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Docosahexaenoic acid
From Wikipedia, the free encyclopedia
Docosahexaenoic acid (DHA) is an omega-3 fatty acid. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain[1] and six cis double bonds; the first double bond is located at the third carbon from the omega end.[2] Its trivial name is cervonic acid, its systematic name is all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid, and its shorthand name is 22:6(n-3) in the nomenclature of fatty acids.
Cold-water oceanic Fish oils are rich in DHA. Most of the DHA in fish and complex organisms with access to cold-water oceanic foods originates in photosynthetic and heterotrophic microalgae, and becomes increasingly concentrated in organisms, as they move up the food chain. DHA is also commercially manufactured from microalgae; Crypthecodinium cohnii and another of the genus Schizochytrium.[3] DHA manufactured using microalgae is vegetarian.[3] Some animals with access to seafood make very little DHA through metabolism, but obtain it in the diet. However, in strict herbivores, and carnivores that do not eat seafood, DHA is manufactured internally from α-linolenic acid, a shorter omega-3 fatty acid manufactured by plants (and also occurring in animal products as obtained from plants).
DHA is metabolized to form the docosanoids, which comprise several families of potent hormones. DHA is a major fatty acid in sperm and brain phospholipids, particularly in the retina. Dietary DHA may reduce the risk of heart disease by reducing the level of blood triglycerides in humans. Low levels of DHA have been associated with Alzheimer's disease.
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Docosahexaenoic acid
IdentifiersCAS number6217-54-5
YPubChem445580ChemSpider393183
YUNIIZAD9OKH9JC
Y
PropertiesMolecular formulaC22H32O2Molar mass328.488 g/mol
Y(what is this?) (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)Infobox referencesDocosahexaenoic acid (DHA) is an omega-3 fatty acid. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain[1] and six cis double bonds; the first double bond is located at the third carbon from the omega end.[2] Its trivial name is cervonic acid, its systematic name is all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid, and its shorthand name is 22:6(n-3) in the nomenclature of fatty acids.
Cold-water oceanic Fish oils are rich in DHA. Most of the DHA in fish and complex organisms with access to cold-water oceanic foods originates in photosynthetic and heterotrophic microalgae, and becomes increasingly concentrated in organisms, as they move up the food chain. DHA is also commercially manufactured from microalgae; Crypthecodinium cohnii and another of the genus Schizochytrium.[3] DHA manufactured using microalgae is vegetarian.[3] Some animals with access to seafood make very little DHA through metabolism, but obtain it in the diet. However, in strict herbivores, and carnivores that do not eat seafood, DHA is manufactured internally from α-linolenic acid, a shorter omega-3 fatty acid manufactured by plants (and also occurring in animal products as obtained from plants).
DHA is metabolized to form the docosanoids, which comprise several families of potent hormones. DHA is a major fatty acid in sperm and brain phospholipids, particularly in the retina. Dietary DHA may reduce the risk of heart disease by reducing the level of blood triglycerides in humans. Low levels of DHA have been associated with Alzheimer's disease.
