Everything you need to know about omega 3, mercury in fish & reducing inflammation through diet

For those OG followers, you would know I am a massive believer in boosting your omega 3: omega 6 ratio to reduce inflammation in the body. 

Before I get into the best food sources of omega 3 and omega 6, let’s first discuss the difference between omega 3 and omega 6, and why we need to consume BOTH in our diet. I will then answer FAQs surrounding fish consumption, mercury and vegan sources of omega 3. 

Omega 3 and Omega 6 are types of polyunsaturated fatty acids (PUFAs) that cannot be synthesised by the body and therefore must be obtained through diet. It is this reason that both omega 3 and omega 6 are also referred to as “Essential Fatty Acids” (EFAs). 


Omega 6 - What is it?

Omega 6 is still an ESSENTIAL fatty acid that we require in our diet so it is definitely NOT something to fear. In fact, adequate intake of good sources of omega 6 (listed below) has been linked to lowering cholesterol and improving blood sugar.

The average Western diet has an omega 6: omega 3 ratio of 15:1 to 17:1, however, it is believed humans evolved eating a diet with a ratio of 1:1 (4) . More research suggests that a diet with a significantly higher ratio of omega-6 to omega-3 has a pro-inflammatory effect on the body, whereas a diet that has an optimum level of omega 3 is said to have an anti-inflammatory effect on the body. 

It all boils down to ratio and what types of omega 6 foods you are consuming. Many processed and refined foods contain high amounts of omega 6. See below for ways to reduce your omega 6 ratio (note* you also need to be boosting your omega three at the same time).

  • Substitute Sunflower oil for olive oil or macadamia oil
  • When purchasing nut butters, look for ones that contain no added vegetable oils
  • Reduce your intake of highly processed foods 
  • Choose grass-fed meats over grain fed
  • Other good sources of omega 6: sunflower seeds, walnuts, pumpkin seeds and nuts

Plantbased and non-plantbased sources of omega 3 + FAQs about adequate intake, mercury in fish and sustainability

The three most common types of Omega 3 include:

  1. Eicosapentaenoic acid (EPA) - Found in marine based fish and fish oil
  2. Docosahexaenoic acid (DHA) - Also found in marine based fish and fish oil, 
  3. Alpha Linolenic Acid (ALA) - Derived from plant sources (canola, soybean oils, chia seeds, hemp seeds, flaxseeds and walnuts). Although the ALA type of omega 3 can be converted into EPA & DHA (which is the most effective form of omega 3), the process is inefficient and a lot slower (the conversion rate is approximately 5%). 

This is why vegans need to consume a lot more ALA sources in order to obtain enough omega 3 in their diet (more on this below)

Research suggests that regular consumption of omega 3 may protect against heart disease, blood clots and some cancers due to its anti-inflammatory properties. In more recent times, studies suggest omega 3’s anti-inflammatory effect may also play a role in reducing inflammation associated with inflammatory skin conditions such as acne and psoriasis. There is also some research to suggest it may play a role in the management of depression, however, more conclusive evidence is needed in this area (1)

Omega 3 Recommended Dietary Intake (RDI) from fish

The Heart Foundation and Australian Dietary Guidelines recommend all Australians aim to consume 2–3 servings of fish per week which provides approximately 250–500 milligrams of marine-sourced omega-3s (both EPA and DHA) per day (7). 


What about mercury?

When it comes to mercury, some fish species contain higher amounts than others meaning the intake of certain fish should be limited in your diet, particularly if you are pregnant. According to Food Standards Australia New Zealand (3), most people can safely consume 2-3 servings of fish per week (when following the guidelines in the table below).  

Generally, “safe” fish include oily varieties such as:

  • Mackerel 
  • Salmon
  • Trout
  • Sardines
  • Pilchards
  • Herring 
  • tuna

Fish that should be limited as per FSANZ guidelines below include:

  • Orange roughy (sea perch)
  • Shark (flake)
  • Billfish (swordfish, broadbill & marlin)

Table sourced from Food Standards Australia New Zealand (3)


Sustainability of our food and fishing practices is an important part of making food choices. If you are in Australia and are looking to make informed, more sustainable seafood choices, checkout the below link. 



If you’re a tuna lover please choose ‘pole and line’ or Fish Aggregation Devices (FAD) FREE tuna products (5). 

Why is FAD caught tuna bad?

