Pub Date: Thursday, Jun 15, 2017
Author: Tracy Severson, RD, LD, and Sergio Fazio, MD, PhD
Affiliation: Oregon Health & Science University
In an era inundated with health information – an online search for “heart-healthy foods” yields almost 50 million hits, one assumes not all backed by science – it is imperative that patients have a trusted source for accurate, up-to-date nutrition recommendations. The topic of dietary fats and their impact on cardiovascular health is relevant, often contentious, and always complicated and evolving, with recent meta-analyses now raising questions about the accuracy and effectiveness of traditional recommendations to simply reduce saturated fats for cardiovascular risk reduction.1 The new Presidential Advisory from the American Heart Association thoroughly examines, organizes, and digests the vast landscape of nutritional literature to provide an authoritative and evidence-based resource on dietary patterns that reduce cardiovascular risk.
The Advisory reviews five key elements:
Saturated fats: It is a well-documented observation that dietary saturated fats raise plasma LDL-cholesterol levels. However, to reduce cardiovascular risk, it is not enough to simply reduce intake of saturated fats, as this Advisory convincingly puts forward with their exhaustive literature review. The greatest cardiovascular benefits are elicited when dietary saturated fats are replaced with polyunsaturated fats. Monounsaturated fats and whole grains also provide a benefit when used to replace saturated fats, though not as great as that seen with polyunsaturated fats. No cardiovascular benefit is elicited when refined carbohydrates and sugar are used to replace saturated fats. Practical nutrition recommendations, therefore, should be focused not only on which foods are to be used sparingly or to be avoided altogether, but also on the healthy foods that should replace them to truly accomplish a cardio-protective dietary regimen.
To translate this into everyday food choices, 1.7 ounces of cheddar cheese contains 9 grams of saturated fat. The 81 calories this fat provides would make up to 4.5% of a 1600-calorie diet. If this high-saturated fat food is replaced with 81 calories from fat-free cookies (no saturated fat, but plenty of refined carbohydrates from white flour and sugar), both common sense and science inform us that this change provides no improvement in health. When the cheese is replaced with equal calories from either oatmeal (everyone’s favorite heart-healthy whole grain) or almonds (with most of its calories coming from monounsaturated fat), cardiovascular risk improves by 9% or 15%, respectively.2 But if the cheese is replaced with walnuts, a rich source of polyunsaturated fat, risk is reduced 25%.2 In addition to the healthier fat profile, the walnuts – like other whole plant foods – also provide a host of other benefits such as vitamins, minerals, antioxidants, phytonutrients, and fiber. This overarching nutritional package tends to be overlooked when we put too much emphasis on specific nutrients in recommendations. See Table for more advice on substitutions.
Dairy products: A specific point furthering confusion in the lay public on the cardiovascular impact of saturated fats has been the discordance shown in recent studies on the impact of dairy fats (about 42% saturated) on cardiovascular risk.3,4 Data collection is historically problematic in nutrition studies, as food frequency questionnaires are subjective and often fail to provide an accurate picture of the participants’ diets. Studies that have examined biomarkers of dairy fat intake – sought out as a more objective dietary measurement tool – have produced inconsistent results with regards to the impact of dairy fats on cardiovascular risk.3,4 This may be due to increased intake of low-fat dairy compared with natural dairy consumption in recent decades, or it may be that these biomarkers do not provide a clear representation of intake. While these studies and other meta-analyses1 garner attention-grabbing headlines leading the public to believe that full-fat cheese and butter are back on their heart-healthy plates, this appears to be only wishful thinking. In addition to the high saturated fat content, dairy fat composition also contains about 3% naturally occurring trans fats, which appear to convey similar risk as industrial trans fats. The Presidential Advisory concludes that, as with other saturated fats, cardiovascular risk is reduced when dairy fats are replaced with PUFAs, MUFAs, and whole grains. For people consuming dairy, low-fat or non-fat products are preferred as a way to reduce saturated fat intake.
