The Fat Ratio That No One Talks About
Westernized diets, characterized by high intakes of processed and packaged food, fried foods, refined grains, high-fructose corn syrup, and high-sugar beverages, have become progressively prevalent. These diets consist of a high omega 6 to omega 3 fatty acid ratio, of which has been associated with increased cardiovascular disease (CVD) risk, inflammation, obesity, and type II diabetes mellitus (DMII) (1). This omega 6 to omega 3 ratio has risen so substantially that researchers are now classifying the American diet as omega 3 deficient. Historically, humans evolved eating a 1:1 omega 6 to omega 3 ratio. Today, that ratio is estimated at 20:1.
This evolving dietary change has important health implications because various pro-inflammatory molecules are derived from omega 6 fatty acids, while various anti-inflammatory molecules are derived from omega 3 fatty acids. A surplus of omega 6, or a high omega 6 to omega 3 ratio, favors the formation of blood clotting and inflammation. CVD is, in itself, an inflammatory disease characterized by the perturbation of the blood vessels and the recruitment, adhesion, and penetration of inflammatory cells (amongst other cell types) to the vessel walls.
So, what are omega 6 and omega 3 fatty acids?
Omega 3 and omega 6 fatty acids are polyunsaturated fatty acids (PUFA). They contain two or more double bonds within the fatty acid chain. These PUFA’s are synthesized from the essential fatty acids (EFA) alpha-linolenic acid (ALA) and linoleic acid (LA). These fats are termed essential because they must be obtained from the diet - humans and mammals cannot synthesize them because they lack a key enzyme needed for their production. Think of it this way, omega 6 fatty acids in the diet represent LA and omega 3 fatty acids in the diet represent ALA. LA converts to arachidonic acid and ALA converts to docosahexaenoic acid (DHA) and eicosapentaenoic (EPA).
Interestingly, ALA and LA also compete for the same enzymes; an overabundance of one will disrupt, or antagonize, the production of the other. Thus, under conditions of a Western diet, inflammatory metabolites of LA are formed more readily than those from ALA and have been shown to contribute to the development of several adverse health outcomes including CVD, inflammation, allergies, cancer, and obesity (2). Put simply, this dietary shift can switch the body from a level of inflammation that is beneficial and necessary for various physiological processes to an environment characterized by a harmful level of inflammation and stress.
Scientific data has shown that as the ratio of omega 6 to omega 3 increases in the diet, so does the risk for CVD. In one study published in the New England Journal of Medicine, researchers identified genetic polymorphisms in an enzyme relating to the biosynthesis of leukotrienes, a downstream product of LA (omega 6) (stay with me here). They collected dietary data on the study participants and found that in those with the genetic variant enzyme, omega 6 competed for omega 3, leading to diet-gene interactions that resulted in omega 6 promoted inflammation. This omega 6 promoted inflammation led to increased CVD risk in a subpopulation of individuals with increased CVD. Even further, researchers found that when omega 3 increased in the diet, the damaging CVD promoting effect of the variant genotypes was blunted.
Another recent study revisited this long-studied concept of the omega 6 to omega 3 ratio by reviewing the current literature. The researchers examined the relationship between the omega 6 to omega 3 ratio and the risk and prevalence of obesity. Collectively, this review provided strong evidence that a high omega 6 to omega 3 ratio increases the risk for obesity and an inverse relationship is seen with increased intake of omega 3, or a low omega 6 to omega 3 ratio. In other words, when omega 3 increases within the diet, the risk and prevalence of obesity decreases; and when omega 6 increases within the diet, the risk and prevalence of obesity increases.
Bottom line:
The omega 6 to omega 3 fatty acid ratio has strong associations with our cardiometabolic health. Too much omega 6 in the diet can lead to adverse cardiometabolic outcomes, and a proper balance of omega 6 to omega 3 is shown to lead to improved health outcomes. We can aim to offset the effects of too much omega 6 intake by not only reducing omega 6 intake from Western diet food sources, but also by adding more omega 3 to our diet. This will favor a more beneficial omega 6 to omega 3 ratio.
Aiming for a 4:1, or even a more ambitious goal of a 1:1 ratio, of omega 6 to omega 3 has been shown to be cardio-protective. This reinforces the notion that when individuals focus on balance within the diet, the proper macro- and micronutrient ratios tend to naturally fall into place. These are simple and practical things to consider when making food choices day in and day out. Afterall, what we choose to fuel our bodies with every day has very important health implications both acutely and long-term.
Further reading:
1 Simopoulos, A. P. (2008). The Importance of the Omega-6/Omega-3 Fatty Acid Ratio in Cardiovascular Disease and Other Chronic Diseases. Experimental Biology and Medicine,233(6), 674-688. doi:10.3181/0711-mr-311
2 Simopoulos, A. (2016). An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients,8(3), 128. doi:10.3390/nu8030128
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