The practice of giving cod liver oil began when the smoke-filled skies of nineteenth-century England deprived youngsters of exposure to the sun. Without sun, their bodies couldn't make vitamin D, and they developed rickets. Because cod liver oil contains large amounts of vitamin D, it cured rickets and made a great contribution to public health. Today, however, other constituents of cod liver and other fish oils have become of interest: the omega-3 fatty acids. Subsequent investigation found that the omega-3 fatty acids found in fish oil can lower blood triglyceride levels, thin the blood, and also decrease inflammation in various parts of the body. These effects, as well as others, may explain many of fish oil's apparent benefits.

Typical dosages of fish oil are 3 to 9gm daily, but this is not the upper limit. In one study, participants ingested 60gm daily. Often there is a digestive disturbance that prevents some people from using fish oils. There are preparations which are coated to overcome this difficulty.

The most important omega-3 fatty acids found in fish oil are called EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). In order to match the dosage used in several major studies, one should probably take enough fish oil to supply about 1,800mg of EPA and 900mg of DHA daily. Certain conditions require a predominance of EPA while others require DHA. Since they compete with each other, careful attention must be paid to their ratio in those conditions which are discussed elsewhere.

Some manufacturers add vitamin E to fish oil capsules to keep the oil from becoming rancid. Another method is to remove all the oxygen from the capsule.

Cod liver oil preparations are much easier to take these days than when we were growing up. They come in flavors such as lemon and orange, making them very easy to take. However, buying a bottle of cod liver oil would seem to be much less expensive than taking fish oil capsules. A tablespoon of flavored cod liver oil may have 500mg of EPA and 350 of DHA. There may be 23 servings in a 12 ounce bottle of cod liver oil. Capsules vary in their EPA / DHA content but may average only 1/4 or 1/5th of the amount in a tablespoon of cod liver oil. Keeping this in mind may help determine if one form turns out to be better priced than the other.

For example, if a bottle of cod liver oil is $12.00, then it would take at least 100 plus capsules to provide the same amount of EPA and DHA. If the capsules cost more than $12.00, then the bottle of cod liver oil would be a better buy. You will need to make your own caculations based upon the amount of EPA and DHA in the capsules you are considering. Caution: Some cod liver oils contain high concentrations of vitamin A. When shopping for naturally occurring vitamin A and D, check the label and make sure the ratio of A:D is 10:1 or less. There are many good sources available.

Questions: How does the absorption of EPA and DHA differ between consuming fish oil supplements and just eating fish?

Answer: EPA, and especially DHA, is much better absorbed from fish than fish oil.

This means that we would need as much as nine times less DHA from fish to obtain the same amount of DHA from fish oil. Put another way, we’d need as much as nine times more DHA from fish oil to obtain the same amount of DHA from fish.

However, taking fish oil capsules with a high-fat meal can greatly improve the absorption of EPA and DHA, nearly making it the same as getting your EPA and DHA from a fish meal. This is likely due to the presence of other fats activating the body’s fat absorption mechanisms.

Side effects: The most likely is to be indigestion, especially if you have a problem digesting fats. People have reported fishy burps, and with prolonged use, a fishy odor from their skin. Some experience diarrhea. Most people do not experience intolerable side effects beyond the fishy burps and mild indigestion. Enteric coated preparations may or may not help someone having these side effects. Those who have used both fish oil and krill oil report that while fish oil supplements sometimes leave a fishy aftertaste, krill oil does not.

Anyone who may have any allergy to seafood would be wise to avoid or try these supplements with caution. Those who are on blood thinners are advised not to use fish oil or krill oil before consulting a physician. The only EPA/DHA fatty acid supplements are those made with fish oil, krill oil, or microalgae (phytoplankton).

Krill oil is another very good source of EPA and DHA and is becoming more readily available as a valuable source of these Omega-3 fatty acids. It is also high in protective phospholipids and potent antioxidants, which make it an ideal source of Omega-3 essential fatty acids, which are subject to rancidity. Fish oil and flax are weak in antioxidant content. Further, the phospholipids found in krill oil aid in the absorption of the essential fatty acids which are present. Being harvested from extremely cold waters and being toward the bottom of the food chain, Krill does not contain contaminants like mercury or PCBs that fish or fish oil may. So, fish oil is good, but krill oil is even better, though more expensive.

"The oil extracted from Antarctic krill is far from just another source of omega-3," says Dr. Sampalis. One reason is that the omega 3 fatty acids in krill are in phospholipid (vs. triglyceride in fish) form. Phospholipids are the building blocks of life; the basic constituents of the cell membrane that envelops each cell in your body and brain. Thus, the omega-3s in krill oil can cross the blood-brain barrier and easily penetrate the cells. (Fish oil's omega-3s must be converted by the body in two difficult steps, making the omega-3s about 30% less bioavailable.) "Phospholipids are also a source of choline, which is a highly important molecule that composes the neurotransmitter acerylcholine. This is what makes phospholipids so important for your brain and nervous system," she explains. Dr. Sampalis adds that there are other phospholipid products on the market, but krill oil is the only one whose fatty acid profiles are optimized for the human brain.