Taking cod liver oil as a supplement goes as far back as the 1700’s when it was used to treat arthritis and treat rickets in the 1800’s. Current times cod liver oil is mainly taken as a supplement because it is a source of omega 3 fatty acids, vitamin D and vitamin A.
Unlike other fish oils, cod liver oil is made specifically from just the liver of cod instead of the whole fish.
Like other fish oils, cod liver oil may have some heart health benefits. There is some evidence to suggest taking cod liver oil may be helpful for lowering triglyceride levels and lowering blood pressure.
There is also some evidence cod liver oil may be helpful in lowering inflammation associated with rheumatoid arthritis.
As with any supplement, consult your healthcare team before taking cod liver oil.
Cod liver oil may interfere with certain medications and may be potentially harmful in high doses.
A 2008 study (1) looked at whether taking cod liver oil would help reduce the amount of nonsteroidal anti-inflammatory drugs (NSAIDS) people with rheumatoid arthritis took on a daily basis.
Consuming consistent, daily amounts of NSAIDS may have some gastrointestinal and cardiovascular risks, so limiting intake of NSAIDS in people with chronic pain conditions like arthritis may be beneficial.
This study found cod liver oil may have a sparing effect of NSAIDS in people with rheumatoid arthritis.
The omega 3 concentration in cod liver oil is thought to provide the anti-inflammatory effect that may alleviate some need to take NSAIDS.
If you have arthritis, speak with your healthcare team before taking cod liver oil. Cod liver oil has not been shown to reverse arthritis or treat it just may alleviate inflammation and/or pain associated with it.
Lowering blood triglycerides
According to the US National Library of Medicine (2), cod liver oil is likely effective for lowering blood triglyceride levels.
WebMD (2) also suggests cod liver oil is likely to help lower high triglyceride levels by 20-50%. University of Michigan Health System (3) suggests there are many studies concluding fish oil and cod liver oil can lower blood triglyceride levels.
Some studies have shown an increase in cholesterol from fish oil or cod liver oil supplements, so speak with your healthcare team if you are wondering if cod liver oil would benefit heart health.
Taking 20 ml of cod liver oil per day is the suggested dose for lowering triglycerides.
Kidney function and type 2 diabetes
Having diabetes may increase risk for kidney disease especially if blood sugar levels are chronically high.
High blood sugar levels can damage small blood vessels in the body including in the kidney.
If kidney blood vessels are damaged, kidney function may be impaired. This could lead to impairment of filtering the blood or removing fluid from the body.
According to the National Kidney Foundation (4), about 30% of people with type 1 diabetes and between 10-40% of people with type 2 diabetes may eventually have kidney failure.
Some research suggests cod liver oil may have a positive effect on kidney health associated with type 2 diabetes.
The US National Library of Medicine (5) suggests cod liver oil may possibly be effective for reducing protein levels in urine.
Having lower protein in the urine is one way to measure kidney function.
Lower blood pressure
The University of Michigan Health System suggests there are 31 clinical trials showing the benefit of fish oil and cod liver oil lowering blood pressure.
WebMD suggests even though the effect cod liver oil has on lowering blood pressure may be small, but it is significant.
Unsubstantiated claims of cod liver oil
There may be other claims associated with taking cod liver oil, but these claims are unsubstantiated.
According to WebMD and the US National Library of Medicine, there is insufficient evidence from research to claim cod liver oil has a benefit for: depression, irregular heart beat, heart disease, lupus, healing skin wounds or glaucoma.
Potential concerns with cod liver oil
Cod liver can be a very potent source of vitamin A. Vitamin A from animal sources does have a tolerable upper intake level (UL) because high doses may negatively affect health.
According to Berkeley Wellness (6), a Norwegian study found young girls who took cod liver oil were twice as likely to have low bone mass as adults compared to young girls who did not take cod liver oil.
The effect on bone mass is thought to be from very high levels of vitamin A from cod liver oil. Berkeley Wellness suggests taking cod liver oil that has a reduced level of vitamin A.
Since cod liver oil is made from the liver, there may be potential concern cod liver oil supplements are contaminated with toxins like PCB’s.
The liver filters toxins in the body, so depending on the diet and environment of the fish, their livers may or may not have higher levels of toxins.
Cod liver oil is supposed to be purified, but there may still be concern of toxin contamination.
Should you take cod liver oil?
Cod liver oil is considered safe for most people, but it is recommended to avoid high doses unless supervised by medical professionals.
The safety of cod liver oil during pregnancy and breast feeding is not known.
If you are taking blood pressure medication, speak with your doctor before taking cod liver oil.
Since cod liver oil can lower blood pressure, there is possibility cod liver oil and blood pressure medication may lower blood pressure too low.
Cod liver oil may also interfere with anti-coagulant medication. For any supplement, it is always advised to consult your healthcare team before taking it.
If you are on blood pressure or anti-coagulation medication, there may be additional concern for taking cod liver oil at the same time.