Docosahexaenoic acid
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Docosahexaenoic acid (commonly known as DHA; 22:6 omega-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, 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 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).
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. DHA 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.(De Caterina, Basta 2001)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 approval by the Food and Drug Administration and Health Canada. It, together with arachidonic acid (ARA), are permitted in infant formula because both are components of breast milk found around the world.
DHA makes infant formula more like human milk than "conventional" formula containing linolenic acid and linoleic acid, which are precursors. Formula sold in North America uses lipids from microorganisms grown in bioreactors as sources of DHA. (Connell, 2001) (Martek)
Comparing Algae vs. Fish Oil as a DHA source in Human Nutrition
A study published in the April 2005 issue of The Journal of Pediatrics (Clandinin, M.T. The Journal of Pediatrics, April 2005; pp 461-467) 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.
External links
- A patent at the WIPO.
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