The two most popular supplements are cod liver oil, and flaxseed oil, and it is often asked which is the best, and why? The answer is not straight forward and does depend on the both the actual manufacturing of the product individual requirements. Both oils fulfil different roles in nutritional supplementation, and although they are both fatty acid supplements, they are not the same. This article will explore the differences between the two oils, so you can understand which one is most suitable for your needs.
Cod Liver Oil
The processing of cod liver oil makes a massive difference to the final product. Everything from sourcing of the cod, to how the oil is extracted and stored. For example, the liver of wild fish tends to be higher than that of farmed fish, and fermented extraction yields a product which contains naturally occurring vitamin A & D, whereas dry rendering extraction will require synthetic vitamins to be added post extraction. Omega-3 content is usually relatively consistent in the various products assuming they are from a reputable brand though, but we know that naturally occurring vitamins are better absorbed than their synthetic counter-parts.
1g of cod liver oil typicaly contains 310mg of omega-3 fatty acids (although there is quite a lot of scope depending on processing). The most abundant of the fats are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), with 1g of cod liver oil can contain approximately 70-110mg of EPA and 100-140mg of DHA. These fatty acids are essential for cognitive function, reducing inflammation and maintaining a healthy cardiovascular system. These fats also assist with a number of other biological functions, and support the immune system.
Cod liver oil also contains small amounts of an omega-3 fatty acid called ALA (alpha-linolenic acid). This fatty acid plays a part in cells signalling and metabolism, and can be converted into DHA and EPA.
Vitamins & Minerals
Cod liver oil contains significant amounts of vitamin A & D. Vitamin A is essential for vision and also fulfils a number of roles in the body, including supporting the immune system, maintaining health skin and gene transcription. Vitamin D also plays a very important role in the immune system, helps to regulate hormones and is essential for maintaining healthy bones. With many cod liver oil supplements vitamin A & D are added post-extraction, as the extraction process itself can damage or remove these vitamins.
The main concern with cod liver oil is the accumulation of toxins in the oil, such as lead and mercury based compounds. These compounds accumulate in the food chain, which means the oil of large fish (such as cod) will contain high levels of these toxins. These toxins are known to damage the nervous system and have a negative impact on cognitive function. These toxins can also have very serious effects on developing foetuses.
Most processing methods for extracting cod liver oil do often try and remove these toxins, with minimises the risk, but there will undoubtedly still be trace amounts present in the oil. All cod liver oil will contain less than the toxic level (or else they simply cannot be sold), but the content will vary from manufacturer. You would have to speak to specific manufacturers to find the levels in their oils.
Flaxseed oil is processed very differently to cod liver oil, but this stage of the product manufacturing is just as important. Flaxseed oil can be extracted in 2 ways – heat extraction, or cold pressing. Heat extraction will produce a higher yield of oil, but will cause some of the oil to react with the oxygen in the air, causing the fats to become oxidized and nutritionally useless. It is because of this that it is important to source cold pressed flaxseed oil to avoid these oxidised fats.
1g of flaxseed oil contains 400-600mg of the omega-3 fatty acid called ALA (alpha-linolenic acid). This is significantly more ALA than cod liver oil, but, flaxseed oil does not contain any aEPA and DHA. ALA can be converted into EPA and DHA (rather inefficiently), so although flaxseed is not a direct source of EPA and DHA, it can still be considered a source of these fats.
1 gram of flaxseed oil can contain up to 180mg of omega-6 fatty acids. Omega-6 fatty acids are essential for the human body, but are relatively abundant in modern diets in various forms and quality. Excess omega-6 fatty acids in the body can be converted into pro-inflammatory agents, which may lead to discomfort and a number of ailments if there are a significant abundance of omega-6 fatty acids. Furthermore omega-6 fatty acids inhibit the conversion of ALA to EPA and DHA, which may reduce the amount of EPA and DHA you will receive from flaxseed oil.
1 gram of flaxseed oil will provide the body with up to 180mg of omega-9 fatty acids. These fatty acids are not considered essential as they can be created in the body from other fatty acids. It is also abundant in modern diets and is found in both animal and vegetable fats.
Vitamins & Minerals
Although flaxseeds contain a number of vitamins such as vitamin K, B-complexes and vitamin E, biologically significant quantities of these vitamins are not found in flaxseed oil supplements. Flaxseeds also contains a number of minerals such as magnesium, zinc and potassium, but again, these are not found in any significant quantities in the supplement either. The levels in oil simply are not tested for, so assumed low. I am sure certain manufacturers would contain more than others, but there is just no way of knowing. The lack of minerals and vitamins in flaxseed oil is a result of the processing method, and the majority of manufacturers do not add the vitamins and minerals back into the end product.
Flaxseed contain a phytoestrogen called lignan. Lignan is usually removed during the extraction process, but some manufacturers do add it to the oil at the end of processing. Lignan has shown remarkable anti-cancer effects (particularly against breast cancer), and also acts as an antioxidant. There will also be other phenolic compounds on flaxseed oil which are not tested for. Research on phenolic compounds shows they have a number of benefits, and often found in vegetable oils. Despite this, they are given little attention though.
Cod liver oil provides EPA, DHA, small amounts of ALA, and contains significant amounts of vitamins A & D. This makes is particularly beneficial for those whose diets do not provide much omega-3. There is the concern that cod liver oil may contain some harmful chemicals which can cause neurological damage, and can detrimental effects to developing fetuses. With this in mind, it is always a good idea to carefully look at how the fish oils are made, because the end products can vary dramatically. You can read a detailed comparison of fish oils here.
Flaxseed oil is a broad spectrum fatty acid supplement, and may be more beneficial for those who are on low fat diets. It provides large amounts of omega-3 fatty acid ALA as well as omega-6 and omega-9, giving your body with a diverse range of fatty acids. EPA and DHA can still be created from flaxseed oil, but it is dependent on a number of biological factors. Some flaxseed oil supplements contain lignan, which provides the additional anti-cancer and anti-oxidant support to the body, not all flaxseed will contain this though. It is most important when looking for at cod liver oil and flaxseed oil that you ensure it is processed in a way which protected the nutrients.