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Setting the Record Straight on Saturated Fat and Heart Disease Risk Ronald M. Krauss Children’s Hospital Oakland Research Institute UCSF and UC Berkeley What is saturated fat? Saturated fats consist of fatty acids where the carbon chains are full (“saturated”) with hydrogen. There are dozens of types with differing chain length; most common are lauric, myristic, palmitic, & stearic. Saturated fats are mainly consumed in animal foods such as dairy products and red meat, and oils such as coconut, palm, and palm kernel oil. Why limit saturated fat? Main rationale is to reduce risk of heart disease: When substituted for other types of fat, saturated fats raise levels of LDL (“bad”) cholesterol. Levels of LDL cholesterol are strongly linked to heart disease risk. Reducing LDL cholesterol can reduce heart disease risk. LDL is comprised of subclasses of particles with differing cholesterol content and CVD risk Large more cholesterol/particle Medium Small and very small less cholesterol/particle Increased CVD risk Reduced plasma clearance Greater entry into artery Greater retention Faster oxidation Distribution of subclasses varies widely among individuals and is independent of total LDL cholesterol Berneis and Krauss, JLR 43:1155, 2002 LDL cholesterol level can misrepresent the number of LDL particles 100 mg/dL LDL-Cholesterol 100 mg/dL Larger LDL particles Smaller LDL particles More cholesterol/particle Less cholesterol/particle Fewer LDL particles More LDL particles Small & very small LDL particles are reduced by low carb (26 vs. 54%) even on high vs. low SFA (15 vs. 8%) Change mg/dL SFA increases large LDL Krauss et al. AJCN 83:1025, 2006 Does increase in LDL cholesterol with higher SFAs translate to higher CVD risk? Main effect of SFAs is on larger LDL particles, which are less strongly associated with CVD risk than smaller LDL Thus, SFA-induced increases in LDL cholesterol may not signify a proportional increase in CVD risk. Carbohydrates (especially sugars) have a major influence on smaller LDL particles Since smaller LDLs have less cholesterol/particle, their levels can increase with higher carb intake without a proportional increase in LDL cholesterol. How much saturated fat should we be eating? There is actually no need for SFAs in the diet since the body can make them from other food sources, primarily carbohydrates. US Dietary and American Heart Association (AHA) Guidelines have traditionally advocated <10% of total calories as saturated fat (~30g/d for men and 20 g/d for women). In the latest guidelines (2010), this has been reduced to <7% of calories. What is the evidence that reducing SFAs will reduce risk of heart disease? To study such an effect without complicating the results by weight loss, something must be substituted for SFAs. The best evidence from clinical trials is that substituting polyunsaturated for saturated fat reduces heart disease risk, although a recent meta-analysis has challenged this. However, from epidemiologic studies, when SFAs are replaced by carbohydrates (both sugars and simple starches) there is no reduction in heart disease risk, and there is some evidence that the risk may be greater. Effects on heart disease risk of replacing SFAs by other fats and carbohydrates Dietary replacement (each 5% of calories) Polyunsaturated fat Predicted from lipid change Randomized clinical trials Observational cohort studies Carbohydrate Predicted from lipid change Randomized clinical trials Observational cohort studies Monounsaturated fat (e.g., olive, canola) Predicted from lipid change Randomized clinical trials Observational cohort studies Relative Risk Mozaffarian et al., PLoS Med Mar 23;7:e1000252, 2010 Consensus statement: Replacing SFAs with polys may be beneficial for heart disease risk The evidence from epidemiologic, clinical, and mechanistic studies is consistent* in finding that the risk of CHD is reduced when SFAs are replaced with polyunsaturated fatty acids. In populations who consume a Western diet, the replacement of 1% of energy from SFAs with PUFAs lowers LDL cholesterol and is likely to produce a reduction in CHD incidence of ~2–3%. Astrup A., et al. Am J Clin Nutr 2011;93:684–688. *challenged by recent meta-analysis Although monounsaturated fats (e.g. olive and canola oil) also reduce LDL, they may not reduce heart disease risk On high cholesterol diets, SFAs and monos have similar effects on atherosclerosis (in monkeys and mice); polys are better than both. Rudel L L et al. ATVB 15:2101-2110, 1995 Mediterranean diet: is it the olive oil? Test of “low-fat” vs. “Mediterranean diet” in 7500 Spaniards. Mediterranean diet: Recommended: Fresh fruits,≥3/d, vegetables ≥2/d, fish (especially fatty fish), seafood ≥3/wk, legumes ≥3/wk, peanuts ≥3/wk, sofrito ≥2 servings/wk, white meat Instead of red meat, wine with meals (optionally, ≥7 glasses/wk) and either: A) Olive oil ≥4 tbsp/day of polyphenol-rich virgin olive oil, or B) Tree nuts: Walnuts 15g, almonds 7.5 g, hazelnuts 7.5 g ≥3/wk Discouraged Soda drinks <1/d, commercial