Omega-3s

You may have heard the term omega-3 fatty acid before, and at best, you knew it was something related to fish oil supplementation, and at worst, you thought it was some science chemical you have to avoid at all costs. In this article, we will learn everything there is to know about omega-3 fatty acids, from what they are, to their benefits, to the types, and more.

What are Omega-3 fatty acids?

Let us break this down from outside in.

Fat is a nutrient that the body needs to live. Now, the fat nutrient is broken up into a few different types from unsaturated, saturated, and to a lesser extent, trans fats [2]. Within each type of fat, there are subcategories of that type of fat; in the case of omega-3 fatty acids, we are discussing unsaturated fat [3]. These fat types are distinguished by their chemical structures, and the same is true of their subgroups. The subgroups of unsaturated fat do not violate the chemical structure differences between fats, so they are still unsaturated fat, but they still vary slightly. Well, unsaturated fats are further divided into monounsaturdated and polyunsaturated fats – the only difference is their degree of unsaturation (mono = 1, poly = more than 1); both are generally recognized as “good” fats in a vacuum (no, we will not cover what “unsaturation” has to do with health, this needs a separate article – sorry)[2].

Okay, now that lesson is taken care of, how do omega-3 fatty acids fit into all this?

Omega-3 fatty acids are polyunsaturated fats under the umbrella of unsaturated fat [1]. Not only that, although the body can synthesize most types of fat (endogenously), it cannot synthesize polyunsaturated fats and must be consumed (exogenously), hence the name “essential fat” when discussing omega-3 fatty acids [2].

 

Types of Omega-3s

A further investigation of omega-3s reveals that there are 5 types of omega-3s that serve different functions. The first, and most well-known, is a-linolenic acid (ALA), the second being eicosapentaenoic acid (EPA), the third being docosahexaenoic acid (DHA), the fourth being docosapentaenoic acid (DPA), and the fifth being stearidonic acid (SDA). Their individual functions are discussed later.

The Biochemistry

Because this is a kick ass article and we are striving for the fullest education, we will delve a bit into the chemistry to understand the structure of significance of omega-3s. The name “omega” comes from the term “end” and is based off the methyl group attached at the end of the fatty acid chain [4]. Meanwhile, the “3” in omega-3 is the unsaturation by indicating the location of the first double bond between carbon atoms of the fatty acid molecules [4]. As for the double bond, unsaturation, it plays a role in determining how the body metabolizes this fatty acid, be it saturated without any double bonds, monounsaturated with one double bond, or polyunsaturated with multiple double bonds – each situation brings about tiny changes in the metabolism of the fatty acid that have an impact on overall health (discussed in the next section)[5][6].
 

As illustrated here among all five of the omega-3s, counting from the methyl group (CH3), the first double bond begins on the third carbon.

Function of Omega-3 fatty acids?

As a whole, all four fatty acids discussed in this section have certain universal roles from supplying energy, forming cell membranes, and being imperative contributors to certain metabolic functions [8].

Eicosapetnaenoic acid (EPA), Docosahexaenoic acid (DHA) & Docosapentaenoic acid (DPA)

As previously mentioned, there are four types of omega-3 fatty acids. We are covering these three together, because they are so similar, there are few distinctions between the three and what distinctions exist come from the amount of impact one has over the other on a particular body mechanism.

Eicosapetnaenoic acid (EPA) & docosahexaenoic acid (DHA) both have a profound effect in terms of reducing chronic inflammation which not only impacts arthritis inflammation, but cardiovascular disease [7][8]. Eicosapetnaenoic acid seems to have the most profound impact on reducing proinflammatory pathways while increasing anti-inflammatory pathways, even over docosahexaenoic acid, although both still aid in reducing overall inflammation [7]. These effects also include positive impact on atherogenic disease, such as heart disease, by slowing arteriosclerosis (hardening of arteries), atherosclerosis (build of plaque in arteries), decreasing blood pressure, decreasing blood triglyceride levels, and increasing high density lipoprotein cholesterol levels (HDL – healthy cholesterol)[7][8][9]. Along with these benefits, there is some evidence that indicates these omega-3s can also act similarly to antioxidants in reducing cancer risk, as well as slowing certain cancer progression [7]. Finally, among more proven benefits, there is association with these omega-3s intake having positive impact on reducing risk of dementia, yet little to no benefit if dementia has already set in; in the scope of dementia benefit, docosahexaenoic acid seems to have the most impact, even over its compatriot fatty acid [8][9]. Other effects have not been adequately substantiated to merit mention.

