Glossary Detail

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name of the term: Docosahexaenoic acid

Short introduction

  • Docosahexaenoic acid (DHA, C22:6) and arachidonic acid (ARA, C20:4) are long chain polyunsaturated fatty acids (LCPUFAs).
  • Recent legislation (EU regulation 2016/127) states that DHA must be added to infant formulas. In HOCHDORF infant formulas DHA is added as refined fish oil. DHA can also be synthesised endogenously (produced within body) from the essential fatty acid α-linolenic acid (ALA).

From ALA to DHA and from LA to ARA

  • ALA is the parent of the Ω/ω/omega-3 or n-3 family. ALA is the precursor (forerunner) of DHA. LA is the parent of the Ω/ω /omega-6 or n-6 family and precursor of ARA.
  • ALA is converted via eicosapentaenoic acid (EPA) with the help of specific enzymes and via various other fatty acids into the LCPUFA docosahexaenoic acid (DHA). LA is converted via -linolenic acid (gamma-linolenic acid, GLA) with the help of specific enzymes and via various other fatty acids into the LCPUFA arachidonic acid (ARA).
  • For the conversion, both families (omega-3 and omega-6) use the same enzymes (e.g. elongase), resulting in competition between the two families. In order to produce the required amount of DHA and ARA, the right balance (good ratio) between ALA and LA is important – e.g. a diet rich in LA reduces ALA conversion. Thus, high LA levels in the diet generally result in low n-3 LCPUFA status.
  • There is no specific (EU 2016) regulation for the ALA/LA ratio. To promote an efficient conversion a low ratio is nutritionally recommended (range: 1:5 – 1:15).

New regulation: DHA now mandatory and ARA optional in IF and FOF

  • Due to insufficient conversion enzyme activity, the rate of conversion of ALA to DHA and LA to ARA is low – especially in early infancy. DHA and ARA levels depend, to a great extent, on dietary intake.
  • Due to the rapid brain and nerve growth in early infancy, the level of DHA and ARA synthesis may be inadequate to keep up with the demand. Therefore, supplementation of IF and FOF with LCPUFAs is now widely recommended.
  • The recent revision of the European legislation that came into force in 2016 stipulates that all IF and FOF must contain DHA; formulas without DHA content will not be permitted in the European Union once this legislation is implemented.
  • The addition of ARA is optional but is justified from an ethical nutritional point of view in line with the latest scientific insights.

Main natural sources

  • Examples include: fish oil and fatty fish such as salmon, herring and sardines; seaweed.
  • DHA (as well as ALA, LA and ARA) is present in breast milk. Numerous studies have documented widely differing DHA concentrations in breast milk; levels are strongly associated with maternal dietary intake.

Main function

LCPUFAs (DHA and ARA) play a beneficial role throughout life.

  • For normal growth and development.
  • For the developing brain, during pregnancy and early childhood and for life-long brain health. For cognitive (brain memory and performance) and behavioural development and function.
    • DHA and ARA are important functional and structural components of the brain.
    • The brain consists of approximately 50-60% fat, around 35% of which is DHA and ARA.
    • The brain in mammals consists of about 60% fat, which requires DHA and ARA for its growth and function. The two fatty acids account for approximately ~25% of its total fatty acid content, predominately in the form of phospholipids, and are thus major structural components of neural cellular membranes.
    • DHA is a major component (50%) of the retina (light-sensitive eye layer) and important for visual development.
    • Omega-3 and omega-6 fatty acids are structural components of cell membranes; DHA and ARA, especially, are found in abundance in the cell membranes of the brain. DHA and ARA increase the flexibility and permeability of the membrane, which provides optimal conditions for a wide range of cell membrane functions. Cell membranes are the ‘communication centres’ of the brain. Nerve cells communicate with each other via membrane processes (e.g. cell signalling) and regulate cell activity. In addition, they allow movement of nutrients into and waste products out of nerve cells.
    • DHA and ARA are vital to the composition of the myelin sheath. Myelin covers the lengthened outgrow of the nerve cell (axon). This ensures fast transmission of information to other nerve cells – without myelin, nerves work slowly and inefficiently. •
  • In cell membranes, LCPUFAs have specific roles that contribute to immune cell responses. Studies show intake of LCPUFAs early in life can influence immune development.
    • Chronic inflammation is the cause of many chronic diseases, including cardiovascular disease. DHA gives rise to compounds involved in anti-inflammation processes. ARA is the precursor of compounds with pro-inflammatory and anti-inflammatory effects, but further research is required.
    • Effects include: lowering cholesterol and blood pressure (lowering the risk of heart attack, stroke, abnormal heart rhythms). DHA plays a role in prevention and treatment of atherosclerosis (fatty plaques inside artery walls).
    • Both omega-3 and omega-6 fatty acids are beneficial for improving lipid profiles in healthy individuals and important for cardiovascular health (from childhood onwards).

Although the speed of accumulation subsequently decreases, the incorporation of DHA and ARA in the brain remains high up to the age of two.

Deficiency disease

  • Risk of cardiovascular diseases (heart attack, stroke) and atherosclerosis.
  • Signs and symptoms of an omega-3/omega-6 deficiency include: allergic or atopic tendencies (eczema, asthma, hay fever), visual symptoms (poor night vision, visual disturbances), attention problems (poor concentration, attention and memory problems), emotional sensitivity (depression, excessive mood swings, anxiety), disturbed sleep-wake cycle and decreased immunity (increased susceptibility to diseases and infection, poor wound healing).
  • Growth may be decreased in infants and children. Studies in children show the negative impact on neurocognitive development – associated with impairment in cognitive (brain memory and performance) and behavioural performance.

DRIs (Dietary Reference Intakes) have not been established for docosahexaenoic acid (DHA).

Synonyms: DHA

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