Considerable confusion and many unsubstantiated beliefs abound when it comes to fish oil supplements.
An estimated one in four Australians currently take them for a wide range of conditions, even though good research is unconvincing.
However, there are suggestions that increased doses of fish oil might provide health benefits.
What are fish oils – and are there any downsides?
Fish is a major source of vitamin D, of long-chain omega-3 fats (including docosahexaenoic acid and eicosapantaenoic acid), selenium and protein. It is also low in saturated fat. According to some ‘authorities’, a healthy diet should include at least two portions of fish a week, including one of oily fish.
Vitamin D is crucial for children’s skeletal development. Deficiency causes rickets – soft and weakened bones, fractures, bone and muscle pains, and bony deformities. Widespread in Victorian times, when it was potentially fatal, it was nearly wiped out during the 1950s, with improved diet, free milk at school, playing outdoors on sunny days and vitamin D supplementation. But with inadequate consumption of milk and dairy products, the lure of computer games and television (which encourage childhood inactivity), and overuse of sun protection (for fear of skin cancer), rickets is on the rise.
Omega-3, which our bodies cannot make, is involved in crucial brain functions. A shortage can adversely affect cognition. While eating oily fish during pregnancy can benefit children’s later cognitive functioning, the notion that young children’s cognition could be enhanced by omega-3 supplementation remains controversial.
While regular fish oil consumption is no way to treat cancer, it might slightly reduce the probability of certain cancers developing as it might have a favourable role in carcinogenesis inhibition and cancer outcomes. Clinical trials have shown no consistent effect on the incidence of chronic obstructive lung disease, or diabetes.
Omega-3 might be helpful for people with inflammatory arthritis, such as rheumatoid arthritis, ankylosing spondylitis and psoriatic arthritis, but there is no strong evidence that it works for osteoarthritis. It might relieve joint pain and stiffness in a similar way to non-steroidal anti inflammatory drugs (NSAIDs), while helping to decrease the incidence of side-effects from these medicines. Long-term intake of omega-3 has been shown, in some cases of arthritis, to reduce reliance on NSAIDs. However, at least 2.7 grams daily of omega-3 is needed to reduce inflammation.
Even though possible side-effects are heartburn, nausea, diarrhoea, and prolonged bleeding and bruising, fish oil is generally well tolerated. Sold as a food, it is not regulated by the Therapeutic Goods Administration (TGA). The Australian Register of Therapeutic Goods currently lists 683 ‘medicinal’ products containing fish oil.
‘Natural’ supplements can result in indirect adverse health effects when they delay or replace more effective conventional treatment or when they compromise the efficacy of proven medications. As with all ‘natural’ supplements, fish oil supplements are poorly regulated; the content and quality can vary significantly and packaging might not contain safety warnings.
A recent study into 32 brands of fish oil found that 92% of them contained less omega-3 than advertised. This meant that patients were under-dosing. In 91% of them “ the fats had oxidised – or were going off “. This rancid contamination has the potential to interfere with efficacy. Researchers also raised concerns about the long-term implications of taking contaminated products; oxidised fish oil might promote the formation of fatty deposits in arteries – just the opposite of patients’ expectations!
When the recommended portions of fish are consumed, as part of a suggested healthy diet, they can provide important health benefits. However, when additional omega-3, found in fish oil, with poor quality control of production and storage, is taken for diseases such as inflammatory arthritis, patients are often under-dosing on potentially contaminated and possibly harmful substances.