Diet and Heart Disease—What Every Cardiologist Should Know

Throughout my training as a cardiologist, from medical school through fellowship, it became increasingly clear that the single major cause of poor health in my patients was poor diet. Yet, like my fellow medical students, house staff, and attendings, I had received very little relevant training in nutrition, lifestyle, or effective behavior change strategies. I could perform and interpret a dizzying array of technologically-based diagnostic tests and interventions, but I had not been given the tools to address the root causes of my patients' illnesses and distress. Remarkably, I faced my patients every day with only a subset of the full complement of necessary information and approaches to improve their health.

Today, many friends, colleagues, and patients in the health care system express these same frustrations. Suboptimal diet remains the leading cause of poor health in the US and globally,1,2 with most of this due to cardiovascular and metabolic diseases. At the same time, tremendous advances in nutritional, behavioral, and policy science provide a clear roadmap for evidence-based dietary priorities,3 clinical behavior-change strategies,4,5 and health systems, community, and national approaches to improve cardiometabolic health.5-7 The disconnect between what we know versus what is being done in nutrition is larger than for anything else in health care. Although this presents a remarkable irony, it also presents a remarkable opportunity to reduce disease and rein in spiraling health care costs.

Cardiologists should be leading this charge. Cardiac disease, stroke, and their related metabolic disorders and risk factors represent eminently preventable conditions that together consume a substantial proportion of national health resources. We are at the front lines of this battle, and we must maximally utilize every defense in our arsenal to make a difference in our patients' lives. Recognizing this, the American Heart Association formally prioritized lifestyle and behavior change in its 2020 Strategic Impact Goals: the mission is no longer just about treating or even preventing disease, but achieving health.8 I was fortunate to participate in the writing of these goals, particularly by contributing to the dietary targets, which appropriately focus on food-based priorities such as increasing fruits, vegetables, seafood, and whole grains, and reducing sugar-sweetened beverages and a pernicious additive, sodium. In the summer of 2015, the American College of Cardiology (ACC) held its first-ever Population Health Retreat, aiming to shift the ACC's paradigm away from disease recognition and management and toward prevention: healthier lifestyles, improved nutrition, and greater physical activity.9 ACC President Kim Allan Williams, Sr., MD, FACC, highlighted this new focus and declared, "We have to become life coaches and good examples of healthy lifestyle in order to promote lifestyle improvement."9

To enable this transformation toward successfully addressing diet and behavior, what should every cardiologist know? First, the historical prioritization on reducing total fat, saturated fat, and dietary cholesterol is outdated and incomplete.10,11 Evidence from a broad range of research paradigms demonstrates that the focus should be on healthful food-based diet patterns, including increased intakes of beneficial foods such as fruits, nuts, vegetables, minimally processed whole grains, legumes, polyunsaturated and phenolic-rich vegetable oils, seafood, yogurt; and reduced intakes of sugar-sweetened beverages, processed (preserved) meats, and foods rich in refined grains, starches, and sugars (Table 1).3 Red meats should be consumed moderately to prevent weight gain and diabetes, and butter used occasionally but not emphasized.12 Two industrial additives – sodium and partially hydrogenated vegetable oils – should also be avoided. Such a diet meaningfully lowers total carbohydrate, due to less refined carbohydrates, and increases total fat – optimally exceeding the previously recommended cap of 35% of calories – due to increased nuts, fish, and vegetable oils.11 However, these macronutrient changes reflect a secondary consequence, not primary aims, of the food-based priorities. By understanding this set of priorities, cardiologists and other allied health professionals can appropriately guide teaching and behavior change efforts.

Table 1: Evidence-Based Dietary Priorities for Cardiovascular and Metabolic Health

 

Target*

Notes

Consume More

Fruits

3 servings per day

Whole fruits (fresh, frozen, canned) are preferable to 100% juice; limit the latter to about 1 glass per day.

Nuts, seeds

4 servings per week

Choose from a variety of different nuts and seeds.

Vegetables, including legumes (excluding white potatoes)

3 servings per day

Minimize starchy vegetables, especially white potatoes.

Minimally processed whole grains

3 servings per day, in place of refined grains

As a practical rule of thumb, choose grain products with at least 1 g of fiber for every 10 g of total carbohydrate (i.e., a carb:fiber ratio of <10:1).27

Fish, shellfish

2 or more servings per week

Aim for oily fish, e.g. salmon, tuna, mackerel, trout, herring, sardines.

Dairy products, especially yogurt and cheese

2-3 servings per day

The choice of whole-fat vs. low-fat can be based on personal preference, as current evidence is insufficient to confirm which is superior.

Vegetable oils

2 to 6 servings per day

Aim for polyunsaturated and/or phenolic-rich oils and soft spreads, such as from soybean oil, canola oil, and extra-virgin olive oil.

