Cod liver oil: properties, benefits and contraindications

Cod liver oil: everything you need to know about properties, benefits, and contraindications

Cod liver oil is a product obtained from cod liver that is rich in omega-3 fatty acids , vitamin A and vitamin D. It appears that as early as the 1700s the liver of this fish was fermented, and the use of its oil for medicinal purposes dates back to at least the 19th century, when it was already finding use in the treatment of rickets. 

Da allora è stato utilizzato a diversi scopi, e ancora oggi è presente sul mercato degli integratori alimentari. C'è, ad esempio, chi lo usa come ricostituente o per promuovere la salute di pelle e capelli. Altri lo assumono contro il colesterolo e i trigliceridi alti, per combattere i problemi renali associati al diabete oppure contro la pressione alta, le malattie cardiovascolari, l'artrosi, la depressione, il lupus eritematoso sistemico, il glaucoma, l'otite media e diversi altri disturbi. 

There is also no shortage of those who apply it directly to the skin to accelerate wound healing. In fact, when taken orally in appropriate doses, cod liver oil supplements seem to really help reduce both triglycerides and high blood pressure. In addition, there is also evidence of their effectiveness in treating some kidney symptoms associated with diabetes, and it appears thattopical application of cod liver oil may also have positive effects. Human health is not the only one to benefit from its use, however, and today cod liver oil is also recommended to promote animal welfare (particularly of dogs, cats, and horses).

Cod liver oil: what it is and how it is obtained

L'olio di fegato di merluzzo si ricava mediante estrazione dal fegato del merluzzo. Per assumere i suoi principi attivi potrebbe essere sufficiente mangiare del fegato di merluzzo fresco. Oggi, però, il mercato offre un'ampia gamma di integratori che hanno come ingrediente principale proprio l'olio estratto dal fegato di merluzzo; affidarsi a questo tipo di prodotti può semplificare l'assunzione di questo rimedio naturale e aiutare a renderla più precisa e più regolare.

Cod liver oil and fish oil: the differences

It happens that cod liver oil is compared withfish oil. Both are sources of fatty acids omega 3, but this does not mean that they are interchangeable products. What makes the difference is first of all the material from which they are derived: the former from liver and the latter from fish muscle. This means that while cod liver oil is a source of vitamin A, fish oil lacks it. Since an excess of vitamin A can be dangerous, until recently the intake of cod liver oil for prolonged periods was not recommended. Indeed, the purification techniques used in the past kept the composition of cod liver oil almost intact, and the final product contained massive doses of both this vitamin and vitamin D (also dangerous, if in excess). That is why its intake was recommended only during the winter months, during which one could literally stock up on its active ingredients. Today, however, molecular purification techniques make it possible to have cod liver oil that is suitable to be taken for longer periods precisely because of its reduced vitamin A content. More modern treatments allow it to be purified of both contaminants and this and other nutrients, such as cholesterol and vitamin D. The molecules of interest (just like vitamins) are then added at the desired dosages.

Cod liver oil: nutritional values

L'olio di fegato di merluzzo è una fonte di grassi. In particolare, in 100 g di olio di fegato di merluzzo sono presenti circa:

• 23 g saturated fat
• 47 g monounsaturated fat
• 22.5 g polyunsaturated fat, including the omega 3 EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
  

In addition, about 570 mg of cholesterol is found in 100 g of cod liver oil. Against this composition, 100 g of cod liver oil provides about 900 Calories and important micronutrients, namely:

• Vitamin A (30 mg, or 100 thousand International Units - IU - in 100 g)
• vitamina D (250 microgrammi di vitamina D2 e vitamina D3, o 10 mila UI, in 100 g)
  

Since it is a fatty substance, cod liver oil facilitates the assimilation of both of these fat-soluble vitamins. Finally, cod liver oil is a source of trace minerals such as sodium, potassium and iron.

