Omega 3 essential fatty acids (EFAs) and their wide-spread benefits have been well publicised – reducing chronic inflammation, improved heart and brain health, improved mood, lowering levels of triglycerides and alleviating joint pain. Omega-3 EFAs are long chain polyunsaturated fatty acids (PUFAs).
The best sources of omega 3 EFAs are found in fish oil and flax seed oil. The omega 3 EFAs found in fish oils are: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) . Plant sources such as flax seed oil contain ALA (alpha-linolenic acid), another form of omega 3 EFAs. Most of the research has been done on DHA and EPA found in fish oils. We can convert plant-sourced ALAs into DHA and EPA but the conversion is unreliable and the rate of conversion is low particularly for the ALA conversion to DHA. Our consumption of omega-6 PUFAs have an impact on the conversion of ALAs – with a diet rich in omega-6 PUFAs, this conversion is reduced by 40-50%. Additionally, only pre-formed DHA can improve blood status of DHA (and not through ALA intake).
Best Fish Sources of Omega-3s
High levels of omega-3 EFAs are found in cold water fish but there is concern about the mercury content in these fish. Tuna has one of the highest levels of mercury. Smaller fish tend to have lower levels of mercury (because they have shorter life spans and therefore don’t accumulate as much mercury as larger fish). The following fish are recommended: salmon, mackerel, anchovies, sardines, herring (known as SMASH).
DHA and EPA for Brain Health
EPAs and DHAs are found in our cell membranes. They are key components of all cell membranes and are abundant in our brain and retina. These omega-3 PUFAs have neuroprotective properties. However it is DHA that is quantitatively the most important omega-3 PUFA in the brain.
Omega 3 Absorption and Genetics
Our omega 3 blood levels are also affected by variations in genes – the single nucleotide polymorphisms (SNPs). Studies show that people with the desaturase genes FADS1 and FADS2 had higher ALA levels but lower DHA and EPA levels, implying different conversion rates from ALA to DHA/EPA. Additionally, those with the apoE-ε4 polymorphism showed a weaker response to DHA/EPA supplementation and the DHA metabolism was suboptimal – the half life of DHA was significantly lower. Individuals with the apoE-ε4 gene have a larger risk of onset of Alzheimer’s disease.