People living in parts of northern Europe have been using cod liver oil for centuries to enhance immunity and protect them from dark, long winters. They have also used cod liver oil as a natural solution for rheumatism, aching joints and stiff muscles.
The primary source of cod liver oil was eating the fresh livers of Gadus morhua fish. While not very appetizing to most people, traditional populations felt it was worth it to benefit from cod liver oil’s numerous health-promoting effects.
What Is Cod Liver Oil?
Cod liver oil is a nutrient-dense source of essential vitamins including vitamin D and vitamin A as well as anti-inflammatory omega-3 fatty acids. Considering most people don’t eat enough anti-inflammatory foods that provide both vitamin D and omega-3s — important nutrients that play a crucial role in cardiovascular, hormonal, immune, reproductive and neurological health — many adults and children can benefit from regularly supplementing with cod liver oil.
Cod liver oil comes from, you guessed it, cod liver! You can consume the oil either from eating fresh cod liver or, more likely, from taking over-the-counter supplements. Each teaspoon of cod liver oil has about 41 calories and 4.5 grams of fat according to the USDA, split between monounsaturated, saturated and polyunsaturated fatty acids.
The most beneficial aspect of taking cod liver oil is that it contains high levels of omega-3 fatty acids, the same type found in oily fish or seafood like salmon, mackerel and sardines. It’s also one of the few and best vitamin D–rich foods.
Omega-3s and vitamin D are known for lowering inflammation, preventing blood clotting, preserving brain health and preventing depression. They’re even capable of causing noticeably reduced levels of pain and swelling due to inflammatory conditions like arthritis.
Dozens of studies have linked cod liver oil with the following benefits:
- lowering high cholesterol and high triglycerides
- preventing and treating diabetes
- lowering high blood pressure
- preventing heart disease
- reducing risk for osteoarthritis
- treating depression
- lowering risk for autoimmune diseases
- fighting eye disorders like glaucoma and protecting eye sight
- treating ear infections, allergies and asthma
- preventing and treating kidney disease
- helping to heal skin wounds
- maintaining bone health and preventing fractures or osteoporosis
11 Benefits of Cod Liver Oil
1. High Source of Anti-Inflammatory Omega-3 Fatty Acids
Cod liver fish oil is one of nature’s richest sources of omega-3 fatty acids, called Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA). Due to their natural anti-inflammatory properties, including the capability to reduce prostaglandin production, omega-3s lower the need for anti-inflammatory drugs and can be used to treat a variety of symptoms naturally, from coronary heart disease risk factors to depression or arthritis pain.
If you aren’t yet familiar with the many benefits of omega-3 foods or supplements, these include lowering the odds of developing: heart disease, ADHD, anxiety, high cholesterol, inflammatory bowel disease, arthritis, cancer and more. How can they do so much? The problem is that the vast majority of Americans have an imbalance of omega-3 to omega-6 fats in their diet. Omega-6 fats aren’t necessarily bad for you, but if they are consumed in large amounts without omega-3s, they cause inflammation, which is at the root of most diseases.
A healthy ratio is ideally around 2:1 omega-6 to omega-3 fats, but most people have about five to ten times more omega-6s than this! Omega-3 deficiency is on the rise because of the overconsumption of processed foods, fast or fried foods that contain refined vegetable oils (like soybean oil, canola oil, cottonseed oil and corn oil) filled with omega-6s. Supplementing with omega-3-rich cod liver oil is one way to lower inflammation and tip your fatty acid ratio back in favor of better health.
2. Supplies Critical Vitamin D
Vitamin D acts more like a hormone in the body than a vitamin, since it effects neurotransmitter functioning, heart health and inflammatory responses. Synthesized by your own skin when you’re exposed to the sun’s UV light, the best way to get enough vitamin D is to spend time outdoors without sunscreen on.
Not only does vitamin D play a part in healthy bone metabolism, but it supports important functions of all of our cells. Because low vitamin D levels can interfere with our cells’ ability to multiply and replenish, vitamin D deficiency might increase the risk of becoming sick short term, or even worse developing a chronic autoimmune disorder, cognitive or cardiovascular disease, diabetes, osteoporosis or cancer.
