Health & beauty

Omega-3 fish oil supplements

Updated: 01 Mar 2010
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Introduction

Omega-3 fish oils are beneficial for health. 

We discuss the benefits, recommended intakes, and give you advice on buying dietary supplements.

Note: this report doesn't contain test results or discuss specific brands of omega-3 fish oil supplements.

Omega-3 - what's the hype?

The potential health benefits of fish oils first received attention in the 1970s when scientists became curious about the low incidence of heart disease among the Inuit Eskimos of Greenland.

Their diets contained a lot of fat, but scientists realised marine (fish) fat was "good" fat because it had high levels of the long-chain omega-3 fats eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), which are essential in our diets (see Fat facts below).

Long-chain omega-3s are incorporated into the membranes of every cell in the body, so they have a wide range of functions.

Heart disease

A World Health Organisation report concluded that the relationship between the omega-3s (EPA and DHA) and heart disease was convincing.

The Nurses' Health Study followed about 80,000 healthy women for up to 14 years. It found that the women with the highest intakes of EPA and DHA intake had a significantly lower risk of both heart disease and strokes.

Controlled clinical trials have confirmed that a steady diet of fish or fish oil supplements works as "secondary prevention", reducing the likelihood of a repeat heart attack in people who have already had a first attack.

A Food Standards Australia New Zealand review has concluded that the evidence for a benefit of EPA and DHA on heart disease is probable. Therefore there's sufficient evidence to support a general level health claim on food products.

Arthritis and joint mobility

Omega-3s are a potent anti-inflammatory. They may support joint comfort, mobility and flexibility - and so can be beneficial for arthritis sufferers.

Depression

The brain is about 60 percent fat, and the fat we eat influences its composition. Omega-3s make the membrane more flexible and the cells more receptive to incoming signals.

In 1998, psychiatrist and biochemist Joseph Hibbeln noticed that depression was up to 60 times less common in countries such as Taiwan and Japan (where people eat a lot of oily fish) compared with countries like the US and Germany (where they don't).

But evidence is mixed. In 2002, a Crop and Food Research study in New Zealand found there was a direct link between fish consumption and mental health status. However, two further studies by the same researcher found no relationship.

Vision

Omega-3s are important in the development of brain and visual function in infants, and are also associated with retaining those functions throughout life.

In one study, men with the highest fish consumption (at least two serves per week) were 45 percent less likely to have age-related macular degeneration, which is the biggest cause of blindness and severe visual impairment in older people.

Fat facts

All fats and oils are a mix of fatty acids - saturated, trans, monounsaturated and polyunsaturated. But one type usually predominates in each oil or fat.

Omega fatty acids are polyunsaturates that are essential for health - the body can't make them, so you need to include them in your diet. They have many actions, which include lowering total and LDL cholesterol, and reducing your risk of heart disease.

There are two types of omega fatty acids.

  • Omega-6 is found in the oils of seeds and grains, like sunflower and corn oil.
  • Omega-3 is found in seafood, and in some plants such as flaxseed and walnuts.

Too much omega-6 suppresses the action of the omega-3s. So it's important to include enough of the omega-3 long-chain fatty acids eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) in the diet.

These fats are found mainly in marine (fish) oils, and they are vital nutrients required by every cell in the body.

Recommended intakes

The Ministry of Health recommends that an adequate intake is 90mg of long-chain omega-3 per day for women and 160mg for men. Men are bigger than women so they have a higher requirement.

But that's a baseline, for "healthy" people.

To help reduce the risk of chronic disease (especially heart disease), it recommends 430mg per day for women and 610mg per day for men. 

Excessive amounts (>3000mg/day) could increase the risk of bleeding. People taking blood thinners, such as daily aspirin or warfarin, should check with their doctor before taking supplements or eating lots of omega-3 fortified foods.

Real food

You can't beat real food for getting your daily intake of omega-3s.

Table of food containing omega-3

Seafood is one of the main dietary sources of omega-3. The omega-3 content varies widely between and within different species depending on factors such as age, environment, season and the tissue being tested.

Oily fish such as salmon have the highest levels. Just eating one 150g piece of salmon per week can give you 4700mg of omega-3 - that's even more than a man's weekly suggested dietary target.

Packaged and pre-prepared fish and seafood products, including canned and packaged salmon, sardines and herrings range from 358 to 9200mgs per 100g.

Not a seafood fan? You can now buy bread, milk and dairy products with added omega-3s (see table above).

Past concerns with omega-3 fortified foods were that the oils could become oxidised, making the food taste and smell rancid. As a result, the food industry has developed a new way to protect the oil. The omega-3s are now microencapsulated in protective edible proteins or carbohydrates, which prevents the oils oxidising and the taste and smell changing.

Mercury concerns

Mercury occurs naturally in the environment and most seafood contains a small amount of mercury.

Some species (such as shark, swordfish, and fresh tuna) have higher levels of mercury.

Pregnant women need to take particular care, because their developing foetus is potentially more sensitive to the effects of mercury - so they should limit their intake of these species to one serving per week.

Fish oil products and supplements aren't a major source of mercury, and there's no health reason for restricting intake.

Buying supplements

A common objection against taking fish oil supplements is a fishy taste and the "burp" effect, both of which may be signs that the oil has started to oxidise.

Fish oils tend to be unstable, and they undergo oxidation during processing and after encapsulation. Oxidation occurs when the oil comes into contact with oxygen. It's accelerated by the presence of light and heat.

Oxidation is inevitable - but oils shouldn't oxidise to the point of rancidity. Rancid oils will taste and smell horrible. There's also concern that rancid oils may have bad health effects.

When we tested omega-3 supplements in 2007 we found four products that had oxidised to unacceptable levels.

Date marking

The older the oil is, the more likely it is to be rancid.

Best-before dates are a worry, because you've got no way of knowing how old the oil is.

We'd like to see a packed-on date - as well as a best-before date - because then you'd know exactly how old the product was. We'd also like the best-before date shortened to one year after manufacture. Some products in our 2007 test had best-before dates as long as three years.

Fish oil per capsule

Don't rely on the "total fish oil per capsule" stated on the label.

A claim of "1000mg of total fish oil" is meaningless if the fish oil is from a species low in omega-3. It's more useful to know the total omega-3 content.

Some labels don't give the total omega-3 content per capsule. We'd like to see this clearly stated.

Our advice

  • Include seafood in your diet. As well as being a good source of omega-3s, it's high in protein and low in saturated fat.
  • Don't buy fish oil supplements that are nearing their best-before date.
  • We'd like to see fish oil supplements with a packed-on date - and with a best-before date that's no more than one year after manufacture. Then we'd all know how fresh the product was.
  • Don't buy supplements from retailers that store them under bright fluorescent lights. Some retailers store their fish oil supplements in the fridge, so buying from these retailers is a good bet.
  • Store your supplements in a cool dark cupboard or keep them in the fridge.
  • People taking blood thinners, such as aspirin or warfarin, should check with their doctor before taking supplements or eating lots of omega-3 fortified foods.

     

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