Centuries ago, the Nordics used cod liver oil to protect them from the cold, and by 1930 AD, scientists found that cod liver oil was helpful in preventing rickets, so it began to be used for diseases caused by vitamin D deficiency and became an essential health supplement for families.
What is cod liver oil? How is it different from fish oil?
Cod liver oil is a fat extracted from the liver of Atlantic cod, and the main difference from fish oil is that in addition to omega-3 fatty acids, cod liver oil is rich in vitamin A and vitamin D.
Today, a large body of literature has also found that the health benefits of cod liver oil are not limited to rheumatism and rickets.
Vitamin A is essential for the immune system, bone growth, night vision, cell growth, testicular and ovarian function.
Not only does vitamin D prevent rickets, low vitamin D levels are associated with an increased risk of type 1 diabetes, cardiovascular disease, certain cancers, cognitive decline, depression, pregnancy complications, autoimmunity, allergies, and even weakness.
What are the benefits of cod liver oil?
1. Cod liver oil is beneficial for rheumatoid arthritis
Rheumatoid arthritis is an autoimmune disease of unknown etiology, chronic, destructive, and debilitating, accounting for about 1% of the adult population.
Epidemiological studies have pointed out that in addition to genetic inheritance, the factors affecting the pathogenesis also include cigarette smoke, exogenous hormone use, female reproductive factors (irregular menstrual cycle, early menarche, breastfeeding), occupational silica dust exposure and mineral oil and other environmental predisposing factors.
A double-blind, placebo-controlled randomized study (9-month study of 97 patients with rheumatoid arthritis) noted that cod liver oil (10 g daily dose) helped reduce the use of nonsteroidal anti-inflammatory analgesics (NSAIDs) (but there was no clear difference in clinical measures). Note 1
*Conclusion: For patients with rheumatoid arthritis, cod liver oil can help reduce the amount of anti-inflammatory painkillers, but more studies are needed to support it due to the small sample size
2. Cod liver oil reduces the incidence of type 1 diabetes
Type 1 diabetes mellitus is a heterogeneous disease characterized by destruction of pancreatic cells, which ultimately leads to absolute insulin deficiency. Most cases are due to autoimmune-mediated cell destruction, and a few cases are caused by idiopathic factors, accounting for about 1-5% of all cases of diabetes worldwide.
Although type 1 diabetes can occur at any age, it is one of the most common chronic diseases in children, peaking between the ages of 5-7 or near adolescence.
A population-based case-control study (85 diabetics versus 1071 controls) found that when mothers took cod liver oil during pregnancy, their offspring had a lower risk of developing diabetes (up to 70% reduction). Note 2
This suggests that vitamin D or n-3 fatty acids in cod liver oil have a protective effect against type 1 diabetes.
*Conclusion: Maternal cod liver oil supplementation during pregnancy can reduce the risk of developing type 1 diabetes in offspring, but further confirmation is needed due to the lack of randomized controlled validation
3. Cod liver oil is beneficial for melancholy symptoms
Depression is a major public health problem affecting patients and society, and the clinical symptoms are called unipolar depression, which manifests as low mood, hopelessness, helplessness, intense guilt, sadness, low self-esteem, self-harm, and suicidal thoughts.
Statistically, the prevalence of depression in women is higher than in men, with a global annual prevalence of 5.5% and 3.2%, respectively, and the incidence in women is 1.7 times that of men.
A population-based cross-sectional study (including 21,835 participants) noted that subjects who took cod liver oil orally were much less likely to experience melancholic symptoms than non-users (and remained so after adjusting for multiple possible confounding factors, such as age, sex, smoking habits, coffee consumption, alcohol consumption, physical activity, and education). Note 3
*Conclusion: Population observation shows that the use of cod liver oil is negatively correlated with melancholic symptoms, but randomized controlled experiments are still needed to verify the causal relationship
4. Cod liver oil is good for glaucoma
Glaucoma is a type of optic neuropathy characterized by progressive degeneration of retinal ganglion cells, affecting more than 7000 million people worldwide, causing bilateral blindness in 10% of the population and the leading cause of irreversible blindness in the world.
Primary glaucoma is common in cases and major risk factors such as intraocular hypertension, vascular insufficiency, glutamate-mediated toxicity, overproduction of nitric oxide, and oxidative stress.
Secondary glaucoma may be due to trauma, drugs such as corticosteroids, inflammation, tumor or pigment dispersion, or pseudoexfoliation
Cod liver oil is rich in vitamin A and Omega-3, so it is considered a health supplement for eye health. Note 4
Among them, vitamin A is important for maintaining normal vision, it prevents oxidative damage (the cause of glaucoma); It is also a key factor in maintaining the integrity of theconjunctiva and corneal surface, and preventing ocular epithelial damage caused by topical antiglaucoma drugs.
Omega-3 fatty acids are beneficial to reduce intraocular pressure, increase ocular blood flow, and improve optic neuroprotective function in glaucoma patients.
*Conclusion: Cod liver oil is beneficial for glaucoma, but it has not been confirmed by human randomized controlled trials and remains to be verified
5. Cod liver oil reduces the mortality rate of coronary heart disease
Coronary heart disease is a lack of oxygen, ischemia, and consequent changes in heart function caused by the narrowing of the heart’s major large vessels (atherosclerosis).
Possible symptoms include exhaustion, shortness of breath, chest pain, and palpitations, which can lead to a heart attack (eg, heart failure, myocardial infarction) if the coronary arteries are suddenly and completely blocked.
A prospective generational study (22 years follow-up, 22,035 participants) found that the use of omega-3 polyunsaturated fatty acid supplementation (mainly cod liver oil) helped reduce coronary heart disease mortality (up to 26%), especially in those with lower fish consumption and an average age of about 60 years. Note 5
*Conclusion: Population observations suggest that daily cod liver oil intake may help reduce coronary heart disease mortality, but more studies are needed to support the possible interfering factors
Are there side effects of cod liver oil?
Cod liver oil is very safe in appropriate doses for most healthy adults and children, and reported side effects or adverse effects include: bad mouth, hiccups, bad breath, heartburn, loose stools, and nausea (recommended with meals to reduce these side effects).
Do not take more than the recommended dose indicated on the product without medical supervision.
Excess vitamin A may cause: nausea, headache, fatigue, loss of appetite, dizziness, dry skin, peeling, cerebral edema, etc., with a maximum tolerable intake of 10,000 IU or 3,000 mcg RAE (retinol activity equivalents) per day.
Excess vitamin D can cause: bone loss, kidney stones, and calcification of organs such as the heart and kidneys, with a maximum tolerable intake of 4,000 IU or 100 mcg per day.
Safety precautions
1. Pregnant or nursing women should use with caution (avoid overdose if taking other forms of vitamin supplements at the same time)
2. Do not use it with blood pressure lowering drugs (cod liver oil may have a blood pressure-lowering effect), related drugs are: captopril (captopril), enalapril (enalapril), losartan (kosua), valsartan (to be stable), diltiazem (Tier Xin), Amlodipine (active luoxi), hydrochlorothiazide (dihydrogram urine plug), furosemide (furosemide)
3. Stop using it two weeks before surgery and do not combine it with anticoagulant drugs (as cod liver oil may have anticoagulant effects, which may increase the chance of bruising and bleeding)