Finally, docosapentaenoic acid (DPA) is far less spoken about, because it is considered an intermediate between eicosapetnaenoic acid and docosahexaenoic acid, and is rarely seen in a pure form (discussed further in the ALA section) [10]. One noted benefit of docosapentaenoic acid is its 10 fold increased ability to help in wound healing over the other molecules [10]. Otherwise, most of the proven health effects of the other two molecules is also seen in docosapentaenoic acid [10].

 

Alpha-linolenic acid (ALA) & Stearidonic acid (SDA)

While there are few differences between a-linolenic acid (ALA) and the other three omega 3 fatty acids (EPA, DHA, DPA), there are still some interesting aspects to this particular fatty acid. ALA seems to usually be metabolized by the body for energy, but that may be due to the overabundance of the molecule in the western nutrition standing at 1.4g ingested per day compared to just 7% and 14% of that number for EPA and DHA, respectively [3]. Another likely reason is the fact that a-linolenic acid can be converted, endogenously, to both eicosapetnaenoic acid and docosahexaenoic acid [3][11]. However, this conversion is tiny in comparison to total need (<4% ALA is converted) and likely cannot support optimal amounts of either DHA or EPA [3][11].

Conversion from ALA to DHA is, by far, the most inefficient; ALA is converted to EPA at a .2% efficiency, .13% from EPA to DPA (the intermediate), and only .05% from DPA to DHA, leading to an incredibly small amount of actual ALA conversion to DHA [11]. It should be noted that there are sex differences in efficiency of ALA conversion to other omega-3 fatty acids, as well. Women tend to synthesize DHA 4 times faster than men, and this is thought to be because of interaction with estrogen, as well as men oxidizing (using) more fatty acids in energy metabolism [11].

So, a-linolenic acid seems to serve two purposes; one, to energy, and the second, to health through the interconversion of other omega 3 fatty acids – the first reason being favored in both sexes, but more so in males [3].

Secondly, just like docosapentaenoic acid (DPA), another source called stearidonic acid (SDA) acts as an intermediate in the conversion of ALA to EPA and DHA [15]. However, because the ingestion of SDA bypasses a rate limiting step between ALA to EPA and DHA, it is faster at being used for the synthesis of EPA and DHA [15]. That said, however, the reason it is still inferior is because there are few sources of SDA and what SDA is in the body is majority from the intermediate conversion of ALA to EPA and DHA [16]. Not only that, although SDA does seem to provide better endogenous synthesis of EPA, it seems to equally fall short in the synthesis of DHA beyond any significant levels [16].

So, theoretically, if a person had a choice between SDA and ALA, they would choose SDA, but since ALA is common in our diet and SDA is rather rare unless one looks for specific SDA rich foods, it offers little to no noticeable advantage.

 

Sources of Omega-3s?

First off, the body cannot synthesize omega-3 fatty acids on its own like it can with other fats [3]. So, omega-3s are considered an “essential” fat. However, the body, once supplied with one omega-3, can convert, albeit small amounts, to other forms of omega-3s [3].

Now, outside sources like fatty fish (salmon, trout, tuna, mackerel, etc.) do supply EPA and DHA [3][9][14]. Flax seed, vegetable oil, and walnuts offer good sources of ALA and some vegetable oils are SDA fortified if you are stubborn and want to convince yourself of that minute benefit in a diet saturated with ALA [3][9][16]. All omega-3s are macronutrients of fat, and therefore, they have a high bioavailability with absorption of over 90% [11]. The only concern with fish sources of omega-3s are the possible toxicities with metals that are passed on with predatory fish, hence the restriction to eating fish 2 times a week [9].

If fish is not in the cards for you, fish oil supplements also offer all the benefits (depending on the reliability of the company) that food sources offer. Another source, for those unable to take fish oil, is krill oil as that source offers the same EPA and DHA omega-3s, yet has an added advantage of being absorbed at a quicker rate, needing less of the supplement, as well as potential further benefits that need further investigation [13].
 

Dosage?

The dosage for this has not exactly been pinpointed and is also dependent on the person and what condition that person is trying to prevent. The American Heart Association recommends no more than 7 oz of fish (although other cultures eat far more), and up to 3 grams of omega-3s, but offers a good number to shoot for at 1 gram of EPA and DHA (500mg of each) as ALA is consumed readily in most diets, already [12]. As always, consult your physician before making any changes.
 

