Fat plays an essential role in our diets and health, especially polyunsaturated fatty acids. These include the much talked about omega-3 and omega-6 fatty acids. Lets take a look at these essential polyunsaturated fatty acids (PUFAs), what they are and where to find them.
Understanding the roles of fat, and which fats to choose, can help you and your clients avoid a fear of dietary fat, which is essential for our health and serves several important functions within the body. These include:
- Energy (providing 9 calories per gram of fat, energy storage)
- Protection (surrounding vital organs, protecting them and helping to keep in place)
- Thermoregulation (insulating from environmental temperatures)
- Nutrient transport (regulation and excretion of nutrients in the cells-- carrying vitamins A,D,E and K)
- Stomach emptying regulation (slows stomach’s hydrochloric acid secretion)
- Hormone synthesis (precursor)
- Satiety and palatability (initiate release of cholecystokinin (CCK) which contributes to satiety)
- Cell membrane (structure and function)
As is discussed in the NASM Nutrition Program course: The fat in our food is made up of fatty acids, which are classified into three major groups based on their chemical configurations: saturated, monounsaturated and polyunsaturated.
All fatty acids are made up of a chain of carbon atoms with hydrogen atoms filling in the spaces around each carbon atom. The configuration of these atoms determines the type and nature of the fat and whether it is a solid or liquid at room temperature.
Additionally the stability of fat, which has implications for health and culinary purposes, depends on its configuration. In general, all fats and oils come from animal and plant sources and are made up of a combination of saturated, monounsaturated and polyunsaturated fatty acids. (Marz, 2002)
Polyunsaturated Fatty Acids (PUFA’s)
Polyunsaturated fatty acids are missing several hydrogen atoms and have two or more double bonds. Due to the chemical nature of polyunsaturated fatty acids, they are very loosely packed, remain in a liquid state, and are highly unstable when exposed to heat and light. Therefore, these oils should be packaged in dark glass and stored away from heat (though most are not).
The unstable nature of polyunsaturated fatty acids makes them susceptible to the formation of free radicals, which are highly reactive molecules that can cause inflammation and tissue damage. They have been implicated in a number of diseases. (Marz, 2002)
PUFAs are considered essential fatty acids because they cannot be synthesized within the human body, and therefore must be obtained from the diet.
There are two classifications of essential fatty acids:
- Omega-3 (n−3)
- Omega-6 (n−6)
Omega-3 fatty acids can be further divided into:
- Alpha-linolenic acid (ALA)
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
The body can convert ALA to EPA and DHA, however the conversion rate is generally inadequate to provide sufficiency of EPA and DHA, the implications of this will be discussed later. Because of the conversion of ALA to EPA and DHA, these fatty acids are considered “conditionally essential.”
Sources of omega-3 fatty acids include:
- Cold-water fish like salmon and mackerel (EPA and DHA)
- Grass-fed beef (ALA)
- Flaxseed (ALA)
- Hemp seeds (ALA)
- Walnuts (ALA)
As mentioned above, because the conversion of ALA to EPA and DHA is suboptimal, plant sources of EFAs may not impart the same health benefits as animal sources, which are further down the biochemical pathway where they can influence anti-inflammatory eicosanoids. (Davis, B. C., & Kris-Etherton, P. M. 2003)
Omega-6 fatty acids primarily consist of linoleic acid (LA) which can be converted to gamma-linolenic acid (GLA) and arachidonic acid (AA). GLA can also be found in black current oil and evening primrose oil, and AA can also be consumed directly from meat.
GLA has therapeutic value for inflammatory conditions that affect the skin and joints as well as for attention deficit-hyperactivity disorder (ADHD), chronic fatigue syndrome, depression, diabetic neuropathy, heart disease, high cholesterol, hay fever, and metabolic syndrome. (WebMD)
AA is the precursor to pro-inflammatory prostaglandins. The Standard American Diet (SAD) provides relatively low levels of DHA and EPA and high levels of AA compared with diets from other industrialized nations.
Sources of omega-6 fatty acids include:
- Safflower
- Sunflower
- Soybean*
- Grapeseed
- Corn
- Canola
- Cottonseed oils
(Marz, 2002)
See this blog post on 10 Foods High in Healthy Fats for more options.
