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Heart Risks Raised by Omega-6 Excess
Long-lost clinical data affirms that America’s high intake of omega-6-rich vegetable oils raises heart risks
2/21/2013
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By Craig Weatherby

Everyone knows that omega-3s from fish are heart-healthy, yet many Americans still don’t get enough. 

But it’s equally critical to know that excess intake of omega-6 fats from vegetable oils is as dangerous as getting too few omega-3s … maybe more dangerous. 

A fast-growing body of contrary evidence culminated with the publication in 2010 of a cogent, devastating critique of conventional wisdom by scientists from the National Institutes of Health. 

Their close reading of the evidence clearly refuted the key claims made by an American Heart Association (AHA) expert panel in a 2009 paper on omega-6 fatty acids in heart health. (See “Heart Group's Omega-6 Advice Takes a Huge Hit”.) 
Are you omega-imbalanced? 
Good food choices begin with good information. It's very hard to achieve optimal health without knowing the balance of omega-3 and omega-6 fats in your body ... and, as needed, adjusting your diet to optimize that balance. 

As Mehmet Oz, M.D., of Columbia University said, “Maintaining the right balance between omega-3 and omega-6 fats is absolutely vital for your health.” (Click to view the Dr. Oz Show on this topic.) 

Our Vital Omega-3 and 6 HUFA Test™ measures the blood levels of these two families of essential nutrients, which strongly influence genetic “switches”, and hormone-like agents called prostaglandins. 

(HUFA stands for “highly unsaturated fatty acids” … namely, the long-chain omega-3 and omega-6 fatty acids essential to brain, eye, and immune system health.) 

In turn, the gene switches and prostaglandins influenced by omega-3 and omega-6 fatty acids control inflammation and key aspects of brain, cardiovascular, immune, and metabolic health. 


That AHA 2009 paper came in response to fast-growing evidence that it’s dangerous to consume as much omega-6 fat as Americans typically do. (See “America's Sickening Omega Fats Imbalance”.) 

(Most of the omega-6 fats Americans consume come from common vegetable oils (corn, soy, cottonseed, safflower, sunflower, and canola) and the countless foods made with them.) 

Now, a new analysis of Australian clinical data further undermines advice to favor polyunsaturated, omega-6-rich vegetable oils over saturated fats from meats and dairy (Ramsden CE et al. 2013). 

The international team says their findings could have important implications for worldwide dietary advice … and other experts agree. 

New analysis affirms dangers of excess omega-6 intake 
This landmark probe into the heart-risks of diets high in omega-6 fats was made possible by the recovery of missing data from the Sydney Diet Heart Study … a randomized, controlled clinical trial conducted from 1966 to 1973. 

Recently, researchers from the U.S. and Australia analyzed the original trial data, using modern statistical methods to compare death rates from all causes among groups eating different diets. 

(The U.S. members included two NIH fatty acid experts – Joseph Hibbeln, M.D., and Chris Ramsden, M.D. – who helped author the rigorous 2010 rebuttal to the American Heart Association’s paper on omega-6s and heart health.)

The trial involved 458 men aged 30-59 years who had recently had a coronary event, such as a heart attack or an episode of angina. Participants were randomly divided into two groups: 
  • Control group: No specific dietary advice. 
  • Test Group: Reduce saturated animal-food fats to less than 10% of daily calories and increase omega-6 intake (from safflower oil and safflower oil margarine) to 15% of daily calories. 
Both groups underwent regular assessments and completed food diaries for an average of 3.2 years. All non-dietary aspects of the study were identical in both groups. 

The results show that, compared with the control group, the test group members – who ate diets with high omega-6 intakes and low saturated fat intakes – were more likely die from any cause, as well as to die from cardiovascular and coronary heart diseases. 

As they wrote, “In this evaluation of data from the SDHS [Sydney Diet Heart Study], selectively increasing the omega-6 [intake] … increased rates of death from cardiovascular disease, coronary heart disease, and all-cause mortality [death] compared with a control diet rich in SFA [saturated fatty acids] ….” (Ramsden CE et al. 2013) 

And, as the U.S.-Australian team noted, theirs is the first published study to link higher risk of death to the very high omega-6 intake typical of American diets. 

The authors then used the new data to update an earlier meta-analysis (a review of all the evidence). 

