text: According to the European Food Safety Authority's (EFSA) Panel on Dietetic Products, Nutrition and Allergies, supplementation of 5 grams of EPA and DHA combined does not pose a safety concern for adults. A 1987 study found that healthy Greenlandic Inuit had an average intake of 5.7 grams of omega-3 EPA per day which had many effects including prolonged bleeding times, such as slower blood clotting.
  Research
  Two 2021 systematic reviews and meta-analyses concluded that more than 1 g/d marine omega-3 fatty acids is associated with an increased risk of atrial fibrillation.
  Vitamins
  The liver and liver products (such as cod liver oil) of fish and many animals (such as seals and whales) contain omega-3, but also the active form of vitamin A. At high levels, this form of the vitamin can be dangerous (Hypervitaminosis A).
  Toxic pollutants
  Consumers of oily fish should be aware of the potential presence of heavy metals and fat-soluble pollutants like PCBs and dioxins, which are known to accumulate up the food chain. After extensive review, researchers from Harvard's School of Public Health in the Journal of the American Medical Association (2006) reported that the benefits of fish intake generally far outweigh the potential risks.
  Fish oil supplements came under scrutiny in 2006, when the Food Standards Agency in the UK and the Food Safety Authority of Ireland reported polychlorinated biphenyl (PCB) levels that exceeded the European Union maximum limits in several fish oil brands,