Contents
[hide]
DHA is the most abundant omega-3 fatty acid in the brain and retina. DHA comprises 40% of the polyunsaturated fatty acids (PUFAs) in the brain and 60% of the PUFAs in the retina. 50% of the weight of a neuron's plasma membrane is composed of DHA.[4]
Of all the fatty acids, DHA has the largest effect on brain PUFA composition.[5] DHA is found in three phospholipids: phosphatidylethanolamine, ethanolamine plasmalogens, and phosphatidylserine (PS). It modulates the carrier-mediated transport of choline, glycine, and taurine, the function of delayed rectifier potassium channels, and the response of rhodopsin contained in the synaptic vesicles, among many other functions.[6]
DHA deficiency is associated with cognitive decline.[7] PS controls apoptosis, and low DHA levels lower neural cell PS and increase neural cell death.[8] DHA is depleted in the cerebral cortex of severely depressed patients.[9][10]
[edit] Metabolic synthesis
In the human body, DHA is either present in the diet or derived from eicosapentaenoic acid (EPA, 20:5, ω-3) via docosapentaenoic acid (DPA, 22:5 ω-3) as an intermediate. This had been thought to occur through an elongation step followed by the action of Δ4-desaturase. It is now more likely that DHA is biosynthesized via a C24 intermediate followed by beta oxidation in peroxisomes. Thus EPA is twice elongated yielding 24:5 ω-3, then desaturated to 24:6 ω-3, then shortened to DHA (22:6 ω-3) via beta oxidation. This pathway is known as Sprecher's shunt.[11][12]
[edit] Health
[edit] Alzheimer's disease and decline of mental health
Docosahexaenoic acid in randomized trials did not slow decline of mental function in those with Alzheimer's disease.[13] These trials were part of a large NIH (US National Institutes of Health) intervention study to evaluate DHA in Alzheimer's disease.[14] This is the first large scale human trial of DHA and Alzheimer's disease.
The NIA trial lasted 18 months and was conducted in people with mild to moderate Alzheimer's. Researchers from the National Institute on Aging (NIA)-supported Alzheimer's Disease Cooperative Study (ADCS), led by Joseph Quinn, MD, Associate Professor of Neurology at Oregon Health and Sciences University, conducted a double blind, randomized, placebo-controlled clinical trial comparing DHA and placebo in 402 people (average age=76) diagnosed with mild to moderate Alzheimer's at 51 sites in the U.S. According to the researchers, treatment with DHA clearly increased blood levels of DHA, and also appeared to increase brain DHA levels, based on a measured increase of DHA in study participants' cerebrospinal fluid (CSF).
However, DHA treatment did not slow the rate of change on tests of mental function (ADAS-cog), global dementia severity status (CDR-SOB), activities of daily living (ADL), or behavioral symptoms (NPI) in the study population as a whole. There was no different treatment effect between the mild and moderate Alzheimer's patients.
"These trial results do not support the routine use of DHA for patients with Alzheimer's," Quinn said.
Animal studies in the TG3 transgenic mouse model of Alzheimer's disease had linked decreases in amyloid plaques and tau to dietary DHA. Animal studies also showed that when combined with arachidonic acid (also present in fish oil), plaque formation was greater than without the arachidonic acid.
DHA deficiency likely plays a role in decline of mental function in healthy adults, this is indicated in a study from 2010 conducted at 19 U.S. clinical sites on 485 subjects aged 55 and older who met criteria for age-associated memory impairment found that DHA taken for six months improved memory and learning in healthy, older adults with mild memory complaints. These findings indicate the importance of early DHA intervention and provided a statistically significant benefit to cognitive function in aging individuals over 50 years of age. [15]
[edit] Cancer
DHA was found to inhibit growth of human colon carcinoma cells,[16][17] more than other omega-3 PUFAs. The cytotoxic effect of DHA wasn't caused by increased lipid peroxidation or any other oxidative damage, but rather decrease in cell growth regulators. However, different cancer lines handle PUFAs differently and display different sensitivities towards them. Such preliminary findings point to the need for further research and are not proof that DHA does or does not provide any benefit for intended treatment, cure, or mitigation of cancer. However, in 2008, DHA was shown to increase the efficacy of chemotherapy in prostate cancer cells,[18] and in 2009, a chemoprotective effect in a mouse model was reported.[19]
[edit] Pregnancy and lactation
DHA concentrations in breast milk range from 0.07% to greater than 1.0% of total fatty acids, with a mean of about 0.34%. DHA levels in breast milk are higher if a mother's diet is high in fish.
