Cod liver oil is a supplement that is not only rich in healthy unsaturated fats, but contains fat-soluble vitamins like vitamin A and vitamin D. However, this product should be consumed in moderation. It's possible to consume excessive amounts of these essential vitamins.
Healthy cod liver oil doses vary between products. However, most cod liver oil products recommend that you take about a teaspoon (5 milliliters) each day.
Taking Cod Liver Oil
Cod liver oil has been a commonly consumed supplement for a long time, and was given to children in schools throughout the mid 20th century.
Cod liver oil is considered healthy, as it's rich in essential polyunsaturated fatty acids like docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which are omega-3 fatty acids. Cod liver oil products typically contain vitamins A and D, but may also contain other added nutrients, too.
Cod liver oil's benefits are primarily due to these three nutrients, which are all essential for your diet. Omega-3 fatty acids are important, as your body is unable to produce them and needs to obtain them from your diet. However, most people who follow a Western diet don't get enough of these fats and consume too many omega-6 fats instead.
Too many omega-6 and too few omega-3 fats are bad for your health. According to an April 2012 study in the Journal of Nutrition and Metabolism and a September 2016 study in the Prostaglandins and Other Lipid Mediators, excessive omega-6 fatty acids and inadequate amounts of omega-3 fatty acids can contribute to weight gain, inflammation and autoimmune diseases.
Vitamin A and Vitamin D are also essential. Most people should consume about 5,000 IU of vitamin A and 400 IU of vitamin D each day. Vitamin D consumption is particularly important. According to the Food and Drug Administration, vitamin D is a nutrient of concern, which means that most people don't get enough of it in their diet.
Healthy Cod Liver Oil Dosages
The cod liver oil dosage you should consume depends entirely on the product. Some products list specific amounts of EPA, DHA, vitamin A and vitamin D in each serving. However, many do not.
For example, take Blue Ice Fermented Cod Liver Oil. This product states that each serving is half a teaspoon (2 milliliters). Each serving contains:
- 20 calories
- 2 grams of fat, 0.5 grams of which are saturated
- 5 milligrams of cholesterol
Blue Ice Fermented Cod Liver Oil states that its products contain a variable amount of "naturally occurring vitamins A and D." This isn't much to go on if you're worried about consuming excessive amounts of these nutrients.
Notably, the serving size for this product is also smaller than average. According to a December 2012 study in the Journal of the Science of Food and Agriculture, most fish oil products have a serving size of about a teaspoon (5 milliliters).
By comparison, the USDA lists the average teaspoon of each cod liver oil product as having 41 calories, as well as:
- 4.5 grams of fat (7 percent of the DV), 1 gram which is saturated (5 percent of the DV)
- 25.7 grams of cholesterol
- 150 percent of the daily value (DV) for vitamin A
- 56 percent of the DV for vitamin D
One hundred and fifty percent of the DV is equivalent to 1,350 micrograms retinol activity equivalents (RAE). Although this amount would allow you to meet and surpass the total DV of vitamin A, 1,350 micrograms per day is not an excessive daily amount.
However, if you're consuming other vitamin A supplements or vitamin A-rich foods like sweet potato, spinach, pumpkin, carrots or beef liver, you could easily be ingesting too much vitamin A. The National Institutes of Health lists the maximum tolerable amount of vitamin A per day as 3,000 micrograms RAE. Given how much vitamin A is in cod liver oil, it is primarily this nutrient that will limit your consumption of this supplement.
Supplements and Excessive Nutrient Consumption
With the exception of a few nutrients that your body excretes in your urine, it's possible to consume too much a good thing. Fortunately, in order to get to such levels, you often have to be consuming very large amounts of nutrients.
While it's possible to consume too many omega-3 fatty acids, very large doses of up to 15 grams per day have been considered safe, according to the National Institutes of Health. However, these high doses have been shown to affect your blood clotting ability. If you're interested in taking cod liver oil or another fish oil to supplement your omega-3 fats, as much as 5 grams per day may be safe for long-term consumption.
Vitamin D is obtained through a variety of sources, including the sun. However, vitamin D from the sun and your diet are processed differently by your body. Most people should not consume more than 4,000 IU (100 micrograms) of vitamin D in a single day. Too much vitamin D can result in weight loss, frequent urination, heart problems and excessive increases to calcium levels. Elevated calcium levels can damage your cardiovascular system and kidneys.
The main risk of excessive nutrient consumption from cod liver oil comes from vitamin A. Your body stores this nutrient in your liver, which means that too much vitamin A can cause liver damage. Excessive vitamin A can also lead to issues like headaches, dizziness, nausea, skin irritation and joint pain.
A teaspoon of cod liver oil can have around 1,500 micrograms of vitamin A. This amount of vitamin A has been associated with reduced bone minerality and increased risk of fractures. Always make sure you know how much vitamin A is in your cod liver oil before consuming this supplement.
Cod Liver Oil Side Effects
Cod liver oil can have side effects regardless of whether or not you're consuming too much of it. According to the Cleveland Clinic, common cod liver oil side effects include bad breath or a metallic taste in your mouth, upset stomach, dry skin and headaches.
You shouldn't worry too much about these side effects, however. They are often easily resolved over time or by switching to a different product manufacturer. However, you should talk to your doctor if you experience side effects such as:
- Changes in the color of your urine
- Changes in your vision
- Yellow eyes or skin
- Skin rashes
- Bruising or excessive bleeding
These side effects are more serious and may be symptoms of too much cod liver oil.
Fish oil is unlikely to cause you any problems if you're consuming about a teaspoon or less per day. However, according to the Cleveland Clinic, even in small doses, the various ingredients in cod liver oil have the potential to interact with medications used to:
- Reduce bile acid from the body, like cholestyramine
- Reduce cholesterol, like colestipol
- Promote bone health, like calcitriol
- Promote weight loss, like orlistat
- Treat kidney disease, like doxercalciferol
- Prevent blood clots, like warfarin
If you have diabetes, high blood pressure, high cholesterol, stomach problems or kidney or liver disease, talk to your doctor before taking cod liver oil or any similar products regularly.
- Cleveland Clinic: "Cod Liver Oil Oral Capsules"
- National Institutes of Health: "Vitamin D Fact Sheet for Health Professionals"
- National Institutes of Health: "Vitamin A Fact Sheet for Health Professionals"
- MyFoodData: "Nutrition Facts for Cod Liver Oil"
- Journal of the Science of Food and Agriculture: "Quality Analysis of Commercial Fish Oil Preparations."
- Green Pasture: "Blue Ice™ Fermented Cod Liver Oil"
- U.S. Food and Drug Administration: "Vitamins and Minerals Chart"
- Prostaglandins & Other Lipid Mediators: "Linoleic Acid and the Pathogenesis of Obesity"
- Journal of Nutrition and Metabolism: "Health Implications of High Dietary Omega-6 Polyunsaturated Fatty Acids"
- Journal of Nutrition and Metabolism: "Health Implications of High Dietary Omega-6 Polyunsaturated Fatty Acids."
- National Institutes of Health: "Omega-3 Fatty Acids Fact Sheet for Health Professionals"
- British Journal of Nutrition: "Cod Liver Oil Consumption at Different Periods of Life and Bone Mineral Density in Old Age"