A Most Pragmatic Panacea: Diet in the 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease
- Discussing dietary patterns and using a whole foods approach to dietary counseling provides a practical way of improving the nutritional quality of patient diets.
- Clinicians should counsel their patients to focus on increasing intake of vegetables, fruits, healthy fats, nuts, whole grains, and fish, while limiting processed meats, refined grains, and sugar-sweetened beverages.
- Dietary counseling by clinicians should take into account body size perception, social and cultural influences, food access and economic factors.
Despite the importance of diet to cardiovascular health, studies have shown that there are multiple perceived barriers by clinicians, including lack of time, compensation, resources or knowledge, that lead to missed opportunities for effective counseling during healthcare visits.1,2 The 2019 American College of Cardiology (ACC)/American Heart Association (AHA) guideline on the primary prevention of cardiovascular disease (CVD) provides guidance for clinicians when counseling their patients on diet.3 The recommendations within these guidelines can be practically applied within the time constraints of a clinical visit.
There has been a shift in contemporary dietary guidelines towards a whole foods approach to dietary counseling rather than focusing on specific nutrients intake. Discussion on dietary patterns such as encouraging consumption of more fresh vegetables and fruits and avoiding processed meats and sugary beverages is much easier to interpret for patients while still indirectly addressing macronutrients and micronutrients needs (i.e. replacing saturated fat intake with mono- and poly-unsaturated fats). Importantly, clinicians should recognize that dietary recommendations included in the 2019 ACC/AHA primary prevention guidelines are evidence-based principles focused on reduction of atherosclerotic cardiovascular disease (ASCVD) risk.
- A diet emphasizing intake of vegetables, fruits, legumes, nuts, whole grains and fish is recommend to decrease ASCVD risk factors (COR: I; LOE: B-R).
- Replacement of saturated fat with dietary monounsaturated and polyunsaturated fats can be beneficial to reduce ASCVD risk (COR: IIa; LOE: B-NR).
- A diet containing reduced amounts of cholesterol and sodium can be beneficial to decrease ASCVD risk (COR: IIa; LOE: B-NR).
- As a part of a healthy diet, it is reasonable to minimize the intake of processed meats, refined carbohydrates and sweetened beverages to reduce ASCVD risk (COR: IIa; LOE: B-NR).
- As a part of a healthy diet, the intake of trans fats should be avoided to reduce ASCVD risk (COR: III; LOE: B-NR).
The dietary pattern with the strongest evidence for reduction of ASCVD risk consists of foods commonly found in a Mediterranean diet, which has been studied in two randomized cardiovascular outcomes trials – PREDIMED (Prevencion con Dieta Mediterranea) in primary prevention patients and the Lyon Heart Study in secondary prevention patients.4,5 PREDIMED randomized primary prevention individuals with CVD risk factors to one of three groups: a Mediterranean diet supplemented by extra-virgin olive oil (recommended at least 4 tablespoons per day per person), a Mediterranean diet supplemented with nuts (recommended 30 grams of mixed nuts consisting of walnuts, hazelnuts and almonds), or control diet (low fat but not low carb). Food choices recommended in the Mediterranean diet group included olive oil, nuts, fresh fruits, vegetables, fish (especially fatty fish), seafood, legumes, and white meat. Food choices recommended in the control group included low-fat dairy products, fresh fruits, vegetables, lean fish and seafood, bread, potatoes, pasta and rice but discouraged use of vegetable oils, nuts and fatty fish. The consumption of commercial bakery goods, sweets and pastries, spread fats, red and processed meats was discouraged in both intervention and control groups. At a median follow-up of 4.8 years, groups of Mediterranean diet supplemented by extra-virgin olive oil or Mediterranean diet supplemented with nuts demonstrated 31% and 28% relative risk reduction in the composite endpoint of myocardial infarction (MI), stroke or death from cardiovascular cause (ARR 0.6% and 1.0%), respectively compared with the control group. This risk reduction was driven primarily by a reduction in stroke (HR 0.65, 95% CI 0.0.44-0.95 for the group with Mediterranean diet supplemented by extra-virgin olive oil and HR 0.54,95% CI 0.35-0.82 for the group with Mediterranean diet supplemented with nuts when compared with control). Meanwhile, the Lyon Heart Study also showed that individuals eating alpha-linolenic acid-rich Mediterranean diet had reduced risk for coronary events and deaths compared to those on a Western diet in a secondary prevention population (RR 0.27, 95% CI 0.12-0.59, p=0.001).
