The scientific evidence
- Epidemiological studies. A growing body of evidence from large, wellconducted epidemiological (population) studies suggests that eating omega-3s — specifically the long-chain fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), but DHA in particular — decreases the risk of cognitive impairment and dementia.
Cognitive impairment ranges from mild to severe, at which point it may be diagnosed as dementia. With mild cognitive impairment, a person has problems with memory, language or another mental function severe enough to be noticeable to other people, but not serious enough to interfere with daily life.
Epidemiological studies can show statistical relationships between elements of diet and illness or mortality — salt intake and high blood pressure, for example — and the evidence is often used to advocate public health interventions such as dietary changes. But, unlike clinical trials, they don’t conclusively show cause and effect.
- Clinical trials. The UK-based Cochrane Collaboration conducted a systematic review of research, looking for randomised, controlled clinical trials of omega-3 supplementation in healthy older adults that might support the evidence from epidemiological studies. It found two trials that met its selection criteria, but they were still being conducted.
They’ve since been completed, but results won’t be published until late this year. Without good-quality clinical trial data the Cochrane Collaboration concluded that omega-3 supplements can’t be recommended for the explicit purpose of preventing cognitive impairment or dementia, although studies do suggest a protective effect.
- It is, however, widely accepted that DHA and EPA can reduce the risk of heart disease and that increasing your omega-3 intake provides a wide range of other health benefi ts. Given the encouraging results from epidemiological studies that omega-3 may also protect against dementia, it’s worth making sure that you’re getting enough.
How much is enough?
To lower your risk of chronic disease, the National Health and Medical Research Council (NHMRC) suggests a dietary target of 430 mg of omega-3 fatty acids a day for women and 610 mg a day for men. You need to eat at least two fish meals (preferably oily fish) per week to get this much, and Omega-3 in fish, below, shows which sources are best.
But a recent seafood consumption survey found that more than three quarters of us eat less than this amount. If you’re in this category, fish oil supplements could be an option.
Omega 3 in fish
Fish vary a lot in how much omega 3 they deliver. To give you some guidelines, the diagram below compares the amounts of omega 3 per 150 g serve from the species of fish you're most likely to find in your local supermarket or fish shop.