Consume Less

Refined grains, starches, sugars

No more than 1-2 servings per day

Do not focus on total or added sugars alone, as low-fiber, high glycemic complex carbs (refined grains, starches) appear similarly harmful.

Processed meats

Don't eat

Avoid meats preserved with sodium or nitrates, e.g. hot dogs, bacon, sausage, pepperoni, salami, and chicken, turkey, ham, or beef deli meats.

Red meats

No more than 2-3 servings per week

Fresh or frozen beef, pork, lamb.

Industrial trans fat

Don't eat

Avoid foods made with partially hydrogenated vegetable oils.

Sugar-sweetened beverages

Don't drink

Avoid sugar-sweetened soda, sports drinks, energy drinks, iced teas, and fruit drinks.

Alcohol

Up to 1 drink per day for women, 2 drinks per day for men

For those who drink alcohol, moderate daily use appears optimal, without clear differences in health effects between wine, beer, or spirits.

Sodium

No more than 2,000 mg/d

Avoid packaged, restaurant, or deli foods high in sodium. Major sources include bread, chicken, cheese, processed meats, soups, and canned foods.

*Based on a 2,000 kcal/day diet. Servings should be adjusted accordingly for higher or lower energy consumption.
Modified from Mozaffarian D. Dietary and policy priorities for cardiovascular disease, diabetes, and obesity: a comprehensive review. Circulation 2016 Jan 8. [Epub ahead of print]

Second, cardiologists should be champions of the distinction between diet quality versus quantity. "Poor diet" and "obesity" are neither synonymous nor interchangeable concepts. Healthful diet patterns operate through numerous mechanistic pathways and risk factors, with obesity representing only a small subset of these pathways.3 Regardless of body weight, healthful diet patterns substantially reduce cardiovascular risk, while also stabilizing long-term weight gain.3,10,13,14 Thus, diet quality, rather than weight and adiposity, should be the primary focus of dietary counselling. Indeed, focus on calorie-counting can lead to paradoxical and potentially harmful recommendations, whereby metabolically harmful, obesogenic "low-calorie" foods are prioritized over minimally processed "high-calorie" foods that improve both metabolism and long-term weight homeostasis.15 Every calorie in a food is thermodynamically equivalent in a test tube. Yet, different foods produce complex and divergent effects on the physiologic compensatory mechanisms for long-term energy balance: satiety, glucose-insulin responses, hepatic fat synthesis, adipocyte function, brain craving, the microbiome, and even metabolic expenditure.13,16,17 For long-term weight homeostasis, foods rich in rapidly digestible, low-fiber carbohydrates appear particularly adverse, while fruits, nonstarchy vegetables, nuts, yogurt, fish, and whole grains appear protective.13,16,17 Of course, for short-term weight loss, calories are king: this explains why nearly any diet can be effective in the short-term. Many overweight and obese patients effectively lose weight on very low-carbohydrate diets, a reasonable first choice for intensive short-term weight loss, especially among patients with insulin resistance.18,19 Once weight loss has been achieved, patients should shift back toward healthful, food-based diet patterns (Table 1).

Third, cardiologists must be familiar with effective behavior change strategies and vigorously advocate for health care system improvements to facilitate these efforts. Successful behavior change methods incorporate shared goal setting, self-monitoring, feedback, scheduled follow-up, and peer support.4 These provider efforts must be potentiated by changes to health systems, including regular clinician training, coordinated care by multi-disciplinary teams, electronic health records that assess and monitor diet, electronic systems for patient feedback and regular follow-up visits, and restructuring of reimbursement guidelines, practice goals, and quality benchmarks to include nutrition.5 The Affordable Care Act's provisions on accountable care organizations, whereby medical groups, physician-hospital organizations, and integrated delivery systems will share medical and financial responsibility for the health of populations, provides a further incentive to align priorities toward nutrition and behavior change.20,21 Novel internet, mobile, and personal technologies may also be effective and complement clinical efforts, but require additional investigation to confirm sustained benefits beyond 6-12 months.

Fourth, cardiologists and our professional societies should be actively leading our communities and our nations toward evidence-based policies and quality standards that protect the public and shift the population toward health, just as we have done for automobile safety, drug safety, air and water quality, worksite safety, building construction standards, food-borne pathogens, and tobacco smoking. A handful of sensible dietary policies and quality standards would produce major health benefits across the population while also reducing inequities in nutrition and health (Table 2).6,7,22,23 Such "soft healing" efforts are crucial complements to the current "hard healing" focus of modern health care and also help to address disparities in knowledge, cost, and access.24

Table 2: Evidence-Based Policy Priorities for Better Population Nutrition

  • State or national tax and subsidy framework to reflect the real costs of food.22
  • Strong, health-aligned quality standards and incentives in all food assistance programs, such as the Supplemental Nutrition Assistance Program (SNAP, formerly Food Stamps).
  • Food industry, retailer, and restaurant incentives (and disincentives) to develop and market healthier foods.
  • Comprehensive school and workplace wellness programs including nutrition education, environmental change, family and peer support, and supportive organizational policies.
  • Quality standards on contents of salt and industrial trans fat; quality standards on foods marketed to children.
  • Health system reimbursement guidelines, practice goals, and quality benchmarks that prioritize nutrition and behavior change.
  • Long-term agricultural policies that encourage the production, storage, transport, and sales of healthier foods.