Coconut oil: Coconut oil has gained popularity in recent years, with purported uses ranging from cooking oil, skin moisturizer, and even coffee creamer. While coconut oil is highly saturated (82%), the primary fatty acid, lauric acid, does not raise LDL-cholesterol to the same extent as myristic and palmitic acids. Lauric acid also raises HDL-cholesterol more than does palmitic acid (though about the same as myristic). The slight decrease in LDL-C to HDL-C ratio caused by lauric acid is the basis for the optimistic cardiovascular health claims made for coconut oil. The higher concentration of medium-chain fatty acids (MCFA) in coconut oil compared with other oils also lead to additional health claims based on the direct absorption of MCFA from the GI tract into the portal system, bypassing the lymphatic system used by long-chain fatty acids. Despite these claims in the literature, the Advisory determined that coconut oil is not expected to have cardiovascular benefit given the causal role of LDL in CVD. Although coconut oil also increases HDL-cholesterol levels, the value of this parameter as risk predictor is currently being questioned, as clinical trials of HDL modulators have failed to provide evidence of CVD benefits.
Trans fats: Little debate remains regarding the negative cardiovascular impact of industrial trans fatty acids. However, this Advisory also clarifies that ruminant trans fatty acids, naturally occurring in beef, lamb, and dairy, appear to have similar negative health consequences. Since the onset of trans fat nutrition labeling in 2006, the majority of industrial trans fats, in the form of partially hydrogenated oils, have been removed from foods and are scheduled to be completed phased out of the food supply by mid-2018.5 This change alone can potentially reduce annual CHD events by 6 to 19 percent.6 Since sources of ruminant trans fatty acids tend also to be high in saturated fat, it is prudent to limit these foods, replacing with protein sources that are not only free of trans fat and low in saturated fat, but also confer cardiovascular benefit, such as fish and legumes.
Omega-3 fatty acids: The Advisory finds that not all polyunsaturated fats of the omega-3 series confer the same cardiovascular benefits. Alpha linolenic acid (ALA), a plant-sourced omega-3 fatty acid, was not linked to lower cardiovascular risk, though higher intake of ALA may reduce fatal coronary heart disease. Given the rise in popularity of ALA sources – as flaxseeds, canola oil, walnuts, and omega-3 fortified eggs (usually from hens fed flaxseeds, and containing the same level of saturated fat and cholesterol as conventional eggs) – it is important to make the public aware that best omega-3 fats for cardiovascular health are the marine-derived omega-3 fatty acids, mostly eicosapentaenoic (EPA) and docosahexaenoic (DHA). Fish oil contains EPA and DHA.
For too long, nutrition recommendations have focused on the nutrients that should be restricted or avoided, with little to no guidance given on how to replace what is removed. One unfortunate consequence of this has been the rise of the reduced-fat diets high in refined carbohydrates, contributing to increased plasma triglycerides, decreased HDL-cholesterol, weight gain, insulin resistance, and a cardiovascular disease risk similar to that of high-saturated fat diets.7,8 There is a question of whether such initial recommendations were at least in part influenced by lobbying efforts from sugar-based industrial interests.9 By encouraging an overall healthful eating pattern, beneficial nutrients are given the spotlight and their consumption is hopefully maximized, which should result in crowding out less healthy dietary elements. The fortuitous result is that both dietary compliance and outcomes improve when the emphasis is placed on what to eat rather than on what to avoid.10 A primarily pescatarian regimen, such as that embodied by the different versions of a Mediterranean diet, to include plenty of fresh vegetables, fruits, whole grains, legumes, and nuts, with the inclusion of fish and liquid plant oils, is beneficial not only for metabolic control and cardiovascular health, but also for the management of many other chronic conditions.10,11,12
Disseminating nutrition research into clear recommendations can be a daunting task. This Presidential Advisory provides specific advice for optimal nutrient intake for cardiovascular risk reduction, identifying beneficial dietary fat sources within the matrix of a balanced diet centered on whole plant foods. This is a big step in the right direction.