The omega-3 fatty acids: ALA, EPA and DHA

Prominent among the active ingredients in cod liver oil are omega 3, fatty acids that are considered essential because the body, while in need of them, cannot produce sufficient quantities to meet its needs. In fact, human cells cannot synthesize alpha-linolenic acid(ALA), the omega-3 fatty acid from which EPA and DHA, the biologically active omega-3s known for their health benefits, are derived.

Le proprietà degli omega-3

Gli acidi grassi omega 3 svolgono un'azione antinfiammatoria che si oppone all'effetto proinfiammatorio dei derivati dell'acido arachidonico (un grasso omega 6). Tale azione è stata associata a effetti benefici contro patologie infiammatorie intestinali come la rettocolite ulcerosa e la malattia di Crohn e contro alcune patologie reumatologiche autoimmuni. Inoltre agli omega 3 è stata associata la capacità di regolare la risposta immunitaria e l'attività di alcuni fattori di crescita. Sembra in particolare che riescano a controllare la proliferazione delle cellule, azione potenzialmente utile contro i tumori. 

Gli omega 3 sono però noti soprattutto come alleati della salute del cuore. La loro azione antinfiammatoria sembra influenzare anche la dilatazione delle arterie; di conseguenza potrebbe aiutare a tenere sotto controllo l'ipertensione, soprattutto nella terza età. Ma non solo: fra i loro effetti benefici sono inclusi un'azione antitrombotica, un'azione antiaritmica e la capacità di controllare i livelli di trigliceridi e di colesterolo nel sangue. In particolare, riducendo la tendenza delle piastrine ad aggregarsi potrebbero ridurre il rischio di trombi associati a gravi eventi cardiovascolari, come infarti e ictus. 

In addition, their intake has been associated with an increase in HDL(High Density Lipoproteins, the "good" cholesterol) and a reduction in triglycerides both after meals and on an empty stomach. Finally, omega 3 is important for vision and nervous system health. In particular, DHA is a key component of the brain necessary for its development, and several studies have associated intake of these fats with improved symptoms of some neurological and psychiatric disorders.

Omega 3s: the food sources

Avere a disposizione una quantità adeguata di omega 3 è fondamentale sin dalla gestazione. Infatti questi grassi favoriscono un corretto sviluppo dell'apparato cardiovascolare, del cervello e della retina. La salute di quest'ultima dipende dagli omega 3 anche durante il resto della vita; eventuali carenze possono portare a problemi della vista, mentre un'assunzione adeguata può aiutare a prevenire la degenerazione maculare senile, una delle principali cause di cecità nella terza età. Le migliori fonti alimentari dipendono dal tipo di omega 3 preso in considerazione. Infatti mentre l'ALA è presente soprattutto in alimenti di origine vegetale (come le noci) EPA e DHA sono contenuti soprattutto in alimenti di origine animale, in particolare nei prodotti della pesca; ne sono ad esempio ricchi il salmone, lo sgombro e le aringhe.

Nel caso in cui si assuma ALA l'organismo dovrà convertirlo in EPA, da cui potrà poi sintetizzare il DHA. Purtroppo, però, la conversione dell'ALA in EPA e DHA non è per nulla efficiente. Secondo le stime solo il 5% di quello che viene assunto sarà convertito in EPA e ancora meno (l'1% circa) in DHA; alcuni studi sono addirittura giunti alla conclusione che meno dello 0,1% dell'ALA viene convertito in DHA e che in totale l'efficienza della conversione dell'ALA in EPA più DHA è inferiore allo 0,4%. La strategia migliore da un punto di vista nutrizionale non è quindi assumere ALA, che per esercitare gli effetti benefici associati agli omega 3 deve essere modificato, ma EPA e DHA pronti all'uso; per questo motivo oggi il pesce è considerato una delle fonti alimentari di omega 3 migliori. Un aiuto per chi vuole aumentarne l'assunzione arriva poi da supplementi e da integratori alimentari come quelli a base di olio di fegato di merluzzo.

