Omega-3-Fatty acid is a groups of three fatty acids namely α-Linolenic acid (ALA), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). These are essential fatty acids because human have limited ability to produce Omega-3-Fatty acid in body so it must include in diet or should be given as external suppliments more over this ability also decrease with age.

Structure and chemical compositions : All fatty acid chains have two ends, one is organic acid or carboxylic acid functional group (-COOH) and the another is a methyl functional group (-CH3). The carboxylic acid functional group is considered as the primary functional group and the beginning of the fatty acid chain so it is termed as alpha or α and methyl functional group is considered as the end so termed as omega or ω (according to the Greek alphabets, where the first one is alpha and the last one is omega). All Omega-3 fatty acids are polyunsaturated fatty acids. The first double bond (C=C ) is present at the third carbon atom from the methyl functional group or the end or the omega position of the carbon chain, that is why these fatty acids are named as Omega-3 fatty acids. The structures of the three Omega-3 fatty acids are given below :

The molecular formula of α-Linolenic acid (ALA) is C18H30O2 and the structural formula is

The molecular formula of Eicosapentaenoic acid (EPA) is C20H30O2 and the structural formula is

The molecular formula of Docosahexaenoic acid (DHA) is C22H32O2

Human body can convert the shorter chain omega 3 fatty acid ALA to longer one EPA and further to DHA but with very limited efficiency. Man have the efficiency below 5%, woman have slightly higher efficiency may be to meet the demand of foetal DHA.

Functions and importance’s : Omega three fatty acids have various important physiological functions as given below:

  • Omega-3-fatty acid helps to reduce blood triglyceride level.
  • Several studies suggests that omega-3-fatty acid may reduce blood pressure in people, those who have hypertension
  • Decrease the aggregation of platelets thus preventing the blood from clotting excessively.
  • Helps in reducing inflammation by reducing the the production of cytokines.
  • DHA is essential for grey matter of the brain and also essential for neurotransmission so it helps in brain developments and improve cognitive abilities.
  • Omega-3-fatty acid reduces depression symptoms and also reduce the risk of dementia.
  • Omega-3-fatty acid increase the secretion of leptin, that improve the ability to respond to insulin, thus reducing the risk of diabetes.
  • Omega-3-fatty acid may also reduce the risk of cancer but this is not yet proven.

Omega-3-fatty acid toxicity : The excess intake of omega-3-fatty acid may cause diarrhea, nausea and increase risk of haemorrhage.

Sources of omega-3-fatty acids :

Animal sources of omega-3-fatty acids : The sources of EPA and DHA are mainly oily fish like salmon, mackerel, herring, tuna etc. A list of animal sources of omega-3 fatty acids are given below:

NamePercentage
Herring, sardines1.3–2
Mackerel1.1–1.7
Salmon1.1–1.9
Halibut0.60–1.12
Tuna0.21–1.1
Swordfish0.97
Greenshell0.95
Tilefish0.9
Tuna (canned, light)0.17–0.24
Pollock0.45
Cod0.15–0.24
Catfish0.22–0.3
Flounder0.48
Grouper0.23
Mahi mahi0.13
Orange roughy0.028
Red snapper0.29
Shark0.83
King mackerel0.36
Hoki0.41
Gem fish0.40
Blue eye cod0.31
Sydney rock oysters0.30
Tuna0.23
Snapper0.22
EggS0.109
Barramundi0.100
Giant tiger prawn0.100
Lean red meat0.031

The plant source of omega-3-fatty acid : The sources ALA are plants

NamePercentage
Kiwifruit63
Perilla61
Chia seed58
Flax53 – 59
Lingonberry49
Camelina36
Purslane35
Black raspberry33
Hemp19
Canola 9 – 11
Flaxseed18.1
Butternuts8.7
Hempseed8.7
Persian walnuts6.3
Pecan nuts0.6
Hazel nuts0.1

Omega-6-fatty acids : Just like omega-3-fatty acids omega-6-fatty acids are the polyunsaturated fatty acids containing the first double bond on the sixth carbon atom from the omega end of the carbon chain. Linoleic acid is the shortest chain omega-6-fatty acid and an essential amino acid. Arachidonic acid is the precursor of prostaglandins and essential for many other physiological functions.

omega-3 fatty acid and omega-6 fatty acid ratio : It is very important to maintain proper omega-3 fatty acid and omega-6 fatty acid ratio in human body. The suggested healthy ratio of omega-3 fatty acid : omega-6 fatty acid is ranges from 1:1 to 4:1. It is important to have more omega-3 fatty acids than omega-6 fatty acid in body to maintain proper metabolic functions. Omega-3 fatty acid and omega-6 fatty acid both need same enzymes for metabolism so increase level of omega-6 fatty acid cause increase competition for the same enzyme and hamper the metabolism. Due to this reason imbalance in this ratio leads to various metabolic changes and increase the risks of cardiovascular and inflammatory diseases.