Cod Liver Oil

Cod Liver Oil is a dietary supplement that is primarily composed of fish oil, vitamin A, D and Krill oil. These are blended into a single capsule or oil to be consumed orally – this combination has traditionally been used to fend off rickets and similar conditions, which may result from a deficiency in vitamin D. Overall, its uses have focused on maintaining proper health and wellness among individuals who don’t have a large dietary intake of fatty fish. This is the usual source of cod liver oil – as the name implies, it is extracted from the livers of cod, reflecting the fact that liver is the most nutrient-dense and health-beneficial meat in most animals.

We truly believe that almost everyone should supplement cod liver oil: for most people in the English-speaking world, fatty fish is uncommon in the diet. Salmons, tuna and other seafoods tend to be very high in these compounds, although they do not make up a large portion of the majority of diets. In this article, we will be discussing the major health benefits associated with supplementing cod liver oil.

Fish Oil

Cod liver oil Fish Oil

1. Omega-3 – Cod Liver Oil

The main ingredient in cod liver oil, fish oil refers more generally to the fatty acids EPA an DHA – two forms of Omega-3 acid which are uncommon in many other dietary products. Especially among plant-based diets, omega-3 intake requires huge doses of supplementary flaxseed or walnut-derived products. Omega 3 is an essential fatty acid (the body cannot produce Omega-3s from non-omega-3s and they must be consumed in the diet) and EPA/DHA are long-chain Omega-3s. Whilst it is possible to convert ALA (another form of omega-3) to these long-chain fats, this is an incredibly inefficient process, especially when we consider that the main role of ALA in the body is to be a component of long-form fatty acids (reports suggest that our conversion rate is as low as 5%) [1].

Omega 3 plays a crucial role in the development and maintenance of a healthy body – when we do not consume enough Omega-3, we risk chronic inflammatory processes occurring throughout the body at unhealthy levels. Omega-3 works against Omega-6 (another form of fatty acid that induces inflammation) and having a diet that is high in O6 but low in O3 can significantly exaggerate inflammation [2]. Cod liver generally has a ratio of 1:9.3 (9.3 times as much Omega-3 as Omega-6).

2. Triglyceride Levels

Blood triglyceride levels are associated with poor health – an increased consumption of fish oil has been reliably shown to reduce the serum levels of triglycerides anywhere between 15 and 30%, with particular effect on those who already suffer from excessively-high concentration in the blood [3]. This means that the consumption of cod liver oil – rich in EPA an DHA – will actively improve the health of the blood and the circulatory system.

3. Depression, Anxiety and Bipolar Disorder

Depression, anxiety and bipolar disorder are incredibly common mental health problems, with some estimates putting instances of clinical depression at around 25% in some age groups. Fish oil has been shown to have comparable results to pharmaceutical interventions in individuals with severe clinical depression [4]. Cinical trials also suggest that there are positive effects on the symptoms of bipolar disorder when supplemented in high enough doses [5]. Finally, symptoms of clinical anxiety have been shown to decrease in response to supplementation of EPA [6].

Overall, there are some conflicting results on the effects of fish oil on mental health concerns, but there are general reports of positive effects and it seems that the overlapping psychological and neurochemical causes and symptoms of depression, anxiety and bipolar disorder corroborate a general improvement on mental health during EPA and DHA supplementation.


Aside from common behavioural-neurochemical disorders such as depression and anxiety, fish oil supplementation has been shown to have positive effects on the symptoms of ADHD [7]. Supplementary doses have been shown to assist in the treatment of symptoms, but not sufficient to replace traditional pharmaceutical treatments. However, because there are very few negatives and various other benefits, fish oil provide a great addition to the diet of those suffering from ADHD.

5. Blood Pressure

Fish oil has been shown to reduce the blood pressure of individuals struggling with medical hypertension, as well as having some benefits noted among regular populations (although these are not statistically significant). Blood pressure is an important precursor for serious problems like stroke, heart attack and heart disease. It is important to note, however, that this is only proven in those populations who are already suffering from hypertension [8].

6. Inflammation

As mentioned above, Omega-3 has an important role in universal inflammation ratios, but it also has specific inflammatory benefits according to some clinical evidence [9]. This clinical evidence suggests that there are some anti-inflammatory effects – primarily in the cardiovascular system – due to changes in triglycerides (as mentioned above) and immune system markers.

7. Cortisol Reduction

Cortisol is an incredibly complicated and interesting hormone that is released in response to stressors (both psychological and physiological, according to recent research). Whilst it plays a necessary role in the body during normal contexts, excessive cortisol can suppress the immune system’s function in quantifiable ways. It also has important roles in the regulation of metabolism and blood sugar, meaning that chronically-elevated levels can have negative effects on these processes. Fish oil has been shown to have some effects in reducing cortisol [10].

8. Post-Exercise Immune System Function

Based on the aforementioned effects of fish oil, it might not be particularly surprising to note that immune system function has been associated with fish oil intake. When we look at the times when immune system would otherwise be suppressed (such as immediately after exercise), fish oil consumption improves the markers associated with protective white blood cells [11].

9. Cognitive Function and Ageing

Fish oil has been associated with a protective effect on the onset of degenerative brain disease such as Alzheimer’s disease. Individuals who were otherwise-healthy improve some areas of memory function by simply supplementing DHA [12]. This seems like a very low-risk way of maintaining or improving cognitive function.

10. Ketones

Ketones have received an unnecessarily trendy status in recent years with the increased popularity of low-carbohydrate, high-fat diets. The consumption of fish oil among those on a caloric surplus has been shown to relate to increased circulation of ketones in the body [13]. This was associated with an increased loss of body fat (24% over placebo), suggesting that a calorie-deficit diet rich in fish oil can improve the rate of weight lost, alongside other positive effects.