Finally, cardiologists must be familiar with major fads and misconceptions in popular nutrition, providing a stout line of defense against the onslaught of variably accurate newspaper and magazine articles, books, television personalities, social media, blogs, and websites. Recognizing the crucial role of nutrition in their health, patients and their families increasingly arrive at their providers' offices with a virtual panoply of confused dietary impressions. These can frustrate and bewilder the practicing clinician, already faced with brief visit durations, increasing administrative paperwork, and complex and growing drug, device, and procedural options. Examples of popular topics in nutrition today include gluten-free, organic, genetic modification, local, grass-fed, paleo, low-carb, and vegan. Because of the dynamic trends in these areas and the naturally evolving science over time, the practicing clinician should regularly refer to updated, reliable sources of scientific information, such as found on academic websites or university nutrition newsletters.25,26 In general, these popular concepts often have a minor or uncertain influence on health, compared with the "big picture" of overall foods and diet patterns consumed. Among current fashionable concepts, a high-fat, Mediterranean dietary pattern is perhaps closest to evidence-based nutritional priorities (Table 1), and thus may be a useful construct for many patients.

In sum, modern evidence provides strong impetus toward healthful, food-based dietary patterns for improving cardiometabolic health, rather than outdated emphases on total fat, saturated fat, or calorie counting. Major questions remain, including the health effects of specific minor fatty acids, different dairy foods, phenolic compounds, other trace bioactives, and different cooking and processing methods; the influence of maternal-fetal exposures, diet-microbiome interactions, and sleep duration and quality; the mechanisms and drivers of long-term weight homeostasis; and the optimal agricultural and food systems to create healthful foods while maximizing sustainability and minimizing disparities. Yet, abundant evidence exists to define and implement specific food-based priorities as well as effective behavior change strategies, supportive health systems enhancements, and robust, complementary population policies. The ACC and all cardiologists must take the lead in translating this modern knowledge into action.

References

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  10. Mozaffarian D. Diverging global trends in heart disease and type 2 diabetes: the role of carbohydrates and saturated fats. Lancet Diabetes Endocrinol 2015;3:586-8.
  11. Mozaffarian D, Ludwig DS. The 2015 US Dietary Guidelines: Lifting the ban on total dietary fat. JAMA. 2015;313:2421-2.
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  14. Dietary Guidelines Advisory Committee. Scientific Report of the 2015 Dietary Guidelines Advisory Committee: Advisory Report to the Secretary of Health and Human Services and the Secretary of Agriculture (health.gov website). 2015. Available at: http://health.gov/dietaryguidelines/2015-scientific-report/PDFs/Scientific-Report-of-the-2015-Dietary-Guidelines-Advisory-Committee.pdf. Accessed: 3/25/2015.
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  23. McGill R, Anwar E, Orton L, et al. Are interventions to promote healthy eating equally effective for all? Systematic review of socioeconomic inequalities in impact. BMC Public Health 2015;15:457.
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Clinical Topics: Diabetes and Cardiometabolic Disease, Clinical Topic Collection: Dyslipidemia, Prevention, Sports and Exercise Cardiology, Lipid Metabolism, Nonstatins, Statins, Diet, Smoking

Keywords: Accountable Care Organizations, Adipocytes, Adiposity, Cardiovascular Diseases, Cholesterol, Dietary, Delivery of Health Care, Integrated, Diabetes Mellitus, Diagnostic Tests, Routine, Diet, Carbohydrate-Restricted, Dietary Fats, Fabaceae, Fatty Acids, Fatty Acids, Monounsaturated, Follow-Up Studies, Glucose, Health Care Costs, Health Expenditures, Health Promotion, Health Resources, Heart Diseases, Homeostasis, Hospital-Physician Joint Ventures, Insulin Resistance, Insulins, Life Style, Microbiota, Motor Activity, Nitrates, Obesity, Overweight, Patient Protection and Affordable Care Act, Poaceae, Risk Factors, Smoking, Sodium, Solanum tuberosum, Sports, Stroke, Students, Medical, Sweetening Agents, Diet, Vegetarian, Water Quality, Weight Gain, Weight Loss


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