How to Substitute 21g (0.7 oz) of Saturated Fat to Improve Heart Health
|Reduce sources of saturated fats||Total calories||SFA content (grams)||Replace with sources of unsaturated fats (MUFA)||Total calories||MUFA content (grams)||Replace with sources of unsaturated fats (PUFA)||Total calories||PUFA content (grams)|
|Butter, 1 tsp (4.7 g)||34||2||Olive oil, 1 tsp (4.5 g)||40||3||Canola oil, 1 tsp (4.5 g)||40||1|
|Coconut oil, 1 tsp (4.5 g)||39||4||Avocado, 1/2 (100 g)||161||10||Grapeseed oil, 1 tsp (4.5 g)||40||3|
|Full fat cheese, 1 oz (28 g)||113||6||Almonds, 1 oz (28 g)||163||9||Walnuts, 1 oz (28 g)||185||13|
|Rib eye beef steak, grilled, 3 oz (85 g)||247||9||Oatmeal, 1/2 cup cooked (117 g)||79||--||Salmon, grilled, 3 oz (85 g)||151||2|
|Ground flaxseeds, 1 tbsp (6.5 g)||30||2|
Source: USDA Food Composition Databases, ndb.nal.usda.gov/ndb/
Sacks FM, Lichtenstein AH, Wu JHY, Appel LJ, Creager MA, Kris-Etherton PM, Miller M, Rimm EB, Rudel LL, Robinson JG, Stone NJ, Van Horn LV; on behalf of the American Heart Association. Dietary fats and cardiovascular disease: a presidential advisory from the American Heart Association [published online ahead of print June 15, 2017]. Circulation. doi: 10.1161/CIR.0000000000000510.
- Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, Franco OH, Butterworth AS, Forouhi NG, Thompson SG, Khaw K-T, Mozaffarian D, Danesh J and Di Angelantonio E. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis Ann Intern Med. 2014:398-406.
- Li Y, Hruby A, Bernstein AM, Ley SH, Wang DD, Chuive SE, Sampson L, Rexrode KM, Rimm EB, Willett WC, Hu FB. Saturated fats compared with unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease. A prospective cohort study. J Am College Cardiol. 2015;66:1538-1548.
- de Oliveira Otto M, Nettleton JA, Lemaitre RN, Steffen LM, Kromhout D, Rich SS, Tsai MY, Jacobs DR, Mozaffarian D. Biomarkers of dairy fatty acids and risk of cardiovascular disease in the Multi-Ethnic Study of Atherosclerosis. J Am Heart Assoc. 2013;2:3000092
- Sun Q, Ma J, Campos H, Hu FB. Plasma and erythrocyte biomarkers of dairy fat intake and risk of ischemic heart disease. Am J Clin Nutr. 2007;86:929-37.
- “Final Determination Regarding Partially Hydrogenated Oils (Removing Trans Fat).” U.S. Food and Drug Administration. 17 Mar. 2017. Web. 4 May 2017.
- Mozaffarian D, Katan MB, Ascherio A, Stampfer MJ, Willett WC. Trans Fatty Acids and Cardiovascular Disease. N Engl J Med. 2006; 354:1601-1613.
- Burr ML, Fehily AM, Gilbert JF, et al. Effects of changes in fat, fish, and fibre intakes on death and myocardial infarction: diet and reinfarction trial (DART). Lancet. 1989; ii:757–761.
- Sacks FM, Carey VJ, Anderson CA, Miller ER 3rd, Copeland T, Charleston J, Harshfield BJ, Laranjo N, McCarron P, Swain J, White K, Yee K, Appel LJ. Effects of high vs low glycemic index of dietary carbohydrate on cardiovascular disease risk factors and insulin sensitivity: the OmniCarb randomized clinical trial. JAMA. 2014;312:2531-2541.
- Kearns CE, Schmidt LA, Glantz SA. Sugar Industry and Coronary Heart Disease Research: A Historical Analysis of Internal Industry Documents. JAMA Intern Med. 2016;176(11):1680-1685.
- Sijtsma FP, Soedamah-Muthu SS, de Goede J, et al. Healthy eating and lower mortality risk in a large cohort of cardiac patients who received state-of-the-art drug treatment. Am J Clin Nutr. 2015;102(6):1527-1533.
- Trichopoulou A, Costacou T, Bamia C, Trichopoulos D. Adherence to a Mediterranean diet and survival in a Greek population. N Engl J Med. 2003;348(26):2599-608.
- Wang DD, Li Y, Chiuve SE, Stampfer MJ, Manson JE, Rimm EB, Willett WC, Hu FB. Association of specific dietary fats with total and cause-specific mortality. JAMA Intern Med. 2016 Aug 1;176(8):1134-45.
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