Dietary Fats (Omega, MUFA, and PUFA): An Overview of What You Need to Know

Dietary fat can be seen as the bane of a healthy lifestyle but the truth is (as I have blogged about several times) that a healthy lifestyle MUST have fats in the diet. And it is CRITICALLY important that one understands what is and what isn't a healthy fat. And not only that what are sources and limitations to important dietary fats. For this reason I felt it appropriate to present an overview as a means to put the public on the correct foundation.

Fats in the diet, as well as fats made in the human body, are of multiple types. When consuming fat in the diet one can obtain free fatty acids, cholesterol, fatty esters of cholesterol, fatty acids in the form of triglycerides (three fatty acids attached to a glycerol backbone), phospholipids (two fatty acids and a phosphate attached to glycerol), and the most complex lipids the glycosphingolipids (carbohydrate and fatty acids attached to a sphingosine backbone). The vast majority of fatty acids consumed in the diet are found in triglycerides.

Fatty acids are linear chains of carbon atoms where all but one carbon atom is bonded only to hydrogen atoms. That one unique carbon has an acidic group attached to it called a carboxylic acid, hence the term fatty acid. Fatty acids found in humans come in many forms divided into two main types: saturated and unsaturated. Within these two broad categories the number of carbon atoms can also be varied. Saturated fatty acids have all their carbon atoms attached to each other by single bonds, whereas, unsaturated fatty acids have at least one pair of carbon atoms bonded together by a carbon-carbon double bond. Several of the biologically and clinically significant unsaturated fatty acids cannot be synthesized from the normal 2-carbon fatty acid precursor, and therefore, humans require two unsaturated fatty acids in their diet. Since these fatty acids must be obtained from the diet they are referred to as essential fatty acids. These essential fatty acids are alpha-linolenic acid (ALA) and linoleic acid.

Saturated fatty acids have gotten a lot of attention in the healthy diet arena as well as in the realm of clinical significance due to that fact that most saturated fats are associated with the development of cardiovascular disease, atherosclerosis, and strokes. However, whereas the consumption of too much of most saturated fatty acids is indeed bad for your health, consumption of the 12-carbon saturated fatty acid, lauric acid is actually quite beneficial. Lauric acid is found in high concentration in coconut and palm kernel oils.

A fatty acid with one double bond is termed a monounsaturated fatty acid, MUFA. A fatty acid with more than one double bond is termed a polyunsaturated fatty acid, PUFA. When a carbon-carbon double bond is present in a fatty acid the hydrogen atoms that are attached to the two carbon atoms can be oriented such that they are on the same side of the double bond or on opposite sides. When the hydrogen atoms are on the same side it is referred to as a cis double bond and the fat structure is "kinked" at these sites. When the hydrogen atoms are on opposite sides it is referred to as a trans double bond and the fat remains linear at these locations. The near "toxic" consequences of trans fatty acids (trans fats) has led to them being banned from manufactured foods in the US and most other industrialized countries. Their "toxicity" is principally due to the fact that the fats remain linear and more of them can stack against one another in cell membranes leading to impaired cellular functioning.

The unsaturated fatty acids are also known by the term omega where the number associated (e.g. omega-3) refers to the position of the first double bond from the omega end of the fatty acid. The omega end is the end farthest from the carboxylic acid group, and hence the last carbon (omega is the last letter of the Greek alphabet). There are numerous types of omega fatty acids with most people being familiar with terms omega-3 and omega-6 fatty acids. Although the omega-3 and omega-6 fatty acids are indeed important in an overall healthy human diet there are others such as the omega-7 MUFA, palmitoleic acid, and the omega-9 MUFA, oleic acid, that are just as important yet they do not get the "press" in the health food and supplement marketplace. The two most important omega-6 PUFA in humans are the essential fatty acid, linoleic acid (an 18 carbon fatty acid with two sites of unsaturation) and arachidonic acid (a 20 carbon fatty acid with four sites of unsaturation). Arachidonic acid is synthesized in humans from linoleic acid. The most important omega-3 fatty PUFA in humans are the essential fatty acid, alpha-linolenic acid, ALA (an 18 carbon fatty acid with three sites of unsaturation), eicosapentaenoic acid, EPA (a 20 carbon fatty acid with five sites of unsaturation), docosapentaenoic acid, DPA (a 22 carbon fatty acid with five sites of unsaturation), and docosahexaenoic acid, DHA (a 22 carbon fatty acid with six sites of unsaturation). DHA is concentrated in the brain of humans and numerous studies have clearly demonstrated the requirements for this PUFA in the development of the fetal and neonatal brain. For breast-fed babies breast milk is a rich source of DHA. For formula fed babies fear not as all formulas have been enriched in DHA for many years. The synthesis of EPA, DPA, and DHA occurs, albeit VERY POORLY, in humans from ALA.

More information on the health benefits of DPA coming in the next blog update!!

Many of the beneficial fatty acids that one should eat come from plant sources such as olive oil, coconut oil, palm kernel oil, borage oil, safflower oil, and flax oil for example. However, the highly beneficial PUFAs, EPA, DPA, and DHA are found almost exclusively in animal byproducts such as cow meat and milk, and chicken eggs for example. This can be problematic for vegetarians and even more so for vegans. Many health food and supplement manufacturers like to claim that vegetarians can get their EPA and DHA by consumption of plant oils (such as flax) that are rich in the essential fatty acid, alpha-linolenic acid (ALA). The problem with these claims is that, although ALA is indeed converted, first to EPA then to DPA and finally to DHA, the rate and efficiency of the conversion is abysmal in humans. In healthy females only around 20% of dietary ALA is converted to EPA and less than 10% is converted to DHA. In healthy males only around 8% of ALA is converted to EPA and there is no conversion to DHA. The rates of EPA and DHA conversion from ALA is reduced by up to 40% when ALA is consumed along with pro-inflammatory omega-6 fatty acids, such as the essential fatty acid linoleic acid and arachidonic acid, as is typical in the Western-style diet. In addition, the consumption of alcohol has been shown to reduce the level of DHA in the liver and the blood. Therefore, direct dietary intake of foods rich in EPA and DHA are of the most benefit clinically. The best dietary sources for EPA and DHA are the oils from cold water fish and Krill. For vegans the sources are limited but the most useful is the blue-green alga, spirulina.

The "big picture" of omega fatty acids is that omega-6 PUFAs are used by the body to make bioactive lipids that promote processes of the immune system and omega-3 PUFAs are used to make bioactive lipids that reduce inflammation. The human body needs a balance between initiating inflammation (e.g. to fight off infections) and bringing the system back to normal, shutting off the inflammatory process. This balance is quite effectively maintained when one consumes a healthy balance of omega-6 and omega-3 PUFA in a range of 2:1. The problem with the American (Westernized) diet is that it is closer to a 40:1 ratio. This results in chronic inflammation in the vasculature contributing to the development of atherosclerosis, heart disease, and strokes.

So what is the TAKE HOME from this overview: Make every effort to get plenty of the PUFAs, EPA and DHA directly in your diet, try to consume more of the MUFAs, palmitoleic acid and oleic acid, and don't forget the beneficial saturated fatty acids such as lauric acid.

Check out the following links to find out more details from my website and prior blog posts:




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