Gli integratori di omega-3: i benefici

A certificare i possibili benefici derivanti dall'assunzione di omega 3 sono i claim nutrizionali e sulla salute autorizzati dall'Efsa (l'Autorità europea per la sicurezza alimentare) per pubblicizzare le loro proprietà e i loro possibili benefici. In particolare, l'EFSA riconosce al DHA:

• The ability to contribute to the proper functioning of the brain; and its normal development;
• the ability to promote proper eye development, vision in the first 12 months of life and, more generally, to good visual health;
• The ability to help maintain normal blood triglyceride levels.
  

La stessa Efsa riconosce ai prodotti contenenti una combinazione di EPA e DHA la capacità di:

• Help maintain normal blood pressure;
• Help maintain normal blood triglyceride levels;
• Helping to make the heart work well.

Integratori di omega-3: le garanzie di purezza, freschezza e concentrazione

La purezza, la freschezza e la concentrazione degli integratori di omega 3 sono invece certificate da laboratori terzi, come quelli del programma IFOS (International Fish Oil Standards) della Nutrasource Diagnostics Inc. A stabilire gli standard di riferimento è la Global Organization for EPA and DHA Omega-3s (GOED). Il programma IFOS è l'unico programma per l'analisi e la certificazione dedicato esclusivamente all'olio di pesce; i prodotti vengono testati lotto per lotto per valutare:

• The amounts of the ingredients (EPA + DHA) compared with that stated on the label;
• The presence of contaminants (polychlorinated biphenyls - PCBs - total, dioxins, furans and dioxin-like PBCs)
• The presence of heavy metals (mercury, lead, total arsenic, cadmium)
• The stability of the product.

The evaluation system is based on the assignment of a maximum of 5 stars, each of which corresponds to a specific evaluation criterion:

• The correspondence between the concentration of active ingredients stated on the label and that detected in the product;
• An oxidation level of less than 75 percent of the standard specified by theCouncil for Responsible Nutrition (CRN);
• A PCB level of less than 50 percent of the CRN standard;
• dioxin levels below 50 percent of the standard specified by the World Health Organization (WHO).

The fifth star is awarded to products that have received positive ratings in all the tests they have undergone. Products such as Omegor Vitality, VitaDHA 1000 and Meaquor 1000 are IFOS 5-star certified products.

Vitamin A

Codliver oil is a source of vitamin A. Concentrations of this micronutrient, which is important for vision health, cellular differentiation, growth, and the proper functioning of the immune system, vary depending on the product: 100 grams of cod liver oil can contain as much as 100 thousand IU. Any deficiencies in vitamin A can impair visual abilities, causing twilight blindness or, in even more severe cases, total blindness. In fact, the absence of this vitamin can cause dryness and ulceration of the conjunctiva and cornea, damaging them to the point of complete loss of vision. In addition, vitamin A deficiencies can slow growth, cause breakage and tooth loss, and affect the health of the skin, which can take on a wrinkled appearance.

Vitamin A: the food sources

Vitamin A can be taken in by eating dairy products, fish, poultry and red meat. It can also be taken in the form of beta-carotene (the pro-vitamin A), a precursor of it that is abundant in carrots, apricots and several other fruits or vegetables (such as broccoli, spinach and most dark green leafy greens). Dietary supplements and supplements such as those made with cod liver oil can also help to fill up on this valuable micronutrient. However, to carry Efsa-authorized claims, a food product must provide at least 15 percent of the recommended daily allowance (RDA, or 800 µg).

Vitamin A: the benefits

When taken orally, vitamin A can exert several benefits. In particular, according to Efsa this micronutrient:

• Helps to metabolize iron well;
• Promotes the proper functioning of the immune system;
• Helps maintain healthy skin and mucous membranes;
• Promotes vision health.

Vitamin D

In 100 g of cod liver oil it is also possible to find 250 µg of vitamin D, a much higher dose than the 5.4 µg found in 100 g of chicken egg yolk or the 1.7 µg contributed by 100 g of yellowfin tuna-two dietary sources of this micronutrient. This vitamin is involved in the process of cell division. It is also a valuable ally of bone health, whose normal growth and strength it promotes. Its deficiencies can cause growth retardation and rickets. In children it can lead to the development of curved legs and protruding abdomen, while in adults it has been associated with bone fragility and muscle twitching and spasms.

