Cod liver oil is a very old home remedy. The reason for its popularity is undoubtedly its high nutrient content.
It contains, in particular:
- of omega-3s (EPA and DHA), at 8 g and 11 g respectively per 100 g of product
- the vitamin A (in the form of retinol): 30,000 micrograms (µg) per 100 g
- the vitamin D : 250 µg per 100 g
Thanks to this composition, it indirectly supports healthy growth, the maintenance of normal bones, good vision, good cardiovascular health, as suggested by this study, as well as immunity and emotional well-being.
More convenient to take in capsule form because of its taste, it is often recommended for the development of young children, but also for adults and older people who tend to become deficient easily.
Is its use, however, safe? Here I break down what the science says about it.
📚 Read also | A pharmacist has selected the best omega-3 capsules
No danger in small quantities
The 16th-century alchemist and physician Paracelsus said, “the dose makes the poison.” And he was partly right. Indeed, a high-quality cod liver oil is not dangerous for a healthy person, provided it is consumed in reasonable amounts.
It is when it is taken in excess that it can lead to health consequences.
A poor-quality cod liver oil should also raise concern and can be harmful to the body.
Risks of overconsumption
Risk of toxicity from excess vitamin A
If you take several dietary supplements containing retinol (and not beta-carotene, whose conversion into vitamin A the body regulates), you risk hypervitaminosis A, because the liver struggles to metabolize this vitamin quickly.
In the short term, this can cause various adverse effects, such as:
- diarrhea
- vomiting
- headaches
- dizziness
- fatigue
If this overexposure to vitamin A persists over time, serious effects may occur such as bone fragility, skin disorders, liver failure or neurological issues.
If this hypervitaminosis A occurs in a pregnant woman, it can affect the fetus and cause congenital malformations.
Note that the recommended doses for a healthy adult are 750 µg for men and 650 µg for women.
Risk of hypercalcemia from excess vitamin D
Même si elle reste rare, il est aussi possible de développer une hypervitaminose D si vous consommez trop de suppléments d’huile de foie de morue.
En effet, si le taux de vitamine D est trop élevé, l’absorption du calcium au niveau intestinal risque d’augmenter fortement également. On peut alors observer une hypercalcémie, un taux de calcium sanguin trop grand, qui a pour conséquence :
- impaired bone metabolism
- digestive discomfort
- muscle weakness
- excessive thirst
- kidney stone formation
- calcification of soft tissues, which can impact cardiovascular, respiratory, and joint health
As a reminder, the recommended vitamin D dose for a healthy adult is 3.1 micrograms/day for adults aged 18-79 according to the recommended daily intakes from ANSES.
Dangers of poor-quality oil
Poor-quality oil can lead to a lack of product purity, but can also affect its efficacy and safety.
The fish used to make cod liver oil may be exposed to pollutants, such as heavy metals, polychlorinated biphenyls or dioxins. These can accumulate in the fish’s liver and end up in the final oil if purification steps are not thorough enough.
These toxins are harmful to health and at very high doses contribute to the development of conditions such as hormonal disorders and cancers.
Side effects and contraindications
Most common side effects
As a general rule, a high-quality oil consumed at recommended doses does not cause any particular adverse effects.
In some people, it is possible to experience some digestive discomfort at the start of a course, which should subside after about ten days.
If you take it as a liquid oil rather than in an ampoule, it can also cause bad breath.
Contraindications to its consumption
The use of cod liver oil is contraindicated in people allergic to fish or seafood.
Because it is rich in vitamin D, it is also not recommended for people with hypercalcemia.
The nutrients contained in cod liver oil can cause interactions with medications. This is the case with anticoagulants, which can have their activity increased if you take a large amount of cod liver oil.
At-risk populations, such as pregnant and breastfeeding women, children and adolescents, as well as anyone already taking supplements containing vitamin D or A…
I recommend that you consult your primary care physician or your pharmacist for a personalized medical opinion before starting any treatment.
Consuming cod liver oil safely
To supplement safely with cod liver oil, I strongly recommend:
- to adhere to the recommended daily dosages, and never combine multiple dietary supplements high in vitamins A and D without seeking advice from a doctor or pharmacist
- to favor quality brands, with patented oils that provide optimal safety and low contaminant levels
- to properly store your oil away from light and keep it cool if it is not in capsule form
Sources and scientific studies
- Elagizi A et al., 2021, An Update on Omega-3 Polyunsaturated Fatty Acids and Cardiovascular Health.
- Silverman AK et al., 1987, Hypervitaminosis A syndrome: a paradigm of retinoid side effects.
- Marcinowska-Suchowierska E et al., 2018, Vitamin D Toxicity-A Clinical Perspective.