DHA has recently gained attention as a supplement for pregnant women,[20] noting studies of improved attention and visual acuity. One recent study indicates that low levels of plasma and erythrocyte DHA were associated with poor retinal development, low visual acuity, and poor cognitive development. In that same study, alpha-linolenic acid was shown as a source of fetal DHA, but that preformed DHA was more readily accredited. A working group from the ISSFAL (International Society for the Study of Fatty Acids and Lipids) recommended 300 mg/day of DHA for pregnant and lactating women, whereas the average consumption was between 45 mg and 115 mg per day of the women in the study. Other requirements are available from other sources.[21]
DHASCO[22] ("docosahexaenoic acid single cell oil"[23]) has been an ingredient in several brands of premium infant formula sold in North America since 2001 after Mead Johnson, the first infant formula manufacturer to add DHASCO and ARASCO (arachidonic acid single cell organism) to its Enfamil Lipil product, received a "Generally Regarded As Safe"status by the Food and Drug Administration and Health Canada.
DHASCO does not make infant formulas more like human milk than "conventional" formula containing Alpha-linolenic acid and linoleic acid, which are precursors to DHA. Formula sold in North America uses lipids from microorganisms grown in bioreactors as sources of DHA.[3][24] There are no scientific review studies showing that DHA additives benefit brain development of term infants, as formula makers claim in their advertisements, which has led some public interest groups to file complaints with the Federal Trade Commission of the United States, alleging false and misleading advertising.[25]
[edit] Nutrition
[edit] Promotion as a food additive
DHA is actively promoted by manufacturers as a food additive. Until recently, sales other than to makers of infant formula have been minimal; however, in 2007, several DHASCO-fortified dairy items (milk, yogurt) began selling in grocery stores.
There is less DHA available in the average diet than formerly, due to cattle being taken off grass and fed grain before butchering; likewise, there is less in eggs due to intensive farming.[citation needed] DHA is widely believed to be helpful to people with a history of heart disease, for premature infants, and to support healthy brain development especially in young children. Some manufactured DHASCO is a vegetarian product extracted from algae. Both types are odorless and tasteless after processing.[26]
[edit] Algae-derived DHA in infant nutrition
A study[27] found that preterm infants fed baby formulas fortified with DHASCO provided better developmental outcomes than formulas not containing the supplement.
[edit] Studies of vegetarians and vegans
Main article: Vegetarian nutrition#Omega-3 fatty acids
Vegetarian diets typically contain limited amounts of DHA, and vegan diets typically contain no DHA. Vegetarians and vegans have substantially lower levels of DHA in their body, and short-term supplemental ALA has been shown to increase EPA but not DHA. However, supplemental preformed DHA, available in algae-derived oils or capsules, has been shown to increase DHA levels. While there is little evidence of adverse health or cognitive effects due to DHA deficiency in adult vegetarians or vegans, fetal and breast milk levels remain a concern.[28]
[edit] DHA and EPA in fish oils
Fish oil is widely sold in gelatin capsules containing a mixture of omega-3 fatty acids including EPA and smaller quantities of DHA. One study found that fish oil higher in DHA than EPA lowered inflammatory cytokines, such as IL-6 and IL-1β, associated with neurodegenerative and autoimmune diseases. They note that the brain normally contains DHA but no EPA, though both DHA and EPA plasma concentrations increased significantly for participants.[29] One study of pure DHA supplementation on children with ADHD found no behavioral improvements,[30] while another study found fish oil containing both EPA and DHA did improve behavior
From Wikipedia, the free encyclopedia
Docosahexaenoic acid (DHA) is an omega-3 fatty acid. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain[1] and six cis double bonds; the first double bond is located at the third carbon from the omega end.[2] Its trivial name is cervonic acid, its systematic name is all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid, and its shorthand name is 22:6(n-3) in the nomenclature of fatty acids.