Considering most adults and children don’t get enough regular sun exposure year round due to living mostly indoor lifestyles, vitamin D supplementation is now recommended for the majority of people. Vitamin D deficiency symptoms can include depression, anxiety, fatigue, low libido, infertility, autism, asthma and more — in addition, the deficiency can lower immunity and even up the risk for cancer.
High doses of vitamin D taken alone might have potential side effects, which is why it’s now recommended to take vitamin D in combination with synergistic vitamin A and omega-3 fatty acids, such as how it’s found naturally in vitamin D–rich foods including cod liver oil.
3. Great Source of Vitamin A
Vitamin A is an important antioxidant that reduces oxidative stress (also called free radical damage) and thereby inflammation levels. It’s tied to the prevention of eye-related disorders, supports brain health, helps fight cancer and is important for hormone production. While most people eating a pretty well-balanced diet get enough vitamin A daily, deficiency is a risk for some people eating highly processed foods or not enough calories in general.
Recently, supplementing with vitamin A has come under debate, since high levels are thought to actually be harmful and potentially toxic. However, it’s important to note that many primitive populations that ate whole-food–based diets consumed plenty of vitamin A (along with vitamin D) and experienced great health. For example, according to the Weston A. Price Foundation, the traditional Scottish diet was high in foods like fish liver oils, organ meats, shellfish and animal fats — all natural sources of vitamins A and D, and these people had very low rates of chronic diseases.
When it comes to obtaining vitamin A from cod liver oil, the quality of the supplement seems to make a big impact. Many brands contain synthetic versions of vitamins A and D that aren’t well absorbed, in addition to dangerous ratios of these two nutrients. While consuming very high levels of vitamin A from supplements alone has been linked to some health concerns, obtaining vitamin A naturally from food sources can help improve the immune system. Eating plenty of vitamin A-rich foods is beneficial for bone growth, night vision, healthy cellular growth, testicular and ovarian function, and much more.
Vitamins A and D are fat-soluble nutrients often found together in animal foods. Both act like precursors to active hormones, so we produce certain enzymes that convert each of these to active forms the body can use to regulate our immune system. In this case, vitamin A is converted to retinol. Obtaining vitamins A and D together is completely natural and allows these processes to happen in a way that protects us from toxicity.
4. Helps Prevent Heart Disease
Evidence shows that cod liver oil taken either in supplement or whole food form can help lower high triglycerides, a type of dangerous fat in the blood that raises the risk for heart disease. Cod liver oil also treats high blood pressure and helps to balance cholesterol levels.
A range of human and animal studies have proven high efficacy of omega-3 polyunsaturated fatty acids obtained from cod liver oil in preventing atherosclerosis (hardening and stiffening of the arteries) and its complications. Treatment either alone or in combination with statin drugs helps reverse risk factors in patients with hypertriglyceridemia and high triglyceride levels.
5. Lowers Risk for Cancer
High levels of vitamin D, obtained from both sun exposure and supplementing with cod liver oil, have been associated with lower risks of cancer. One study found that vitamin D from both the sun and cod liver oil could help prevent breast cancer in women due to having antiproliferative and proapoptotic effects on breast cancer cells, thereby reducing mammary tumors. While sun exposure still seems to be the most relevant protective factor for getting enough cancer-busting vitamin D, cod liver oil also seems to help offset common deficiencies.
6. Prevents or Treats Diabetes
As a great source of essential healthy fats, cod liver oil can help control insulin resistance, inflammation and manage glucose (sugar) levels in the blood. It’s even been shown to help lower symptoms of complications related to diabetes like kidney disease. Use of cod liver oil and vitamin D supplements during the first year of a baby’s life and use of cod liver during pregnancy can also help lower the risk for developing diabetes.