11. Skin Health

Vitamin A is one of the main components of cod liver oil and has profound effects on the way that various bodily systems function. Primary among these is the role that it plays in dermatology, reducing the appearance of fine wrinkles, skin dryness, skin quality and collagen content [13].

12. General Immune System Function

Beyond these superficial effects, Vitamin A is essential for a number of internal processes such as the processing and transcription of DNA, as well as the continued health of the immune system. The protection and proper transcription of DNA reduces the possible health problems associated with cell mutation and cancerous tumours.

The combination of Vitamin A and Fish oil in cod liver oil provides a major improvement in immune system function and health. The short and long-term health of the immune system are protected and enhanced by the supplementary doses seen in cod liver oil [14]. The combination of these two ingredients and their scientifically-verified effects provide a comprehensive, albeit mild, positive outcome.

Vitamin D is an essential vitamin that has a wide variety of applications in the human body. It is arguably the most beneficial supplement, being almost impossible to achieve sufficient doses from sunlight alone. Whilst some foods such as dairy are fortified, the main sources are fatty fish – something that cod liver oil aims to mimic in the diet. Salmon, for example, provides over 100% of the RDA for vitamin D.

13. Bone Health and Fracture Risk

Vitamin D is essential for the mineral uptake of bone hard-tissue, meaning that it is closely tied to the health of bones, especially in advanced age. The maintenance of bone mineral density during ageing reduces the risk of osteoporosis and fall-based fractures [15]. This is essential to the uptake of calcium, particularly, which is why it is fortified in dairy. However, the relative dosage found in dairy products is low – it would be necessary to consume around half a litre of fortified milk daily in order to meet necessary minimums.

14. Parathyroid Hormone

Vitamin D has a strong, clinically-proven positive effect on the body’s thyroid function, reducing the extent to which the parathyroid hormone is secreted and, thereby, reducing the chance of developing hypothyroid disorders [16]. Clearly, Vitamin D is a multi-faceted vitamin.

15. Colorectal Cancer

Colorectal cancer, which has been associated with red meat consumption and is the cause of the buzz surrounding the “red meat causes cancer” myth, is reduced by the consumption of vitamin D. The supplementary dosing of vitamin D has been shown to reduce the odds of developing severe colorectal cancer by 53% – a significant reduction [17]

Sources and References

[1] Thomas, B.J. (2002): ‘Efficiency of conversion of alpha-linolenic acid into long chain n-3 fatty acids in man’. Current opinion in clinical nutrition and metabolic care, 5(2), pp.127-132
[2] Simopoulos, A.P. (2002): ‘The improtane of the ratio of Omega-6/Omega-3 essential fatty acids’. Biomedicine and pharmacotherapy, 56(8), pp.365-379
[3] Fakhrzadeh et al (2010): ‘The effects of low dose n-3 fatty acids on serum lipid profiles and insulin resistance of the elderly: a randomized controlled clinical trial’. International journal for vitamin and nutrition research, 80(2), pp.107-116
[4] Sublette et al (2011): ‘Meta-analysis of the effects of eicosapentaenoic acid in clinical trials in depression’. Journal of clinical psychiatry, 72(12), pp.1577-1584
[5] Stoll et al (1999): ‘Omega 3 fatty acids in bipolar disorder: a preliminary double-blind, placebo-controlled trial’. Archives of general psychiatry, 56(5), pp.407-412
[6] Kiecolt-Glaser et al (2011): ‘Omega-3 supplementation lowers inflammation and anxiety in medical students: a randomized controlled trial’. Brain, behaviour and immunity, 25(8), pp.1725-1734
[7] Bloch and Qawasami (2011): ‘Omega-3 fatty acid supplementation for the treatment of children with attention-deficit/hyperactivity disorder symptomatology: systematic review and meta-analysis’. Journal of the American academy of child and adolescent psychiatry¸ 50(10), pp.991-1000
[8] Campbell et al (2013): ‘A systematic review of fish-oil supplements for the prevention and treatment of hypertension’. European journal of preventative cardiology, 20(1), pp.107-120
[9] Ciubotaru et al (2003): ‘dietary fish oil decreases C-reactive protein, interleukin-6 and triacylglycerol to HDL-cholesterol ratio in postmenopausal women on HRT’. Journal of nutritional biochemistry, 14(9), pp.513-521
[10] Michaeli et al (2007): ‘Effects of fish oil on the neuro-endocrine reponses to an endotoxin challenge in healthy individuals’. Clinical nutrition, 26(1), pp.70-77
[11] Gray et al (2012): ‘Fish oil supplementation augments post-exercise immune function in young males’. Brain, behaviour and immunity, 26(8), pp.1265-1272
[12] Arguello et al (2010): ‘Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline’. Alzheimers and dementia, 6(6), 456-464
[13] Kafi et al (2007): ‘Improvement of naturally aged skin with vitamin A (retinol)’. Archives of dermatology, 143(5), pp.606-612
[14] Mora et al (2008): ‘Vitamin effects on the immune system: vitamins A and D take centre-stage’. National review of immunology, 8(9), pp.685-698
[15] Bischoff-Ferrari et al (2009): ‘Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials’. British Medical Journal, 339, 3692
[16] Yurko-Mauro et al (2013): ‘Supplementation with 1000 iu vitamin D/d leads to parathyroid hormone suppression, but not increased fractional calcium absorption, in 4-8-y-old children: a double-blind randomized controlled trial’. American journal of clinical nutrition, 97(1), pp.217-223
[17] Gorham et al (2007): ‘Optimal vitamin D status for colorectal cancer prevention: a qualitative meta-analysis’. American journal of preventative medicine, 32(3), pp.210-216