Cod liver oil is a type of fish oil available in liquid and capsule form. Sourced from the liver of cod fish, the oil is rich in vitamin A, vitamin D and omega-3 fatty acids. Due to its high omega-3 content, cod liver oil is found in many natural products marketed as omega-3 supplements.
Uses for Cod Liver OilIn the 1800s, cod liver oil became popular as a dietary supplement for children whose lack of sunlight exposure increased their risk for rickets (a disease caused by vitamin D deficiency). Today, proponents claim that cod liver oil can help treat or prevent a wide range of health problems, including:
- heart disease
- high blood pressure
- high cholesterol
Benefits of Cod Liver Oil
According to the National Institutes of Health (NIH), fish oil is probably effective for prevention of heart disease. In addition, the NIH states that fish oil may help lower blood pressure and cholesterol, manage asthma and rheumatoid arthritis, ease menstrual pain, reduce stroke risk, protect against osteoporosis and slow the progression of atherosclerosis. However, the NIH does not specify whether cod liver oil in particular (rather than fish oil sourced from other types of fish) might produce these health benefits.
Although research on the specific health effects of cod liver oil is somewhat limited, some studies show that cod liver oil may help with the following conditions:
1) Upper Respiratory Tract Infections
Cod liver oil may help prevent upper respiratory tract infections, according to a 2004 study of 94 children. Published in the Annals of Otology, Rhinology, and Laryngology, the study found that participants who received cod liver oil and a multivitamin-mineral each day from late autumn through early spring experienced a significant decrease in the number of upper respiratory tract infections (such as the common cold).
Taking cod liver oil during pregnancy may reduce the baby's risk of type 1 diabetes, suggests a 2000 report from the journal Diabetologia. Analyzing data on 85 expectant mothers with diabetes and 1,071 diabetes-free pregnant women, the study's authors found a significantly lower diabetes risk among children born to participants who had consumed cod liver oil while pregnant.
In addition, a 2003 study of 2,213 people (published in the American Journal of Clinical Nutrition) found that taking cod liver oil during the first year of life was linked to a reduced risk for childhood-onset type 1 diabetes.
For people with rheumatoid arthritis, taking cod liver oil may reduce the need for non-steroidal anti-inflammatory drugs (NSAIDS). For a 2008 study published in Rheumatology, researchers assigned 97 rheumatoid arthritis patients to nine months of treatment with either cod liver oil or a placebo. Looking at data on the 58 people who completed the study, they found that 39 percent of the cod liver oil group was able to reduce their daily NSAID intake by more than 30 percent (compared to 10 percent of patients in the placebo group).
In an earlier study from Advances in Therapy, scientists discovered that taking cod liver oil may help alleviate stiffness, pain, and swelling in people with rheumatoid arthritis.
Cod Liver Oil vs. Fish Oil
Since some species of cod are thought to be endangered, getting your omega-3s from other types of fish oil (such as salmon) may be more ecologically responsible. If you're vegetarian, you can obtain omega-3 fatty acids from plant sources like flaxseed.
What Is Fermented Cod Liver Oil?
Proponents of fermented cod liver oil claim that this form of cod liver oil is more pure and higher in vitamin A, vitamin D and omega-3 fatty acids than heat-processed forms of cod liver oil. However, there is currently a lack of scientific evidence to support this claim.
While fish oil is likely safe for most people when taken in low doses (such as three or fewer grams per day), it may cause a number of side effects (including bad breath, heartburn, nausea and belching).
When overused, cod liver oil may lead to toxic levels of vitamins A and D. Additionally, high doses of fish oil may prevent blood clotting, damage the immune system and increase blood levels of LDL ("bad") cholesterol.
If you're considering the use of cod liver oil in combination with other supplements or medications, talk to your doctor before beginning treatment. It's also important to note that avoiding standard medical care and self-treating a chronic condition with cod liver oil (or any other type of alternative medicine) may have serious health consequences.
American Cancer Society. "Omega-3 Fatty Acids". November 2008.
Galarraga B, Ho M, Youssef HM, Hill A, McMahon H, Hall C, Ogston S, Nuki G, Belch JJ. "Cod liver oil (n-3 fatty acids) as an non-steroidal anti-inflammatory drug sparing agent in rheumatoid arthritis." Rheumatology (Oxford). 2008 May;47(5):665-9.
Gruenwald J, Graubaum HJ, Harde A. "Effect of cod liver oil on symptoms of rheumatoid arthritis." Adv Ther. 2002 Mar-Apr;19(2):101-7.
Linday LA, Shindledecker RD, Tapia-Mendoza J, Dolitsky JN. "Effect of daily cod liver oil and a multivitamin-mineral supplement with selenium on upper respiratory tract pediatric visits by young, inner-city, Latino children: randomized pediatric sites." Ann Otol Rhinol Laryngol. 2004 Nov;113(11):891-901.
National Institutes of Health. "Fish oil: MedlinePlus Supplements". August 2011.
Stene LC, Joner G; Norwegian Childhood Diabetes Study Group. "Use of cod liver oil during the first year of life is associated with lower risk of childhood-onset type 1 diabetes: a large, population-based, case-control study." Am J Clin Nutr. 2003 Dec;78(6):1128-34.
Stene LC, Ulriksen J, Magnus P, Joner G. "Use of cod liver oil during pregnancy associated with lower risk of Type I diabetes in the offspring." Diabetologia. 2000 Sep;43(9):1093-8.