Was your Grandmother right about cod liver oil?

Cod Liver Oil for Immune System

Omega 3 Rich Oils & Supplements

Some of you may be old enough to have memories of mothers forcing them to take cod liver oil.  Centuries ago, northern Europeans used cod liver oil to protect them from the cold and was also said to relieve such complaints as rheumatism, aching joints, and stiff muscles. At the beginning of the 20th century, scientists established that cod liver oil was a source of vitamin D and therefore a remedy to cure rickets.  Although cod liver oil may have gone out of fashion, fish oil is having a moment.  Omega 3 rich oils & supplements now being touted as natural wonder drugs.  But with so many types trying to get your attention, it can be hard to figure out which one (if any) you should choose. I’m not going to go into detail of the huge literature of scientific and clinical studies exploring the benefits of fish oil.

Omega 3’s refers to the family of fatty acids that are nutritionally deemed essential – meaning we need to get them from diet as our bodies can’t synthesise them.  If we don’t get them from our diet in adequate amounts, then we are at risk of deficiency and associated diseases.  The three most prominent types which you may have heard of are ALA (alpha-linolenic acid), DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). 

First take a look at what makes these essential fats so special.

Omega 3’s play many important roles in the body.   They are important components of our cell membranes, affecting how fluid and permeable they are.  They are a launch pad for making hormones and used by the immune system as specialised pro-resolving mediators, playing a role in taming inflammation and suppressing key inflammatory genes.  This is highly important for healing and resolving at the end of infection or trauma.  Though critical to our immune defences, inflammation can be problematic in chronic situations where it is involved in a plethora of diseases including rheumatoid arthritis, atherosclerosis, asthma, inflammatory bowel disease, depression, Crohn’s disease, ulcerative colitis, psoriasis, lupus erythematosus, multiple sclerosis, migraine headaches, and diabetes. Omega 3’s can help mitigate some of the symptoms of chronic inflammatory disease and omega 3 supplementation has been shown to reduce serum levels of pro-inflammatory immune system communication molecules in the blood called tumor necrosis factor alpha (TNF-alpha) and interleukin 1 (IL-1), both markers of inflammation. Although the suppression of inflammatory responses resulting from increased omega-3 fatty acid intakes may benefit individuals with inflammatory or autoimmune diseases, very high doses of omega-3 fatty acids in healthy individuals could decrease the potential of the immune system to destroy infections.  In addition to their role in immunity, omega 3’s are also key to maintaining correct vision and vital to correct brain development and function since approximately 50-60% of the adult brain is composed of fats, of which around 10-20% is the omega 3 DHA!  Clinical signs of omega 3 deficiency include a dry scaly rash, decreased growth in infants and children, increased susceptibility to infection, and poor wound healing. Even with no apparent deficiency signs, a diet rich in omega 3’s is considered to play a key role in many aspects of overall health and wellbeing including proper cognitive development and function, reduced risk of certain cancers and taking care of mental health to reduced all-cause mortality. There is much debate regarding how our ancestors came by these essential fats in their diet. For those near the sea, the answer is probably straight forwards - exploiting tides and foraging the marine food chain. But for those in land, it is not so clear. Scientists have shown that omega 3 is not readily accessible from the muscle tissue of land animals, and that the form of these essential fats such as that found in shellfish—is incorporated into the developing rat brain with 10-fold greater efficiency than plant-sourced ALA. Some have suggested that our ancestors ate the fat rich brains of land animals!

ALA, EPA and DHA are all omega 3 fatty acids, but they have some potentially important differences in terms of sources, how they work in the body and how easily we can absorb and use them.  Then there’s the bigger issue of whether or not some of these omega 3 sources are sustainable and/or economically viable.  Let’s look at each one in turn:

ALA – the parent one.

ALA comes from plant food sources (for example flaxseeds, chia seeds and walnuts to name a few).  ALA is considered the essential omega 3 since it cannot be synthesised by us humans. ALA can be converted to DHA and EPA in the body via a series of enzymatic reactions in the body.  The conversion of ALA (which occurs primarily in the liver) to EPA and, particularly, DHA is relatively inefficient, requiring several enzymes and is ‘rate-limiting’ – like a metabolic bottleneck, with reported rates of less than 15%.  Ethnic distribution of genetic variations appears to have a huge impact on how efficient people can make the conversion.  Because we can actually make EPA and DHA, albeit not very well, they are considered conditionally essential nutrients.   Therefore, consuming EPA and DHA directly from foods and/or dietary supplements is a practical way to increase levels of omega 3’s in the body.  Interestingly, the capacity to generate EPA and DHA from ALA is higher in women than men.  This appears to be related to the effects of oestrogen and an evolutionary adaptation to meet the increased demands by the foetus during pregnancy.

EPA – the anti-inflammatory one.

EPA is mostly found in animal products, such as fatty fish and fish oil. However, some microalgae also contain EPA.  It has several functions in the human body but primarily considered in its anti-inflammatory capacity.  EPA can also be converted into DHA.

