Results of a recent meta-analysis published in the Annals of Internal Medicine call into question the long-standing advice to replace foods high in saturated fatty acids with foods high in unsaturated fatty acids as a means of preventing cardiovascular disease. This study has been met with a hefty dose of criticism for its methods of analysis on one hand, and with claims that guidelines have been wrong in demonizing saturated fatty acids on the other.
One difficulty in drawing conclusions from this study is that the field is complicated by the diverse nature of which specific compounds get termed omega oils. The omega naming system describes oils that have a high percentage of unsaturated fatty acids. Technically speaking, there are no saturated fats or unsaturated fats — only fats and oils that are rich in saturated or unsaturated fatty acids.
These fatty acids are the carbon chains that determine the characteristics of fats and oils. Three fatty acids make up a triglyceride, the term we give to stored fats and oils such as olive oil, butter and in unwanted places that make themselves known whenever we try on new clothes.
There are three primary classes of unsaturated fatty acids: omega-3, omega-6 and omega-9. They differ by shape, specifically the position of bends in the fatty acid chain as determined by double-bonded carbon atoms. Within each class, fatty acids differ by the length of the chains and number of bends in each chain.
This is how the omega-3 fatty acid in flax seed and greens (18 carbon, three bends) differs from the omega-3 fatty acids in fish oils, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (20 carbons, five bends, and 22 carbons, six bends, respectively). These fatty acids result from modification of the omega-3 fatty acids found in algae.
Two classes of fatty acids are considered essential, omega-3 and omega-6. This is not only because they are precursors to other important compounds, but because animals cannot make them. Animals can make saturated fatty acids that have no bends in the fatty acid chain, and omega-9 fatty acids that have one bend (aka monounsaturated fatty acids).
The prime example of a monounsaturated fatty acid is oleic acid, dominant in olive oil and many other sources. We also can make oleic acid from stearic acid, the saturated fatty acid found in beef. Surprising as it might seem, the body turns a significant portion of beef fat into the dominant fatty acid found in olive oil, avocados, cashews, peanuts and macadamia nuts.
It’s been known for a long time that most unsaturated fatty acids can help lower plasma cholesterol levels, unlike most saturated fatty acids. But the story isn’t that simple, because many factors affect cholesterol levels, especially genetics and obesity.
Studying fatty acids is further complicated by their unique characteristics. Omega-6 fatty acids tend to favor inflammatory pathways, whereas omega-3 fatty acids act in the opposite manner. Omega-3 fatty acids also act as blood thinners, reducing platelet aggregation in much the same manner as aspirin. And DHA has gained recent attention because of its role in brain development.
Over the past several decades, there has been a shift in our dietary ratio of omega-6 to omega-3 fatty acids, from 2-3:1 to 10-20:1. This reflects the increased use of oils from corn, soy and seed oils rich in omega-6 fatty acids and with a shift from grass-fed to grain-fed cattle. Green plants are the ultimate sources of omega-3 fatty acids, and the germ of most grains are rich sources of omega-6.
Another complicating factor in studying the health effects of oils is oxidation: The higher the degree of unsaturation (increased number of double bonds, or “bends,” in the fatty acid chain), the greater the potential for oxidation. This translates to decreased shelf life for products made with unsaturated fatty acids and difficulty in interpreting results from epidemiological studies on fatty acids and health effects.
Both fatty acids and the source are important factors to consider. For processors including healthy omega oils in foods and beverages, a combination of expertise from oil ingredient experts and up-to-date marketing strategies will help best reformulate and position omega-containing products.
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