AHA Champions Omega-6 PUFAs to Counter Popular Nutrition Advice
January 28, 2009 (Dallas, Texas) — Contrary to advice from some popular diet books, people should not consider reducing their intake of omega-6 fatty acids, found in vegetable oils, in proportion to their intake of omega-3 polyunsaturated fatty acids (PUFAs), found in oily fish, a new statement from the American Heart Association (AHA) is stressing [1].
According to the science advisory released by the AHA this week, people should aim to get 5% to 10% of their daily calories from omega-6 fatty acids, primarily linoleic acid, a proportion they are likely already getting if they follow dietary recommendations from the AHA.
According to Dr Dariush Mozaffarian (Harvard University, Boston, MA) one of the advisory writing group members, the AHA has zeroed in on omega-6s to counter nutritional advice from other sources that has deemphasized the role for plant-based PUFAs.
"Although I think most scientists and clinicians generally recognize evidence demonstrating the benefit of omega-6 fatty acids, there are a minority of scientists who have vocally proposed that omega-6 fatty acids are harmful and advise reducing intake of omega-6," he told heartwire . "The goal of this advisory was to review and clarify the evidence for benefit vs harm."
Lead author for the writing group, Dr William S Harris, explained to heartwire that recommendations to reduce omega-6 intake come from a handful of scientific studies whose findings have been taken up and incorporated into popular nutrition books. One such book, cited in the AHA advisory, is the Omega Rx Zone, by Dr Barry Sears, whose wildly popular, low-glycemic-load "Zone diet" has been championed by movie stars and professional athletes since the early 21st century.
According to Harris, one of the ideas promulgated by diet and nutrition books is the idea of an optimal omega-6:3 ratio, something he says is based on an "misinterpretation of the science." The rationale for reducing linoleic-acid intake comes from research showing that it is metabolized to arachidonic acid, which is involved in the synthesis of proinflammatory molecules. But omega-6 PUFAs also have powerful anti-inflammatory properties that counteract any proinflammatory activity, say the advisory authors. "It's incorrect to view the omega-6 fatty acids as 'proinflammatory,' " Harris spells out in an AHA press release. "Eating less linoleic acid will not lower tissue levels of arachidonic acid because the body tightly regulates the synthesis of [arachidonic acid] from [linoleic acid]," he stated.
"Cardiologists, I think, have had a good feeling about vegetable oils for years and years--things like corn and saffron oil; they've been a good and healthy replacement for saturated fats in the diet since the 1970s, and the AHA has been promoting them for years," Harris told heartwire . "This paper serves as a review, pulling together the many lines of evidence in humans, to say that higher omega-6 intake is associated with better cardiovascular health. . . . We're basically not telling people to start doing something different; we're telling people not to stop eating their omega-6."
But Dr Artemis Simopoulos (Center for Genetics, Nutrition, and Health, Washington, DC), a leading proponent of reducing omega-6 intake, disputes the AHA advisory, arguing to heartwire that US and other Western diets include far too much omega-6 PUFAs, in levels far higher than intake of omega-3s (a ratio of 16:1, she says). "The studies that have been done very clearly show that [eicosapentaenoic acid] EPA and [docosahexaenoic acid] DHA are very potent anti-inflammatory agents, whereas linoleic and arachidonic acids areonly slightly so. And when you have them in high amounts as they exist in Western diets, they interfere with the incorporation and the elongation and saturation going from alpha-linolenic acid to EPA and DHA," she said. "Second, it's important to think in terms of evolution and evolutionary biology. We evolved on a diet that was never, until 150 years ago and in particular the past 50 years, so high in omega-6 fatty acids. This is an artificial way and a general experiment, being done without any scientific evidence."
She says that a ratio of 2:1 or even 1:1 omega-6 to omega-3 fatty acids is better. "Whether you look in terms of evolution, whether you look in terms of genetic variation, high amounts of omega-6 fatty acids are not consistent with health or normal development."
Authors of the AHA statement, however, respectfully disagree. According to Mozaffarian, people should focus on eating a healthy diet. "Focusing on specific ratios is not useful," he said.
In the paper, Harris discloses receiving research grants and being a consultant/advisory board member for Monsanto. Disclosures for other writing group members are listed in the paper.