A plant-based diet is in a sense an extension of the Mediterranean diet that recommends replacing animal protein with plant protein. A post hoc analysis from the PREDIMED cohort that assessed participants based on pro-vegetarian food pattern, showed that a high adherence to a diet composed primarily of plants and lower in animal-derived foods resulted in a 41% relative risk reduction between the high adherence group compared to the lowest adherent group (absolute death rate: 8.68 vs. 14.9 deaths per 1,000 person-years).6 Several large observational studies have also demonstrated reduction of risk for ASCVD as well as heart failure with a plant-based dietary pattern.7,8 However, clinicians must clarify with their patients that not all plant-based diets are created equal. In a large cohort of more than 73,000 women from the Nurses' Health Study, a diet high in healthful plant-based foods (fruits, vegetables, nuts, legumes, oils, tea and coffee) was associated with significantly lower risk for incident coronary heart disease (CHD) whereas intake of a plant-based diet that emphasized less healthy plant foods (juices, sweetened beverages, refined grains, potatoes, fries and sweets) was associated with increased risk for CHD.7 Sugar-sweetened and sweetened beverages are linked to increased risk for diabetes and sweets and refined carbohydrates are associated with increased risk for coronary events.9,10 Thus, while a dietary pattern that is in line with the Mediterranean or healthy plant-based diet should be promoted, clinicians should counsel their patients to avoid dietary patterns that include processed meats, refined carbohydrates and sweetened beverages, as these food products have been associated with increased risk for ASCVD.3
When counseling about diet, the optimal intake of dietary lipids is often one of the most confusing aspects for patients. Dietary lipids including cholesterol and fats (fatty acids) have a direct impact on cardiovascular health. Limiting dietary cholesterol is perhaps the most intuitive intervention, as this has been shown to decrease levels of circulating low-density lipoprotein cholesterol (LDL-C), which is a causal risk factor for ASCVD. Dietary fatty acids including saturated fats, mono- and poly-unsaturated fats and trans fats, on the other hand, include concepts and terminologies that are nuanced and may often be confusing to clinicians and patients alike. Chemically, saturated fats are composed of fatty acid hydrocarbon chains with predominantly single bonds (easier to "pack together") and are solid at room temperature whereas mono- and poly-unsaturated fats contain fatty acids that have one or more double bonds and tend to be liquid at room temperature. Saturated fats have been shown to increase LDL-C and worsen insulin resistance. However, intake of saturated fat has also been shown to increase levels of high-density lipoprotein cholesterol (HDL-C) and a large randomized trail aimed at limiting intake of saturating fat showed no reduction in ASCVD events.11 Replacement of saturated fats with mono- (excluding trans fats) and poly-unsaturated fats have been shown to lower LDL-C as well as risk for CVD and mortality.12 Major sources of dietary saturated fats include but are not limited to animal fats from pork (lard), beef (tallow) and other red meat, dairy fat (butter) as well as tropical oils such as palm, palm kernel and coconut oils. Monounsaturated fats are found in both plants as well as animal sources such as red meat and dairy sources. However, the latter also contain high levels of saturated fats, cholesterol and can lead to increase in metabolites such as trimethylamine N-oxide (TMAO), which may attenuate the positive effects of the unsaturated fats. Polyunsaturated fatty acids are predominantly found in plant sources as well as seafood, especially oily fish. In addition to LDL-C lowering properties of polyunsaturated fatty acids (PUFAs) when taken instead of saturated or trans fats, some PUFAs like the omega-3 class of fatty acids have also been shown to improve insulin resistance and exhibit anti-inflammatory properties.13,14 Evidence for cardiovascular risk reduction in primary prevention with dietary supplements of omega-3 fatty acids has been inconsistent based on modern clinical trials. Clinical efficacy is likely influenced by dose, specific types of PUFAs (i.e. eicosapentaenoic acid) and by long-term achieved levels of PUFAs in circulation, and more studies are needed to establish any CVD benefit of supplements more clearly.15,16
