Storage

• The long chain omega-3 fatty acids contained in fish oil are oxidisable. Most oils will contain the antioxidant, alpha tocopherol, to protect the EPA and DHA from degrading. It is best practice to make sure that capsules are in date, stored in the purchased container and kept in a consistently cool environment (a fridge is also fine) away from direct light.

Bleeding

• The European Food Safety Authority considers intakes up to 5 grams of fish oil per day safe.⁶ The EPA active component of fish oil can modify the coagulation properties of the blood involved bleeding. However, a recent randomised placebo-control trial reported no increased risk of peri-operative bleeding⁷ and a systematic literature review (of 52 studies) concluded that fish oil supplementation did not increase the risk of bleeding during or after surgery.⁸ In the advent that surgery is required, some pre-operative assessments will request information about current fish oil consumption.

Gastrointestinal discomfort, allergies and the vegan diet

• Research involving therapeutic doses (>5 g of total oil) have sometimes reported gastrointestinal discomfort, in a minority of participants. Consuming the fish oil (capsule) with other foods results in the digestion and absorption occurring alongside other macro and micronutrients. The capsules are also designed to dissolve slowly and in time for movement of the oil into the duodenum (small intestine). Consuming a non-capsulated fish oil product (usually a teaspoon of oil) without other foods, is more likely to result in reflux and after taste, although some of these non-capsulated oils are flavoured to improve palatability.
• A small proportion of the population are allergic to fish and seafood products. Before consuming, it is worth considering if this applies to each individual.
• Athletes consuming a plant based diet will most likely have a low omega-3 status (reflected by the O3I <4.5%). Although fish oil is avoided in the vegan diet, EPA and DHA can be sourced from algal oil and has been demonstrated to be effective in the wider population in raising the O3I.

Fish oil in combination capsules

• Several major brands combine fish oil with either anti-oxidants, such as curcumin, or vitamin D. To date, there are few studies published exploring the efficacy of combined capsules although some seem promising. For example, a combined fish oil and vitamin D supplement was reported to reduce the number of URTI symptom days in recreational athletes.⁹
• Krill oil also contains a good source of EPA and DHA. Krill oil differs from fish oil in that the major form of the long chain omega-3 fatty acids are phospholipids. This factor may improve membrane incorporation although studies in trained groups are limited.¹⁰ Krill oil also naturally contains the antioxidant astaxanthin which provides an opportunity combining their intake.