Cod liver oil. Image credit: Flickr
Cod liver oil. Image credit: Flickr

Cod liver oil is oil procured from livers of a type of fish called Atlantic cod (Gadus morhua), which belongs to the Gadidae genus. Cod liver oil is a popular dietary or health supplement since it’s a huge repository of omega-3 fatty acid. It also comprises good quantities of vitamin D and vitamin A. The nutrient makeup of cod liver oil varies with the species from which the oil is made.


The practice of harvesting cod liver oil has been there since the Viking Age (late 8th century). The diet of people back then was rich in fresh fish-extracted oil. Sunlight wasn’t in abundance during the period as days were shorter. Fishing was a major pastime/vocation, especially during winter. Because there wasn’t much natural sunlight, the fishes stayed fresh for days together, which made cod liver oil extraction a bit easy.

To extract the oil, the Vikings boiled the extracted liver. A large pan or kettle with a few branches of birch (tree) atop were used. The liver was placed on the branches while the steam rose out of the pan. The heat caused the liver to secrete oil that settled in the boiling water underneath. Once good amount of oil was secreted, the oil was separated from the water.


Cod liver oil has several health benefits. During the early 1700s, anglers used the oil topically to subside muscle and joint soreness. Reportedly, cod liver oil was first used in 1789 in England by Dr. Barbey who treated rheumatism using the oil. Quite a few decades later in 1824, the oil was used to treat rickets. In a century, cod liver oil’s therapeutic properties became quite well-known and the oil was frequently administered to address rickets.

Atlantic cod (Gadus morhua). Image credit: Flickr
Atlantic cod (Gadus morhua). Image credit: Flickr

Cod liver oil also helps with arthritis-linked joint stiffness, cardiovascular health, and issues relating to hair, skin, nails and teeth. Basically, most health conditions caused due to omega-3, vitamin D and vitamin A deficiency can be addressed with cod liver oil.

Side Effects

Cod liver oil is predominantly good for health. But there are some side effects to the oil too. Users of the oil could have issues such as dry skin, bad breath, headaches, and also an upset stomach. Some brands of cod liver oil supplements could be more problematic at times. In such cases, switching to another brand may remedy the issues.

Usage Restrictions

Cod liver oil is safe to be administered by people of all ages. But certain medical conditions may not appreciate cod liver oil’s presence in the body. For instance, people on blood thinners, kidney disease medications, etc. could worsen their condition administering cod liver oil. Therefore, people with diabetes, high blood pressure and high cholesterol must consult a doctor before administering cod liver oil. Also, pregnant ladies are not advised to take cod liver oil as too much of vitamin A could lead to congenital birth defects such as malformations of the skull, eye, heart and lungs.

Cod Liver Oil Supplement Quality

Cod liver oil supplement. Image credit: Flickr
Cod liver oil supplement. Image credit: Flickr

Cod liver oil can be consumed directly from fresh cod liver. Taking a spoon of cod liver oil is an option too, but it’s the least popular way of consumption since the oil tastes bad. The more practical option is a cod liver oil supplement. A supplement is in fact a more popular form of consumption since there’s no preparation and cooking involved when administering supplements.

However, not all cod liver oil supplements are made the same. The ratio or doses of omega-3 fatty acids, vitamin A and vitamin D could vary across brands. Some supplements may comprise synthetic vitamin D and vitamin A, and some may not have any at all. Also, some supplements may comprise harmful constituents such as mercury and polychlorinated biphenyl (PCB) compounds. PCBs are human-made organic chemicals consisting of hydrogen, chlorine and carbon atoms. These compounds are toxic in nature and used in several commercial and industrial applications. Fortunately, most brands purify their extractions using a technique called molecular distillation.