Trans fat, which are chemically trans-isomeric configurations of unsaturated fatty acids, are found naturally in low levels in the meat and dairy of ruminant animals such as cows and sheep. However, trans fats are also artificially synthesized via hydrogenation of vegetable oils in order to improve shelf life. Artificial trans fats have been used as deep fry oils in restaurants and fast food outlets, as baking grease in packaged baked goods, pre-made crusts and mixes and in margarine and other spreads. Dietary intake of trans fats should be minimized or avoided as studies have shown that intake is consistently associated with increased in risk for CVD.12 In 2018, the Food and Drug Administration (FDA) mandated a phase-out of artificial trans-fats.17
With respect to sodium intake, a dietary pattern emphasizing vegetables, fruits, whole grain and including fish, poultry, low fat dairy products, non-tropical oils and nuts in conjunction with reduction in dietary sodium was shown in the DASH (Dietary Approaches to Stop Hypertension) trial to reduce blood pressure.18 Long-term follow-up data from TOHP (Trials of Hypertension Prevention) further showed that reduction in dietary sodium was associated with cardiovascular events.19 The 2013 ACC/AHA guidelines on lifestyle management to reduce cardiovascular risk recommends no more than 2400 mg of daily sodium with further reduction in blood pressure (BP) achieved with daily sodium intake to 1500 mg/day.20 Dietary sodium can be difficult to track for patients and it is important for patients to understand that limiting processed and fast foods will reduce their sodium intake to a far greater extent than ceasing to use salt in their own cooking.
Lastly, there are numerous barriers to effective dietary counseling by cardiology providers. The guidelines recommend assessment of body size perception, social and cultural influences, food access and economic factors. Such factors may be especially important in patients in poor socioeconomic settings as well as in the elderly. Practitioners further need to overcome clinical inertia that results from perceived poor response by patients to counseling and over-reliance on pharmacologic therapies, limited time to fully understand causes of poor dietary patterns (i.e. socioeconomic constraints) and lack of resources or knowledge. However, studies have shown that even succinct discussions on nutrition can lead to meaningful impact. A previous ACC.org expert analysis provides several basic steps that can be effective when counseling about diet.21 These include: 1) gathering baseline diet information; 2) starting with small dietery pattern changes; 3) using food-based approaches to target specific risk factors; 4) being sensitive to patient-specific cultural, religious, and economic factors; 5) using motivational and behavioral approaches; and 6) making use of outside nutrition resources. The full article can be found here. When more in depth or complex planning is needed, clinicians may consider partnering with dieticians to help develop personalized strategies to improve dietary patterns for their patients.
- Kolasa KM, Rickett K. Barriers to providing nutrition counseling cited by physicians: a survey of primary care practitioners. Nutr Clin Pract 2010;25:502-9.
- Kushner RF. Barriers to providing nutrition counseling by physicians: a survey of primary care practitioners. Prev Med 1995;24:546-52.
- Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA guideline on the primary prevention of cardiovascular disease: a report of the American College of Cardiology/American Heart Association task force on clinical practice guidelines. J Am Coll Cardiol 2019;74:e177-e232.
- Estruch R, Ros E, Salas-Salvadó J, et al. Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts. N Engl J Med 2018;378:e34.
