The exact concentration of nutrients in cod liver oil depends on the species of cod, or Gadus, the oil comes from.
Cod liver was first used in medicine in 1789, to treat rheumatism, followed by rickets in 1824. By the 1930s, it was frequently given to children to help prevent rickets and other conditions caused by vitamin D deficiency.
Other fish oils are extracted from the tissue of deep sea cold water fish, including tuna, trout, mackerel, herring, salmon, and cod.
Cod liver oil comes only from the livers of cod. It contains less omega-3 fatty acids than regular fish oils, but more vitamins A and D.
Possible health benefits of cod liver oil
Cod liver oil supplements offer a range of possible health benefits.
Cod liver oil is an excellent source of nutrients, and it may have some important therapeutic properties.
However, there is not enough evidence to prove all of these claims.
1) The right kind of fat
Every single body cell needs fat. Fats such as omega-3 fatty acids, found in cod liver oil, will promote skin health, increase vitamin and mineral absorption, and boost the immune system.
Fat keeps you feeling full. When you consume fat, your brain receives a signal to turn off your appetite.
Eating healthy fats with a meal helps slow the breakdown of carbohydrates into sugar. This helps to keep blood sugars levels stable. The brain needs fat to function properly.
Fish oils are known to reduce inflammation, which can explain how older large studies found that pain, tenderness, and stiffness were reduced with supplementation.
3) Age-related macular degeneration
Some studies have suggested that omega-3 oils might support eye health and prevent age-related macular degeneration. Higher intakes of the nutrients in cod liver oil such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) lead to less or delayed occurrence of macular degeneration.
Other nutrients that may help prevent AMD are carotenoids. Cod liver oil is also high in carotenoids, which people need to produce vitamin A.
4) Coronary artery disease
The buildup of plaque in the circulatory system is a result of inflammation.
Therefore, regular intake of fish oils can help protect against arteriosclerosis. They also provide protection against blood clots.
5) Repairing wounds
A mouse study, published in 2009, found that topically applying a 25-percent cod liver oil ointment to ear wounds could promote healing.
The scientists concluded that topically applying the ointment "significantly accelerated both the epithelial and the vascular component of healing, compared with saline."
They believed that vitamin A may be the key component in this process.
6) Cognitive performance
Cod liver oil contains a high amount of vitamin D. A link between vitamin D and cognitive performance was identified in a study in rats. The researchers concluded that Vitamin D may play a key role in maintaining good brain function in old age.
In 2011, scientists gave cod liver oil to rats that were experiencing chronic stress. Results of tests of memory, locomotor skills, and anxiety behavior indicated that the cod liver oil helped prevent cognitive impairment in these rats.
In 2017, scientists reported discovering a previously unknown group of molecules that may have anti-inflammatory properties. They come from cannabinoids that derive from omega-3 fatty acids.
The researchers suggest that these molecules could be extracted from omega-3 fatty acids for therapeutic purposes. The effect, they say, could be similar to that produced by medicinal marijuana, but without the psychological risks.
Cod liver oil - the forgotten food
In this video, originally featured on America Now, wellness and nutrition expert Peggy Hall discusses the possible health benefits of cod liver oil and the differences between cod liver oil and fish oils.
Cod liver oil and vitamin D
Cod liver oil is one of the richest sources of vitamin D available. Sun exposure is also important, because the body cannot get all of its vitamin D needs from food sources.
Vitamin D deficiency has been associated with osteomalacia and osteoporosis.
However, more reliable studies are needed to confirm some of these associations.
Nutritional profile of cod liver oil
According to the United States Department of Agriculture (USDA), one teaspoon of cod liver oil, weighing 4.5 g, contains:
- Energy: 41 calories
- Vitamin A: 4,500 international units (IU)
- Vitamin D: 450 IU
- Saturated fatty acids: 1.017 g
- Monounsaturated fatty acids: 2.102 g
- Polyunsaturated fatty acids: 1.014 g
- Cholesterol: 26 milligrams (mg)
Potential health risks of cod liver oil
Research published in the American Journal of Cardiology cautions that high fish consumption can cause side effects because of environmental toxins in fish, such as mercury, polychlorinated biphenyls, dioxins, and other contaminants.
However, the authors note that the processing that is involved in preparing supplements reduces the risk of environmental toxins and hypervitaminosis, or excess consumption of vitamins.
Too much vitamin D from food sources may lead to anorexia, weight loss, polyuria, and irregular heart rhythms. It can also lead to excess levels of calcium in the blood, resulting in calcification of tissues and blood vessels. Kidney stones may develop.
The tolerable upper limit of vitamin D is 4,000 IU a day for adults aged 19 years and over.
Should I get supplements?
Cod liver oil supplements may have health benefits. They are available to purchase online
It is important to ensure that cod liver oil and other supplements come from a reputable source and that they meet the requirements of the Food and Drug Administration (FDA).
Anyone who is considering taking supplements should speak to a doctor before starting. Do not take more than the recommended dose without medical supervision.
The 2015-2020 Dietary Guidelines for Americans recommend meeting nutritional needs with food sources, as far as possible.
The maximum daily intake that is recommended for vitamin D is 4000 IU per day.