DHA – the brain one.

DHA is perhaps the most important omega-3 fatty acid in the human body. It is a key structural component of the brain, the retina of the eyes and numerous important parts of the body.  Like EPA, it is mostly found in animal products like fatty fish and fish oil. Meat, eggs and dairy products from grass-fed animals can also contain significant amounts.  It is particularly important when pregnant and breastfeeding to get enough DHA as it can affect the future health and intelligence of the baby. 

Where can get these omega 3s from?

Eating oily fish. 

Now there might be many reasons why you don’t eat oily fish but before we move on to supplements, fish consumption is associated with reduced risk of heart disease in both epidemiology and clinical trials and appears to help curb depression risk. In addition there is evidence that the benefits of eating fish extend beyond those found from omega 3-based supplementation alone.  One reason for this is the form of oil found in fish and in particular fish roe (more caviar please?!), known as the triglyceride form, is more bioavailable and preferentially imported into the brain.  When the oil is harvested into supplements, it undergoes a process known as molecular distillation to remove pollutants such as mercury.  This converts the omega 3 oils into an ethyl ester form found in most supplements which is substantially less bioavailable.

Cod Liver oil. 

As well as EPA & DHA, cod liver oil contains an impressive amount of vitamin A and vitamin D. Vitamin A and D play quite key roles in the immune system, and our bodies don’t produce it so we must get it from an outside source. Vitamin A deficiency causes an increased risk of infection. But catching an infection increase the body’s need for vitamin A, which creates a downward cycle.  Although direct sunlight is the best source of vitamin D, seasonal changes, sunscreen and indoor lifestyles affect the amount we receive.  Adequate Vitamin D not only prevents rickets but reduces the risk of common cancers and other diseases including type I diabetes, multiple sclerosis, heart disease, rheumatoid arthritis, and more. It is important to AVOID cod liver oil that contains low levels of vitamin D in relationship to vitamin A. The ideal ratio of A to D is no greater than 10:1 (for every one unit of vitamin D there should be no more than 10 units of vitamin A).  With industrialized processing, these ratios can become imbalanced and the risk for vitamin A toxicity becomes greater. You will find that the purest, least processed cod liver oils have a ratio near the ideal 10:1, because when the vitamins are naturally occurring, rather than synthetic, they are naturally balanced. While vitamin A is a powerful antioxidant, take too much of it and you’re at risk of vitamin A toxicity. This is when large amounts build up in your body over time, which can lead to liver damage and could even harm your vision.  As mentioned earlier certain chronic inflammatory conditions require a high, clinical dose of omega 3 to see any benefit - and if you took cod liver oil at the same dosage, you’d be getting too much vitamin A.  

Fish oil.

Unlike cod liver oil, omega 3 fish oil comes from the body of oily fish such as sardines, herring and mackerel.  It contains both EPA & DHA and some vitamin A and vitamin D but not as much as cod liver oil. Not sure whether to take Omega 3 or cod liver oil?  It’s no surprise you’re confused – first is to think of your why? If you are a healthy adult with no underlying conditions and not pregnant or breastfeeding, then it’s probably fine to take cod liver oil.  Although, because the function of fish livers is to filter out toxins, it’s possible that cod liver oil is likely to contain more environmental nasties compared to fish oil.

Pure Omega 3 oil. 

Capsules labelled as omega 3 oil from a marine source are normally from oily fish and generally contains only EPA & DHA but won’t have vitamin A and vitamin D.

Krill Oil.

A crustacean, krill are tiny, shrimp-like creatures that live in the Antarctic.  A deep red colour, krill oil contains EPA & DHA albeit at lower amounts – they are in the much more bioavailable phospholipid form which has a higher rate of absorption.  So a lower dose of krill oil gives the same effect as a fish oil supplement. It also contains a powerful antioxidant called astaxanthin which gives the oil its deep, red colour.  Astaxanthin accumulates in cell membranes where is protects omega 3 fats like DHA which are delicate and prone to oxidation.  You can also find astaxanthin in more sustainable sources, like wild salmon, red trout, crab and lobster.  From a sustainability perspective, krill oil is possibly more controversial than fish oil because krill make up a vital part of the Antarctic food chain and a huge number of Antarctic species are directly or indirectly affected by their declining numbers.  

Algae Oil. 

Algae oil comes from marine algae and is high omega 3 fatty acids EPA and DHA, making it suitable for vegetarians looking for an alternative to fish oil.   In fact, the DHA and EPA that is present in fish oils and krill oils are originally synthesized by microalgae, not by the fish. When fish consume phytoplankton that consumed microalgae, they accumulate the omega-3s in their tissues.  So, it would follow that by taking an algae supplement you are getting vital omega 3s right from the source?  Unfortunately, that’s not quite the case. By taking an algae oil you’ll get the brain and eye boosting benefits of DHA, but you’ll be missing out on all the anti-inflammatory properties of EPA. here are thousands of species of algae, and they vary in their ability to make EPA and/or DHA.  Some make both, some make just DHA, and to varying levels. This can be problematic for people relying on these for their oils.  This isn’t ideal if you were looking to help inflammatory conditions like eczema or wanted to protect your heart.