bakery goods, sweets, and pastries <3/wk, spread fats <1 /d, red and processed meats <1/d Estruch et al., N Engl J Med. 368:1279-90, 2013 Incidence of primary CVD endpoint Mediterranean diet: is it the olive oil? 30% reduction in CVD (most significant for stroke) Significant diet differences in Med diets vs. control: virgin olive oil(w/ polyphenols) nuts, fish and seafood, legumes Estruch et al., N Engl J Med. 368:1279-90, 2013 Substitution of high glycemic starch for SFAs increases risk for heart attack Relative risk of heart attack per 5% energy substitution 1.4 1.2 1 0.8 0.6 0.4 0.2 0 Lowest Medium Highest Tertiles of glycemic starch intake Jakobsen et al.,Am J Clin Nutr. 91:1764-8, 2010 The role of reducing intakes of SFAs in prevention of heart disease: where does the evidence stand? No clear benefit of substituting carbohydrates for SFAs has been shown, although there might be a benefit if the carbohydrate is unrefined and has a low glycemic index. No clear association between SFA intake relative to refined carbohydrates and the risk of insulin resistance and diabetes has been shown. Astrup A., et al. Am J Clin Nutr 2011;93:684–688. Women's Health Initiative trial of low-fat diet: no reduction risk of heart disease or stroke >45,000 women; LDL-C reduced by 3.6% Stroke Cumulative Risk Heart disease Years Years Howard, B. V. et al., JAMA 295:655-666, 2006 Meta-analysis of 21 prospective cohort trials shows no significant association of saturated fat intake with heart disease or stroke Coronary heart disease relative risk = 1.07 Stroke relative risk =0.81 Overall risk = 1.00 Siri-Tarino et al., Am J Clin Nutr. 91:535-546, 2010 Hazard ratio But - higher red meat intake is associated with increased mortality Men (n=51,529) Hazard ratio Women (n=121,700) Total red meat intake, servings per day Pan et al., Arch Intern Med. 172:555-563, 2012 SFAs from meat are associated with higher CHD risk while SFAs from dairy are associated with lower risk Meat SFAs Other SFAs Dairy SFAs % increase high vs. low SFAs Increase in LDL particles with high SFAs is much higher when beef is the major protein source 12 Same increase in saturated fat (8% 15%) 10 8 6 4 2 0 Mixed proteins Krauss et al., AJCN 2006 High beef Mangravite et al., J, Nutr. 2011 Recipe for disaster + + ? We should focus on eating healthy foods and worry less about grams of saturated fat The effect of particular foods on coronary heart disease cannot be predicted solely by their content of total SFAs because: individual SFAs may have different cardiovascular effects and major SFA food sources contain other constituents that could influence CHD risk. Astrup A., et al. Am J Clin Nutr 2011;93:684–688. Maintaining a healthy LDL level is important but there are many other effects of foods that can affect heart disease risk The effect of diet on a single biomarker [such as LDL cholesterol] is insufficient evidence to assess heart disease risk. The combination of multiple biomarkers and the use of clinical end-points could help substantiate the effects on heart disease. Astrup A., et al. Am J Clin Nutr 2011;93:684–688. More on foods vs. saturated fat LDL cholesterol levels are lower after eating cheese than after eating butter with the same amount of saturated fat. Recent epidemiologic studies suggest that fermented dairy products are associated with reduced risk of heart disease independent of saturated fat. It may be that intake of red meat is responsible for much of the risk of heart disease (and diabetes) attributed to saturated fat. And new evidence that it’s not just the fat in beef that contributes to risk. Summary: Points to consider about saturated fat It is not clear to what extent dietary saturated fat has effects that are directly harmful to arteries as opposed to having a neutral role; whereas other dietary factors have more direct effects: Good: Fatty fish, nuts, other polyphenol-rich foods, legumes Bad Trans fats Sugars, glycemic starches The foods with which SFAs are eaten can make a difference The Family Heart & Nutrition Center A unique program that brings clinicians, clinical research centers, health experts and advocates together in a unified center to directly address CVD risk now and for the future. CLINICAL RESEARCH INTEGRATIVE CARE MISSION: To develop and apply knowledge of genetic, lifestyle, and drug effects to improve management of CVD risk for patients of all ages in a community-based clinical research program. Scientific Discovery TRANSLATION & OUTREACH THE FHNC’s 3 FUNCTIONAL CORES Community Benefit 2013: The Oakland Heart Initiative CVD risk screenings at local health fairs Comprehensive screenings at clinic Dietary and lifestyle modification counseling Unique programs for mindfulness, stressreduction, and behavior modification Nutrition education Long-term participation with follow-up CLINICAL RESEARCH INTEGRATIVE CARE TRANSLATION & OUTREACH WE ARE CURRENTLY BUILDING A VOLUNTEER CADRE OF DIETITIANS AND NUTRITIONISTS TO PARTICIPATE IN COMMUNITY OUTREACH EVENTS. Contact Patty Siri-Tarino for more information! [email protected]