Added Omega-6 Decreases Effect of Omega-3 Even after watching Dr. Lands's presentation several times and puzzling over this slide, I wasn't sure that I understood its significance. So I finally wrote Dr. Lands: "In your recent NIH talk to U.S. Army doctors, you state (at around 29 minutes) that a lot of articles in the literature say that the short-chain omega-3 is not very effective. But, you add, that was because they were all done in the presence of substantial excesses of omega-6.
"Does that mean that when we have a more balanced omega-3/omega-6 ratio, a much higher proportion of ALA [alpha linolenic acid, the short-chain fatty acid that is our only vegetarian source of omega-3] is converted into the long-chain n-3 fatty acids than the 4 to 8 percent that studies like the 2007 Circulation report, which you co-authored, state? Because of this apparently low conversion, I have been largely discounting the importance of ALA even in a balanced diet like mine. So if I understand you correctly, this is very important."
Dr. Lands replied that, "It is true. The accumulation of n-3 [omega-3] HUFA [highly unsaturated fatty acid] in tissues from dietary n-3 PUFA [polyunsaturated fatty acid] is higher when competition by dietary n-6 [omega-6] PUFA is lower." In other words, until we reduce the amount of omega-6 in our systems, the omega-3 fats that we get from vegetarian sources contribute essentially nothing to balancing the effect of omega-6 fats with which they are in competition.
How, then, do we best cut back on omega-6? And what do we cut back on?
The absolute amount of omega-6 fatty acids in the individual foods that we eat is more important that the ratio of omega-6 to omega-3, even though almost all Americans need to bring the overall ratio way down. In other words, we don't have to stop eating otherwise healthful foods that are high in omega-6.
Let me give an example. One California avocado has 3,323 mg of pro-inflammatory short-chain omega-6 (linoleic acid) and just 199 mg of anti-inflammatory short-chain omega-3 (alpha-linolenic acid). But it also has lots of healthy monounsaturated fats, so avocados remain a staple of my diet.
What we do have to eliminate as much as possible are those foods that are sky-high in omega-6 that don't give us much in return. The first to go need to be the most common cooking oils, none of which has any redeeming value.
Soybean oil is the dominant one, followed by corn oil, canola oil, and cottonseed oil. These four make up 96 percent of all the vegetable oil sold in this country, according to Evelyn Tribole in her book The Ultimate Omega-3 Diet (McGraw Hill, 2007, pp. 28-29). In addition to cooking with them, manufacturers use them to make margarine, shortening, and salad dressings.
But just one tablespoon of soybean oil has 6,161 mg of short-chain omega-6. That amount of corn oil is even higher in short-chain omega-6 with 7,888 mg. By comparison, canola oil has considerably less, 2,842 mg -- but some experts, including Dr. Mary Enig, are concerned enough about canola oil to call it "The Great Con-ola" and "a poisonous substance, an industrial oil that does not belong in the body." Dr. Enig is vice president of the Weston A. Price Foundation and the author of Know Your Fats: The Complete Primer for Understanding the Nutrition of Fats, Oils, and Cholesterol, (Bethesda Press, 2000). The fourth big one, cottonseed oil, is almost as high as corn oil with 7,004 mg.
We have others that we can use for cooking. For example, olive oil has many redeeming values. And it has only 356 mg of short-chain omega-6 per tablespoon. Coconut oil is even better with just 81 mg. Macadamia oil is likely to have even less, but we have no official measurements by the U.S. government, and this oil is expensive.
The gold standard for finding nutrition data for thousands of foods is the U.S. Department of Agriculture's National Nutrient Database. It's online at http://www.nal.usda.gov/fnic/foodcomp/search/
But when we use the USDA's tables, we can check only one food at a time. The USDA also uses the technical terms for the many types of omega-3 and omega-6 fats. When I use those tables, I still have to use a cheat sheet:
18:2 n-6 is linoleic acid (the short-chain omega-6)
18:3 n-3 is alpha-linolenic acid (the short-chain omega-3)
20:4 n-6 is arachidonic acid (the long-chain omega-6)
20:5 n-3 is EPA (eicosapentaenoic acid, a long-chain omega-3)
22:5 n-3 (DPA) (docosapentaenoic acid, a long-chain omega-3)
22:6 n-3 is DHA (docosahexaenoic acid,a long-chain omega-3)
But a free software program that Dr. Lands developed for the National Institutes of Health makes it easier for us to choose foods higher in omega-3 and lower in omega-6. It runs on either a PC or a Mac.
This program is KIM-2 (Keep in Managed, version 2), and it shows both short-chain and long-chain omega-3 and omega-6 content of more than 9,000 food servings. This is the same data that the U.S. Department of Agriculture's National Nutrient Database has, except that the USDA presents its data in grams and KIM-2 presents them in milligrams. KIM-2 is much easier to use than the USDA's tables once you download it at http://efaeducation.nih.gov/sig/kim.html and get the hang of it.
Still, KIM-2 can be frustrating, because its main menu is not intuitive. This program can do a lot, but I use it simply to find the omega-3 and omega-6 content of foods. To do that, from the main menu I go to "Recipes" button and from there click on "New choice," which brings up the entire list of foods. From there I can scroll through the list, but I usually click on the "Find a specific food" button.
I continue to be amazed at what I find when searching through the KIM-2 database! For example, let's consider tree nuts like walnuts and almonds and ground nuts like peanuts.
Walnuts have a positive reputation as being high in omega-3 fats. For example, a recent email newsletter from Dr. Andrew Weil says this: "A mainstay of Dr. Weil's nutrition recommendations, walnuts are an excellent vegetarian source of omega-3 fatty acids, protective fats that promote cardiovascular health, cognitive function, and anti-inflammatory activity."
But the most common species of walnuts, often called the English walnut, has 45,712 mg of omega-6 in each cup of the chopped pieces and 10,986 mg of omega-3 (the other main type, black walnuts, has almost as much omega-6). This is indeed one of the highest levels of omega-3 of any nut, but the pro-inflammatory effect of its omega-6 content far outweighs that.
Learning about the omega-6 level in the ubiquitous peanut -- whether shelled, made into peanut butter, or into peanut oil -- was a great disappointment to Dr. Lands, he says. For example, one cup of raw Valencia peanuts has 21,431 mg of omega-6.
Among the tree nuts, the otherwise wonderful almond has 17,344 mg of omega-6 in each cup. One cup of raw macadamias has 1,737 mg, making it the best of the nuts in terms of omega-6, although three little-known seeds actually have more omega-3 than omega-6 (watch for a forthcoming article here). My conclusion is that the easiest way to cut back on our omega-6 intake is to focus on those foods that we eat a lot and also have a lot of omega-6, even if they also have a decent amount of omega-3. For most of us this means avoiding the four most common cooking oils as well as most nuts and seeds.