Omega-3 fatty acids are blood thinners

The U.S. Food and Nutrition Board (U.S. Food and Nutrition Office) has the Upper limit for EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) from food supplements set at 3 g per day.

People who are more prone to bleeding, such as from medication, should exercise greater caution. The risk group of sensitive people with an increased tendency to bleed includes people who take anticoagulants (blood clotting inhibitors) of the coumarin type (e.g. Marcumar). Omega-3 fatty acids can increase the effect of anticoagulants due to an effect that is independent of vitamin K.

The long-chain omega-3 fatty acids EPA and DHA are recognized as generally safe (GRAS status, generally recognized as safe) and the study situation shows that the daily intake of up to 3 g EPA and DHA does not increase the bleeding tendency with a high probability [1].

Serious adverse reactions are regarding omega-3 fatty acids (EPA, DHA) from dietary supplements have not been reported. The most common side effects are limited to a fishy aftertaste, belching, and occasionally heartburn. High doses can cause nausea and loose stools.

As undesirable effects of a high intake of long-chain omega-3 fatty acids (EPA and DHA) a prolongation of the bleeding time, a suppression of the immune system and an increase in the LDL cholesterol level are discussed.

Extension of the bleeding time: The potential of high doses of omega-3 fatty acids, especially EPA and DHA, to increase bleeding time has now been well researched. This effect could play a role in the cardioprotective effect (protective function for the cardiovascular system) of the omega-3 fatty acids. Among the Eskimos on Greenland were excessively long bleeding times and also an increased incidence (frequency) for Cerebral hemorrhage found what is likely to be due to the ingestion of very high doses of omega-3 fatty acids (around 6.5 g per day) is due to food. However, it is not known whether the omega-3 fatty acids are the only reason for this. In a study of adolescents and young adults with hypercholesterolemia (high cholesterol levels in the blood), a lot of 1.5 g of omega-3 fatty acids, taken for several months, to increased Nosebleeds [2]. In another study, after administration of 2 g EPA (Eicosapentaenoic acid) taken for 12 weeks, one prolonged bleeding time measured [3].

Suppression of the immune system: Omega-3 fatty acids have an anti-inflammatory (anti-inflammatory) effect and can be used therapeutically in the case of corresponding diseases. Anti-inflammatory (anti-inflammatory) effective doses of omega-3 fatty acids can potentially decrease the effectiveness of the immune system [4]. In vitro studies have shown that this is already possible at a dose of 0.9 g / day for EPA and 0.6 g / day for DHA can occur. In a human study with 48 healthy people, the Taking fish oil capsules (720 mg EPA + 280 mg DHA) over a period of 12 weeks to one decreased activity of natural killer cells by 48% as well as one decreased proliferation (Growth and reproduction) of T lymphocytes by up to 65% [5, 6]. These effects will usually interpreted positively as anti-inflammatory, however, they also mean one Weakened immune response on pathogens. For the healthy and especially the elderly population, suppression of the specific as well as the unspecific immune defense is undesirable and involves a risk [7].

Increase in LDL cholesterol levels: Almost all of the studies on omega-3 fatty acids found an increase in LDL cholesterol (low-density lipoproteins containing cholesterol). A study was able to show that the increase in LDL cholesterol with amounts of 2.4 g DHA and EPA per day is higher (26% increase) than with very large amounts of DHA and EPA of over 4 g per day (11% increase) [8]. In another study, an amount of 700 mg DHA, taken for 3 months, led to a slight increase in the LDL cholesterol level of 7% [9].


  1. Kris-Etherton PM, Harris WS, Appel LJ: Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation. 2002; 106 (21): 2747-2757.
  2. Clarke JTR, Cullen-Dean G, Regelink E, Chan L, Rose V: Increased incidence of epistaxis in adolescents with familial hypercholesterolemia treated with fish oil. J. Pediatr. 116 (1990) 139-141
  3. Emsley R, Niehaus DJ, Oosthuizen PP, Koen L, Ascott-Evans B, Chiliza B, van Rensburg SJ, Smit RM: Safety of the omega-3 fatty acid, eicosapentaenoic acid (EPA) in psychiatric patients: results from a randomized, placebo-controlled trial. Psychiatry Res. 2008 Dec 15; 161 (3): 284-91. Epub 2008 Oct 29.
  4. Hard LS: Fatty acids, the immune response, and autoimmunity: a question of n-6 essentiality and the balance between n-6 and n-3. Lipids. 2003; 38 (4): 323-341.
  5. Thies F, Nebe-von-Caron G, Powell JR, Yaqoob P, Newsholme EA, Calder PC: Dietary sup-plementation with gamma-linolenic acid or fish oil decreases T lymphocyte proliferation in healthy older humans. J Nutr. 2001 (a) Jul; 131 (7): 1918-27.
  6. Thies F, Nebe-von-Caron G, Powell JR, Yaqoob P, Newsholme EA, Calder PC: Dietary sup-plementation with eicosapentaenoic acid, but not with other long-chain n-3 or n-6 polyunsatu-rated fatty acids, decreases natural killer cell activity in healthy subjects aged> 55 y. At J Clin Nutr. 2001 (b) Mar; 73 (3): 539-48.
  7. Federal Institute for Risk Assessment; The BfR recommends setting maximum levels for the fortification of foods with omega-3 fatty acids; BfR Opinion No. 030/2009 of May 26, 2009
  8. Hooper L, Thompson RL, Harrison RA, Summerbell CD, Moore H, Worthington HV, Durring-ton PN, Ness AR, Capps NE, Davey Smith G, Riemersma RA, Ebrahim SB: Omega 3 fatty acids for prevention and treatment of cardiovascular disease . Cochrane Database Syst Rev. 2004 Oct 18; (4): CD003177.
  9. Theobald HE, Chowienczyk PJ, Whittall R, Humphries SE, Sanders TA: LDL cholesterol-raising effect of low-dose docosahexaenoic acid in middle-aged men and women. At J Clin Nutr. 2004 Apr; 79 (4): 558-63.
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