Vitamin D: the food sources

To get your fill of vitamin D, it is good to expose your skin to sunlight. In fact, the UVB rays in it allow cholesterol to be used precisely to produce this molecule. Food sources of vitamin D, on the other hand, are very few. This is why cod liver oil products can be an important aid for those who want to increase their intake, as long as they provide at least 15 percent of the recommended daily allowance (RDA, or 5 µg).

Vitamin D: the benefits

Efsa has recognized several benefits of vitamin D. In particular, this micronutrient:

• helps absorb and use calcium and phosphorus;
• Promotes good bone and tooth health;
• Promotes good functioning of the muscles and immune system.

The benefits of cod liver oil: what it is used for and when to take it

Gli integratori di olio di fegato di merluzzo possono essere utili quando i livelli di trigliceridi nel sangue sono troppo alti. Eccessi di questi grassi sono pericolosi per la salute, soprattutto per le donne, che con i trigliceridi vedono aumentare anche il rischio di ritrovarsi alle prese con una coronaropatia. Per questo concentrazioni di trigliceridi troppo alte dovrebbero essere riportate nella norma; l'olio di fegato di merluzzo può aiutare a ridurle di una quota variabile tra il 20% e il 50%. Assumere olio di fegato di merluzzo potrebbe inoltre essere utile in caso di ipertensione moderata. 

Avoiding hypertension helps protect the health of the heart and arteries because too high a pressure can subject them to excessive workload, thus decreasing their efficiency. What's more, over time, the force and friction exerted by the blood can damage the inner lining tissue of the arteries; this phenomenon can, in turn, promote the formation of cholesterol buildup (so-called atherosclerotic plaques) and, thus, atherosclerosis. The latter can worsen to the point of significantly narrowing the inside of the arteries, consequently causing pressure to rise. What sets in, then, is a vicious cycle that endangers the heart and arteries, leading to problems such as arrhythmias, heart attacks, and strokes. When hypertension is moderate, taking cod liver oil could help promote a slight but significant reduction. 

L'olio di fegato di merluzzo sembra anche essere effettivamente utile per combattere i problemi ai reni associati al diabete di tipo 2. In particolare, la sua assunzione è stata associata alla riduzione del livello di proteine nelle urine, un marcatore della gravità delle patologie renali. Nel corso degli anni l'assunzione di olio di fegato di merluzzo è stata poi consigliata anche nel trattamento della depressione, delle irregolarità del battito cardiaco associate alle malattie cardiovascolari, delle infezioni dell'orecchio in età pediatrica, delle malattie cardiache, del lupus eritematoso sistemico, del glaucoma e di diversi altri problemi di salute. Il suo impiego sarebbe utile anche per promuovere la guarigione delle ferite. 

For the time being, however, the scientific evidence for the use of cod liver oil for these purposes is not yet sufficient to warrant its efficacy. Finally, cod liver oil products are not likely to be useful in cases of osteoarthritis and familial hypercholesterolemia.

Cod liver oil for dogs, cats and horses

In addition to human health, cod liver oil is considered an ally of animal welfare. It appears, for example, to promote good growth in dogs and to be helpful in their pregnancy. It is also recommended to address vitamin deficiencies in their diet and as a restorative and to promote healthy skin and hair after trauma. Cats, on the other hand, are recommended primarily to avoid vitamin A deficiencies that could impair vision and to promote healthy skin and fur, but that's not all: some recommend its administration to combat diseases associated with inflammation, promote heart and immune system health, strengthen bones, promote proper functioning of the nervous system and muscles, and fight cancer. It is also recommended for horses to protect eyesight, bones and coat. It also appears to promote hoof health, help fight lung disease, promote growth and increase energy.

Cod liver oil supplements.