That updated meta-analysis showed no evidence of benefit from diets high in omega-6 fats, and suggested that they raise the risk of developing cardiovascular disease

The researchers conclude that recovery of these missing data “has filled a critical gap in the published literature archive” and that these findings “could have important implications for worldwide dietary advice to substitute omega-6 linoleic acid (or polyunsaturated fatty acids in general) for saturated fatty acids.” (Ramsden CE et al. 2013) 

In an accompanying editorial, fatty acid expert Philip Calder, Ph.D., from the University of Southampton says the new analysis of these old data “provides important information about the impact of high intakes of omega-6 fats, in particular [omega-6] linoleic acid [from plant foods], on cardiovascular mortality at a time when there is considerable debate on this question.” (BMJ 2013) 

Calder says the findings argue against the “saturated fat bad, omega-6 good” dogma and suggest that the American Heart Association guidelines on omega-6s may be misguided. 

He added that they also “underscore the need to properly align dietary advice and recommendations with the scientific evidence base.” (BMJ 2013) 

 
Sources 
  • Baum SJ, Kris-Etherton PM, Willett WC, Lichtenstein AH, Rudel LL, Maki KC, Whelan J, Ramsden CE, Block RC. Fatty acids in cardiovascular health and disease: a comprehensive update. J Clin Lipidol. 2012 May-Jun;6(3):216-34. doi: 10.1016/j.jacl.2012.04.077. Epub 2012 Apr 13. Review. 
  • Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. Am J Clin Nutr. 2011 May;93(5):950-62. doi: 10.3945/ajcn.110.006643. Epub 2011 Mar 2. Br J Nutr. 2010 Dec;104(11):1586-600. doi: 10.1017/S0007114510004010. 
  • British Medical Journal (BMJ). Study raises questions about dietary fats and heart disease guidance. Tuesday, February 5, 2013. Accessed at http://www.bmj.com/press-releases/2013/02/04/study-raises-questions-about-dietary-fats-and-heart-disease-guidance 
  • Macintosh BA, Ramsden CE, Faurot KR, Zamora D, Mangan M, Hibbeln JR, Mann JD. Low-n-6 and low-n-6 plus high-n-3 diets for use in clinical research. Br J Nutr. 2013 Jan 18:1-10. [Epub ahead of print] 
  • Ramsden CE, Faurot KR, Carrera-Bastos P, Cordain L, De Lorgeril M, Sperling LS. Dietary fat quality and coronary heart disease prevention: a unified theory based on evolutionary, historical, global, and modern perspectives. Curr Treat Options Cardiovasc Med. 2009 Aug;11(4):289-301. 
  • Ramsden CE, Hibbeln JR, Lands WE. Letter to the Editor re: Linoleic acid and coronary heart disease. Prostaglandins Leukot. Essent. Fatty Acids (2008), by W.S. Harris. Prostaglandins Leukot Essent Fatty Acids. 2009 Jan;80(1):77; author reply 77-8. doi: 10.1016/j.plefa.2008.12.002. Epub 2009 Jan 14. 
  • Ramsden CE, Hibbeln JR, Majchrzak SF, Davis JM. n-6 fatty acid-specific and mixed polyunsaturate dietary interventions have different effects on CHD risk: a meta-analysis of randomised controlled trials. 
  • Ramsden CE, Hibbeln JR, Majchrzak-Hong SF. All PUFAs are not created equal: absence of CHD benefit specific to linoleic acid in randomized controlled trials and prospective observational cohort. World Rev Nutr Diet. 2011;102:30-43. doi: 10.1159/000327789. Epub 2011 Aug 5. 
  • Ramsden CE, Ringel A, Feldstein AE, Taha AY, MacIntosh BA, Hibbeln JR, Majchrzak-Hong SF, Faurot KR, Rapoport SI, Cheon Y, Chung YM, Berk M, Mann JD. Lowering dietary linoleic acid reduces bioactive oxidized linoleic acid metabolites in humans. Prostaglandins Leukot Essent Fatty Acids. 2012 Oct-Nov;87(4-5):135-41. doi: 10.1016/j.plefa.2012.08.004. Epub 2012 Sep 5. 
  • Ramsden CE, Zamora D, Leelarthaepin B, Majchrzak-Hong SF, Faurot KR, Suchindran CM, Ringel A, Davis JM, Hibbeln JR. Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ. 2013 Feb 4;346:e8707. doi: 10.1136/bmj.e8707.
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