Cold-water oceanic Fish oils are rich in DHA. Most of the DHA in fish and complex organisms with access to cold-water oceanic foods originates in photosynthetic and heterotrophic microalgae, and becomes increasingly concentrated in organisms, as they move up the food chain. DHA is also commercially manufactured from microalgae; Crypthecodinium cohnii and another of the genus Schizochytrium.[3] DHA manufactured using microalgae is vegetarian.[3] Some animals with access to seafood make very little DHA through metabolism, but obtain it in the diet. However, in strict herbivores, and carnivores that do not eat seafood, DHA is manufactured internally from α-linolenic acid, a shorter omega-3 fatty acid manufactured by plants (and also occurring in animal products as obtained from plants).
DHA is metabolized to form the docosanoids, which comprise several families of potent hormones. DHA is a major fatty acid in sperm and brain phospholipids, particularly in the retina. Dietary DHA may reduce the risk of heart disease by reducing the level of blood triglycerides in humans. Low levels of DHA have been associated with Alzheimer's disease.
Jump to: navigation, search
Docosahexaenoic acid
Other names[hide]
cervonic acid, DHA
cervonic acid, DHA
IdentifiersCAS number6217-54-5
[show]
InChI=1S/C22H32O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22(23)24/h3-4,6-7,9-10,12-13,15-16,18-19H,2,5,8,11,14,17,20-21H2,1H3,(H,23,24)/b4-3-,7-6-,10-9-,13-12-,16-15-,19-18-
Y
Key: MBMBGCFOFBJSGT-KUBAVDMBSA-N
Y InChI=1/C22H32O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22(23)24/h3-4,6-7,9-10,12-13,15-16,18-19H,2,5,8,11,14,17,20-21H2,1H3,(H,23,24)/b4-3-,7-6-,10-9-,13-12-,16-15-,19-18-
Key: MBMBGCFOFBJSGT-KUBAVDMBBZ
InChI=1S/C22H32O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22(23)24/h3-4,6-7,9-10,12-13,15-16,18-19H,2,5,8,11,14,17,20-21H2,1H3,(H,23,24)/b4-3-,7-6-,10-9-,13-12-,16-15-,19-18-
Key: MBMBGCFOFBJSGT-KUBAVDMBSA-N
Key: MBMBGCFOFBJSGT-KUBAVDMBBZ
PropertiesMolecular formulaC22H32O2Molar mass328.488 g/mol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)Infobox referencesDocosahexaenoic acid (DHA) is an omega-3 fatty acid. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain[1] and six cis double bonds; the first double bond is located at the third carbon from the omega end.[2] Its trivial name is cervonic acid, its systematic name is all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid, and its shorthand name is 22:6(n-3) in the nomenclature of fatty acids.
Cold-water oceanic Fish oils are rich in DHA. Most of the DHA in fish and complex organisms with access to cold-water oceanic foods originates in photosynthetic and heterotrophic microalgae, and becomes increasingly concentrated in organisms, as they move up the food chain. DHA is also commercially manufactured from microalgae; Crypthecodinium cohnii and another of the genus Schizochytrium.[3] DHA manufactured using microalgae is vegetarian.[3] Some animals with access to seafood make very little DHA through metabolism, but obtain it in the diet. However, in strict herbivores, and carnivores that do not eat seafood, DHA is manufactured internally from α-linolenic acid, a shorter omega-3 fatty acid manufactured by plants (and also occurring in animal products as obtained from plants).
DHA is metabolized to form the docosanoids, which comprise several families of potent hormones. DHA is a major fatty acid in sperm and brain phospholipids, particularly in the retina. Dietary DHA may reduce the risk of heart disease by reducing the level of blood triglycerides in humans. Low levels of DHA have been associated with Alzheimer's disease.