SUMMARY

Alright, now that you’ve ignored everything written above, let us get you squared away with the basics. Omega-3 fatty acids are essential fats that must be consumed in one’s diet for basic life functioning like supplying energy, synthesizing cell membrane layers, among other metabolic processes. Considering Omega-3 fatty acids are polyunsaturated fats, they have a series of health benefits from decreasing blood triglyceride levels, decreasing systemic inflammation due to arthritis and hypertension, increasing good cholesterol (HDL), among other such benefits; however, to see these benefits, one should focus on consuming docosahexaenoic acid (DHA) and eicosapetnaenoic acid (EPA) in the right doses. Sources of both can be found in fatty fish like salmon, trout, among others. If fish is not an option, then fish oil and krill supplements can offer a good alternative. In terms of dosage, it is recommended a person consume at least 500mg of each DHA and EPA, which one would receive from 7 oz of fatty fish, or a supplement. One can also go up to 3 grams of fish oil for possible added benefit. Finally, although there is at least one more omega-3 fatty acid in alpha-linolenic acid (ALA), this omega-3 is consumed readily in the western diet and likely not something to worry over.
 

Writer: Nicolas Verhoeven
This is educational material only and not meant to be prescripton, consult your physician before making any changes.

                                                                                                           Citations

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[2] The truth about fats: the good, the bad, and the in-between - Harvard Health. (n.d.). Retrieved from http://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good

[3] Omega-3 Fatty Acids: An Essential Contribution – The Nutrition Source – Harvard T.H. Chan School of Public Health. (n.d.). Retrieved from http://www.hsph.harvard.edu/nutritionsource/omega-3-fats/

[4] Essential Fatty Acids | Linus Pauling Institute | Oregon State University. (n.d.). Retrieved from http://lpi.oregonstate.edu/mic/other-nutrients/essential-fatty-acids#metabolism-bioavailability

[5] Fat Oils in Human Nutrition [Chapter 3 : Aspects of fat digestion and metabolism]. (n.d.). Retrieved from http://www.fao.org/docrep/v4700e/V4700E08.htm#Oxidation of fatty acids

[6] Fernandez, M. L. (2005). Mechanisms by which Dietary Fatty Acids Modulate Plasma Lipids.Journal of Nutrition, 135(9), 2075-2078. Retrieved from http://jn.nutrition.org/content/135/9/2075.full

[7] Siriwardhana, N. (2012). Health benefits of n-3 polyunsaturated fatty acids: eicosapentaenoic acid and docosahexaenoic acid. Advanced Food Nutrition Resources, 65, 211-222. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22361189

[8] Swanson, D., Block, R., & Mousa, S. A. (2012). Omega-3 Fatty Acids EPA and DHA: Health Benefits Throughout Life. Advances in Nutrition: An International Review Journal,3(1), 1-7. Retrieved from http://advances.nutrition.org/content/3/1/1.full

[9] Omega-3 fatty acids | University of Maryland Medical Center. (n.d.). Retrieved from http://umm.edu/health/medical/altmed/supplement/omega3-fatty-acids

[10] Kaur, G., Cameron-Smith, D., Garg, M., & Sinclair, A. J. (2011). Docosapentaenoic acid (22:5n-3): A review of its biological effects. Progress in Lipid Research, 50(1), 28-34. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/20655949

[11] Kaur, G., Cameron-Smith, D., Garg, M., & Sinclair, A. J. (2011). Docosapentaenoic acid (22:5n-3): A review of its biological effects. Progress in Lipid Research, 50(1), 28-34. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/20655949

[12] Kris-Etherton, P. M. (2003). Omega-3 Fatty Acids and Cardiovascular Disease. Arteriosclerosis, Thrombosis, and Vascular Biology, 23, 151-152. Retrieved from http://atvb.ahajournals.org/content/23/2/151.full

[13] Krill Oil - Scientific Review on Usage, Dosage, Side Effects | Examine.com. (n.d.). Retrieved from https://examine.com/supplements/krill-oil/

[14] Fish and shellfish | nidirect. (n.d.). Retrieved from https://www.nidirect.gov.uk/articles/fish-and-shellfish-0

[15] Walker, C. G., Jebb, S. A., & Calder, P. C. (2013). Stearidonic acid as a supplemental source of ω-3 polyunsaturated fatty acids to enhance status for improved human health. Nutrition,29(2), 363-369. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/23102888

[16] Michael, J. Metabolism of stearidonic acid in human subjects: comparison with the metabolism of other n−3 fatty acids. (n.d.). American Journal of Clinical Nutrition, 77(5), 1140-1145. Retrieved from http://ajcn.nutrition.org/content/77/5/1140.full



 

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