Oggi il mercato degli integratori offre diversi prodotti a base di olio di fegato di merluzzo in differenti formulazioni. È possibile ad esempio acquistarlo in forma di capsule (anche molli), di perle, di softgel o di opercoli contenenti un concentrato oleoso; oppure è possibile acquistarlo liquido, anche in forma di sciroppo adatto per bambini. Difficile dire quale sia la migliore marca. Chi è alla ricerca di un integratore dovrebbe esigere un prodotto di grado farmaceutico, cioè rispondente a standard adatti all'uso medicinale. Dove si compra? In erboristeria, farmacia e nelle parafarmacie. Inoltre può essere acquistato sul web, ma attenzione: è fondamentale accertarsi di rivolgersi a canali di vendita sicuri. 

The price can vary greatly from case to case: alongside products that cost less than 5 euros, the market offers others for which you have to pay, instead, almost 50. Evaluating the affordability of a supplement, however, should not be based only on the price per package: to choose well, it is necessary to read its label just as well. The first aspect to pay attention to is the EPA and DHA content per capsule (not per package). Multiplying it by the number of capsules can be traced to the total EPA + DHA content of the package. By dividing the price per pack by the total EPA + DHA content, it is possible to trace the price per 1,000 mg of EPA + DHA and compare it for different products, thus coming up with the cheapest one.

Dosages and how to take cod liver oil

Different supplements may contain different amounts of cod liver oil. The most suitable dosage and dosage depends on several factors. The first is the concentration of the active ingredients, which means that to achieve a given dosage it may be necessary, for example, to take a different number of capsules depending on their EPA and DHA content. 

The second factor to consider is why they are taken. Data in the scientific literature, for example, seem to indicate that to reduce blood triglyceride levels it is necessary to take 20 ml of cod liver oil daily. The same indication seems to be valid when the intent is to lower blood pressure.

On the other hand, if cod liver oil is taken against high cholesterol, doses should increase to 30 ml per day. Finally, it is also necessary to take into consideration who should take it. In particular, depending on the product being considered, the dosage may be different for children and adults.

Side effects of cod liver oil

Cod liver oil is considered a safe remedy for most people in good health. It can sometimes cause side effects such as belching, bad breath, heartburn and nosebleeds, but taking it at mealtimes can help reduce these problems. However, it is good to remember that at high doses, cod liver oil can hinder blood clotting and increase the risk of bleeding. Therefore, it is always a good idea to discuss its intake with your doctor and make sure there are no contraindications. Other possible side effects of taking high doses of cod liver oil are nausea and the production of soft stools. In addition, the side effects of excess vitamin A and D should not be forgotten. 

In particular, too much vitamin A can cause such ailments as nausea, vomiting, loss of appetite, skin changes, fatigue and drowsiness, dizziness, severe headaches and pain in the stomach, behind the eyes, bones, or joints, changes in the menstrual cycle, vision problems, growth retardation, hair loss, and jaundice.

Excesses of vitamin D are rare, but they can cause increases in blood calcium levels, which in turn can trigger nausea or vomiting and reduce appetite and promote calcium accumulation in soft tissues, such as of the heart or lungs. In addition, excessive vitamin D intake may be associated with weakness, weight loss, confusion and disorientation, frequent urination, and kidney problems. Finally, some less serious problems can then arise from the taste of cod liver oil, which can be quite unpleasant. Some formulations help to reduce this inconvenience, for example by enclosing the oil in capsules or opercula or by offering it flavored.

Contraindications of cod liver oil

There are no known interactions between the intake of cod liver oil and the consumption of specific foods. However, care should be taken with simultaneous intake of active ingredients that, just like cod liver oil, may affect blood pressure and blood clotting. The main possible interactions are summarized in Table 1.   

Table 1  

Inoltre, ad oggi, non sono state raccolte informazioni sufficienti a garantire la sicurezza dell'assunzione di olio di fegato di merluzzo in gravidanza; per questo è bene non assumerlo durante i mesi della gestazione senza aver prima consultato il proprio medico. La stessa raccomandazione è valida durante l'allattamento al seno.  

Source:

Averna MR et Al. Omega 3 e riduzione del rischio cardiovascolare. PPG Edizioni scientifiche, 2003 Baker EJ et Al. Metabolism and functional effects of plant-derived omega-3 fatty acids in humans. Prog Lipid Res. 2016 Oct;64:30-56. doi: 10.1016/j.plipres.2016.07.002. Epub 2016 Aug 3 Berbert AA et Al.