Do we need to supplement with omega 3? 

How do we know if we should supplement with omega 3 rich oils to get optimal benefits? In nutrition, I advocate a movement towards food-based recommendations because ultimately your diet is the sum of its parts. But if you are considering taking an omega 3 rich supplement, you actual need for it depends on many things. Some of which I’ve mentioned above such as whether you have an inflammatory disease, age, pregnant or breastfeeding and lifestyle choices around consumption of fish.  As always, consensus in nutrition is challenging and always evolving. Ultimately your diet is the sum of its parts. Go for a food first approach if you eat fish – two portions of oily fish per week is recommended.  If you are supplementing with omega 3 in one form or another, they generally are tolerated well. But large amounts may have mild side effects, increase your risk of bleeding and might suppress your immune response.  Think about sustainability of the source and if it’s suitable for your situation.  And of course, consider your overall dietary pattern, giving a thought to the possible sources of unnecessary omega 6’s or saturated fats that you may be consuming.

One last point.

As I said, your diet is the sum of its parts and the effectiveness of your omega 3 supplements may also depend on what else you are eating and how much - in particular your omega 6 consumption.  Omega 6 in our diet is mostly linoleic acid (LA).  Omega 6 fats are also defined as an essential fats since they are not synthesised in the body and must be obtained from the diet.  The most common source of LA include  corn oil, soybean oil, safflower oil, cottonseed oil, sunflower oil, poultry, and some nuts and seeds.  These fatty acids also play vital roles in the body, helping with brain function, muscle growth, and hormone production.  Unlike the anti-inflammatory omega 3’s, LA omega 6 fats are the raw materials for inflammation - a vital function performed by the immune system in response to infection, damage or danger.  To do this LA is metabolised to arachidonic acid (AA) – a proinflammatory inflammatory signalling molecule.  But this requires the same enzymatic pathways as omega 3’s.   Such that they compete for the same desaturase enzymes.  So, one way to look at it is omega 3 and omega 6 having opposing functions in the body – like a switch between pro- and anti-inflammatory.  But it would be an oversimplified view to think of omega 3 as good and omega 6 are bad – we need both and biology is never that simple.  But a higher concentration of omega 6’s in the system could preference the proinflammatory AA pathway over the anti-inflammatory omega 3 pathway.  Because of this, some researchers propose that the relative intakes of omega-6s and omega-3s – known as the omega-6/omega-3 ratio - may have important implications for the pathogenesis of many chronic diseases, such as cardiovascular disease and cancer.   While it’s true that the western diet has changed over the decades to be lower in omega 3 and higher in omega 6, the optimal ratio - if any - has not been well defined.  This dietary shift centred on more processed and fast food which is confounded by the fact that such eating patterns also tends to contain higher saturated fat which we know isn’t good for health. While studies examining higher dietary omega 6 and associated cardiovascular disease risk did not account for the dietary source of omega-6 LA, with margarine often used which has a significant confounder due to its trans-fat content.

So what appears to be a seemingly simple metric of omega 3:6 ratio, has both theoretical and practical difficulties resulting it is being somewhat controversial in its applicability.  Because of this, the focus has shifted towards a newer measure focussing on dietary deficiencies that lead to a lack of EPA and DHA.  This is known as the omega-3 index and defined as the amount of EPA plus DHA in red blood cell membranes.  Several observational studies indicate that a lower omega-3 index is associated with an increased risk of heart disease death. Despite disagreement over the importance of the omega 3-6 ratio, most agree that raising EPA and DHA blood levels using the newer omega-3 index metric might be a better focus than lowering omega 6 levels. That being said, excess omega 6 does appear to be one contributing factor to chronic low-level inflammation. On a population level we have increased omega 6 consumption in the last 100 years due to the development of technology at the turn of the century that marked the beginning of the modern vegetable oil industry.  Vegetable oil is a common component in more foods than we realise so it’s possible to be consuming far more than we are aware.  Studies show that when supplementing with omega 3, the dose required is decreased when the omega 3:6 ratio is lowered.  Thus, it may still be an important determinant of health.

My personal favourites.

Sustainability & provenance are high on my list when purchasing a product. Please note I do not have any affiliation with any of the brands that I mention. I love Bare Biology Omega 3 products. As well as great all round high quality omega 3 oil capsules, they also have products specialised for pregnancy, babies chad children & mental health. The company is local to me in Brighton and they only use small wild fish, like anchovies and sardines, from clean and deep waters - as these are purer, safer & more sustainable. The omega 3 based second product I like is by Fiscolia. I love their ASTAXOMEGA - which is a blend of herring fish oil (so it also contains vitamin A & D, unlike pure omega 3. But also has astaxanthin, an antioxidant. Their responsibly controlled herring fisheries also develop a sustainable base for employment in rural Icelandic fishing villages. I’d love to hear your suggestions for vegan omega 3 oils too.