Chronic inflammatory diseases: how lipids can help

Lifestyle and food choices have an impact on health. Among other things, unsaturated oils have been recognized for their beneficial effects on cardiovascular diseases. In the supermarket, we find a variety of vegetable oils such as corn, sunflower, canola, peanut, olive and linseed. But, from a health point of view, are those oils equal?

The “Western diet” is known to be rich in calories, sugars, animal proteins and satured fat. Progressively, due to consumer increased interest for healthy food, fats from animal origins have been replaced by vegetable oils. But a fact is important to note. The vegetable oil supply in North America comes mostly from oils rich in omega-6 polyunsaturated fatty acids (Walls et al., 2010). Western diet has omega-6/omega-3 ratios of 15/1 to 16.7/1 which is beyond recommended values (4/1 and lower) (Simopoulos, 2008).Corn and sunflower constitute the major vegetable oils available at the supermarket. These oils have low concentrations of omega-3 fatty acids. Studies have shown that the omega-6/omega-3 ratio in the diet, that is to say the proportion of the two families of fatty acids ingested, is an important variable that can impact on the inflammatory response (Simopoulos, 2008).

Inflammation is an essential and natural process that induces healing of wounds and infections. It provokes redness, swelling and the affected region becomes warm and painful. For some affections however, this state becomes permanent, we talk then about chronic inflammatory diseases, like in rheumatoid arthritis and neurodegenerative diseases (Walls et al., 2010).

Linoleic acid (18:2 ω-6, see footnote for an explanation of the notation) is found in sunflower and corn oils and is the main omega-6 fatty acid that we find in our diet. α-linolenic acid (18:3 ω-3) is the main omega-3 fatty acid and is found in canola and linseed oils. EPA (20:5 ω-3) and DHA (22:6 ω-3) are also part of food omega-3 but are almost only found in marine oils. Next figure shows a simplified scheme of the body metabolic reaction pathways underwent by ingested fatty acids.

The process by which inflammation proceeds is complex, however, for the needs of this text, we will focus on the role of eicosanoids. Eicosanoids are molecules formed from fatty acids. Fatty acids from the omega-6 and the omega-3 families, by the use of the same enzymatic system (E1 to E4 on the scheme), undergo transformations that yield to the formation of active molecules. Eicosanoids formed from fatty acids of the omega-6 family induce in general more inflammation compared to those formed from fatty acids of the omega-3 family. As the two families of fatty acid share the same enzymatic system, there is a competition between fatty acids from the omega-6 and the omega-3 families. This competition is the reason why omega-6/omega-3 ratio can influence the inflammatory response. Many studies support this theory. Effects of lowering omega-6/omega-3 ratios have been measured on the diminution of the incidence of cardiovascular diseases (Kris-Etherton et al., 2002), cancer and inflammatory bowel disease (Walls et al., 2010). Asthma symptoms in children have also been diminished by the decrease of omega-6/omega-3 ratio in the diet (Oddy et al., 2004).

Does food supply in North America allow us to easily reach recommended omega-6/omega-3 ratio in our diet?

Some would want to benefit from the positive effects of omega-3 on their health by taking food supplements. Does taking omega-3 food supplements compensate for the omega-6 supplied by our diet?

Note: Fatty acids are noted this way: (Carbon Nb: Unsaturation Nb ω-fatty acid family)