Docosahexaenoic acid

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Docosahexaenoic acid

The chemical strucuture of docosahexaenoic acid showing physiological numbering (red) and chemical numbering (blue) conventions.
Chemical name	(4Z,7Z,10Z,13Z,16Z,19Z)-docosa- 4,7,10,13,16,19-hexaenoic acid
Chemical formula	C₂₂H₃₄O₂.
Molecular mass	328.488 g/mol
CAS number	[?]
PubChem	445580
SMILES	CCC=CCC=CCC=CCC=CCC=CCC=CCCC(=O)O
Disclaimer and references

Docosahexaenoic acid (commonly known as DHA; 22:6(ω-3), all-cis-docosa-4,7,10,13,16,19-hexaenoic acid; trivial name cervonic acid) is an omega-3 essential fatty acid. Chemically, DHA is a carboxylic acid with a 22-carbon chain and six cis double bonds; the first double bond is located at the third carbon from the omega end.

DHA is most often found in fish oil. Most of the DHA in fish and other more complex organisms originates in microalgae of the genus Schizochytrium, and concentrates in organisms as it moves up the food chain. Most animals make very little DHA metabolically, however small amounts are manufactured internally through the consumption of α-linolenic acid, an omega-3 fatty acid found in chia, flax, and many other seeds and nuts.

DHA is a major fatty acid in sperm and brain phospholipids, and especially in the retina. Dietary DHA can reduce the level of blood triglycerides in humans, which may reduce the risk of heart disease. Low levels of DHA cause reduction of brain serotonin levels^[1] and have been associated with ADHD, Alzheimer's disease, and depression, among other diseases, and there is mounting evidence that DHA supplementation may be effective in combating such diseases (see external links at the end of this article).

1 Metabolic synthesis
2 DHA in Alzheimer's Disease
3 DHA in breast milk and infant formula
4 Promotion of DHA as a food additive
5 See also
6 References

[edit] Metabolic synthesis

In the human body, DHA is either present in the diet or it is derived from eicosapentaenoic acid (EPA, 20:5, ω-3) via docosapentaenoic acid (DPA, 22:5 ω-3) as an intermediate. This is done with an elongation step followed by the action of Δ4-desaturase. Another pathway has also been described in peroxysomes and mitochondria. EPA is twice elongated yielding 24:5 ω-3, then desaturated to 24:6 ω-3, then shortened to DHA via beta oxidation. This pathway is known as Sprecher's shunt.^[2]^[3]

[edit] DHA in Alzheimer's Disease

A large NIH drug trial is currently recruiting patients for evaluating DHA in Alzheimer's disease. More details on the clinicaltrials.gov website. ^[4]

[edit] DHA in breast milk and infant formula

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 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 DHA and ARA (arachodonic acid) to its Enfamil Lipil product, received approval by the Food and Drug Administration and Health Canada. Both DHA and ARA are permitted in infant formula as both are components of human breast milk. The addition of DHA at dose effective levels has been shown to improve congitive function in both term and preterm infants.

DHA makes infant formula more like human milk than "conventional" formula containing 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.^[5]^[6]

A study^[7] found that preterm infants fed baby formulas fortified with DHA derived directly from algae gained weight faster than infants fed formula fortified with DHA from fish oil. Additionally, there are no risks of harmful contaminants such as methyl mercury or dioxins, which are present in fish and fish oils.^{[citation needed]} This is especially important for pregnant and nursing women and young children.

Vegans and vegetarians have markedly lower stores of DHA. Their bodily DHA levels do not rise much even with high dietary levels of linolenate. This, and features of the production and distribution of DHA in pregnant and lactating women, indicates that DHA per se is an essential nutrient.^[8]

[edit] Promotion of DHA as a food additive

DHA is actively promoted by its major manufacturer, Martek Biosciences, as a food additive; however, sales other than to makers of infant formula have been minimal. 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 factory farming. However, nutritionists are sceptical regarding its value to the general population; although, it is known to be helpful to people with a history of heart disease and premature infants. In anticipation of demand Martek had by 2007 increased its manufacturing capacity to three times the amount which was able to sell. Manufactured DHA is a vegetarian product extracted by a patented process from algae, but costs approximately twice as much as fish oil. Both are odorless and tasteless after processing.^[9]