Supplementation of fish oil in patients with rheumatoid arthritis. Nutrition. 2005 Feb;21(2):131-6 Bourre JM.

Roles of unsaturated fatty acids (especially omega-3 fatty acids) in the brain at various ages and during ageing. J Nutr Health Aging. 2004;8(3):163-74 Conklin SM et Al.

Serum omega-3 fatty acids are associated with variation in mood, personality and behavior in hypercholesterolemic community volunteers. Psychiatry Res. 2007 Jul 30;152(1):1-10. Epub 2007 Mar 23 Drugs.com.

Vitamin A EU Register of nutrition and health claims made on foods Fontani G et Al.

Cognitive and physiological effects of Omega-3 polyunsaturated fatty acid supplementation in healthy subjects. Eur J Clin Invest. 2005 Nov;35(11):691-9 Germano M et Al.

Plasma, red blood cells phospholipids and clinical evaluation after long chain omega-3 supplementation in children with attention deficit hyperactivity disorder (ADHD). Nutr Neurosci. 2007 Feb-Apr;10(1-2):1-9 Grimble RF, Tappia PS.

Modulation of pro-inflammatory cytokine biology by unsaturated fatty acids. Z Ernahrungswiss. 1998;37 Suppl 1:57-65 Harris WS. Achieving optimal n-3 fatty acid status: the vegetarian's challenge... or not. Am J Clin Nutr. 2014 Jul;100 Suppl 1:449S-52S. doi: 10.3945/ajcn.113.071324. Epub 2014 Jun 4 Hussein N et Al.

Long-chain conversion of [13C]linoleic acid and a-linolenic acid in response to marked changes in their dietary intake in men. J. Lipid. Res. 46: 269-280, 2005 IFOS – The international fish oil standards program Johnson EJ et Al.

The influence of supplemental lutein and docosahexaenoic acid on serum, lipoproteins, and macular pigmentation. Am J Clin Nutr. 2008 May;87(5):1521-9 Lauritzen L et Al.

Maternal fish oil supplementation in lactation: effect on visual acuity and n-3 fatty acid content of infant erythrocytes. Lipids. 2004 Mar;39(3):195-206 Mayo Clinic. Nutrition and healthy eating. What is vitamin D toxicity, and should I worry about it since I take supplements? MedlinePlus. Cod Liver Oil MedlinePlus. Vitamin A Medline Plus. Vitamin D Medline Plus. Vitamin D Deficiency Miller PE et Al. Long-chain omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid and blood pressure: a meta-analysis of randomized controlled trials. Am J Hypertens. 2014 Jul;27(7):885-96. doi: 10.1093/ajh/hpu024. Epub 2014 Mar 6 Neuringer M et Al.

The role of n-3 fatty acids in visual and cognitive development: current evidence and methods of assessment. J Pediatr. 1994 Nov;125(5 Pt 2):S39-47 Pawlosky, R. J., et al .

Physiological compartmental analysis of alpha-linolenic acid metabolism in adult humans. J. Lipid Res. 42(8):1257-1265, 2001 Poli A. Acidi grassi omega-3 e prevenzione cardiovascolare. Trends in Medicine vol 2 num 3, PPG Edizioni Scientifiche, 2002 Querques G, Souied EH. The role of omega-3 and micronutrients in age-related macular degeneration. Surv Ophthalmol. 2014 Sep-Oct;59(5):532-9. doi: 10.1016/j.survophthal.2014.01.001. Epub 2014 Jan 27 Saldeen P, Saldeen T. Women and omega-3 Fatty acids. Obstet Gynecol Surv. 2004 Oct;59(10):722-30; quiz 745-6 Sapermangiare.mobi.

Tabelle di composizione degli alimenti. Olio di fegato di merluzzo USDA – National Nutrient Database for Standard Reference Release 28. 04589, Fish oil, cod liver