Cod Liver Oil
Our ancestors have been eating fish as a part of a healthy diet for centuries. (1) Today, health experts value the consumption of fish because of the nutritional content available in various types of seafood. Cod liver oil, in particular, shows some promising results.
What is Cod Liver Oil?
Fish oil and cod liver oil are different compounds but are often confused. Fish oil is made from the whole body of fatty fish, such as trout, mackerel, tuna, herring, sardines, and salmon. By contrast, cod liver oil is extracted solely from the livers of cod. The typical cod fish used in cod liver oil supplements is Atlantic cod (Gadus morhua), because it has more nutrients than other types of cod, but Pacific cod (Gadus macrocephalus) is also sometimes used in products. These fish are found in the cold waters of the Atlantic ocean, typically around Northwestern Europe.
While both fish oil and cod liver oil contain omega-3 fatty acids and vitamins A and D, which are all vital to our bodies in helping to maintain optimal health, studies suggest cod liver oil may have higher amounts of vitamins A and D than fish oil, among other potential health benefits. Also, the vitamin A and D in fish oil is negligible, since it doesn't usually show up on the nutritional fact panel of most fish oil supplements. (2)
Important Nutrients in Cod Liver Oil
The main appeal of cod liver oil is its nutritional content. The omega-3 essential fatty acids, vitamin A, and vitamin D found naturally in cod liver oil are crucial to the body’s overall health.
Omega-3 Fatty Acids
Omega-3 fatty acids are found in plant and marine life, especially in the tissue of fatty fish. The three main types of omega-3s are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found in the oils of plants, such as flaxseed and soybean, while DHA and EPA are synthesized by microalgae and then consumed by fish. The fish we eat, in turn, deliver these important nutrients into the human body. (3)
Omega-3s, such as those found in cod liver, are important components of the phospholipids that form the structures of cell membranes. Along with omega-6 fatty acids derived from vegetable oils, such as linoleic acid, these nutrients provide energy and help in the development of signaling molecules known as eicosanoids, which play a role in the body’s cardiovascular, pulmonary, immune, and endocrine systems.
According to the National Institutes of Health, omega-3s, primarily EPA and DHA, support healthy cardiovascular function, cognitive function, vision, cellular membranes, fetal growth and development, prostate function, normal aging, digestion, joint comfort, mood health, skin health, and more.
EPA is a precursor to the chemicals involved in the body’s natural blood clotting and inflammatory reactions. DHA makes up 40 percent of the polyunsaturated fatty acids (PUFAs) in the brain and 60 percent of the PUFAs in the retina of the eye. It also found in breast milk and sperm.
Omega-3s must be obtained in the diet from food sources or through supplementation of cod liver oil, fish oil, or krill oil. Cold-water fatty fish, such as salmon and tuna, contain a slightly higher amount of omega-3s than fish with a lower fat content, such as bass, tilapia and cod. However, cod does contain higher amounts of other nutrients, such as vitamins A and D, which have been shown to have a supportive effect on the immune system.
Are You Deficient in Omega-3s?
A deficiency in omega-3 fatty acids may lead to internal and external health challenges affecting the skin, eyes, brain, and immune system. Clinical research suggests that people with heart conditions may benefit from supplementing their diet with omega-3s, such as those found in cod liver oil. Other risk groups for omega-3 deficiency are people who don’t eat fish regularly, vegans (who follow a plant-based diet), and lacto-ovo vegetarians (who don’t eat meat, fish, and poultry but still eat dairy and eggs).
The 2015-2020 Dietary Guidelines for Americans suggests consuming 8 ounces per week from a variety of seafood. (4) The National Academy of Medicine recommends a daily dietary intake specifically of omega-3s as follows. (5)
Table 1: Recommended Daily Intakes for Omega-3s
Vitamin A is a fat-soluble vitamin that acts as an antioxidant to support healthy vision, teeth, skin, bones, tissues, and the immune system. It is stored in the liver, which is why cod liver oil is a good source of this vital nutrient. (6)
The best sources of vitamin A are:
- Cod liver oil
- Fortified foods such as cereal, or fortified milk
- Orange and yellow fruits and vegetables
- Dark green leafy vegetables
Table 2: Recommended Daily Intakes for Vitamin A
Vitamin D is synthesized by the human body when the skin is exposed to the sun’s ultraviolet (UV) rays. Vitamin D’s importance in the body is undeniable. It helps the body absorb and utilize calcium and phosphorus for strong bones and teeth. It also supports a healthy brain, nervous system, immune system, respiratory system, and cardiovascular system. In addition, vitamin D helps regulates cell growth and cell-to-cell communication.
