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Dean Pomerleau posted a topic in CR Practice[Another one for the "Non-CR Health forum"...] Recently there has been much hype in the popular press, including a Time Magazine story, with this provocative cover: that claim we've been wrong about saturated fat (like butter) all along. These stories have been based on meta-analyses like this one , that purport to find no association between saturated fat and chronic diseases, even cardiovascular disease. One of my favorite nutrition bloggers, PlantPositive, did a thorough debunking of the Time story and the people & studies it uses as sources. Among other faults of these previous meta-analyses outlined in PlantPositive's post, some of the biggest problems include: Over correction by factoring out serum cholesterol in the analysis - which is elevated by saturate fat intake and so shouldn't be controlled for. Failing to factor out the low cholesterol of saturated fat eaters who take statins to control their cholesterol. Failing to account for the health effects of what people choose to eat instead when they don't eat saturated fat-rich foods. As I recall (but an unable to verify due to the archives being down... ), we talked about all these studies and their shortcomings on the CR email list before. But now, we have something even better than critical analysis of flawed studies. We have a new prospective cohort study  of some of the best data available on diet, lifestyle and health from the Health Professionals and Nurses Health Studies. It appears to do a much better job, particularly with respect to the third confounder - food substitution effects. Here is popular press coverage of the new study. The Harvard researchers have followed these two cohorts of 42K men and 84K women for over 30 years, assessing their diet, lifestyle and health repeatedly during that time. This study looked at their fat consumption habits, and in particular changes in those habits over time and how those changes relate to coronary heart disease (CHD). In a nutshell, they found that: Replacing 5% of energy intake from saturated fats with equivalent energy intake from PUFAs, monounsaturated fatty acids, or carbohydrates from whole grains was associated with a 25%, 15%, and 9% lower risk of CHD, respectively (PUFAs, HR: 0.75, 95% CI: 0.67 to 0.84; p < 0.0001; monounsaturated fatty acids, HR: 0.85, 95% CI: 0.74 to 0.97; p = 0.02; carbohydrates from whole grains, HR: 0.91, 95% CI: 0.85 to 0.98; p = 0.01). Replacing saturated fats with carbohydrates from refined starches/added sugars was not significantly associated with CHD risk (p > 0.10). Here is a graphical depiction of these results: As you can see, trans fat is toxic relative to any other foods, including saturate fat - no surprise. More interestingly, it is about a wash to substitute saturated fat with refined carbohydrates when it comes to heart disease risk. But substituting any of the following for saturated fat results in significantly reduced CHD risk - MUFA, PUFA and whole grain carbohydrates. PUFAs appear particularly protective. Unfortunately the study did not address other healthy carbohydrate sources besides whole grains, like fruits, vegetables or legumes (which I willing to bet would do at least as well as whole grains at reducing CHD risk relative to saturated fat). They also didn't discriminate between the health effects of different types of saturated fats, some of which might not be as bad as others (i.e. those found in plants vs. animal sources). One concern is that when people clean up their diet by eliminating saturated fat, they might also undertake other health promoting lifestyle changes, making it appear that reducing saturated fat was beneficial when it actually was the other changes that made the difference. The authors addressed this potential problem by controlling for a host of other factors in their analysis, including: The multivariable model was adjusted for total energy intake, the energy contribution from protein, cholesterol intake, alcohol intake, smoking status, body mass index, physical activity, use of vitamins and aspirin, family history of myocardial infarction and diabetes, and presence of baseline hypercholesterolemia and hypertension. These results confirm what I think most people have believed all along - that saturated fat is detrimental to heart health, but probably no more so than what people will normally eat instead, crappy carbs. This explains those previous studies that found lower saturated fat intake was often not associated with lower risk of heart disease - people who ate less saturated fat were eating more refined carbs instead, and so weren't any better off. But when you replace saturated fat-rich foods with healthy fats or healthy carbs, you reduce your risk of heart disease dramatically. --Dean ---------------  BMJ. 2015 Aug 11;351:h3978. doi: 10.1136/bmj.h3978. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. de Souza RJ(1), Mente A(2), Maroleanu A(3), Cozma AI(4), Ha V(5), Kishibe T(6), Uleryk E(7), Budylowski P(8), Schünemann H(9), Beyene J(10), Anand SS(11). OBJECTIVE: To systematically review associations between intake of saturated fat and trans unsaturated fat and all cause mortality, cardiovascular disease (CVD) and associated mortality, coronary heart disease (CHD) and associated mortality, ischemic stroke, and type 2 diabetes. DESIGN: Systematic review and meta-analysis. DATA SOURCES: Medline, Embase, Cochrane Central Registry of Controlled Trials, Evidence-Based Medicine Reviews, and CINAHL from inception to 1 May 2015, supplemented by bibliographies of retrieved articles and previous reviews. