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Nutrient - Supplementing fish oils

By Dr Pieris Nicola PhD BSc (Hons) DipION

A large and growing body of scientific literature suggests that eating fatty fish not only enhances early growth of the brain and retina, but also provides protection against cardiovascular disease, stroke, some cancers, arthritis, mental decline and prostate cancer, later in life. Moreover, researchers believe that the lion’s share of fish’s health benefits come from two very-long-chain omega 3 fatty acids found naturally in fatty fish, namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). 

Why consume oily fish?

There is general scientific agreement that we should consume more omega 3, and fewer omega 6, fatty acids for good health. In addition to providing healthy omega 3 fats, eating oily fish has other advantages. Fish is an excellent source of protein, and those who eat fish generally tend to eat less red meat and cheese – two potent sources of saturated fat.

However, there are limits on the maximum number of portions of oily fish that should be consumed each week. The UK’s Food Standards Agency (FSA) recommends:

  • Two portions of oily fish per week (one ‘portion’ is about 140 grams) for women that are pregnant, intending to become pregnant or breast-feeding.
  • Four portions of oily fish per week for women who do not intend to become pregnant in the future, and also for men and boys.

Why limit the amount of oily fish consumed?

Unfortunately, there is a “catch” to this health benefit. While fish have been promoted for their health benefits, they may also contain pollutants absorbed from the waters in which they swim. For this reason, the consumption of too much fish is not recommended because of the high levels of contaminants, such as mercury, dioxins and polychlorinated biphenyls (PCBs). Farmed fish contain less mercury, but they may contain PCBs.

The effects of mercury and PCBs are known to be dangerous in high doses. Mercury is a neurotoxin and can affect the developing brain and nervous system, which is why the current advice on limiting fish consumption is targeted at pregnant and breast-feeding women and young children.

Going off the deep end

If you are concerned about mercury, eating a variety of fish will help keep overall exposure low. It is also prudent for women of childbearing age, pregnant women and young children to completely avoid eating predatory fish at the top of the aquatic food chain, such as swordfish and shark, which often have the highest concentrations of methyl mercury. In contrast, sardines, anchovies and mackerel are herbivorous fish, which are lower down in the food chain and have lower concentrations of mercury.

Some may choose to avoid fish completely because of potential contamination; others may simply dislike fish, and the high price of fish puts it beyond the budget of many.

Omega 3 fish oil supplements offer an alternative way to increase intake of these important fatty acids. Because mercury concentrates in the muscle (fillets), rather than the fat of fish, fish oil supplements have not been implicated as a source of mercury exposure. Organic carcinogens, including PCBs, dioxins and certain pesticides, are fat-soluble and can enter the oil.

Fish oil quality and purity

There is such a variety of fish oil supplements on the market that it is easy to get confused. So, how does one go about selecting a good fish oil?

1. The source of the fish

The level of contaminants in a fish oil preparation is likely to depend on the source of the fish. Good fish oil supplements come from wild fish that are freshly caught and harvested by fisherman from a sustainable resource found in relatively uncontaminated oceans, including the Indian and Pacific oceans. Choose fish oil from the body of fish, as oil from the liver is more likely to contain higher levels of fat-soluble contaminants.

2. The type of fish used

Many fish oils on the market are derived from cheaper, more polluted, farmed fish. Farmed fish may have more PCBs than wild fish, and may also contain antibiotics, growth hormones and colouring agents. High-quality fish oil is rendered from wild, freshly caught fish, such as mackerel, sardines and anchovies, which are lower in the food chain.

3. The method by which the oil is processed

Oils from good-quality fish do not require the complex processing that is normally utilised for oils sourced from poor-quality or farmed fish.

High-quality fish oil supplements are filtered to remove particles and then undergo a purification process to remove all traces of pollutants. Removal of impurities from fish oil is very important for producing purified oil with an acceptable shelf-life. Good-quality oil does not require further processing. The resultant food-grade oil is encapsulated or bottled in its whole, naturally-balanced form, retaining its synergistic spectrum of naturally-occurring fatty acids and antioxidants, including carotenoids and tocopherols, which are present naturally in the wild fish. The result is a food-grade oil, retaining its golden colour, which looks and tastes as you would expect fish oil to.

In contrast, pharmaceutical-grade fish oils have undergone heavy, industrial processing, including deodorisation, to remove the fishy taste and odour – a process that can also remove valuable nutrients. The more processing fish oil undergoes, the more likely it is to lose its full nutritional value, because such processing can degrade the oil, damaging the fragile unsaturated fatty acids, as well as removing flavours, colours and nutrients. Many fish oil supplements are artificially high in omega 3 fatty acids as a result of processing by very-high-temperature distillation, resulting in a distorted ratio of EPA and DHA. The result is a product that is very different from the one found in nature. Is such fish oil natural?

4. Is the oil tested by independent laboratories?

Following purification, fish oil should be scrutinised by a third party to ensure purity, safety, stability and efficacy. European approval is known to be far more stringent than the rest of the world, and the best fish oils should meet the strict European standards on contaminants.

Fish oils are known to become rancid, even when kept at low temperatures, resulting in the generation of free radicals. Rancidity is due to the reaction between oxygen and unsaturated fatty acids present in fish oils. This reaction can be slowed to maintain quality throughout the shelf-life by the addition of antioxidants to fish oil.

In summary, high-quality fish oil supplements provide an alternative and convenient way to ensure daily intake of long-chain omega 3 fatty acids, as well as providing the additional assurance of consistent potency. Look for sources derived from wild fish found lower in the food chain, and make sure the product is screened to ensure negligible amounts of potential contaminants. In short, a good fish oil supplement is more than just fish oil.

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