It’s the moment you’ve all been waiting for… It’s time for the release of the second installment of the 3 part Big “Fat” Blog post! We received lots of great comments last week and are looking forward to hear what you’ve got to say this time around. Now, without further adieu we present – Big “Fat” Blog Post #2. Enjoy!
If you haven’t seen it yet, check out Part 1 here
Question #1 – Answered By Elizabeth Legg, MS, RD
What is the difference between omega-3 (n-3) and omega-6 (n-6) fatty acids?
Last week we discussed the importance of the n-3:n-6 ratio. So what’s happening under the hood when it comes to the balance of these fatty acids? What physiological effects might we see with varying intakes of these essential fatty acids (EFA)? When we study the difference between n-3 and n-6’s and their effects on the body, it’s necessary to look down stream at the signaling molecules they create. These signaling molecules, or eicosanoids, are a major function of these EFAs in the body. Let’s follow one of each down their signaling cascade and see what they might do (but keep in mind this is just a peek at some of the biological effects of these EFAs).
Linoleic acid (LA) is an 18 carbon long n-6 with 2 double bonds (the first double bond located at the sixth carbon counting from the methyl end of the molecule). It’s an essential fat that is easily obtained from the diet (many sources from vegetable oils and nuts to meat and eggs). LA undergoes a series of reactions resulting in the production of metabolites (gamma linolenic acid, dihomo-gamma-linolenic acid, and arachidonic acid). These metabolites are involved in production and/or regulation of other fatty messenger molecules belonging to the eicosanoid family (prostaglandins, leukotrienes, and tromboxanes to name some of the biggies). These chemicals are vital for regulating normal inflammation and homeostatic functions in the body, however when over produced can exacerbate inflammatory diseases or predispose one to systemic inflammation (which is what we see with typical Western diets heavy on the n-6, light on the n-3).
On the other hand, we have the example of Eicosapentaenoic Acid (EPA). A 20 carbon long n-3 with 5 double bonds (the first double bond located at the third carbon counting from the methyl end of the molecule). EPA is obtained in the diet from eating fatty fish (wild salmon, sardines, trout, mackerel, herring, and cod liver are all rich sources). It should be noted that EPA can be derived from alpha-linolenic acid (ALA) from flax and other plant sources; however this conversion rate is quite small making EPA a much more potent precursor for the anti-inflammatory eicosanoids. The metabolic pathway of EPA to the anti-inflammatory eicosanoids is similar to that of the n-6 family. These pathways compete for the same desautrase and elongase enzymes; therefore excessive intake of n-6 will hog the resources and lead to a more inflammatory profile (remember the importance of the n-3:n-6 ratio). We want to stimulate the n-3 pathway as it may decrease inflammation, the risk for chronic disease (like diabetes, cancer, arthritis, obesity, and cardiovascular disease), and improve mental health. Want to know more about why n-3s are so important? Stay tuned for next week with part 3!
Question #2 – Answered By Amy Kubal, MS, RD, LN
Are the n-6’s that are typically found in grain-fed beef somehow different than those found in vegetable oils? If so, is one type of n-6 better or worse than the others?
When comparing the fatty acid profiles of grass-fed and grain-fed beef it’s easy to see why the pasture grazers are the best choice. The ratio of Omega-6 (n-6) to Omega-3 (n-3) fatty acids is around 20:1 in grain-fed animals while in grass-fed it’s about 3:1. The ultimate goal is to achieve a n-6:n:3 ratio of 1:1 this makes the choice a no-brainer! Unfortunately getting a hold of grass-fed meat isn’t always financially or geographically possible. There are 11 different n-6 fatty acids. The most prominent being Linoleic Acid (LA, 18:2), it is the shortest chain polyunsaturated fatty acid (PUFA) and is abundant in vegetable oils.
Grain-fed beef contains a mix of saturated, monounsaturated, and both n-6 and n-3 polyunsaturated fatty acids. While differences between the n-6 PUFA’s found in grass-fed beef, grain-fed beef, and vegetable oils are minimal; the amounts they contain vary greatly (as illustrated in the chart below). In the end the dose is of greatest importance as the goal is to minimize the amount of dietary n-6 PUFA in favor of n-3 PUFA. Which is worse? You be the judge! I’ll give you hint – the worst choice never mooed.
Big FAT Comparison Chart
|Lard (Pork Fat)||5.0||5.8||1.4||0.0|
|Source: USDA National Nutrient Database for Standard Reference. Release 21|
Question #3 – Answered By Stephanie Greunke, RD
Is the saturated fat found in coconut oil the same saturated fat that is contained in meat?
There are two methods of classifying fatty acids. The first is based on the level of saturation (saturated, monounsaturated, and polyunsaturated) and the second is based on the molecular size/length of the carbon chain. Coconut oil is composed of about 90% saturated fat and predominately consists of medium-chain fatty acids. Lauric acid, the major fatty acid found in coconut oil, has a vast number of health benefits including anti-microbial and anti-fungal properties. The majority of saturated fats from meat are long chain fatty acids that are both saturated and unsaturated. They include saturated fats such as palmitic acid, stearic acid, and myristic acid. Saturated fat coming from animal sources contain more monounsaturated and polyunsaturated fats, so the oxidation of the fats and n-6:n-3 ratio becomes more of a concern. Coconut oil is very stable under heat due to its high saturated fat level. Due to the grain-feeding of animals in the U.S., the saturated fat found in animal meat is abnormally high. Try to stick with grass fed meat whenever possible. Also make sure you stick with organic virgin coconut oil and stay away from the refined types!