*Current research on soybean oil shows that it is obesogenic and diabetogenic. Unfortunately, this oil is ubiquitous in many processed foods. (Deol, P., Evans, 2015)
Some sources say that humans evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids of approximately 1:1. The modern Western diet typically has a ratio of ~15:1. It is generally deficient in omega-3 fatty acids and has excessive amounts of omega-6 fatty acids compared to the ancestral diet, on which genetic patterns were established.
Excessive intake of omega-6 fatty acids and a very high omega-6:omega-3 ratio have been shown to promote the pathogenesis of many ailments, including cancer, cardiovascular disease, inflammatory and autoimmune diseases.
Increased levels of omega-3 fatty acids (a low omega-6:omega-3 ratio) have been shown to exert favorable effects on asthma, certain cancers, cardiovascular disease and inflammation. Following a diet with a lower ratio of omega-6:omega-3 fatty acids is more desirable in reducing the risk of many of the chronic inflammatory diseases that are highly prevalent in Western societies. (Simopoulus, 2002, Chan, 2009)
Practical Eating Tips
- Cook with extra virgin coconut oil, organic (preferably grass-fed) butter, extra virgin olive oil, or avocado oil. Each oil has a different smoke point based on its chemical structure. Be sure not to heat an oil beyond its smoke point as this leads to free radical formation.
- Avoid polyunsaturated vegetable oils: corn, cottonseed, safflower, soybean, and sunflower . These are unstable and pro-inflammatory. If you use canola oil, make sure it’s organic (otherwise it will be genetically modified).
- Avoid deep-fried foods, unless they have been cooked in a good quality oil (extra virgin coconut oil, red palm oil or avocado oil) that has not been reused.
- Avoid anything that is made with hydrogenated or partially hydrogenated oils. This includes shortening and margarine, doughnuts, French fries, onion rings, tempura, and most processed, commercially prepared baked foods such as cakes and pastries, chocolate bars, cookies, crackers, and potato chips.
- Avoid nuts and seeds roasted in oil as these are usually polyunsaturated oils. You’re better off roasting them yourself.
- Eat healthy, concentrated sources of fat from plant foods, including avocado, coconut milk, unsweetened coconut, virgin coconut oil, olives and extra virgin olive oil, raw nuts and raw seeds,.
- If consuming fat from animal sources, choose organic chicken, organic eggs from free-range birds, cold-water fish, wild game and grass-fed butter, red meat (beef, buffalo, and lamb).
Supplementing with Essential Fatty Acids
Fish oil (EPA and DHA) doses vary depending on the goal of supplementation. (Consult with your healthcare provider for your specific needs and recommendations.)
- General health: 250mg of combined EPA and DHA is the minimum dose and can be obtained via fish intake
- Cardiovascular health: 1g daily
- Anti-inflammatory: 6g spread over the course of a day
- Pregnant women: should increase their intake of DHA by at least 200mg a day, as long as there is no risk of elevated mercury levels.
References
Chan EJ, Cho L. What can we expect from omega-3 fatty acids? Cleve Clin J Med. 2009 Apr;76(4):245-51. Review.
Davis, B. C., & Kris-Etherton, P. M. (2003). Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. The American journal of clinical nutrition, 78(3), 640S-646S.
Deol, P., Evans, J. R., Dhahbi, J., Chellappa, K., Han, D. S., Spindler, S., & Sladek, F. M. (2015). Soybean Oil Is More Obesogenic and Diabetogenic than Coconut Oil and Fructose in Mouse: Potential Role for the Liver. PloS one,10(7).
http://examine.com/supplements/fish-oil/
Marz, R. (2002) Medical Nutrition From Marz, 2nd edition. Oregan. Omni-Press.
Simopoulus, AP. The importance of the ratio of omega-6/Omega-3 essential fatty acids. Biomed Pharmcother. 2002 Oct;56(8):365-79.
Siri-Tarino, P, Sun, Q, Hu, F and Krauss, R. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. AJCN. January 13, 2010.