Contents
[hide]
- 1 Central nervous system constituent
- 2 Metabolic synthesis
- 3 Health
- 4 Nutrition
- 5 Hypothesized role in evolution
- 6 See also
- 7 Notes and references
- 8 External links
DHA is the most abundant omega-3 fatty acid in the brain and retina. DHA comprises 40% of the polyunsaturated fatty acids (PUFAs) in the brain and 60% of the PUFAs in the retina. 50% of the weight of a neuron's plasma membrane is composed of DHA.[4]
Of all the fatty acids, DHA has the largest effect on brain PUFA composition.[5] DHA is found in three phospholipids: phosphatidylethanolamine, ethanolamine plasmalogens, and phosphatidylserine (PS). It modulates the carrier-mediated transport of choline, glycine, and taurine, the function of delayed rectifier potassium channels, and the response of rhodopsin contained in the synaptic vesicles, among many other functions.[6]
DHA deficiency is associated with cognitive decline.[7] PS controls apoptosis, and low DHA levels lower neural cell PS and increase neural cell death.[8] DHA is depleted in the cerebral cortex of severely depressed patients.[9][10]
[edit] Metabolic synthesis
In the human body, DHA is either present in the diet or derived from eicosapentaenoic acid (EPA, 20:5, ω-3) via docosapentaenoic acid (DPA, 22:5 ω-3) as an intermediate. This had been thought to occur through an elongation step followed by the action of Δ4-desaturase. It is now more likely that DHA is biosynthesized via a C24 intermediate followed by beta oxidation in peroxisomes. Thus EPA is twice elongated yielding 24:5 ω-3, then desaturated to 24:6 ω-3, then shortened to DHA (22:6 ω-3) via beta oxidation. This pathway is known as Sprecher's shunt.[11][12]
[edit] Health
[edit] Alzheimer's disease and decline of mental health
Docosahexaenoic acid in randomized trials did not slow decline of mental function in those with Alzheimer's disease.[13] These trials were part of a large NIH (US National Institutes of Health) intervention study to evaluate DHA in Alzheimer's disease.[14] This is the first large scale human trial of DHA and Alzheimer's disease.
The NIA trial lasted 18 months and was conducted in people with mild to moderate Alzheimer's. Researchers from the National Institute on Aging (NIA)-supported Alzheimer's Disease Cooperative Study (ADCS), led by Joseph Quinn, MD, Associate Professor of Neurology at Oregon Health and Sciences University, conducted a double blind, randomized, placebo-controlled clinical trial comparing DHA and placebo in 402 people (average age=76) diagnosed with mild to moderate Alzheimer's at 51 sites in the U.S. According to the researchers, treatment with DHA clearly increased blood levels of DHA, and also appeared to increase brain DHA levels, based on a measured increase of DHA in study participants' cerebrospinal fluid (CSF).
However, DHA treatment did not slow the rate of change on tests of mental function (ADAS-cog), global dementia severity status (CDR-SOB), activities of daily living (ADL), or behavioral symptoms (NPI) in the study population as a whole. There was no different treatment effect between the mild and moderate Alzheimer's patients.
"These trial results do not support the routine use of DHA for patients with Alzheimer's," Quinn said.
Animal studies in the TG3 transgenic mouse model of Alzheimer's disease had linked decreases in amyloid plaques and tau to dietary DHA. Animal studies also showed that when combined with arachidonic acid (also present in fish oil), plaque formation was greater than without the arachidonic acid.
DHA deficiency likely plays a role in decline of mental function in healthy adults, this is indicated in a study from 2010 conducted at 19 U.S. clinical sites on 485 subjects aged 55 and older who met criteria for age-associated memory impairment found that DHA taken for six months improved memory and learning in healthy, older adults with mild memory complaints. These findings indicate the importance of early DHA intervention and provided a statistically significant benefit to cognitive function in aging individuals over 50 years of age. [15]
[edit] Cancer
DHA was found to inhibit growth of human colon carcinoma cells,[16][17] more than other omega-3 PUFAs. The cytotoxic effect of DHA wasn't caused by increased lipid peroxidation or any other oxidative damage, but rather decrease in cell growth regulators. However, different cancer lines handle PUFAs differently and display different sensitivities towards them. Such preliminary findings point to the need for further research and are not proof that DHA does or does not provide any benefit for intended treatment, cure, or mitigation of cancer. However, in 2008, DHA was shown to increase the efficacy of chemotherapy in prostate cancer cells,[18] and in 2009, a chemoprotective effect in a mouse model was reported.[19]
[edit] Pregnancy and lactation
DHA concentrations in breast milk range from 0.07% to greater than 1.0% of total fatty acids, with a mean of about 0.34%. DHA levels in breast milk are higher if a mother's diet is high in fish.
