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I have heard that omega-3 fatty acids found in fish are a good way to prevent/reduce cholesterol problems.

My question is how do omega-3 fatty acids do that: what are they doing on a chemical level to produce this effect? And is there any way to maximize this effect through other substances, that may work in concert with them?

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    $\begingroup$ What do you mean when you say "maximize this effect through other substances"? Are you asking if there are co-factors that have no/little effect on their own, but act synergistically with omega-3 fatty acids to reduce cholesterol problems? Or are you simply asking if there are other substances that reduce cholesterol problems? $\endgroup$
    – blep
    Commented Apr 10, 2013 at 17:44
  • $\begingroup$ The former. Is there anything that works with them. $\endgroup$
    – zeel
    Commented Apr 10, 2013 at 18:15
  • $\begingroup$ i dont think they REDUCE cholesterol.. omega-3 fatty acids comprise the essential fatty acids (omega 3 refers to the position of double bond from non carboxyl end).. and BTW cholesterol is also important for the body- it makes up the membranes and also serves as a precursor of vitamin D [sunlight basically converts 7-dehydrocholesterol to vit-d]. excess causes problems $\endgroup$
    – WYSIWYG
    Commented Apr 10, 2013 at 19:16
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    $\begingroup$ the above answer is going in the right direction - unsaturated fatty acids keep the membrane more pliable and cholesterol, which is an inflexible planar molecule tends to make it more rigid I think. $\endgroup$
    – shigeta
    Commented Apr 11, 2013 at 5:09
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    $\begingroup$ @shigeta - Re cholesterol"... cholesterol possesses a slick and rigid structure. ...this would naturally result in a stiffer membrane. Yet, for the past 10 or so years, physicists and biologists have assumed that cholesterol had nearly no effect on the stiffness of membranes ...", sciencedaily.com $\endgroup$
    – Peter Bernhard
    Commented Nov 14, 2021 at 13:25

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I found this research paper (pdf) by D. Roger Illingworth, William S. Harris, and William E. Connor (Journal of the American Heart Association, 1984) that offers some help. Its abstract says:

Diets rich in omega-3 fatty acids derived from fish oils lower the plasma concentrations of low density lipoproteins (LDL) and very low density lipoproteins in humans. The present study was designed to examine the mechanism(s) by which diets enriched in omega-3 fatty acids reduce plasma LDL cholesterol levels in normal subjects.

In the Dicussion part, you will find your answer:

Reductions in the plasma concentrations of LDL in human subjects consuming diets rich in long-chain omega-3 fatty acids from fish oils or omega-6 fatty acids from vegetable oils may be due to a reduction in LDL synthesis, an increased fractional rate of catabolism of LDL, or a combination of both... The present study indicates that the hypocholesterolemic effects of long-chain omega-3 fatty acids present in fish oils results from a reduction in the rate of LDL apoprotein B synthesis and that such oils do not stimulate the fractional rate of catabolism of LDL. These observations imply that the incorporation of omega-3 fatty acids into cellular or lipoprotein lipids does not enhance the rate of receptor-mediated catabolism of LDL as has been observed with omega-6 fatty acids in vitro.

The Effects of Dietary Omega-3 Fatty Acids upon the Fatty Acid Composition of Plasma Phosphollplds and Cholesterol Esters

I could not find a paper on its exact mechanism, so I'd rather say that the process is still not clear. Yet, as the paper suggests, the main effects of omega-3 fatty acids are reducing LDL synthesis and/or increasing fractional rate of catabolism (FRC) of LDL.

A similar article can be found here:

Omega-3 fatty acids have been shown to lower triglycerides, which are a type of fat in the bloodstream. Experts aren't sure of the exact mechanism. Omega-3 fatty acids may also slow down the growth of plaques in the arteries and reduce inflammation throughout the body.

A number of studies going back years have shown the benefits of fatty fish. In an important review of studies, researchers found that getting daily omega-3 fatty acids from fish oil could lower triglyceride levels by 25%-30%. The results were published in The American Journal of Clinical Nutrition in 1997.

BUT, I would also like to point out that the question itself "omega-3 fatty acids found in fish are a good way to prevent/reduce cholesterol problems" seems to be a matter of debate because of articles like this:

New data presented this week provide clues as to why eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)--both components of omega-3 fatty acids--have differential effects on LDL cholesterol.

Presenting the results of the laboratory study here at the National Lipid Association (NLA) 2011 Scientific Sessions, senior investigator Dr Preston Mason (Brigham and Women's Hospital, Boston, MA) said that EPA is an inhibitor of lipid oxidation at normal and elevated cholesterol levels in the presence and absence of DHA, while DHA seems to have no real effect on lipid peroxidation. This trial was one of a number of studies that attempted to address the clinical question as to why LDL-cholesterol levels increase in patients treated with the triglyceride-lowering omega-3 fatty acids. In his trial, Mason et al compared the effects of EPA and DHA--alone or in combination with statins--on lipid peroxidation in polyunsaturated fatty-acid– and cholesterol-enriched vesicles.

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  • $\begingroup$ Re "may be due to a reduction in LDL synthesis," Do you have any more reference on mechanism which you state as not established yet? Are there any "shunts" in liver, i.e. liver packing its "self-made", i.e. unsaturated fatty acids made from glucose, into LDL, in contrast to unsaturated fatty acids that it does not produce? Would you be interested in some other answer elaborating on that point? $\endgroup$
    – Peter Bernhard
    Commented Nov 14, 2021 at 13:37

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