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Observational studies reporting associations of saturated fat and/or trans unsaturated fat (total, industrially manufactured, or from ruminant animals) with all cause mortality, CHD/CVD mortality, total CHD, ischemic stroke, or type 2 diabetes. DATA EXTRACTION AND SYNTHESIS: Two reviewers independently extracted data and assessed study risks of bias. Multivariable relative risks were pooled. Heterogeneity was assessed and quantified. Potential publication bias was assessed and subgroup analyses were undertaken. The GRADE approach was used to evaluate quality of evidence and certainty of conclusions. RESULTS: For saturated fat, three to 12 prospective cohort studies for each association were pooled (five to 17 comparisons with 90 501-339 090 participants). Saturated fat intake was not associated with all cause mortality (relative risk 0.99, 95% confidence interval 0.91 to 1.09), CVD mortality (0.97, 0.84 to 1.12), total CHD (1.06, 0.95 to 1.17), ischemic stroke (1.02, 0.90 to 1.15), or type 2 diabetes (0.95, 0.88 to 1.03). There was no convincing lack of association between saturated fat and CHD mortality (1.15, 0.97 to 1.36; P=0.10). For trans fats, one to six prospective cohort studies for each association were pooled (two to seven comparisons with 12 942-230 135 participants). Total trans fat intake was associated with all cause mortality (1.34, 1.16 to 1.56), CHD mortality (1.28, 1.09 to 1.50), and total CHD (1.21, 1.10 to 1.33) but not ischemic stroke (1.07, 0.88 to 1.28) or type 2 diabetes (1.10, 0.95 to 1.27). Industrial, but not ruminant, trans fats were associated with CHD mortality (1.18 (1.04 to 1.33) v 1.01 (0.71 to 1.43)) and CHD (1.42 (1.05 to 1.92) v 0.93 (0.73 to 1.18)). Ruminant trans-palmitoleic acid was inversely associated with type 2 diabetes (0.58, 0.46 to 0.74). The certainty of associations between saturated fat and all outcomes was "very low." The certainty of associations of trans fat with CHD outcomes was "moderate" and "very low" to "low" for other associations. CONCLUSIONS: Saturated fats are not associated with all cause mortality, CVD, CHD, ischemic stroke, or type 2 diabetes, but the evidence is heterogeneous with methodological limitations. Trans fats are associated with all cause mortality, total CHD, and CHD mortality, probably because of higher levels of intake of industrial trans fats than ruminant trans fats. Dietary guidelines must carefully consider the health effects of recommendations for alternative macronutrients to replace trans fats and saturated fats. © de Souza et al 2015. PMCID: PMC4532752 PMID: 26268692 ------------  J Am Coll Cardiol. 2015 Oct 6;66(14):1538-48. doi: 10.1016/j.jacc.2015.07.055. Saturated Fats Compared With Unsaturated Fats and Sources of Carbohydrates in Relation to Risk of Coronary Heart Disease: A Prospective Cohort Study. Li Y(1), Hruby A(1), Bernstein AM(2), Ley SH(1), Wang DD(1), Chiuve SE(3), Sampson L(1), Rexrode KM(4), Rimm EB(5), Willett WC(5), Hu FB(6). BACKGROUND: The associations between dietary saturated fats and the risk of coronary heart disease (CHD) remain controversial, but few studies have compared saturated with unsaturated fats and sources of carbohydrates in relation to CHD risk. OBJECTIVES: This study sought to investigate associations of saturated fats compared with unsaturated fats and different sources of carbohydrates in relation to CHD risk. METHODS: We followed 84,628 women (Nurses' Health Study, 1980 to 2010), and 42,908 men (Health Professionals Follow-up Study, 1986 to 2010) who were free of diabetes, cardiovascular disease, and cancer at baseline. Diet was assessed by a semiquantitative food frequency questionnaire every 4 years. RESULTS: During 24 to 30 years of follow-up, we documented 7,667 incident cases of CHD. Higher intakes of polyunsaturated fatty acids (PUFAs) and carbohydrates from whole grains were significantly associated with a lower risk of CHD comparing the highest with lowest quintile for PUFAs (hazard ratio : 0.80, 95% confidence interval [CI]: 0.73 to 0.88; p trend <0.0001) and for carbohydrates from whole grains (HR: 0.90, 95% CI: 0.83 to 0.98; p trend = 0.003). In contrast, carbohydrates from refined starches/added sugars were positively associated with a risk of CHD (HR: 1.10, 95% CI: 1.00 to 1.21; p trend = 0.04). Replacing 5% of energy intake from saturated fats with equivalent energy intake from PUFAs, monounsaturated fatty acids, or carbohydrates from whole grains was associated with a 25%, 15%, and 9% lower risk of CHD, respectively (PUFAs, HR: 0.75, 95% CI: 0.67 to 0.84; p < 0.0001; monounsaturated fatty acids, HR: 0.85, 95% CI: 0.74 to 0.97; p = 0.02; carbohydrates from whole grains, HR: 0.91, 95% CI: 0.85 to 0.98; p = 0.01). Replacing saturated fats with carbohydrates from refined starches/added sugars was not significantly associated with CHD risk (p > 0.10). CONCLUSIONS: Our findings indicate that unsaturated fats, especially PUFAs, and/or high-quality carbohydrates can be used to replace saturated fats to reduce CHD risk. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved. PMCID: PMC4593072 [Available on 2016-10-06] PMID: 26429077