Fish oil omega-3 fatty acids do not increase bleeding risk
Fish oil is typically banned for consumption prior to surgery based on the unproven assumption that it must increase bleeding risk since it helps to prevent excessive coagulation. This assumption has weighty consequences because fish oil omega-3 fatty acids can act as an effective regulator of inflammation to speed recovery and reduce complications. In fact, a paper recently published in Clinical Nutrition adds to the body of evidence showing that fish oil does not increase bleeding risk, even for patients on anticoagulants, offering further assurance that it is safe to benefit from before and after surgery.In addition to concerns around the time of surgery the authors note:
"The increased consumption of fish oil enriched-products exposes a wide diversity of people, including elderly and those with impaired health to relatively high amounts of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs). There is an ongoing debate around the possible adverse effects of n-3 LC-PUFAs on bleeding risk...This might be particularly relevant considering the specific recommendations to people with a medical history of cardiovascular events or patients in preparation for upper gastrointestinal surgery, who frequently use antithrombotic drugs (anticoagulant (AC) or platelet aggregation inhibitors (PAI) drugs)."
Evaluating the safety of omega-3 fatty acids from fish oil
There is a plausible mechanism by which omega-3 fatty acids might possibly increase bleeding.
"EPA and DHA are incorporated into cell membranes, where they shift the n-3/n-6 ratio of LC-PUFAs, partly replacing the n-6 LCPUFA arachidonic acid (AA) which is the precursor for the synthesis of many eicosanoids, including prostaglandins, thromboxjnes, and leukotrienes. At higher n-3 LC-PUFA concentrations, the competition with AA for cyclooxygenase enzymes leads to a reduction in synthesis of thromboxane A2, a potent promoter of platelet aggregation, and an increase in the formation of thromboxane A3 from EPA, which is a weak platelet aggregation factor...These effects have also raised a concern about the potential effects of high n-3 LC-PUFA intake on blood coagulation in various patient groups."
To evaluate the safety of fish oil omega-3 fatty acids, they evaluated blood coagulation parameters and bleeding-related adverse events for eight clinical studies involving patients with a variety of diseases taking 1.5 g EPA + DHA/day.
EPA and DHA safe at up to 5.4 grams per day
The authors evaluated a total of 1245 randomized subjects with 617 who received at least one intake of EPA + DHA from fish oil and the rest a control product. Those on anti-platelet treatments included acetylsalicylic acid, and vitamin K antagonists (VKA: warfarin, acenocoumarol, fluindione), and a small number on Clopidogrel. Their data establish that at least 5.4 grams per day of omega-3 fatty acids from fish oil is safe even for patients on anti-coagulants.
"This paper addresses the debate about the potential adverse effect on blood coagulation as a consequence of n-3 LC-PUFA [omega-3 long-chain polyunsaturated fatty acids] supplementation. We assessed the impact of DHA and EPA intake from enteral medical nutrition products on coagulation parameters (PT and (a)PTT) and (S)AEs related to clinical bleeding manifestations in various vulnerable patient populations including subjects on concomitant antithrombotic medication."
Furthermore, they were able to include exposure various levels and durations of fish oil in a population that also varied according to age, medical history and medical conditions. The result was, across the board, that supplementation was safe with no increase in bleeding risk.
In expert opinions, the supplementation of EPA and/or DHA is generally considered safe at doses up to 5 g/day or 5.4 g/day in adults, respectively in a healthy population or with anticoagulation treatments. At these doses, no impact on BT [bleeding time] can be expected.
Other studies have shown the same safety
The authors cite a number of other studies performed with subjects on different anticoagulant regimens that document the same absence of bleeding risk.
"This lack of effect of n-3 LC-PUFAs on bleeding is in line with other studies. Watson et al. [retrospectively studied the risk of bleeding in 182 patients with cardiovascular disease receiving aspirin + clopidogrel in addition to high doses of n-3 LC-PUFAs (mean dose: 3 ± 1.25 g/day)...The authors concluded that in their study, the use of high doses of n-3 LC-PUFAs was not associated with an increased risk of bleeding in subjects already receiving the anticoagulant combination of aspirin + clopidogrel. In another study, 551 patients undergoing cardiac surgery (percutaneous transluminal coronary angioplasty) were randomized to receive a daily dietary supplement of ten capsules containing ethyl esters of n-3 LC-PUFAs, providing a total of 4.1 g/day EPA and 2.8 g/day DHA or an equal amount of an ethyl ester of corn oil for 6 months. All patients also received a dose of 325 mg/day of aspirin throughout the 6 months of the study. No significant differences in AEs occurred between the groups, and there were 3% bleeding episodes noted in each group...Similar investigations were conducted in subjects taking warfarin (VKA) concomitantly to high intakes of n-3 LC-PUFAs (up to 3.3 g/day) and no difference in international normalized ratio, a standardized value to express PT time, was observed and no increase in bleeding events was reported. This suggests that subjects could be treated safely with warfarin and fish oil in combination."
No need to stop fish oil before surgery
The evidence strongly confirms that it is not necessary to decline the anti-inflammatory and other benefits of fish oil omega-3 fatty acids prior to surgery, even when combined with other medications that affect bleeding.
"One review from Wachira et al. looked at recent publications investigating the effects of n-3 LC-PUFAs on coagulation parameters and bleeding events in a wide variety of clinical settings. The authors concluded there was no support for discontinuing the use of different doses of n-3 LC-PUFAs as a treatment (doses range: 0.84–10 g EPA + DHA/day) before invasive procedures or when given in combination with other agents that affect bleeding. A Cochrane review of 48 randomized controlled trials (involving around 37,000 subjects) and 41 cohort analyses concluded that 0.4–7 g/day EPA + DHA did not lead to any change in clinical bleeding manifestations in adults with or without risk factors for cardiovascular disease."
The authors emphatically conclude:
"Because we have addressed so many different groups including some taking antithrombotic medications, and with the support of other clinical trials investigating the impact of fish oil on coagulation, we conclude that our findings on the safe use of n-3 LC-PUFAs are applicable to a diverse clinical population including those on concomitant anticoagulant medications as used here."
Moreover...
"This analysis of 8 different clinical studies conducted with n-3 LC-PUFA enriched enteral medical nutrition products addresses adverse event occurrence, particularly bleeding events, and laboratory analysis of coagulation parameters. In the populations considered, from moderately to severely diseased, at home or in ICUs, no sign of increased risk of clinical bleeding has been reported. The doses of n-3 LC-PUFAs used ranged from 1.5 to 10.2 g/day. There were no statistically significant changes from baseline for the coagulation parameters (PT, PTT, aPTT). There was no increase in bleeding-related events, even with the concomitant use of platelet aggregation inhibitors such as aspirin, VKA or clopidogrel. The findings of this review support the safe consumption of n-3 LC-PUFAs, even at high doses, in vulnerable and sensitive populations such as subjects with gastrointestinal cancer or subjects in the ICU, since no increased risk of clinical bleeding manifestations has been identified."
Readers may also be interested in the topic of fatty acid balance addressed in Omega-3 Index for cardiovascular health, inflammation.