1.Harris WS, Mozaffarian D, Rimm E, et al. Omega-6 fatty acids and risk for cardiovascular disease. Circulation 2009; DOI: 10.1161/CIRCULATIONAHA.108.191627. Available at: http://circ.ahajournals.org. Abstract
According to the science advisory released by the AHA this week, people should aim to get 5% to 10% of their daily calories from omega-6 fatty acids, primarily linoleic acid, a proportion they are likely already getting if they follow dietary recommendations from the AHA.
According to Dr Dariush Mozaffarian (Harvard University, Boston, MA) one of the advisory writing group members, the AHA has zeroed in on omega-6s to counter nutritional advice from other sources that has deemphasized the role for plant-based PUFAs.
"Although I think most scientists and clinicians generally recognize evidence demonstrating the benefit of omega-6 fatty acids, there are a minority of scientists who have vocally proposed that omega-6 fatty acids are harmful and advise reducing intake of omega-6," he told heartwire . "The goal of this advisory was to review and clarify the evidence for benefit vs harm."
Lead author for the writing group, Dr William S Harris, explained to heartwire that recommendations to reduce omega-6 intake come from a handful of scientific studies whose findings have been taken up and incorporated into popular nutrition books. One such book, cited in the AHA advisory, is the Omega Rx Zone, by Dr Barry Sears, whose wildly popular, low-glycemic-load "Zone diet" has been championed by movie stars and professional athletes since the early 21st century.
According to Harris, one of the ideas promulgated by diet and nutrition books is the idea of an optimal omega-6:3 ratio, something he says is based on an "misinterpretation of the science." The rationale for reducing linoleic-acid intake comes from research showing that it is metabolized to arachidonic acid, which is involved in the synthesis of proinflammatory molecules. But omega-6 PUFAs also have powerful anti-inflammatory properties that counteract any proinflammatory activity, say the advisory authors. "It's incorrect to view the omega-6 fatty acids as 'proinflammatory,' " Harris spells out in an AHA press release. "Eating less linoleic acid will not lower tissue levels of arachidonic acid because the body tightly regulates the synthesis of [arachidonic acid] from [linoleic acid]," he stated.
"Cardiologists, I think, have had a good feeling about vegetable oils for years and years--things like corn and saffron oil; they've been a good and healthy replacement for saturated fats in the diet since the 1970s, and the AHA has been promoting them for years," Harris told heartwire . "This paper serves as a review, pulling together the many lines of evidence in humans, to say that higher omega-6 intake is associated with better cardiovascular health. . . . We're basically not telling people to start doing something different; we're telling people not to stop eating their omega-6."
But Dr Artemis Simopoulos (Center for Genetics, Nutrition, and Health, Washington, DC), a leading proponent of reducing omega-6 intake, disputes the AHA advisory, arguing to heartwire that US and other Western diets include far too much omega-6 PUFAs, in levels far higher than intake of omega-3s (a ratio of 16:1, she says). "The studies that have been done very clearly show that [eicosapentaenoic acid] EPA and [docosahexaenoic acid] DHA are very potent anti-inflammatory agents, whereas linoleic and arachidonic acids areonly slightly so. And when you have them in high amounts as they exist in Western diets, they interfere with the incorporation and the elongation and saturation going from alpha-linolenic acid to EPA and DHA," she said. "Second, it's important to think in terms of evolution and evolutionary biology. We evolved on a diet that was never, until 150 years ago and in particular the past 50 years, so high in omega-6 fatty acids. This is an artificial way and a general experiment, being done without any scientific evidence."
She says that a ratio of 2:1 or even 1:1 omega-6 to omega-3 fatty acids is better. "Whether you look in terms of evolution, whether you look in terms of genetic variation, high amounts of omega-6 fatty acids are not consistent with health or normal development."
Authors of the AHA statement, however, respectfully disagree. According to Mozaffarian, people should focus on eating a healthy diet. "Focusing on specific ratios is not useful," he said.
In the paper, Harris discloses receiving research grants and being a consultant/advisory board member for Monsanto. Disclosures for other writing group members are listed in the paper.
1.Harris WS, Mozaffarian D, Rimm E, et al. Omega-6 fatty acids and risk for cardiovascular disease. Circulation 2009; DOI: 10.1161/CIRCULATIONAHA.108.191627. Available at: http://circ.ahajournals.org. Abstract
posted by vanwash at 10:11 PM
0 Comments:
Post a Comment
<< Home