One 2007 study published in the Journal of Pharmacy and Pharmacology found that giving diabetic rats cod liver oil supplements for 12 weeks acted as a natural diabetes treatment. The cod liver oil supplements completely prevented endothelial deficiency and helped correct several biochemical markers for metabolic syndrome (a combination of diabetes and cardiovascular disorder risk factors).
Prior to supplementing with cod liver oil, the rats experienced elevated plasma glucose (sugar) levels and high triacylglycerol and high cholesterol concentrations in their blood. Cod liver oil helped manage the rats’ weight gain and entirely prevented plasma lipid abnormalities while also controlling insulin sensitivity and other factors.
7. Helps Treat Arthritis
At the beginning of the 20th century, scientists established that cod liver oil was a natural “antirachitic,” which meant thousands of mothers began forcefully spoon-feeding the stuff to unwilling children! Cod liver oil use is associated with a reduction in pain, joint stiffness and swelling in patients with arthritis and other inflammatory conditions.
Cod liver oil is an effective natural treatment for arthritis because it mimics the effects of medications. It acts as a non-steroidal anti-inflammatory drug, improves chief clinical symptoms, and can be used as a safe alternative to medications, or simply a complementary supplement, in treating rheumatoid arthritis.
8. Boosts Fertility and Helps with Growth and Development
Fats are critical for reproductive health and a vibrant pregnancy because they help the body produce sex hormones including estrogen and progesterone. Cod liver oil is linked with healthier ovarian and testicular function since it provides critical nutrients (omega-3s and vitamin D) that help keep the endocrine system running smoothly.
With multiple anti-inflammatory nutrients, cod liver oil supports the adrenal, hyptothalamic and pituitary glands that control the release of sex hormones involved in libido, pregnancy and reproduction. DHA also plays a crucial role in the mobility and health of sperm in men.
As the Weston A. Price Foundation points out, women who used liquid cod liver oil early in their pregnancy have a higher likelihood of giving birth to heavier babies, which is associated with a lower risk of diseases later in life. Women using cod liver oil also have significantly higher levels of DHA and EPA in their breast milk, which positively impacts development of breast-fed infants.
Results from a 2003 study conducted at the University of Oslo in Norway showed that children who were born to mothers who had taken cod liver oil during pregnancy and lactation scored higher on intelligence tests at age four compared with children whose mothers had taken corn oil instead.
9. Improves Brain Function
Regularly supplementing with fish oil for depression has been associated with lower risks for depressive symptoms, due to both the higher intake of essential omega-3 fats and vitamin D.
A 2007 study published in the Journal of Affective Disorders found that omega-3 fatty acids from cod liver oil improved the outcome of depression and anxiety in the general population. The Hordaland Health Study followed 21,835 adults living in Norway for two years and discovered that the prevalence of depressive symptoms in those who used cod liver oil daily was 2.5 percent, as compared to 3.8 percent in the rest of the population. They also found that the prevalence of high levels of depressive symptoms decreased with increasing duration (0–12 months) of cod liver oil use.
There’s a strong connection between omega-3 intake or fish oil supplementation and prevention of cognitive decline, including Alzheimer’s disease. Studies show consistent results: The essential fatty acids vital for brain function are found in fish oil and help prevent brain disorders in older adults.
10. Helps Maintain Bone Health
Vitamin D is important for building and maintaining strong bones. Studies show that women who live in cold, northerly latitudes and don’t get enough sunlight tend to produce less vitamin D, which increases the risk for bone turnover, bone loss, fractures and also obesity. Vitamin D supplementation, including from cod liver oil, has been associated with a significantly lower risk of bone fractures and might help naturally prevent osteoporosis from developing.
11. Fights Ulcers
In laboratory settings, cod liver oil has shown benefits for improving gastric ulcer healing and reducing gastric antisecretory effects observed in rats. The oil also seems to produce gastric cytoprotective effects and causes a significant reduction in the development of stress and pain caused by gastric ulcers.
