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  1. Dean Pomerleau

    Omega-6 PUFA the Healthiest Fat?

    All, This new study [1] published today in JAMA (popular press account) seems to suggest Omega-6 PUFA is the type of fat associated with the lowest all-cause mortality. If followed the 80K women and 40K men in the Nurses/Health Professionals Studies checking their dietary intake of fats through food frequency questionnaires every couple years. During the followup period of 1980-2012, 33K of them died. Interestingly, being in the quintile that ate the most fat and the least carbs was associated with a 16% reduction in total mortality compared with the other extreme. Just goes to show how crappy the carbs are that the average American eats... Regarding the association of specific fats and mortality, here was the ordering of most-healthy to least-healthy: Omega-6 PUFA > MUFA > Omega-3 PUFA > Saturated Fat > Trans-fat. Here are the mortality hazard ratios (95% CI) associated with being in the top (vs. bottom) quintile for consumption of each fat type, after controlling for "known & suspected risk factors": ω-6 PUFA 0.81 (0.78-0.84) MUFA 0.89 (0.84-0.94) ω-3 PUFA 0.96 (0.93-1.00) Saturated 1.08 (1.03-1.14) Trans-fat 1.13 (1.07-1.18) I don't have the full text yet, so I haven't looked at the details, but it is interesting to see that omega-6 PUFA came out on top as the healthiest fat to consume. This seem to contradict the conventional (folk?) wisdom that Omega-6 PUFA is pro-inflammatory and so we shouldn't eat very much of it, at least without balancing it with sufficient Omega-3 fats (e.g. in a 3:1 ratio). Some interesting quotes from the popular press interview with one of the authors: f people replaced a mere 5% of their calorie intake from "bad" fats with polyunsaturated fats, they could reduce their risk of death by 27%. If those calories came from monounsaturated fats, the risk of mortality dropped by 13%. One reason MUFA may not have done better is the fact that a large fraction of the MUFA in the average American diet comes from animal products, which contain saturated fat along with other unhealthy components, which the researchers couldn't entirely control for: "A large proportion of food sources of monounsaturated fat in the typical American diet are animal-sourced, such as dairy and red meats," Hu said, pointing out that those are also major sources of saturated fats. "Therefore, current analysis may not be able to completely distinguish the benefits of monounsaturated fat from the effects of food source and saturated fats." The Omega-6 PUFA that was protective was, not surprisingly linoleic acid: One polyunsaturated fat, an omega-6 fatty acid called linoleic acid, was shown in the Harvard study to be especially protective against death by cancer and coronary artery disease, Hu said. Prior studies showed linoleic acid to reduce total and bad cholesterol, and to be associated with better blood pressure and insulin sensitivity. Though some studies have connected too much omega-6 with inflammation in the body, others find no such link. Linoleic acid is found in sunflower, soybean and safflower oils, as well as nuts and seeds. Walnuts, Brazil nuts and peanuts are excellent sources, as are safflower, pumpkin and squash seeds. Omega-3 Alpha-linolenic acid (e.g. from flax seeds and walnuts) wasn't protective against all-cause mortality, but does appear to be healthy for the brain, as other studies have found: Another key polyunsaturated fat, the omega-3 fatty acid called alpha-linolenic, was not associated with "all-cause mortality," Hu said, but "interestingly, we found that alpha-linolenic acid was protective against death due to neurodegenerative disease." I'd be really interested to hear Michael's take on this one, particularly the Omega-6 vs. Omega-3 finding - even if it's just an off-the-cuff remark. As Sthira mentioned yesterday in the olive oil thread, a little of Michael's insight is better than an in-depth report from him that he never has time to finish to his own satisfaction... --Dean ----------- [1] JAMA Intern Med. Published online July 05, 2016. doi:10.1001/jamainternmed.2016.2417 Association of Specific Dietary Fats With Total and Cause-Specific Mortality Dong D. Wang, MD, MSc1,3; Yanping Li, PhD1; Stephanie E. Chiuve, ScD1,2; Meir J. Stampfer, MD, DrPH1,2,3,4; JoAnn E. Manson, MD, DrPH2,3,4; Eric B. Rimm, ScD1,3,4; Walter C. Willett, MD, DrPH1,3,4; Frank B. Hu, MD, PhD1,3,4 ABSTRACT Importance Previous studies have shown distinct associations between specific dietary fat and cardiovascular disease. However, evidence on specific dietary fat and mortality remains limited and inconsistent. Objective To examine the associations of specific dietary fats with total and cause-specific mortality in 2 large ongoing cohort studies. Design, Setting, and Participants This cohort study investigated 83 349 women from the Nurses’ Health Study (July 1, 1980, to June 30, 2012) and 42 884 men from the Health Professionals Follow-up Study (February 1, 1986, to January 31, 2012) who were free of cardiovascular disease, cancer, and types 1 and 2 diabetes at baseline. Dietary fat intake was assessed at baseline and updated every 2 to 4 years. Information on mortality was obtained from systematic searches of the vital records of states and the National Death Index, supplemented by reports from family members or postal authorities. Data were analyzed from September 18, 2014, to March 27, 2016. Main Outcomes and Measures Total and cause-specific mortality. Results During 3 439 954 person-years of follow-up, 33 304 deaths were documented. After adjustment for known and suspected risk factors, dietary total fat compared with total carbohydrates was inversely associated with total mortality (hazard ratio (HR) comparing extreme quintiles, 0.84; 95% CI, 0.81-0.88; P < .001 for trend). The HRs of total mortality comparing extreme quintiles of specific dietary fats were 1.08 (95% CI, 1.03-1.14) for saturated fat, 0.81 (95% CI, 0.78-0.84) for polyunsaturated fatty acid (PUFA), 0.89 (95% CI, 0.84-0.94) for monounsaturated fatty acid (MUFA), and 1.13 (95% CI, 1.07-1.18) for trans-fat (P < .001 for trend for all). Replacing 5% of energy from saturated fats with equivalent energy from PUFA and MUFA was associated with estimated reductions in total mortality of 27% (HR, 0.73; 95% CI, 0.70-0.77) and 13% (HR, 0.87; 95% CI, 0.82-0.93), respectively. The HR for total mortality comparing extreme quintiles of ω-6 PUFA intake was 0.85 (95% CI, 0.81-0.89; P < .001 for trend). Intake of ω-6 PUFA, especially linoleic acid, was inversely associated with mortality owing to most major causes, whereas marine ω-3 PUFA intake was associated with a modestly lower total mortality (HR comparing extreme quintiles, 0.96; 95% CI, 0.93-1.00; P = .002 for trend). Conclusions and Relevance Different types of dietary fats have divergent associations with total and cause-specific mortality. These findings support current dietary recommendations to replace saturated fat and trans-fat with unsaturated fats. PMID: 27379574
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