Vitamin D deficiency is common among the elderly, infants, or people who don’t spend much time in the sun. Also, people with darker skin tones do not synthesize vitamin D as easily when exposed to the sun, so supplementation is especially important. That’s why it is important to eat foods rich with vitamin D, such as cheese, egg yolks, or fortified foods, or by taking dietary supplements of cod liver oil. (8) Vitamin D is concentrated in the liver of cod fish and thus is plentiful in cod liver oil.
To ensure you’re not getting too much vitamin D, which may have potential adverse effects, make sure you get the recommended doses of vitamin D in combination with synergistic vitamin A and omega-3 fatty acids, such as in cod liver oil. This can be accomplished through diet alone or by taking dietary supplements. (9)
The Food and Nutrition Board recommends a daily intake of vitamin D as follows. However, current research indicates these amounts are insufficient, so supplementation is crucial to maintaining optimal health. (10)
Table 3: Recommended Daily Intakes for Vitamin D
Brief History of Cod Liver Oil
Fish has long been an important staple in the diets of many civilizations, largely due to the environment, tools, and resources available during each era in history. Humans have been eating fish since at least the Upper Paleolithic period – between 50,000 and 10,000 years ago. Around 15,000 years ago, tools such as fishing spears, hooks, and nets became commonplace as the Cro-Magnon began hunting fish in a new way as a food source. (11)
Centuries ago, northern Europeans used cod liver oil from the livers of Atlantic cod and other species of cod to keep themselves warm in cold climates and to help relieve aching joints and muscles. (12) Eating fish also has religious connotations to some civilizations. (13)
Traditional manufacturing of cod liver oil involved filling a wooden barrel with fresh cod livers and seawater until the mixture fermented after one year. Modern cod liver oil involves cooking the whole fish body during the manufacture of fish meal. (14)
In 1789, Dr. Darbey of the Manchester Infirmary in England used the cod liver oil to treat rheumatism. In 1824, cod liver oil was used as a remedy against rickets, a condition causing soft bone deformities in children due to vitamin D deficiency. (15)
Without enough vitamin D or calcium in the diet, bones become prone to fractures. By the 1930s, scientists established that cod liver oil is important in maintaining bone health for growing children by providing a good source of vitamin D. In the U.S. prior to the 1950s, it became fairly commonplace for mothers to give their children a spoonful of cod liver oil a day. Today, with the prevalence of fortified foods, vitamin D deficiency is rare in industrialized nations, but it is still fairly common in some developing countries. (16)
However, even now, many North Americans still lack proper nutrition in their diets, since they eat a lot of meat but eat little or no fish, such as cod. (17) That means many of us aren’t getting enough omega-3s, or vitamins A or D in our diets. The lack of these vital nutrients may lead to bone loss or brittle bone conditions. Eating a diet rich in a variety of seafood and taking cod liver oil supplements may help fill nutritional gaps and offer potential health benefits.
Potential Health Benefits of Cod Liver Oil
Cod liver oil is considered “good” fat, because it helps you feel full and slows the breakdown of carbohydrates into sugar, helping to maintain healthy blood sugars levels in the normal range throughout the body. Rich in nutrients, cod liver oil also provides a wealth of potential health benefits as outlined below.
