Omega 3 fats
What are Omega-3 fats?
Omega 3 or n-3 fatty acids are a type of PUFA (polyunsaturated fatty acids) that need to be supplied through the diet since the body cannot manufacture it. Important dietary omega-3 fatty acids (FA) are α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
There are also omega-6 (n-6) FA occurring in fat and oil sources, the commonest being linoleic acid (LA) and arachidonic acid (AA).
Omega 3 and 6 are the two types of polyunsaturated fats present in various oils as given in detail below.
What is the importance of Omega-3 fatty acids?
Both omega-3 and omega-6 FA are necessary to maintain good health.
Benefits of omega 3 fatty acids lie in health promotion and disease prevention. Omega 3 fats, most notably DHA (docosahexanoic acid) and EPA (eicosapentanoic acid) have anti-inflammatory effects. They prevent health problems such as heart disease mainly cardiac arrhythmias, reduces risk of ischemic and thrombotic stroke, certain cancers, joint problems, rheumatoid arthritis, improve mood and enhance memory.
In pregnancy, enhanced immune functions and good development of a baby were seen. Several research findings support the role of Omega-3 fats (specifically DHA) in brain development during the first two years after birth (infancy).
In children with learning and behavioral problems particular in ADD (Attention deficit disorder). When they were given 3g/day omega-3 and omega-6 FA with vitamins and minerals showed improved developmental health especially regarding learning and focus. Omega-3 fatty acids reduced hyperactivity in children with autism.
The 3 Main Functions of Omega-3 or n-3 PUFAs (Linolenic acid)
1) Improved cognitive functions / brain development (DHA in early years of life <2 yrs has been proved)
2) Visual acuity (DHA in early years of life <2 yrs has been proved)
3) Heart disease prevention
- effective in lowering serum TAGs and VLDL lipoproteins (Leaf and Weber, 1988)
- Reduce blood clotting
- Prevent irregular heartbeat
- Role to play in lowering BP
Which are the food sources of Omega3 fatty acids?
Food Sources of Omega-3:
Plant sources (present as ALA): Flaxseeds, mustard, soya, nuts like walnuts (present as N-3 fats, there is limited conversion to EPA and DHA), canola, soy, acai palm fruit, chia seeds, leafy vegetables. LA is found in vegetable oils.
Flaxseeds or linseeds have 6 times more omega-6 than most fish oils. They have 55% ALA which is converted to EPA at 2-15% and DHA at 2-5% efficiency. Oil extracted from brown algae (kelp) is a good source of EPA.
Animal sources (good sources of EPA and DHA): Fish particularly fatty fish – salmon, mackerel, sardines, herring, tuna (present as EPA in fish oils). Cold water fish are the highest source of EPA and DHA omega 3 fats effective for reducing heart disease risk. Other fish contain these fatty acids but in small amounts.
Dosage Recommendations for Omega-3 Fatty Acids
WHO recommends LA (omega-6) to ALA (omega-3) ratio of 5-10:1 in the diet. Every week 7-11 grams of omega-3 fats are currently recommended. 2 to 3 servings of fatty fish or fish oils twice or thrice a week is adequate. For vegetarians, foods fortified with omega-3 fats would use ALA from flaxseed or rapeseed oils rather than fish oils. Marine microalgae produce EPA and DHA so currently increasing number of products are fortified with oils from these algae, so these oils are considered vegetarian and omega-3 rich.
Omega-3 fats Challenges
The omega-3 present in vegetarian sources is alpha-linolenic acid (ALA) and the omega-3 present in fish oils is eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). Health benefits mentioned above are derived from EPA and DHA. At each step for conversion of ALA to EPA and DHA a smaller percentage is converted. ALA is converted to EPA and DHA in the body but the conversion rate is just 5% in men and somewhat higher in women. So it is advantageous to consume DHA and EPA rather than ALA as one would have to consume several times higher quantities of ALA for the same benefits.