Fish oil supplements – your ultimate guide


Fish oil is one of the most commonly consumed dietary supplements. But what are fish oil supplements and do their health benefits live up to the hype. If you do take them, how can you get it right?

Polyunsaturated Fatty Acids– what are they?

Polyunsaturated Fatty Acids (PUFA’s) are essential fats. This means that you must get them from your diet as your body can’t make them. The term “polyunsaturated” refers to the chemical structure. “Poly” means many and “unsaturated” refers to double bonds. Multiple double bonds in PUFA’s are crucial structure components in cell membranes. Each double bond causes a kink in the fat molecule which produces a complex 3-dimensional shape. These highly specific shapes run major signalling systems throughout the body. The signalling molecules are called prostaglandins and are involved in regulating various biological processes such as the inflammatory response.

There are two major families of essential fatty acids. Omega-3 and omega-6. “Omega” 3 refers to the position of the final double bond in the chemical structure which is three carbon atoms from the “omega” or tail end of the molecular chain.

  • Omega (Ω) 3 fats. Those with most power in the body are called eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA). They are primarily found in oily fish. Smaller Ω3 fatty acids are found in plants, such as flaxseed and pumpkin seeds. Though somewhat beneficial, mammals are poor at utilising them to generate the more useful EPA and DHA. Omega-3s contribute to typical brain and eye development. They fight inflammation and may help prevent heart disease and a decline in brain function.
  • Omega (Ω) 6 fats. Sources of Ω6 fatty acids include refined vegetable oils, such as sunflower, corn and rapeseed oil, nuts and seeds.  Omega-6 fats are involved in signalling pathways and also provide energy for the body. In our normal modern diets, almost all of us consume more Ω6 than required. 

Many people think of omega-9 fatty acids as essential however they aren’t as the body can product them. Omega-9 fatty acids are monounsaturated meaning they only have one double bond. Replacing some saturated fats with omega-9 fats maybe beneficial to your health. Omega-9 fats are common in vegetable and seed oils, nuts and seeds.

Docosahexaenoic acid

Recommended intake of Essential fatty acids

Recommendations for essential fats vary widely from country to country however most health organizations recommend an intake of at least 250-500mg of combined EPA and DHA per day. The World Health Organisation recommends an increase in dosage to 1.1–1.6 grams of omega-3 fatty acids per day if you are pregnant, breastfeeding or at risk of heart disease.

To meet the recommended intake of essential fats in the diet it is recommended that you eat two portions of fish per week, one of which should be oily. One portion of fish being 140g of fresh fish or 1 small can of fish. Oily fish includes mackerel, kippers, pilchards, sardines, trout, herring, salmon, crab(fresh) and whitebait.

If you are not a fish fan then you may consider a fish oil supplement. Supplements are not recommended for the general public, however if you are considering a supplement you need to be make sure you are taking the right one.

Which fish oils to choose

  • Type of supplement. Omega-3 supplements come from many different sources and in many different forms. One key thing to consider if the amount of EPA or DHA a supplement contains as these are the most important types of omega-3. Choose omega – 3 rather than fish liver oil supplement as liver oil comes with vitamin A which should be linked to no more than 1.5mg a day from supplements and food combined.
  • Amount of omega 3.
    • A supplement may say it contains 1000mg of fish oil per capsule, however on the back you’ll read that EPA and DHA are only 200mg when combined. Read the label and choose a supplement that contains at least 500 mg of EPA and DHA per 1,000 mg of fish oil.
  • Purity. Omega-3 fatty acids are prone to oxidation which makes them go rancid. To avoid this, choose a supplement that contains an antioxidant 
  • Freshness. Omega-3’s are prone to going rancid. Antioxidants like vitamin E help with preservation. Once they go bad, they’ll have a foul smell and become less potent or even harmful. Always check the date, smell the product. Always keep your supplements away from light – ideally in the fridge. If your omega.3 supplements has a rancid smell or is out of date – don’t use it.
  • Sustainability: Choose a fish oil supplement that has a sustainability certification, such as from the Marine Stewardship Council (MSC) or the Environmental Defence Fund. The production of fish oil from anchovies and similar small fish is more sustainable than that from large fish.
  • Seek advice from a dietitian if in doubt!

Krill or fish oil?

While fish oil is derived from fatty fish, krill oil is made from tiny crustaceans called Antarctic krill. Some studies have shown that krill oil maybe better absorbed by the body however more studies are needed to confirm these findings.  Krill oil also contains a powerful antioxidant called astaxanthin which may protect it from oxidation and provide some additional heart health benefits. Fish oil is a reasonable choice if you are looking for quality omega-3 at a low price. On the other hand, if you are willing to spend extra money you may want to consider krill.

Can you overdose?

As with all things in nutrition – remember more is not better! According to the European Food Safety Association, omega-3 fatty acid supplements can be safely consumed at doses up to 5000mg per daily. However, consuming too much could actually take a toll on your health and lead to side effects such as high blood sugar and an increased risk of bleeding. So it’s important to stick to the recommended dose and aim to get a lot of your intake from food sources or be working with a health professional.