Eating a variety of World's Healthiest Foods is the best strategy for shifting the omega-6:omega-3 ratio of your diet. In a bit, I'm going to give you two concrete examples of simple changes you can make that will help you to do so. But first I want to go over a little background on the ratio itself.
Although researchers have tried to discover the omega-6:omega-3 ratio in the diet of our ancestors, the jury is out on exactly what this ratio was. In all likelihood, the ratio varied from location to location. For example, coastal communities living on the water probably consumed more fish and were likely to get more omega-3 fatty acids in this way. I haven't seen any research that says the ratio of omega-6:omega-3 was historically greater than 4:1, and I've read articles that have suggested 3:1, 2:1, and 1:1.
The controversy over 6:3 ratio has been further extended by the establishment of revised Dietary Reference Intake (DRI) guidelines for omega-6 and omega-3 fats in 2005. These guidelines set a target range of 12-17 grams for linoleic acid (LA), the essential omega-6 fatty acid that forms the starting point for production of all other omega-6 fatty acids. They also set a target range of 1.1-1.6 grams for alpha-linolenic acid (ALA), the essential omega-3 fatty acid that is the starting point for production of all other omega-3 fatty acids. When it comes to these two essential omega-6 and omega-3 fatty acids, the DRI guidelines in effect have set forth a 6:3 ratio of 10:1 or 11:1. In actual practice, according to the most recent data from the U.S. Department of Agriculture (USDA), the average U.S. diet contains approximately 15 grams of LA and 1.5 grams of ALA, for a 6:3 ratio of approximately 10:1 in the case of these two essential fatty acids.
Lower 6:3 ratios appear to offer potential health benefits. For example, a ratio of 6:1 has been associated with decreased risk of certain cardiovascular problems. A ratio of 3:1 or 2:1 has been associated with decreased inflammatory activity in healthy subjects who achieved this ratio by following a Mediterranean-style diet. I am expecting future studies to uncover many more benefits of balanced omega 6:3 ratio in relationship to the Mediterranean diet, since this diet takes an approach to food that should result in a lower 6:3 ratio than currently being experienced in the U.S. diet.
So, how can you go about lowering your 6:3 ratio? One excellent approach is to look for foods in your diet that are relatively high in omega-3s and low in omega-6s .
For an example, let's take almonds. With no omega-3s and about 4-5 grams of omega-6s per cup, your almonds are a member of the nut family with the highest possible 6:3 ratio. Once you've located a food like almonds with a very high 6:3 ratio, look inside of that same food group (in this case nuts) for a food with the most possible omega-3s. In this case, walnuts would make an outstanding choice within the nut group because walnuts have about 2.25 grams of omega-3s per quarter cup and a 6:3 ratio of about 4:1. Just by replacing almonds with walnuts, you could make an important shift in your 6:3 ratio.
Here's one specific example to show you how just making one simple substitution can really make a difference:
Let's start with a situation in which your diet is already pretty healthy, but does not contain a healthy balance of omega-6 and omega-3 fats. Let's say that you are eating about 1,800 calories per day, and that you are getting about 20 grams of omega-6 fat and 2 grams of omega-3s for a ratio of 10:1. Throughout the day, several different foods are probably contributing to this overall ratio. Let's also say that one factor in your overall fat consumption is the vegetable oil you are using on your dinner salad, and in this example, I'll say you are making your dinner salad using 1 tablespoon of sunflower oil. One tablespoon of sunflower oil contains about 4 grams of omega-6s and only .005 grams of omega-3s.
Now let's say that instead of using sunflower oil, you substitute 1 tablespoon of flaxseed oil, which has about 7 grams of omega-3s and about 1.75 grams of omega-6s. By making this swap from sunflower oil to flaxseed oil, you will be lowering your omega-6 intake by about 2.25 grams (to a level of 17.75 grams), while simultaneously increasing your omega-3 intake to about 7 grams. This simple change from sunflower oil to flaxseed oil will be changing your omega-6 to omega-3 ratio from 8:1 to approximate 2.5:1!
The key to establishing a healthy omega 6:3 ratio is to make as many changes of this type as possible, in which you swap foods with very little omega-3 fat for foods like walnuts, salmon, and flaxseeds that provide a significant amount of omega-3s. You can use our website profile of omega-3 fatty acids to get a more complete list of these foods. Rather than avoiding omega-6 fatty acids and the foods that contain them, I encourage you to make simple changes like the ones above to maintain your intake of nourishing omega-6 foods while simultaneously creating a healthy balance between omega-6s and omega-3s.
For more information on this topic, see:
Ambring A, Johansson M, Axelsen M, et al. Mediterranean-inspired diet lowers the ratio of serum phospholipid n-6 to n-3 fatty acids, the number of leukocytes and platelets, and vascular endothelial growth factor in healthy subjects. Am J Clin Nutr 2006 Mar;83(3):575-81.
Bjorkkjaer T, Brun JG, Valen M, et al. Short-term duodenal seal oil administration normalised n-6 to n-3 fatty acid ratio in rectal mucosa and ameliorated bodily pain in patients with inflammatory bowel disease. Lipids Health Dis 2006;5:6.
Griffin MD, Sanders TA, Davies IG, et al. Effects of altering the ratio of dietary n-6 to n-3 fatty acids on insulin sensitivity, lipoprotein size, and postprandial lipemia in men and postmenopausal women aged 45-70 y: the OPTILIP Study. Am J Clin Nutr 2006 Dec;84(6):1290-8.
Hall JA, Picton RA, Skinner MM, et al. The (n-3) fatty acid dose, independent of the (n-6) to (n-3) fatty acid ratio, affects the plasma fatty acid profile of normal dogs. J Nutr 2006 Sep;136(9):2338-44.
Korotkova M, Telemo E, Yamashiro Y, et al. The ratio of n-6 to n-3 fatty acids in maternal diet influences the induction of neonatal immunological tolerance to ovalbumin. Clin Exp Immunol 2004 Aug;137(2):237-44.
Leitzmann MF, Stampfer MJ, Michaud DS, et al. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr 2004 Jul;80(1):204-16.
Sanders TA, Lewis F, Slaughter S, et al. Effect of varying the ratio of n-6 to n-3 fatty acids by increasing the dietary intake of alpha-linolenic acid, eicosapentaenoic and docosahexaenoic acid, or both on fibrinogen and clotting factors VII and XII in persons aged 45-70 y: the OPTILIP study. Am J Clin Nutr 2006 Sep;84(3):513-22.
Weiss LA, Barrett-Connor E, von Muhlen D. Ratio of n-6 to n-3 fatty acids and bone mineral density in older adults: the Rancho Bernardo Study. Am J Clin Nutr 2005 Apr;81(4):934-8.
Wijendran V, Hayes KC. Dietary n-6 and n-3 fatty acid balance and cardiovascular health. Annu Rev Nutr 2004;24:597-615.