  • FADs are pretty much giant fish magnets placed in the middle of the ocean by fish companies to attract large schools of fish and marine life. Once enough fish has aggregated around the device, it alerts these fishing companies which then come and scoop up all of the fish (and other marine life in the vicinity) into large nets. This method of fishing increases capacity and is more profitable, however, it has an extremely detrimental effect on our marine ecosystem (5).
  • FADs attract undersized tuna. As these fish have not yet matured, they have not had the opportunity to breed, which directly influences the future number of tuna in our ocean.
  • FADs also attract other marine species (sharks, turtles and other fish species). This increases “bycatch”, meaning these companies aren’t just catching tuna
  • FAD methods are increasing and subsequently influencing/having an adverse effect on the migratory pattern of tuna
  • Other “pole and line” methods of catching tuna have a considerably lower impact on our marine ecosystem (5)


According to Greenpeace (5), the below is a list of Australian canned tuna brands (ranked in order of best practice) with the most commitment to sustainability and human rights. All of the below do not use FADs.

  • Fish 4 Ever (the benchmark for responsible tuna in Australia)
  • John West
  • Safcol
  • Aldi
  • Sirena
  • Coles
  • IGA
  • Woolworths
  • Sole Mare
  • Greenseas


NOTE* Greenseas tuna has only JUST agreed to only source FAD-free tuna 


Can I overdose on fish oil?

Australian Nutrient Reference Values (8) claim there is no Upper Limit for ALA (plantbased) sources of omega 3 because there is no known level at which adverse effects may occur.

However, the UL for non-plant based sources of omega 3 is 3000mg/day for children, adolescents and adults. 

One standard fish oil capsule contains approximately 1000mg of fish oil. One piece of fish contains approximately 250mg-1500mg of omega 3 (depending on the fish).

Obtaining your dietary requirement of omega 3 through food is always recommended over supplements. However, if you choose to take a supplement, it is important to remember that high intakes of omega 3 may:

  • Increase bleeding time
  • Interfere with wound healing
  • Raise LDL cholesterol 
  • Suppress immune function

Therefore, you should always consult your doctor or health professional before taking an omega 3 supplement, particularly if you are taking medication. 


What if i’m vegan?

Interestingly, the primary source of omega 3 in fish is from micro-algae. If you are vegan you can go direct to the source and supplement with Micro Algae Supplementation which contains both EPA+DHA. I recommend Algae Omega by Nordic Naturals as it is made from sustainably-sourced microalgae, the original source of marine omega-3 (https://www.nordicnaturals.com/consumers/algae-omega

If you would prefer to obtain omega 3 from diet alone, it is advised that you increase your consumption of ALA containing foods to BOOST conversion into EPA+ DHA. See below for qtys of ALA in different sources.


2 TBSP of CHIA SEEDS = 5000mg ALA

2 TBSP of HEMP SEEDS = 5000mg ALA





As discussed above, ALA to EPA & DHA has a conversion rate of 5%. Based on this conversion rate, let’s see how many servings of plantbased omega 3 (ALA sources) you would need to meet the equivalent of 2-3 servings of fish per week.

To convert ALA to EPA & DHA, multiply by 0.05 to get the approximate quantity of fish equivalent omega 3. 

2 TBSP CHIA SEEDS = 250mg of EPA & DHA (equivalent to 1 serving of fish)

1 TBSP FLAXSEED OIL = 549mg of EPA & DHA (equivalent to almost 2 servings of fish)

2 HANDFULS OF WALNUTS = 250mg of EPA & DHA (equivalent to 1 serving of fish)



  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481805/
  2. Omega-3 Polyunsaturated Fatty Acids & Anxiety (Su K, Tseng P, Lin P, et al. Association of Use of Omega-3 Polyunsaturated Fatty Acids With Changes in Severity of Anxiety Symptoms: A Systematic Review and Meta-analysis. JAMA Netw Open. Published online September 14, 20181(5):e182327. doi:10.1001/jamanetworkopen.2018.2327)
  3. https://www.foodstandards.gov.au/consumer/chemicals/mercury/Pages/default.aspx
  4. https://scialert.net/fulltextmobile/?doi=ijbc.2016.1.6 
  5. https://www.greenpeace.org.au/what-we-do/protecting-oceans/canned-tuna-guide/what-sustainable-tuna/
  6. https://www.annualreviews.org/doi/abs/10.1146/annurev-food-111317-095850 (health benefits of omega 3)
  7. https://www.heartfoundation.org.au/images/uploads/main/Programs/Sources_of_omega_3.pdf
  8. https://www.nrv.gov.au/nutrients/fats-total-fat-fatty-acids