Study Reviews

Polyunsaturated fatty acids: structures, metabolism and functions

  • 01/25/2016


  • Numerous health organisations and bodies agree on recommending consumption of 500 mg/day of EPA and DHA.
  • In its recommendations on consumption and dietary supplementation with omega-3 (EPA and DHA), the National Expert Group sets intake at between 0.5 and 1.5 g (average 1 g/day).
  • To obtain health benefits, the omega-6/omega-3 ratio in the diet should be 4:1.
  • Omega-3 polyunsaturated fatty acids reduce platelet aggregation, prolonging bleeding time. Their concomitant application with platelet antiaggregants could strengthen the response. The omega-3 dose in patients taking platelet antiaggregants should not exceed 1g/day
  • In patients at high risk of cancer or heart, rheumatic and neurodegenerative disease, the dose of EPA and DHA can be increased to 1.5 g/day. In the treatment of hypertriglyceridemia, omega-3 supplements can be used under medical supervision at doses of 2 to 4 g/day.
  • Consuming omega-3 in the daily diet is particularly beneficial in combination with statin or fibrate therapy and is especially recommended in mixed dyslipidemia.
  • According to the FDA, consumption of up to 3 g/day of omega-3 should not induce adverse effects; however high doses should be reserved for special situations and used under medical supervision.
  • However, the EFSA suggests caution with the size of fish due to their content of mercury and other heavy metals.


  • Omega-6 and omega-3 long-chain polyunsaturated fatty acids cannot be synthesised by humans in sufficient quantities, so they have to be provided by food, hence the term ‘essential’.
  • Fish oil is the ideal source of EPA and DHA, whose amount and availability through diet is comparatively limited with respect to amounts of omega-6 provided by plants.
  • Omega-3 has a particularly beneficial effect on brain, cardiovascular system and retina system function, due to the presence and number of double bonds in its molecule.
  • Double bonds are a particularly important molecular property; they facilitate reactions with radicals, promote their oxidation and change their characteristics.
  • It is worth noting that omega-3 does not produce significant adverse reactions.
  • Omega-3 fatty acids should not substitute or replace pharmacological therapy.
  • Due to their role in health maintenance, they should be ingested in sufficient quantities, if possible through a balanced diet or pharmacological preparations, as dietary supplements which should also contain lipophilic properties and antioxidants such as vitamin E.