By: Justin Budz, PharmD Candidate c/o 2023

                 In the United States (US), heart disease is the leading cause of death for both men and women of most racial and ethnic groups, followed by cancer and coronavirus disease 2019 (COVID-19).¹ About 659,000 people in the US die from heart disease each year, which encompasses about 1 in every 4 deaths.² From 2016-2017, the total cost of health care services, medications, and loss of productivity due to heart disease was approximately $363 billion.² Heart disease broadly categorizes several heart conditions, the most common being coronary artery disease (CAD).³ 

CAD, also referred to as coronary heart disease (CHD), is caused by plaque buildup on the walls of the arteries. A major component of plaque is cholesterol. As the amount of plaque increases, the arterial lumen begins to narrow which can limit or completely block blood flow.³ Risk factors for heart disease include hypertension, hyperlipidemia, diabetes, obesity, an unhealthy diet, physical inactivity, and excessive alcohol use.³ Patients with heart disease are advised to make necessary lifestyle modifications such as increasing physical activity, quitting smoking, and eating a diet low in sodium and fat. Medications may be initiated to treat different risk factors. Depending on disease severity, surgical procedures may be considered to help restore blood flow to the heart.³ 

The Impact of Dietary Patterns on Cardiovascular Disease 

According to the American Heart Association (AHA), poor diet quality is strongly associated with increased risk of cardiovascular disease (CVD) morbidity and mortality.⁴ Adherence to a heart-healthy diet is associated with optimal cardiovascular health. A heart-healthy diet consists of fruits, vegetables, whole grains, healthy sources of protein, liquid plant oils, and minimally processed foods.⁴ The Dietary Patterns Methods Project found a 14-28% lower CVD mortality among adults with high adherence compared with low adherence to heart-healthy dietary patterns.⁵ A suspected culprit behind worsening CVD is dietary fat. A diet high in fat can increase low-density lipoproteins (LDL). Guidelines for reducing CVD risk recommend limiting dietary cholesterol to decrease LDL levels.⁴ 

It is a common misconception to assume that all fats are unhealthy. Dietary fats are essential nutrients that provide energy for the body, support cellular function, protect organs, provide insulation, absorb nutrients, and produce certain hormones.⁶ There are four types of dietary fat: saturated, trans, monounsaturated, and polyunsaturated fats. Saturated and trans fats are solids at room temperature and are known to increase LDL levels. Saturated fats are mainly found in animal-based foods like beef, pork, poultry, full-fat dairy products, eggs, and tropical oils (coconut and palm).⁶

Trans fats are naturally produced in the gut of certain animals and artificially produced by hydrogenated vegetable oils.⁶  In June 2015, the Food and Drug Administration (FDA) determined that partially hydrogenated oils are no  longer Generally Recognized as Safe (GRAS) in human food.⁷ Trans fats are typically found in fried foods, baked goods, and stick margarine. The AHA recommends limiting calories to 5-6% from saturated fat while also cutting out foods containing partially hydrogenated vegetable oils to reduce consumption of trans fats.⁶ 

Polyunsaturated and monounsaturated fats are both liquid at room temperature and are known to decrease LDL levels. Polyunsaturated fats are mainly found in plant-based oils (soybean oil, corn oil, sunflower oil) but can also be found in walnuts, sunflower seeds, tofu, and soybeans.⁶ Monounsaturated fats are mainly found in plant-based oils (olive oil, canola oil, peanut oil, safflower oil, and sesame oil) but can also be found in avocados, peanut butter, and many nuts and seeds.⁶ The AHA recommends having a nutritionally balanced diet where the majority of saturated and trans fats are replaced by polyunsaturated and monounsaturated fats to lower the risk of heart disease.⁶ 

Observational Study: Analyzing Risk of Cardiovascular Disease from Vegetable, Dairy, and Animal Derived Fat 

The AHA’s Scientific Sessions 2021 is a premier global exchange of the latest scientific advancements, research, and evidence-based clinical practice updates in cardiovascular science.⁸ At this event, Dr. Fenglei Wang, Ph.D., a postdoctoral fellow in the Department of Nutrition at Harvard’s T.H. Chan School of Public Health, presented a study which indicated that the type of fat and food source are more important than the total amount of dietary fat in the prevention of CVD. The study, funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health, analyzed 27 years of follow-up data from 117,136 participants in the Nurses’ Health Study (1984-2016) and Health Professionals Follow-up Study (1986-2016).⁸ The average age of participants was 50 years old. Of the participants, 63% were women, 97% were white, and all were free of heart disease at enrollment. At the beginning of the study and every 4 years after,  participants completed food frequency questionnaires that were used to calculate the amount, source, and types of fat in their diets.⁸ 

Throughout the duration of the study, 6,189 participants had strokes. Participants who consumed high amounts of non-dairy animal-derived fat were 16% more likely to experience a stroke than those who ate less amounts of non-dairy animal-derived fats. Those who consumed one additional serving of total red meat daily had an 8% higher risk of stroke while those who consumed one additional serving of processed red meat had a 12% higher risk of stroke. In comparison, participants who ate the most vegetable-derived fat and the most polyunsaturated fat were 12% less likely to experience a stroke compared to those who ate the least. Dairy fat was not associated with a higher risk of stroke.⁸ Based on these results, it can be assumed that CVD risk is decreased when saturated and trans fats in red and processed meat are replaced with polyunsaturated and monounsaturated fats in non-tropical vegetable oils.⁸ It should be noted that this study was observational, and therefore, results cannot establish a cause-and-effect link between fat consumption and stroke risk. Additionally, this study primarily included health care professionals of European descent, and thus the findings may not be generalizable to diverse populations.⁸ 

