Omega 3 Side Effects: Beyond Fish Burps
Omega 3 side effects tend to kick in with doses higher than 1 g per day. The most common problem that comes up is the "fish burps," as many people who have taken fish oil capsules can tell you. But other side effects include nausea and greasy, loose stools (1). Some of the more serious side effects that can occur at even higher doses are changes in platelet aggregation capacity (2). This article covers the risks of fish oil.
Fish oil has been consumed in clinical trials at levels over 10 grams per day. In the US, 3 g per day is considered generally recognized as safe (GRAS), while the UK allows up to 4 g per day (1,3). In fact, only about 3 g/day can be incorporated into the body (4). The higher end of this spectrum is where omega 3 side effects start to kick in. Fortunately, doses of 1-2 g fish oil, especially when enriched in DHA/EPA provide adequate supplementation. Personally, I take about 1.5 g of DHA/EPA enriched fish oil per day, giving 1 g combined DHA/EPA.
People who are at risk for omega 3 side effects
The more serious omega 3 side effects relate to bleeding issues surrounding the production of the thromboxane clotting factors. In very high dose studies, and also in studies of Greenland Eskimos, thromboxane production is reduced and bleeding time is subsequently increased (5). As a result, patients who are on anticoagulant therapies or have a tendency to haemorrhage should supplement with caution and only under the supervision of a doctor.
Patients with diabetes by definition have less control over their metabolism than healthy people. As a result, numerous benefits can be derived from fish oil supplementation. However, some studies have shownt that fasting and meal-stimulated glucose levels are increased with fish oil supplementation (6). While these results would suggest that diabetics should also supplement with caution, more extensive meta-analysis studies have argued otherwise (7).
The bottom line?
Omega 3 side effects are not that big a deal. For the most part, we are talking about fish burps here. If you are interested in taking larger and larger quantities, then you are exposing yourself to risks of more serious issues, but probably not much worse than loose stools. If you have a serious medical condition, then as always, check with your doctor before begining any kind of supplementation program.
There's an excellent discussion of omega 3 side effects at the LPI website
Free, in-depth article on omega 3 side effects here
1. Mehta, D, ed. British national Formulary. London: British Medical Association and Royal Pharmaceutical Society of Great Britain. 2004.
2. Bilo, HJG, Gans, ROB. "Fish oil: a panacea?" Biomed and Pharmacother. 44 (1990) 169-74.
3. Kris-Etherton, PM, Harris, WS, Appel, LJ. "Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease." Circulation. 106 (2002) 2747-57.
4. Blonk, MC, Bilo, HJ, Nauta, JJ, et al. "Dose-response effects of fish-oil supplementation in healthy volunteers." Am J Clin Nutr. 52 (1990) 120-7.
5. Knapp, HR, Reilly, IA, Alessandrini, P, FitzGerald, GA. "In vivo indexes of platelet and vascular function during fish-oil administration in patients with atherosclerosis." N Engl J Med 314 (1986) 937-42.
6. Friday KE, Childs, MT, Tsunehara, CH, et al. "Elevated plasma glucose and lowered triglyceride levels from omega-3 fatty acid supplementation in type II diabetes." Diabetes Care. 12 (1989) 276-81.
7. Friedberg, CE, Janssen, MJ, Heine, RJ, Grobbee, DE. "Fish oil and glycemic control in diabetes. A meta-analysis." Diabetes Care. 21 (1998) 494-500.