Side Effects of Fish Oil Capsules

In the olden days, everybody knew all about fish oil side effects. When cod liver oil taken straight from the bottle was the only form of fish oil supplements, children around the world knew that it tasted nasty and made you burp. Nowadays, however, fish oil side effects are very rare, and only occur in low-grade products.

What Is It About Fish Oil that Causes Fish Oil Side Effects?

Let's face it. Oil without the fish it comes from isn't very tasty. And some fish oil capsules have an after-taste that is decidedly fishy. That is because these products have a relatively low content of the DHA and EPA your body actually needs to get from fish oil capsules.

Some products contain as little as 120 milligrams of DHA and 180 milligrams of EPA in a 1,000 milligram capsule. The other 700 milligrams of fluid in the capsule is a "marine oil product," which is the various kinds of fish fluid the manufacturer did not bother to take out of the oil.

If you take just one of these fish oil capsules, you'll probably be OK. If you take the 10 capsules you would need to get the 3 grams of omega-3 essential fatty acids you need for lowering blood pressure, however, then you might notice some unpleasant side effects.

An intimate acquaintance, or a total stranger, might inform you that you have fish breath. You might have a problem with burping. Or flatulence. Or you might have to run to the bathroom to take care of diarrhea.

Pharmaceutical Grade Fish Oil and Fish Oil Side Effects

The way to get the benefits of fish oil without the side effects is to take pharmaceutical grade fish oil. Ideally, this would be a fish oil that is at least 99 per cent free of any liquids other than the DHA and EPA you need from the fish oil for your health. Unfortunately, in the US, EU, Australia, and New Zealand, there is no standard, legal definition of what "pharmaceutical grade" fish oil has to be.

To make sure your fish oil is pharmaceutical grade, you need to look on the label. If your product provides 650 to 850 milligrams of DHA and EPA together in a single capsule, then it's either pharmaceutical grade or close enough that your digestive tract will be spared any ill effects.

Having more DHA and EPA in each capsule means you take fewer capsules, and your digestive tract does not have to do as much work. There will also be less "filler" that can combine with bile salts in your colon to make need to run to the bathroom.

Beware of Ethyl Esters

Not every product that has a relatively high concentration of DHA and EPA is what your body needs, however. Some companies increase the fatty acid content of their capsules by adding a processed form of DHA or EPA called an "ethyl ester" to the natural DHA and EPA extracted from the fish. Don't buy products that are made with ethyl esters.

The problem with ethyl esters is that your body can't absorb them. Unlike the natural triglyceride form of the essential omega-3 fatty acids in fish oil, ethyl esters need 50 to 300 times more digestive enzymes in the small intestine to be broken down into the smaller molecules the body can use.

Most of the time these enzymes are available, but natural fish oil is absorbed 3 times faster. Fish oil products that are made in Iceland, Norway, and Sweden are always the natural, triglyceride form that is easily assimilated into the bloodstream and transported throughout the body.

Selected References:
  • Carlier H., Bernard A, Caseli A. (1991). Digestion and absorption of polyunsaturated fatty acids. Reprod Nutr Dev; 31: 475-500.
  • Segura R. (1988). Preparation of fatty acid methyl esters by direct transesterification of lipids with aluminum chloride-methanol. J Chromatogr.;441:99-113.
  • Saghir M, Werner J, Laposata M. (1997). Rapid in vivo hydrolysis of fatty acid ethyl esters, toxic nonoxidative ethanol metabolites. Am J Physiol.;273:G184-90.
  • Mogelson S, Pieper SJ, Lange LG. (1984). Thermodynamic bases for fatty acid ethyl ester synthase catalyzed esterification of free fatty acid with ethanol and accumulation of fatty acid ethyl esters. Biochemistry. 1984 Aug 28;23(18):4082-7.
  • Fave G, Coste TC and Armand M. (2004). Physicochemical properties of lipids: New strategies to manage fatty acid bioavailability. Cellular and Molecular BiologyTM 50 (7), 815-831.
  • Lambert MS, Botham KM, Mayes PA. (1997). Modification of the fatty acid composition of dietary oils and fats on incorporation into chylomicrons and chylomicron remnants. Br J Nutr.;76:435-45.
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