Meta-Analysis Study: Systematic Review of Associations Between Cardiovascular Disease and Intake of Saturated and Trans Fats 

The authors of a meta-analysis, funded by the World Health Organization (WHO), conducted independent searches for relevant observational studies assessing the association between saturated and trans fats and health outcomes up to May 2015.⁹ Eligible studies included any observational study conducted in humans that reported a measure of association between intakes of saturated or trans fats and all-cause mortality, CHD, stroke, or type 2 diabetes.⁹ 

In the analysis of saturated fats, 20,413 potentially eligible articles were identified. After full text review, the analysis included 73 of those publications.⁹ The authors used risk ratio to analyze the health effects caused by a high intake of saturated fat. For saturated fats and all-cause mortality, the risk ratio was 0.99 (95% CI 0.91 to 1.09; P=0.91; I2=33%).⁹ For saturated fats and CHD mortality, the risk ratio was 1.15 (95% CI 0.97 to 1.36; P=0.10; I2=70%).⁹ For saturated fats and total CHD, the risk ratio was 1.06 (95% CI 0.95 to 1.17; P=0.29; I2=47%).⁹ Interpretation of these results indicates that there is no significant association between a higher intake of saturated fats and all-cause mortality, CHD mortality, and total CHD.⁹ However, the authors acknowledge that other meta-analyses have found that foods high in saturated fats have been associated with increased mortality.¹⁰ This could relate to the LDL raising effect of saturated fat; replacing saturated fats with polyunsaturated and monounsaturated fats improves LDL levels.¹¹ 

In the analysis of trans fats, 18,835 potentially eligible articles were identified. After full text review, the analysis included 50 of those publications.⁹ The authors used risk ratio to analyze the health effects caused by a high intake of trans fat. For trans fats and all-cause mortality, the risk ratio was 1.34 (95% CI 1.16 to 1.56; P<0.001; I2=70%).⁹ For trans fats and CHD mortality, the risk ratio was 1.28 (95% CI 1.09 to 1.50; P=0.003; I2=0%)⁹. For trans fats and total CHD, the risk ratio was 1.21 (95% CI 1.10 to 1.33; P<0.001; I2=0%)⁹. Interpretation of these results indicates that consumption of trans fats was significantly associated with a 34% increase in all-cause mortality, a 28% increased risk of CHD mortality, and a 21% increased risk of CHD.⁹  

Conclusion 

Heart disease currently reigns as the leading cause of death in the US, inciting lifestyle modifications to prevent future development of various heart conditions.¹ Results indicating which macronutrient is associated with CVD varies. Out of the four dietary fats, trans fat is the only nutrient known to be directly associated with an increased risk for CVD and should therefore be limited to < 1% of total calories from a daily diet, as per AHA guidelines.^6,8,9 To obtain a nutritionally balanced diet, the AHA recommends approximately 5-6% of calories are from saturated fat;any remaining sources of fat should be replaced by polyunsaturated and monounsaturated fats to lower the risk of heart disease.⁶ In addition to dietary fat consumption, Americans should implement adherence to heart-healthy diets, increased physical activity, and smoking cessation to see benefits in cardiovascular health.⁶ Implementation of these lifestyle modifications can help towards decreasing heart disease mortality in the US.  

References

1. Centers for Disease Control and Prevention. Underlying Cause of Death, 1999–2018. CDC WONDER Online Database. Atlanta, GA: Centers for Disease Control and Prevention; 2018. Accessed January 31, 2022. 
2. Virani SS, Alonso A, Aparicio HJ, Benjamin EJ, Bittencourt MS, Callaway CW, et al. Heart disease and stroke statistics—2021 update: a report from the American Heart Association. Circulation. 2021;143:e254–e743. 
3. Heart Disease. Centers for Disease Control and Prevention. https://www.cdc.gov/heartdisease/index.htm. Published January 28, 2022. Accessed January 31, 2022.  
4. Lichtenstein AH, Appel LJ, Vadiveloo M, et al. 2021 dietary guidance to improve Cardiovascular Health: A Scientific Statement from the American Heart Association. Circulation. 2021;144(23). doi:10.1161/cir.0000000000001031  
5. Liese AD, Krebs-Smith SM, Subar AF, George SM, Harmon BE, Neuhouser ML, Boushey CJ, Schap TE, Reedy J. The Dietary Patterns Methods Project: synthesis of findings across cohorts and relevance to dietary guidance.J Nutr. 2015; 145:393–402. doi: 10.3945/jn.114.205336 
6. Eat Smart – Fats. American Heart Association. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats. Accessed January 31, 2022.   
7. Center for Food Safety and Applied Nutrition. Final determination regarding partially hydrogenated oils. U.S. Food and Drug Administration. https://www.fda.gov/food/food-additives-petitions/final-determination-regarding-partially-hydrogenated-oils-removing-trans-fat. Accessed February 1, 2022.
8. Vegetable fat may decrease stroke risk, while animal fat increases it. American Heart Association. https://newsroom.heart.org/news/vegetable-fat-may-decrease-stroke-risk-while-animal-fat-increases-it. Accessed February 1, 2022.  
9. de Souza RJ, Mente A, Maroleanu A, et al. 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. BMJ. 2015;351:h3978. Published 2015 Aug 11. doi:10.1136/bmj.h3978 
10. Larsson SC, Orsini N. Red meat and processed meat consumption and all-cause mortality: a meta-analysis. Am J Epidemiol 2013. 
11. Franz MJ, Bantle JP, Beebe CA, et al. Evidence-based nutrition principles and recommendations for the treatment and prevention of diabetes and related complications. Diabetes Care 2003;26 Suppl 1:S51-61.

Published by Rho Chi Post