. Effects of docosahexaenoic acid on serum lipoproteins in patients with combined hyperlipidaemia: a randomized, double-blind, placebo-controlled trial. J AM Coll Nutr. 1997;16:236-243. View Abstract 22 Lovegrove JA, Lovegrove SS, Lesauvage SV, et al. Moderate fish-oil supplementation reverses low-platelet, long-chain n-3 polyunsaturated fatty acid status and reduces plasma triacylglycerol concentrations in British Indo-Asians. Am J Clin Nutr. Jun2004;79(6):974-82. View Abstract 23 Simon J, et al. Serum Fatty Acids and Risk of Coronary Heart Disease. American Journal of Epidemiology. 1995;142(5):469-476. View Abstract 24 Stark KD, Holub BJ. Differential eicosapentaenoic acid elevations and altered cardiovascular disease risk factor responses after supplementation with docosahexaenoic acid in postmenopausal women receiving and not receiving hormone replacement therapy. Am J Clin Nutr. May2004;79(5):765-73. View Abstract 25 Nestel P, Shige H, Pomeroy S, Cehun M, Abbey M, Raederstorff D. The n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid increase systemic arterial compliance in humans. American Journal of Clinical Nutrition. Aug2002;76(2):326-330. View Abstract 26 Birch EE, et al. A randomized controlled trial of early dietary supply of long-chain polyunsaturated fatty acids and mental development in term infants. Dev Med Child Neur. 2000;(42):174-181. View Abstract 27 Uauy R, Mena P. Requirements for long-chain polyunsaturated fatty acids in the preterm infant. Curr Opin Pediatr. Apr1999;11(2):115-20. View Abstract 28 Werkman S, et al. A Randomized Trial of Visual Attention of Preterm Infants Fed Docosahexaenoic Acid Until Nine Months. Lipids. 1996;31(1):91-97. View Abstract 29 Ranjekar PK, Hinge A, Hegde MV, et al. Decreased antioxidant enzymes and membrane essential polyunsaturated fatty acids in schizophrenic and bipolar mood disorder patients. Psychiatry Res. Dec2003;121(2):109-22. View Abstract 30 Laugharne J, et al. Fatty Acids and Schizophrenia. Lipids. 1996(Suppl.);31-S-163 - S-165. View Abstract 31 Peet M, Laugharne JD, Mellor J, Ramchand CN. Essential fatty acid deficiency in erythrocyte membranes from chronic schizophrenic patients, and the clinical effects of dietary supplementation. Prostaglandins Leukot Essent Fatty Acids. Aug1996;55(1-2):71-5. View Abstract 32 Tomer A, Kasey S, Connor WE, et al. Reduction of pain episodes and prothrombotic activity in sickle cell disease by dietary n-3 fatty acids. Thromb Haemost. Jun2001;85(6):966-74. View Abstract 33 Hoffman DR, DeMar JC, Heird WC, et al. Impaired synthesis of DHA in patients with X-linked retinitis pigmentosa. J Lipid Res. Sep2001;42(9):1395-401. View Abstract 34 Hoffman DR, Locke KG, Wheaton DH, Fish GE, Spencer R, Birch DG. A randomized, placebo-controlled clinical trial of docosahexaenoic acid supplementation for X-linked retinitis pigmentosa. Am J Ophthalmol. Apr2004;137(4):704-18. View Abstract 35 Wheaton DH, Hoffman DR, Locke KG, Watkins RB, Birch DG. Biological safety assessment of docosahexaenoic acid supplementation in a randomized clinical trial for X-linked retinitis pigmentosa. Arch Ophthalmol. Sep2003;121(9):1269-78. View Abstract 36 Takemoto Y, Suzuki Y, Horibe R, Shimozawa N, Wanders RJ, Kondo N. Gas chromatography/mass spectrometry analysis of very long chain fatty acids, docosahexaenoic acid, phytanic acid and plasmalogen for the screening of peroxisomal disorders. Brain Dev. Oct2003;25(7):481-7. View Abstract 37 Martinez M. Restoring the DHA levels in the brains of Zellweger patients. J Mol Neurosci. Apr2001;16(2-3):309-16. View Abstract 38 Booyens J, et al. The role of unnatural dietary trans and cis unsaturated fatty acids in the epidemiology of coronary artery disease. Med Hypotheses. Mar1988;25(3):175-82. View Abstract 39 Horrobin DF. Loss of delta-6-desaturase activity as a key factor in aging. Med Hypotheses. Sep1981;7(9):1211-20. 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