Supports Breast Health
A study in Ontario suggests possible correlations between vitamin D from sun exposure early in life (from ages 10 to 19), particularly during breast development, with a slightly reduced risk of breast cancer. The results were also based on cod liver oil use and milk consumption. However, further clinical research is needed. (18)
Supports Healthy Eyes
Cod liver oil nutritional supplementation is believed to have potential therapeutic value when it comes to protecting the body against age-related visual impairment. As an antioxidant, vitamin A helps preserve normal vision, preventing oxidative damage and maintaining the integrity of the surface and underlying layers of the eye. In addition, cod liver oil contains omega-3 fatty acids, which support normal blood flow and optic neuroprotective function. (19)
Supports Heart Health
According to the Scripps Center for Integrative Medicine in San Diego, adding omega-3 supplements into the diet may help support optimal heart health and balanced triglycerides already in the normal range. (20) In a study on diabetic rats, scientists also found that cod liver oil supplementation may have a positive effect on cardiovascular health and cellular metabolism by protecting the body against abnormalities in the metabolism of essential fatty acids and the effects of oxidative stress. (21)
Supports A Healthy Mood
In a Norwegian study of almost 22,000 people over age 40 who took cod liver oil regularly, symptoms of depression among the cod liver oil users was reported at 30% less than other subjects. (22) Another clinical trial suggests that regular intake of omega-3 fatty acids from cod liver oil helps to temporarily improve symptoms of depression. (23) In addition, since vitamin D is naturally synthesized in the human body when the skin is exposed to direct sunlight, taking a cod liver oil supplement during the fall or winter months, when people don’t spend as much time outdoors, may support nutritional needs and promote a healthy mood during seasonal changes. This is a common practice in many Nordic countries. (24)
Supports Skin Health
According to the British Journal of Ophthalmology, cod liver oil, when applied topically, may support the growth of natural tissues, helping to heal wounds and inhibit scar tissue. (25)
Supports Healthy Teeth
The vitamin D in cod liver oil supports the body’s ability to absorb and utilize calcium and phosphorus for healthy bones, an effect which also promotes the healthy development of teeth. Vitamin D is active in calcification and may have a synergistic effect on dental health due to its inclusion of vitamin A, as well. (26)
Supports Kids’ Health
Cod liver oil is important to kids’ health, because it contains vitamin A, vitamin D, and omega-3 fatty acids, which are essential to healthy growth and development.
While kids should get most of their vitamins from a balanced, healthy diet, finicky eaters or kids who aren’t eating well-balanced meals may need dietary supplements to help fill the gaps in their nutrition. Some of the most important nutrients kids need to support their developing bodies are vitamin A, B-complex vitamins, vitamin C, vitamin D, calcium, and iron. (27)
Vitamin A is essential for children, because it supports the health of the immune system, eyes, skin, bones, and tissues. Vitamin D is also important for the growth and development of children, especially of their bones and muscles. (28) Vitamin D deficiency affects basic cell functions such as metabolism, and it has been linked to crippling bone conditions in children. (29)
Signs of a vitamin D deficiency may include:
- Bone tenderness
- Bone pain
- Bones break easily
- Bone deformities
- Stunted physical growth
- Uncontrolled muscle spasms
- Low calcium blood levels
When it comes to another important nutrient for children’s health, omega-3 fatty acids impact kids from the start of life – even before they’re born. These nutrients pass from the mom to the baby, supporting the healthy development of the eyes and brain during pregnancy and later during breastfeeding. Later in life, omega-3s also provide mood support, which may benefit children who have recurring feelings of sadness or have trouble focusing in school. In addition, use of cod liver oil during the first year of life is associated with lower risk of childhood-onset type 1 diabetes, according to a case-control study, but further research is needed. (30)
According to the Journal of the American Board of Family Medicine: “Cod liver oil contains both vitamin D and omega-3s. Individuals at higher risk for vitamin D deficiency may wish to consider substituting cod liver oil for fish oil supplementation.”(31) That is why many foods are now fortified with vitamin D, helping to supplement the nutrition in the diet.
Just keep in mind, getting too much of a good thing can be toxic to their health. Megavitamins are not ideal for kids, but special formulations of supplements designed just for kids may have just the right dosage. Always talk to a healthcare professional before giving your child any medication or dietary supplement.
What to Look for When Buying Cod Liver Oil
If you’re getting most of your omega-3s from eating seafood such as cod, it’s important to make sure you’re shopping for fresh, certified organic or wild-caught fish free of mercury, polychlorinated biphenyls (PCBs), dioxins, or other contaminants.
Shop for high quality cod liver oil supplements that are tested for purity during processing from Natural Healthy Concepts, and experience the difference it may make to your health! (32)