ARE YOU HOOKED ON FISH OIL YET? The experts reveal all you need to know about the supplement that fights heart disease, eases arthritis and even staves off blindness...(Features) - Daily Mail (London)

WHAT'S SO GREAT ABOUT IT?

ALL fish oils contain omega-3s, types of polyunsaturated fatty acid which are essential for health.

FISH such as mackerel, salmon, trout, sardines, pilchards and fresh tuna, which are known as oily fish, are the richest sources.

NUTRITIONIST Dr Carrie Ruxton says: 'There are different types of omega-3 fatty acids, but the key health benefits are believed to come from the very long chain omega-3s, called docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA].'

EXPERTS recommend we eat at least two portions of fish each week -- one of which should be an oily fish (one portion is about 140g). This provides a daily intake of 450mg of EPA and DHA.

TODAY many supplements will specify which type they contain, and in what concentration.

EPA and DHA have different roles in the body. Dr Ruxton says: 'Studies suggest DHA is more important for the brain, retina and infant development, while EPA is more important for vascular health [blood vessels].'

THE difficulty we have is that around two-thirds of people don't actually eat oily fish,' she says. 'The main source of long chain omega-3s in the diet is oily fish, and if we can't get them from that, we need to consider a supplement to top up our diet.'

CHOOSE THE RIGHT ONE

SUPPLEMENTS fall into three categories: fish oil, cod liver oil and krill oil. Which one you choose will depend on how much money you want to spend and what benefit you're trying to get.

NUTRITIONIST Shona Wilkinson says: 'Cod liver oil comes direct from the liver; fish oil comes from the flesh of oily fish. Krill are shrimp-like crustaceans that live in the ocean. The oil found in them contains omega-3s similar to those found in fish oils.'

DR RUXTON says: 'If you're on a budget, cod liver oil or a standard omega-3 are the ones to go for. You don't need to buy the most expensive brands to get the basic benefits. If you have a specific condition and need a high dose or are pregnant and don't want the vitamin A, the cost rises.'

COD liver oil generally has lower levels of EPA and DHA but also differs from fish oil as it naturally provides vitamin A, which is important for good eyesight and healthy skin, and vitamin D for bone and immune health. Cod liver oil isn't suitable for pregnancy as it provides too much vitamin A.

DR RUXTON'S advice is not to look at the total amount of omega-3s when choosing a supplement, but at the total amount of EPA and DHA combined that a supplement provides. This should add up to 450mg per day.

'ALGAE supplements for vegetarians also contain EPA and DHA -- fish have EPA and DHA in their flesh because they feed on algae,' says Dr Ruxton. Alpha-linolenic acid (ALA) is another omega-3 fatty acid. It's plant-based and found in dietary sources such as vegetable and flaxseed oils. Our bodies can convert ALA into EPA and DHA but the process depends on how much EPA and DHA you take as well.

FOOD FOR THOUGHT

ACCORDING to the International Cod Liver Omega-3 Foundation, many fortified foods contain insignificant levels of omega-3 fats, although 60 per cent of shoppers believe they offer health benefits. For an adult to reach the recommended amounts by relying on foods fortified with omega-3 fats, the foundation says they would need to eat 16 slices of fortified bread, five omega-3 enriched eggs, six omega-3 drinks or a litre of omega-3 enriched milk a day. Another downside is the after-taste such foods can leave. 'Eat oily fish every week instead -- it's much cheaper,' says Bond.

IS THERE A TOXIN RISK?

FISH oils came under scrutiny in 2006 when the Food Safety Authority of Ireland (FSAI) reported that some exceeded the recommended levels of toxins linked to cancer. Batches of all the affected supplements were withdrawn from the market. 'Be cautious buying non-EU supplements over the internet, as quality cannot be guaranteed,' says Helen. The FSAI lists their fish oil requirements on fsai.ie

TAKE THE RIGHT DOSE

IT IS possible to overdose but ill-effects are unlikely to be more serious than a tummy upset or nausea. In a six-month trial providing 275 patients with 6.9g of EPA and DHA in ten capsules daily, there was no difference between the fish oil and corn oil control groups for any adverse effect. American regulators report that prolonged bleeding has never been reported in those taking less than 3mg of the above. Very large doses may increase the risk of blood in the urine or nose-bleeds. 'Stick to the recommended doses to avoid side effects,' says nutrition scientist Dr Elizabeth Weichselbaum.

DON'T BOTHER FOR...

