By Amy Campbell | February 2, 2009 4:51 pm
Talk about timing. Last week (in "Essential Fatty Acids: What You Need to Know [Part 2]"), I reviewed some key sources of omega-6 fatty acids: evening primrose oil, borage oil, and black currant oil. If you recall, these oils (which are typically taken as supplements) are prime sources of gamma-linolenic acid (GLA), one of the "good guy" omega-6’s that seems to have anti-inflammatory properties, helping with such conditions as rheumatoid arthritis, heart disease, diabetic neuropathy, and skin conditions like eczema and psoriasis.
Omega-6 fatty acids have traditionally been given a bad rap, however, and in the first part of this series, I mentioned how nutrition researchers are concerned about our “ratio” of omega-6 to omega-3 fatty acids. We apparently get too much of the former and not enough of the latter. But why, if some omega-6’s are good, are we told to cut back on our intake?
Arachidonic Acid: The Culprit?
The “culprit” may just turn out to be arachidonic acid (AA), one of the omega-6 fatty acids. I have to quote a researcher who wrote about this fatty acid. He describes AA as “a slippery molecule that owes its mobility to its four cis double bonds.” This fluid-like fat helps cell membranes stay flexible. Many of the cells in our bodies contain a high percentage of AA, including platelets, skeletal and cardiac muscle cells, and liver cells.
AA is made from linoleic acid, but it’s also found in some of the food we eat, including eggs, meat, and fish. We need AA to form eicosanoids, hormone-like substances that play a role in inflammation, blood clotting, and blood vessel dilation. Prostaglandins, leukotrienes, and thromboxanes are examples of eicosanoids. Some eicosanoids are helpful in squelching inflammation (which is a good thing), whereas others, such as those made from AA, actually promote inflammation (not a good thing). You might be interested to know that some of the common drugs that we take work to block prostaglandins in the body, including aspirin, nonsteroidal anti-inflammatory drugs, or NSAIDS (such as ibuprofen), and some steroids.
Not all researchers are convinced that AA is harmful, however. One researcher points out that AA is needed for neurological development, and points out that AA is a component of breast milk and therefore needed for normal growth and development. So, it’s likely that some AA is good, but too much isn’t. (Everything in moderation, right?)
Back to the timing, then. Just this past week, a position paper was published in Circulation, which is a journal of the American Heart Association. The committee that composed this “science advisory” consists of well-known nutrition scientists, some who are from Harvard University. Without focusing too much on the details, the basic premise of this paper is to refute the current thinking on omega-6 fatty acids and suggest, instead, that 5% to 10% of daily calories (or about 12 to 22 grams a day) should come from omega-6’s (remember that that includes most of the vegetables oils, such as corn, sunflower, safflower, and soybean oil, as well as nuts and seeds). You can download a PDF of the position paper here.
Why the sudden change of heart? The committee spent two years reviewing previous research and concluded that linoleic acid, an omega-6 fatty acid, may actually help lower LDL cholesterol and, therefore, lower the risk of heart disease. In addition, linoleic acid may help lower blood pressure and insulin resistance, thereby decreasing the risk of Type 2 diabetes. It will be interesting to see what the rest of the medical community has to say, as undoubtedly not everyone will agree with this committee’s conclusions.
So, if all of this leaves you scratching your head about whether you should reach for the bottle of corn oil, or olive oil, or go and eat some salmon, don’t get too distraught. Keep in mind that we need both omega-6 and omega-3 fatty acids, and since we do tend to fall short on the omega-3’s, try to include more of them in your diet (we’ll talk more about sources next week). Also, remember that the overall goal is to replace saturated and trans fat with healthier, unsaturated fats. So save the Crisco for the Thanksgiving pie crust, and choose healthier oils for cooking, baking and for drizzling over salads and bread.
Next week: Omega-3 fatty acids.
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