The Potential Dangers of Fish Oil

The Potential Dangers of Fish Oil

Fish oil supplements contain omega-3 fatty acids, which are healthy fats that have been associated with a lower risk of heart problems and improved cognitive function. While many people take these supplements for a wide range of health conditions, they could potentially cause other health issues. Here’s a closer look at the possible dangers of fish oil that consumers should be aware of before taking these supplements.


There’s a reason why people are supposed to limit how much seafood they eat, and that reason is mercury. This substance can build up inside people and cause several health issues, including high blood pressure, memory problems and heart disease. Mercury has been found in many types of fish that fish oils are derived from, including salmon.

Dioxins and Polychlorinated Biphenyl or PCB’s are another concern when it comes to fish oils because they’re known to cause cancer and birth defects. PCBs have been banned since 1979, but they’re still around in water. That means fish are exposed to them, which also means that people who consume these fish or products made from them are at risk of PCB contamination. A lawsuit filed against several fish oil companies and retailers in 2010 came about because environmental activists found evidence of PCB contamination in ten different supplements.

The good news is that Consumer Lab tested several fish oil products in 2012 for contaminants and only found trace PCB levels in most of them. None of the fish oil supplements tested contained mercury. Many companies are able to keep these levels low or nonexistent by using sardines and other fish that are lower down on the food chain. Fish that are higher up on the food chain tend to have higher levels of contaminants because they consumer smaller fish that also have them. Some companies also distill fish oils, which helps get rid of these contaminants.


While it’s not surprising that fish oil can produce a fishy aftertaste, it shouldn’t have a rancid taste or smell. Fish oil supplements can spoil due to oxidization, which can cause health issues ranging from a bout of unpleasant fishy burps or a higher risk of plaque buildup in the arteries. Consumers can reduce the chances of having rancid fish oil supplements by purchasing smaller amounts of supplements or keeping liquid fish oil (not capsules) in the fridge or freezer. Consumers can also look for fish oil supplements that contain vitamin E, which helps slow spoilage.

High Doses

It’s certainly possible to have too much of a good thing with fish oil supplements. In general, healthy individuals can take up to three grams a day. More than this amount could lead to blood clotting problems and increased bleeding, especially in those with liver scarring. Taking more than the recommended amount of fish oil might also lower immune system activity, which makes it harder to fight illnesses and infections. Those with diabetes might have difficulty controlling their blood sugar levels if they also take higher amounts of fish oil.

Health Warnings

The National Institutes of Health list several warnings about fish oil for those who have certain health conditions. Those who should avoid taking these supplements include:

  • Those with a seafood allergy, since fish oil might cause an adverse reaction.
  • Those with a pacemaker, since these supplements might lead to a higher risk of an irregular heartbeat.

Those who should consult their doctor before taking fish oil include:

  • Those with bipolar disorder or depression, since these supplements might make symptoms worse.
  • Those who take medication to lower high blood pressure, since their blood pressure levels could drop too low.
  • Those with familial adenomatous polyposis, since there might be a higher risk of developing cancer with this condition when taking fish oil.
  • Those with compromised immune systems, since high amounts of fish oil supplements can further weaken their immunity.

Taking fish oil might also lead to lower levels of vitamin E, although researchers aren’t entirely sure why this happens. Vitamin E helps prevent cell damage and helps make red blood cells. Having low levels of this nutrient can cause health problems, such as muscle weakness, vision problems and an unsteady gait.


There are many types of fish oil supplements available, but they’re not all equal in terms of quality. Purchasing ones that are lower in quality could increase the risk of ending up with a spoiled product or a brand that contains contaminants, depending on where the oil is sourced from. Consumers should make sure that they find fish oil supplements from companies that follow the United States Pharmacopeia’s (USP) voluntary regulations for contaminant levels and follow all mandatory laws and regulations on quality. These companies typically share the results of contaminant testing and are usually verified by USP or other third parties that enforce quality laws and regulations.

While fish oil supplements are usually safe for most people to take, it’s also important to consider the potential dangers associated with their use. Consumers who are interested in taking these supplements should check with their doctor first, look for high-quality brands and only take the recommended amount per day.

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  • Franklin VanOs