It is possible to combine fish oil and cod liver oil supplements, but doing so requires careful attention to the total dosage of certain nutrients. Both oils are valued for their omega-3 polyunsaturated fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The primary concern when taking both together is not the fats themselves, but the cumulative intake of fat-soluble vitamins found in one of the supplements. Combining these products safely depends on understanding their distinct compositions and monitoring the total amount consumed daily.
How Fish Oil and Cod Liver Oil Differ
Fish oil is extracted from the flesh of fatty fish like anchovies, sardines, or mackerel. This oil is typically refined and concentrated to deliver a high dose of the omega-3 fatty acids EPA and DHA. Standard fish oil supplements contain negligible amounts of vitamins unless they have been specifically fortified.
Cod liver oil (CLO) is derived solely from the livers of codfish, which naturally store fat-soluble vitamins. Consequently, CLO is a natural source of both omega-3s and significant amounts of Vitamin A and Vitamin D. The oil extracted from the liver typically has a lower concentration of EPA and DHA per serving compared to concentrated fish oil supplements. This difference in vitamin content is the most important factor when considering combining the two oils.
Safety Considerations for Taking Both
The main safety concern when combining omega-3 sources is the overall dosage of EPA and DHA. High consumption of omega-3 fatty acids has been linked to a theoretical risk of excessive blood thinning or increased bleeding. However, clinical trials have largely failed to find a significant increase in clinically relevant bleeding events, even in individuals taking high doses.
The American Heart Association (AHA) considers consuming up to 3,000 milligrams (3 grams) of combined EPA and DHA daily to be safe for most people. Individuals taking both oils must calculate the total omega-3s from both labels to ensure the amount remains within established guidelines. Exceeding this amount consistently can increase the chance of minor side effects like nosebleeds or bruising. It is prudent to discuss any combined supplementation plan with a healthcare provider, especially if you take medications that affect blood clotting.
Managing Total Vitamin A Consumption
The presence of preformed Vitamin A in cod liver oil makes its dosage the limiting factor when combining supplements. Vitamin A is a fat-soluble nutrient, meaning the body stores excess amounts instead of excreting them, which can lead to toxicity over time. This condition, known as hypervitaminosis A, is the primary danger associated with over-consuming CLO.
The symptoms of chronic Vitamin A toxicity can include severe headaches, dry skin, hair loss, and, in severe cases, liver damage. The Tolerable Upper Intake Level (UL) for preformed Vitamin A for adults is 3,000 micrograms (µg) Retinol Activity Equivalents (RAE) per day. When combining supplements, it is necessary to check the Vitamin A content listed on the cod liver oil label.
To prevent toxicity, the total amount of Vitamin A ingested from all sources, including CLO and multivitamins, should not exceed the UL of 3,000 µg RAE daily. If you are taking a separate fish oil supplement, you must select a low-dose cod liver oil. This ensures the Vitamin A content does not push your total intake past the safe upper limit.