The Best Kind of Cod Liver Oil to Buy and Dosage
Most fish oil supplements available today are unhealthy, contain fillers or synthetic ingredients, can be rancid and are not an ideal ratio of fatty acids. Look for a reputable brand and ideally one that also contains antioxidants like astaxanthin to keep the oil from oxidizing. Fermented cod liver oil is also available by some brands, which means the livers were fermented to produce more vitamins and make it more digestible prior to the oil being extracted. This type is usually a good choice and nothing to fear, since fermenting fish has been a practice around the world for thousands of years.
You want to stick to a dose of no more than 1,000 milligrams of omega-3s daily unless working with a doctor for a specific condition. Each brand of cod liver oil provides different levels of omega-3s, vitamin D and vitamin A, so it’s difficult to give one over-arching dosage recommendation.
The Weston A. Price Foundation is a great resource for ongoing updates regarding different cod liver oil manufacturers who have products available in various countries. As a general guideline, they recommend the following doses of cod liver oil:
- Children age 3 months to 12 years: A dose of cod liver oil that provides about 5,000 IU vitamin A daily and 500–1,000 IU vitamin D. This is equal to about 1 teaspoon of regular cod liver oil or 1/2 teaspoon of high-vitamin cod liver oil. Check the brand’s label; you may need to give a child as little as 1/8 of a teaspoon.
- Children over 12 years and adults: A maintenance dose of cod liver oil that provides about 10,000 IU vitamin A daily and 1,000–2,000 IU vitamin D. This is about 2 teaspoons of regular cod liver oil or 1 teaspoon of high-vitamin cod liver oil, but again the amount varies by company.
- Pregnant and nursing women: A dose of cod liver oil that provides about 20,000 IU vitamin A daily and 2,000–4,000 IU of vitamin D. This is about 4 teaspoons regular cod liver oil or 2 teaspoons high-vitamin cod liver oil.
How should you consume your fish oil? It’s recommended that you mix it with a small amount of juice, lemon water, a smoothie, apple sauce, yogurt, almond butter or anything else that helps disguise the slightly fishy taste. A reputable brand will not add flavor enhancers or remove the odor or taste, so be prepared! Some brands will add natural extract to improve the taste (like mint or lemon), so this is an option. Store your bottle of cod liver oil in a cool, dark place or in the refrigerator to keep it from spoiling and going rancid.
Are There Any Risks or Side Effects?
When it comes to cod liver oil, and any type of fish oil or omega-3 supplement for that matter, it all comes down to the need for balance. Omega-3 fatty acids and omega-6 fatty acids need to have a balanced ratio, with slightly more omega-6 fats in the diet than omega-3s being the ideal. It isn’t beneficial or wise to take high amounts of cod liver oil, because more is not better; it’s a healthy ratio that we’re after!
Omega-6 fatty acids aren’t inherently bad for you and play an important role in immune system function, so too much cod liver oil can actually cause harm. That’s because omega-3 fatty acids suppress inflammation and omega-6 fatty acids promote inflammation, but we need some of both. This delicate relationship keeps your immune system working properly so you produce “defense mechanisms” against posed threats (toxins, bacteria, pathogens) when you need to, but don’t become overly inflamed in the process.
In general, the best way to achieve balance is by getting your omega-3s from food sources like wild-caught fish (such as salmon), grass-fed or pasture-raised meat or cage-free eggs. Nuts and seeds are also good choices but supply a different kind of omega-3 known as ALA, while animal sources provide the preferred types called EPA and DHA.
If you’re consuming wild-caught fish a couple of times a week and have a diet high in pastured animal fats and plant-based omega-3 foods, then taking an omega-3 supplement might not be totally necessary. However, the average person can really benefit from supplementing and eating well.
Cod liver oil can act like a blood thinner, so pregnant women, asthmatics or people taking high blood pressure medication or anticoagulants should speak to their doctor before beginning a fish oil regimen. While it’s safe for most people, there are some possible side effects, such as belching (having “fish burps”), bad breath, heartburn, nausea, blood stools, low blood pressure, high vitamin A and D levels, and nosebleeds.
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