INFANT DEVELOPMENT

OMEGA-3S are essential for brain development in the first year or two because this is when the brain is at its most malleable. Catherine Collins says: 'If you're breastfeeding, your body will produce omega-3s regardless of the amount of fish oils in your diet, and if you are bottle-feeding they are added to all formulas.' But studies show no benefit beyond the second year. Collins adds: 'Irondeficiency anaemia is more of an issue, affecting verbal learning and memory in children. It is found in fortified toddler milks, red meat and fortified cereals but it could be worth giving your child an iron supplement if they don't have much of these in their diet.'

CANCER

ALTHOUGH dietary influences on cancer are complex, research indicates fish oil may have an effect on colorectal, prostate and breast cancers. According to Collins, the reasons are unknown, but it may be to do with reducing inflammation associated with cell changes or that fish oils provide vitamin D that helps immune cells identify rogue cells for destruction. 'We don't know for sure if fish oils will help with cancer. Evidence is speculative and data is limited,' says Helen Bond.

ALZHEIMER'S DISEASE

A REVIEW suggested last month there is no evidence omega-3 provides a benefit for memory in later life. 'It's a disease of ageing so the notion fish oils can stop its development is unlikely,' says Collins. 'Low levels of omega-3 have been reported in Alzheimer's sufferers,' says Bond. 'But we don't know if it's a cause or effect.'

SUPPLEMENTS HAVE BEEN PROVEN TO TREAT...

ARTHRITIS

PROOF: STUDIES have shown benefits from fish oils for those suffering from rheumatoid arthritis.

Dietician Catherine Collins says: 'Fish oils have an anti-inflammatory effect that targets the cause of joint pain and helps the body deal with the pain.

'But this effect is irrelevant if you're eating a diet full of omega-6 unsaturates [including corn and sunflower oils], and saturated fats. These counteract the effects of the beneficial oils.' Fish oils work with monounsaturated fats to reduce cell inflammation that reduces pain and maintains health.

DOSE: A minimum of 3,000mg of EPA and DHA a day for maximum benefits. 'These doses are more than six times the daily recommendation, so you must take medical advice,' says dietician Helen Bond. 'Fatty acids can interact with other medications.' TRY: RxOmega-3, 400mg EPA and 200mg DHA, [euro]25, iherb.com

HEART DISEASE

PROOF: THE anti-inflammatory effects of fish oils also have benefits for the heart. They reduce the blood-vessel inflammation that can lead to heart disease. There are large studies dating back 30 years that show fish oils play a part in preventative cardiology. 'They also stabilise heart rhythm, especially in patients who have suffered a previous heart attack,' says Collins.

DOSE: A report reviewed the results of clinical trials involving more than 11,000 survivors of heart attacks and found that supplementing their diet with a gram a day of fatty acids reduced the occurrence of cardiovascular death by 30 per cent and sudden cardiac death by 45 per cent. In a 2009 review, experts recommended that healthy people take a daily dose. TRY: Nature's Best Fish Oil, 360g EPA and 240g DHA, [euro]17.40, 180 capsules, naturesbest.co.uk

VISION PROBLEMS

PROOF: STUDIES have shown there is a link between omega-3s and staving off the deterioration of sight, such as age-related macular degeneration (AMD), which damages the centre of the eye and can lead to blindness. A Harvard University study of 38,000 women found those who ate the most fish oils had a 38 per cent lower risk of developing AMD compared with those who ate least. The highest concentration of DHA in the body is found in the eye. Collins says: 'Fish oils also contain vitamin A, which is essential for healthy eyes.'

DOSE: 'A supplement providing lutein, zeaxanthin and omega-3s could protect eyes against future age-related changes when diet alone fails to deliver,' says ophthalmology professor Ian Grierson.

TRY: Bausch & Lomb Ocuvite Complete, which contains high-quality omega-3 fatty acids (of which 360g is DHA), lutein, zeaxanthin, vitamins C and E, and zinc, [euro]19.64, 60 gels, lensbase.ie

PREMATURE BIRTH

PROOF: SUPPLEMENTATION studies in pregnancy show fish oils may reduce the risk of early birth. As they may provide vitamin A, it's essential to pick a product suitable for pregnancy -- just twice the RDA of vitamin A early in pregnancy can increase risk of birth defects. The guidelines for eating oily fish changed recently from once a week to two or three times. Studies suggest omega-3s are key in the third trimester, to promote baby's IQ and immunity.

DOSE: Choose a specific pregnancy supplement only.

TRY: Equazen Mumomega -- high in DHA -- good for baby's eyes, [euro]13.35, 30 capsules, thenaturalway.ie