Monday, August 10, 2009

Fish Oil Decreases Inflammatory and Atherogenic Gene Expression

Salmon contains more than 2 grams of omega-3 fatty acids per 100 grams.
Salmon contains more than 2 grams of omega-3 fatty acids per 100 grams. (Photo by Marco Veringa)

While the argument over polyunsaturated fats in general continues, most people consider omega-3 fatty acids to be very beneficial.

The most important omega-3 fatty acids are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). EPA and DHA are often marketed as good for heart health, and indeed there is a lot of evidence to support this claim. ALA, on the other hand, is much less effective, because it first needs to be converted to EPA and DHA by the body to be usable, and only a very small amount gets converted (link).

One of the best and easiest sources of EPA and DHA is fatty fish such as salmon. Another good option is fish oil or fish liver oil, which contain high amounts of EPA and DHA. While several studies have shown beneficial effects from consuming these omega-3 fatty acids, the mechanism of action has not been clear.

To shed light what EPA and DHA actually do in the human body, a new study looked at changes in gene expression after consuming fish oil (link). In healthy subjects, daily ingestion of fish oil changed the gene expression profile to a more anti-inflammatory and antiatherogenic status.

Study method

The study included 111 healthy elderly subjects (at least 65 years old) who did not take fish oil supplements and ate fish no more than four times a week. They were randomized to receive either fish oil with a low or high omega-3 content or sunflower oil.

The high-dose fish oil contained on average 1,093 mg of EPA and 847 mg of DHA, while the low-dose fish oil provided 226 mg of EPA and 176 mg of DHA. The total amounts omega-3 polyunsaturated fatty acids were 1.94 grams and 0.4 grams, respectively. According to the authors, the higher dose is about the same as eating 10 portions of fatty fish weekly, and the lower dose equals 2 portions weekly.


Consuming the high-dose fish oil resulted in gene expression changes of 1040 genes, whereas sunflower oil changed the expression of 298 genes. Out of these, 140 genes were overlapping, meaning that the combination of EPA+DHA uniquely changed 900 genes. Except for one gene, the direction of change was the same in both groups.

Supplementation with a high dose of EPA+DHA for six months significantly decreased the expression of genes involved in the inflammatory pathways, including eicosanoid synthesis, interleukin signaling, and MAP kinase signaling.

Moreover, a similar effect was seen in processes involved in the formation of atherosclerosis. Decreased gene expression was observed in pathways related to cell adhesion, scavenger receptor activity, and adipogenesis. Participants taking the high-dose fish oil also showed a reduction in oxidative stress. You can find the full figures from the paper here and here.

In the low-dose fish oil group, only a small sample of the genes were measured for changes in expression. The results showed that the lower dose of EPA+DHA also resulted in a down-regulation of genes and that this change was somewhere in between those seen from high dose EPA+DHA and sunflower oil.


Supplementing with 1.9 grams of EPA and DHA (~1.1 g EPA and ~0.8 g DHA) daily resulted in favourable changes in gene expression related to inflammation and atherosclerosis in elderly subjects. Among the genes whose expression was decreased were NF-kappa-beta targets, proinflammatory cytokines, and genes involved eicosanoid synthesis.

These results are in agreement with earlier ex vivo studies and support the idea that EPA and DHA, two omega-3 polyunsaturated fatty acids found in fish, are beneficial in reducing inflammation and preventing atherosclerosis.

For more information on inflammation and fish oil, see these posts:

Swine Flu and Avoiding the Cytokine Storm: What to Eat and What Not to Eat?
Examining Possible Causes for Slower Wound Healing
Green Tea Protects from Arthritis in Rats
Intermittent Fasting with a Condensed Eating Window – Part III: Fasting Blood Glucose, Cortisol & Conclusion

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2 kommenttia:

Anonymous August 27, 2009 at 3:28 AM  

Fantastic blog! Have you looked at Coconut oil? What are your thoughts on it? What about the role of antioxidant supplementation on endurance related exercise?

JLL August 27, 2009 at 9:49 AM  


Thank you! I have looked at coconut oil, and I'm pretty convinced it's one of the best oils for eating and cooking. Here's an earlier post on coconut and cholesterol:

Coconut Lowers LDL, VLDL and Triglycerides, Raises HDL

I don't use as much coconut oil as I would like, because it's expensive where I live, but I do use a lot of coconut milk (which contains coconut oil). Here's a post about my latest cholesterol levels.

Here's a review of studies on coenzyme Q10 and exercise. In general, I'm not too impressed. I think there's a potential benefit from antioxidants in performance, but antioxidants can inhibit the hormetic stress response from exercise, which is what makes exercise healthy in the first place.

In fact, I'm not too impressed by antioxidants in general anymore. They've constantly failed to increase lifespan in vivo, probably because they can't enter the mitochondria. Berries, for example, are healthy not because they contain antioxidants, but because the polyphenols have other functions. ORAC scores etc. are therefore pretty useless in vivo.

Thanks for reminding me that I need to reorganize the label tags and add a search function to the blog :)


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