The Idea of an Optimal Omega-6 to Omega-3 Ratio
Omega-3 and omega-6 fatty acids are polyunsaturated fatty acids that have been linked to a number of health benefits. However, it has also been suggested that having too much of these essential fatty acids, particularly omega-6s which factor heavily in the Western diet, can also cause health problems. The current omega-6 to omega-3 ratio in modern Western diets has been estimated to be somewhere between 14:1 and 25:1, which is way too much skewed towards omega-6s if you compare it with the polyunsaturated fatty acid intake of our ancestors. But what then is the ideal ratio of omega-6 to omega-3 fatty acids?
Unfortunately, researchers have not reached consensus on the ideal ratio. In a paper published in Nutrition et Santé in 2010, Dr. Artemis Simopoulos, a leading international expert on essential fatty acids, proposes an omega-6 to omega-3 ratio of 1:1 to 2:1 as the general target ratio. Another study, published in the Journal of Food Science, suggests that the ratio of omega-6 to omega-3 fatty acids should not exceed 4 to 1 in order to optimize the bioavailability, metabolism, and incorporation of anti-inflammatory omega-3 fatty acids into membrane phospholipids. However, many other authorities suggest that there is no such a thing as the optimal omega-6 to omega-3 ratio, and that the key is to simply increase the omega-3 intake.
In this article, we take a look at some common arguments and recent evidence that support the idea of an optimal omega 6 to 3 ratio. After reading this article, we recommend that you also read the article The Perfect Omega 6 to 3 Ratio - Just a Myth? to hear some arguments and evidence presented by opponents of the theories presented below.
The Paleo Argument
Advocates of the Paleo diet maintain that our bodies are genetically programmed to thrive on a diet similar to that of our hunter-gatherer ancestors who lived during the Paleolithic Age, a time period that began about 2.6 million years ago and ended around 10,000 BP. This view is based on the assumption that the dietary changes that began with the introduction of agriculture and domestication of animals some 10,000 years ago occurred too recently for the human genome to adapt. According to a paper published in the journal Biomedicine & Pharmacotherapy, the ratio of omega-6s to omega-3s was around 1:1 during the Paleolithic Era, while another paper, published in The American Journal of Clinical Nutrition, suggests that the ratio was probably somewhere between 2:1 and 3:1. In any case, it is clear that our current ratio, estimated to be somewhere between 14:1 and 25:1, is a far cry from the omega-6 to omega-3 ratio of our ancestors' diets during the Paleolithic Era.
In fact, even the people who lived just a few hundred years ago had much lower levels of omega-6 fatty acids in their diets. This is because it wasn't until the 20th century that vegetable oils, such as sunflower oil and corn oil, became a significant part of the Western diet. Most vegetable oils have very high omega-6 to omega-3 ratios, and according to USDA data, 66 percent of all the polyunsaturated fatty acids in the American diet came from salad/cooking oils in 2010, so it is easy to see why proponents of a low omega-6 to omega-3 ratio recommend cutting back on vegetable oils.
Omega-3 Fatty Acids Compete with Omega-6 for Enzymatic Metabolism
The view that lowering your omega-6 to omega-3 ratio can impart health benefits is also supported by the idea that omega-6s fatty acids tend to be inflammatory while omega-3 fatty acids are anti-inflammatory. Here's a bit more detailed explanation:
Linoleic acid (LA), which is the primary omega-6 fatty acid, is used in the biosynthesis of arachidonic acid (AA). When oxidized by certain enzymes, arachidonic acid is further transformed into a variety of products, some of which mediate or modulate inflammatory reactions. Alpha-linolenic acid, or ALA, competes with omega-6 fatty acids for enzymatic metabolism, and can antagonize the pro-inflammatory effects of omega-6s. According to a paper published in the Journal of the American College of Nutrition, evidence also suggests that when diets are supplemented with omega-3 fatty acids, pro-inflammatory omega-6 fatty acids are replaced with omega-3 fatty acids in the membranes of practically all cells, including erythrocytes, monocytes, lymphocytes, granulocytes, platelets, endothelial cells, neuronal cells, fibroblasts, retinal cells, hepatic cells and neuroblastoma cells.
Studies That Suggest a Balanced Omega-6 to Omega-3 Ratio Confers Health Benefits
There are also a number of studies that have specifically investigated the effects of low omega-6 to omega-3 ratio, as opposed to only investigating the effects an increased omega-3 intake. While some of these studies suggest that the omega 6 to 3 ratio might not matter after all, several studies suggest that lower omega-6 to omega-3 ratios are associated with health benefits. A study published in the August 2011 issue of the American Journal of Kidney Diseases, for example, found that higher omega-6 to omega-3 ratios were associated with both worsening inflammation, measured by serum C-reactive protein (CRP) levels, and a trend toward higher death risk in hemodialysis patients. In regression models adjusted for case-mix, dietary calorie and fat intake, body mass index and history of hypertension, each one-unit increase in the dietary omega-6 to omega-3 ratio was associated with a 0.55-mg/L increase in serum CRP levels. A higher omega-3 intake alone was associated with a non-significant trend towards a decrease serum CRP. In the fully adjusted model, death HRs for the first, second, third, and fourth quartiles of dietary omega-6 to omega-3 ratio were 0.39, 0.30, 0.67, and 1.00 (reference), respectively.
A study published in the journal Lipids in 2000 found that people with Alzheimer's disease (AD), people with other types of dementia (OD), and patients who were cognitively impaired but not demented (CIND) had lower levels of total polyunsaturated fatty acids and DHA (a type of omega-3 fatty acid), as well higher omega 6 to 3 ratios, than the control subjects with normal cognitive functioning. What's more, omega-6 levels were higher in the AD and CIND groups than in the control group.
An animal study published in the journal Lipids in Health and Disease in 2013 found that a balanced omega-6 to omega-3 ratio was important for healthy reproduction in male rats. In this study, 80 male rats were supplemented with diets containing different omega-6 to omega-3 ratios (0.13, 0.40, 0.85, 1.52 and 2.85) over a three-month period. The researchers discovered that that the sperm density and sperm motility were higher in the 1.52 group than other groups, and that the development of testis and the morphological structure of sperm were better in the 1.52 group than in the other groups. Furthermore, the rats who received their omega-6s and omega-3s in a 1.52 ratio produced more offspring, and the birth weights of the offspring were higher.
Another animal study, published in the March 2011 issue of the Canadian Journal of Physiology and Pharmacology, found that an increase in the dietary intake of omega-3s, at the expense of omega-6s, reduces infarct size in rats. In this study, male rats were divided into three groups, with each group receive omega-6 and omega-3 fatty acids in a different ratio for two weeks (the ratios were 5:1, 1:1 and 1:5). The researchers found that myocardial infarct size was reduced by 32% in groups 1:5 and 1:1 vs. group 5:1.
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