Risk Factors for Coronary Heart Disease
“Each year, about 370,000 Americans die from coronary heart disease.”— National Heart, Lung, and Blood Institute
What is Coronary Heart Disease?
Patients diagnosed with coronary heart disease (CHD) fail to maintain an adequate supply of oxygen to heart muscle cells due to atherosclerosis in the coronary artery. Atherosclerosis involves the buildup of plaque, which is composed of cholesterol, calcium, and other fatty substances. Over time, the hardening of plaque narrows the blood vessel, making it increasingly difficult to deliver blood cells. Further, plaque deposits can rupture, stimulating the formation of blood clots that can then block the artery. During physical activity, patients often experience angina pectoris, described as discomfort or pressure in the chest, shoulders, arms, and surrounding areas of the body. In severe cases, coronary heart disease can cause myocardial infarctions, or heart attacks.
Common Risk Factors for CHD
High Consumption of Red Meat
Beyond the high fat content in red meat, scientists have identified an additional harm: the chemical production of trimethylamine N-oxide (TMAO) by gut bacteria. A byproduct in the digestion of red meat, TMAO increases cholesterol accumulation in arteries and stimulates platelets. Researchers at the Cleveland Clinic recently performed a study confirming the positive correlation between red meat consumption and TMAO levels. The study rotated 113 healthy subjects on three distinct diets (red meat, white meat, and non-meat), each for a month in a randomized order. Half of the subjects were given high-fat versions of the three diets, each of the same number of calories.
In the red meat diet, each subject consumed 8 ounces of steak per day, which amounted to about two quarter-pound beef patties.
Upon analyzing results after each diet, the researchers concluded that the TMAO levels after a month of consuming the red meat diet were three times greater than during white meat or non-meat diets (“Study Links Frequent Red Meat Consumption to High Levels of Chemical Associated With Heart Disease”, 2018). Furthermore, the same trend was seen in the group participating in the high-fat diets, affirming that the increased TMAO levels were independent of fat intake and, rather, dependent on the protein source. In addition, results concluded that abstaining from red meat can help lower the amount of TMAO in one’s blood, providing a hopeful remedy for those with high TMAO levels.
A Short Video Explaining TMAO
Cholesterol is a lipid, or fat, required for basic biological functions, such as the construction of cell membranes, and transported within the body in lipoproteins. High-density lipoprotein (HDL) helps carry cholesterol from the cells to the liver, where it is then prepared for excretion as waste; thus, it is healthy to have high HDL. The second lipoprotein is low-density lipoprotein (LDL), responsible for providing cells with cholesterol for usage; however, a high amount of LDL can cause cholesterol deposits in artery walls, contributing to plaque buildup (“High Cholesterol”, 2018).
High Blood Pressure
Blood pressure is measured by the pressures, or forces exerted, in blood vessels as the heart beats and during pauses between beats, specifically the systolic blood pressure and diastolic blood pressure, respectively. High blood pressure can cause damage to the inner walls of the inflexible arteries, resulting in small tears where LDL cholesterol can build up (“What is High Blood Pressure?”, 2016).
When smoking, the incomplete combustion of the cigarette produces carbon monoxide, which, when inhaled, combines with hemoglobin in the blood, resulting in a decrease of oxygen in the blood (“Smoking”). In addition, tobacco smoke consists of free radicals, or highly reactive atoms with unpaired electrons. These free radicals, containing oxygen and thus known as reactive oxygen species, oxidize LDL cholesterol in blood vessels, causing the oxidized LDL to become reactive with its environment (Yugar-Toledo et al., 2018). The resulting inflammation of vascular walls leads to the increased production of the pro-inflammatory and procoagulant cytokine interleukin 6 (IL-6) and consequently thrombosis, or blood clot formation in blood vessels that blocks blood flow (Tapson, 2005).
Diabetes is a disease where the body is unable to utilize or produce insulin, a hormone that assists cell absorption of glucose, thus contributing to high glucose levels in the blood. Patients with diabetes lack the enzyme extracellular signal-related kinase 5 (ERK-5) because of the body’s increased production of advanced glycation end products (AGEs), proteins or lipids that form covalent bonds with sugars. These AGEs interfere with the functioning of ERK-5 by encouraging its attachment to a protein tag in cells, specifically to small ubiquitin-related modifiers (SUMO). Without ERK-5, diabetic patients experience restricted blood vessels that can contribute to high blood pressure and consequently coronary heart disease. However, scientists believe that by removing the SUMO tag, they can combat the effects of AGEs and allow ERK-5 signalling for the creation of more nitric oxide to help dilate blood vessels (“How Diabetes Drives Atherosclerosis”, 2008).
These risk factors compose a non-exhaustive list of contributors to coronary heart disease. Additional elements include age, gender, race, and family history; however, these characteristics cannot be controlled, and thus it becomes especially crucial to manage a healthy lifestyle to prevent the advent of coronary heart disease.
“High Cholesterol.” NHS Choices, NHS, 30 July 2018, www.nhs.uk/conditions/high-cholesterol/.
“How Diabetes Drives Atherosclerosis.” ScienceDaily, University of Rochester Medical Center, 17 Mar. 2008, www.sciencedaily.com/releases/2008/03/080313124430.htm.
“Smoking.” British Heart Foundation, British Heart Foundation, www.bhf.org.uk/informationsupport/risk-factors/smoking.
“Study Links Frequent Red Meat Consumption to High Levels of Chemical Associated with Heart Disease.” National Heart Lung and Blood Institute, U.S. Department of Health and Human Services, 10 Dec. 2018, www.nhlbi.nih.gov/news/2018/study-links-frequent-red-meat-consumption-high-levels-chemical-associated-heart-disease.
Tapson, V. F. "The Role of Smoking in Coagulation and Thromboembolism in Chronic Obstructive Pulmonary Disease." Proc Am Thorac Soc 2.1 (2005): 71-7. Print.
“What Is High Blood Pressure?” American Heart Association, American Heart Association, 31 Oct. 2016, www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure/what-is-high-blood-pressure.
Yugar-Toledo, Juan Carlos, et al. “Chapter 36 Smoking and the Endothelium.” Endothelium and Cardiovascular Diseases, Elsevier, 2018.
© 2018 Michelle Tram