DHA has recently gained attention as a supplement for pregnant women,[20] noting studies of improved attention and visual acuity. One recent study indicates that low levels of plasma and erythrocyte DHA were associated with poor retinal development, low visual acuity, and poor cognitive development. In that same study, alpha-linolenic acid was shown as a source of fetal DHA, but that preformed DHA was more readily accredited. A working group from the ISSFAL (International Society for the Study of Fatty Acids and Lipids) recommended 300 mg/day of DHA for pregnant and lactating women, whereas the average consumption was between 45 mg and 115 mg per day of the women in the study. Other requirements are available from other sources.[21]
DHASCO[22] ("docosahexaenoic acid single cell oil"[23]) has been an ingredient in several brands of premium infant formula sold in North America since 2001 after Mead Johnson, the first infant formula manufacturer to add DHASCO and ARASCO (arachidonic acid single cell organism) to its Enfamil Lipil product, received a "Generally Regarded As Safe"status by the Food and Drug Administration and Health Canada.
DHASCO does not make infant formulas more like human milk than "conventional" formula containing Alpha-linolenic acid and linoleic acid, which are precursors to DHA. Formula sold in North America uses lipids from microorganisms grown in bioreactors as sources of DHA.[3][24] There are no scientific review studies showing that DHA additives benefit brain development of term infants, as formula makers claim in their advertisements, which has led some public interest groups to file complaints with the Federal Trade Commission of the United States, alleging false and misleading advertising.[25]
[edit] Nutrition
[edit] Promotion as a food additive
DHA is actively promoted by manufacturers as a food additive. Until recently, sales other than to makers of infant formula have been minimal; however, in 2007, several DHASCO-fortified dairy items (milk, yogurt) began selling in grocery stores.
There is less DHA available in the average diet than formerly, due to cattle being taken off grass and fed grain before butchering; likewise, there is less in eggs due to intensive farming.[citation needed] DHA is widely believed to be helpful to people with a history of heart disease, for premature infants, and to support healthy brain development especially in young children. Some manufactured DHASCO is a vegetarian product extracted from algae. Both types are odorless and tasteless after processing.[26]
[edit] Algae-derived DHA in infant nutrition
A study[27] found that preterm infants fed baby formulas fortified with DHASCO provided better developmental outcomes than formulas not containing the supplement.
[edit] Studies of vegetarians and vegans
Main article: Vegetarian nutrition#Omega-3 fatty acids
Vegetarian diets typically contain limited amounts of DHA, and vegan diets typically contain no DHA. Vegetarians and vegans have substantially lower levels of DHA in their body, and short-term supplemental ALA has been shown to increase EPA but not DHA. However, supplemental preformed DHA, available in algae-derived oils or capsules, has been shown to increase DHA levels. While there is little evidence of adverse health or cognitive effects due to DHA deficiency in adult vegetarians or vegans, fetal and breast milk levels remain a concern.[28]
[edit] DHA and EPA in fish oils
Fish oil is widely sold in gelatin capsules containing a mixture of omega-3 fatty acids including EPA and smaller quantities of DHA. One study found that fish oil higher in DHA than EPA lowered inflammatory cytokines, such as IL-6 and IL-1β, associated with neurodegenerative and autoimmune diseases. They note that the brain normally contains DHA but no EPA, though both DHA and EPA plasma concentrations increased significantly for participants.[29] One study of pure DHA supplementation on children with ADHD found no behavioral improvements,[30] while another study found fish oil containing both EPA and DHA did improve behavior