- de Lorgeril M, Renaud S, Mamelle N, et al. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. Lancet 1994;343:1454-9.
- Martínez-González MA, Sánchez-Tainta A, Corella D, et al. A provegetarian food pattern and reduction in total mortality in the Prevención con Dieta Mediterránea (PREDIMED) study. Am J Clin Nutr 2014;100:320S-8S.
- Satija A, Bhupathiraju SN, Spiegelman D, et al. Healthful and unhealthful plant-based diets and the risk of coronary heart disease in U.S. adults. J Am Coll Cardiol 2017;70:411-22.
- Lara KM, Levitan EB, Gutierrez OM, et al. Dietary patterns and incident heart failure in U.S. adults without known coronary disease. J Am Coll Cardiol 2019;73:2036-45.
- Lofvenborg JE, Andersson T, Carlsson PO, et al. Sweetened beverage intake and risk of latent autoimmune diabetes in adults (LADA) and type 2 diabetes. Eur J Endocrinol 2016;175:605-14.
- Yang Q, Zhang Z, Gregg EW, Flanders WD, Merritt R, Hu FB. Added sugar intake and cardiovascular diseases mortality among US adults. JAMA Intern Med 2014;174:516-24.
- Howard BV, Van Horn L, Hsia J, et al. Low-fat dietary pattern and risk of cardiovascular disease: the Women's Health Initiative Randomized Controlled Dietary Modification Trial. JAMA 2006;295:655-66.
- Sacks FM, Lichtenstein AH, Wu JHY, et al. Dietary fats and cardiovascular disease: a presidential advisory from the American Heart Association. Circulation 2017;136:e1-e23.
- Grundy SM. Monounsaturated fatty acids and cholesterol metabolism: implications for dietary recommendations. J Nutr 1989;119:529-33.
- Hodson L, Skeaff CM, Chisholm WA. The effect of replacing dietary saturated fat with polyunsaturated or monounsaturated fat on plasma lipids in free-living young adults. Eur J Clin Nutr 2001;55:908-15.
- Albert CM, Campos H, Stampfer MJ, et al. Blood levels of long-chain n-3 fatty acids and the risk of sudden death. N Engl J Med 2002;346:1113-8.
- EPA Levels and Cardiovascular Outcomes in the Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial. Presented by Deepak L. Bhatt at American College of Cardiology 2020 Scientific Session, March 30, 2020.
- Final Determination Regarding Partially Hydrogenated Oils (Removing Trans Fat) (FDA website). 2018. Available at: https://www.fda.gov/food/food-additives-petitions/final-determination-regarding-partially-hydrogenated-oils-removing-trans-fat. Accessed 06/30/2020.
- Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. N Engl J Med 2001;344:3-10.
- Cook NR, Cutler JA, Obarzanek E, et al. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ 2007;334:885-8.
- Eckel RH, Jakicic JM, Ard JD, et al. 2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: a report of the American College of Cardiology/American Heart Association task force on practice guidelines. J Am Coll Cardiol 2014;63:2960-84.
- Fleming J, Aspry KE, Resnicow K, Kris-Etherton PM. Translating the ACC/AHA lifestyle management guideline into practice: advice for cardiologists from experts in nutrition behavioral medicine and cardiology. http://www.acc.org. Jan 06, 2016. Accessed 07/01/2020. https://www.acc.org/latest-in-cardiology/articles/2015/12/31/10/12/translating-the-acc-aha-lifestyle-management-guideline-into-practice.
Keywords: Primary Prevention, Secondary Prevention, Vegetables, Fruit, Diet, Mediterranean, Diet, Nuts, Corylus, Juglans, alpha-Linolenic Acid, Solanum tuberosum, Control Groups, Coffee, Plant Oils, Cholesterol, LDL, Cholesterol, HDL, Cholesterol, Dietary, Fast Foods, Risk Factors, Fatty Acids
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