What is cardiovascular disease?
Cardiovascular disease (CVD) refers to a cluster of disorders affecting the heart and blood vessels, including coronary heart disease (CHD) - restriction of blood flow to the heart, cerebrovascular disease - restriction of blood flow to a region of the brain, and peripheral vascular disease - restriction of blood flow to the arms and legs.
These conditions are all linked by a common underlying factor, atherosclerosis, which is characterized by the buildup of cholesterol-laden plaques in the arteries, leading to restricted blood flow to various parts of the body. Atherosclerosis is a chronic condition that can have serious consequences, such as heart attack, stroke, and limb ischemia.
Cholesterol types and the heart
Cholesterol moves through the arteries packaged in tiny molecules called lipoproteins.
Three key types of cholesterol, low-density lipoprotein (LDL, (18% protein, 22% phospholipid, 58% triglyceride, or richer still in triglyceride), high-density lipoprotein (HDL, (78% protein, 12% phospholipid, 9% Triglyceride) and very-low-density lipoprotein (VLDL) have the biggest effect on heart health. It is excessive amounts of circulating LDL (considered bad) that results in this build-up and atherosclerosis (see figure 1).
Establishing a link between diet and heart disease
It wasn’t until the middle of the last century that we started to investigate a link between our diet and heart disease. Up until this point in time infectious diseases such as influenza and tuberculosis had been the leading cause of death. In the late 1940’s and early 1950’s large studies began to focus on diet as a cause of skyrocketing rates of heart disease.
The Seven Countries Study by Ancel Keys and the Framingham Heart Study started tracking this relationship between diet and health. In the Seven Countries Study, there were two major, early findings. When they compared average values in one country with another, there was a strong positive relationship between serum cholesterol and prevalence of CHD, and a strong positive relationship between consumption of saturated fatty acids (SFAs) and serum cholesterol.
Similarly with the Framingham Heart Study, an early finding was that high levels of cholesterol was often an early sign of impending heart disease.
In 1980 the Nurse’s Health study tracked 80,082 women for 14 years. This study looked at how different types of fat in our diet affect the risk of getting heart disease. They found that for every 5% increase in saturated fat, there was a 17% increase in the risk of getting heart disease. Trans fats, which are found in some processed foods, were even worse - every 2% increase in trans fats led to a nearly twofold increase in the risk of heart disease.
On the other hand, monounsaturated and polyunsaturated fats, found in foods like nuts and fish, were associated with a lower risk of heart disease. Overall, the total amount of fat in the diet did not significantly affect the risk of heart disease. The study estimated that replacing some saturated or trans fats with unsaturated fats could significantly reduce the risk of heart disease. (Hu, 1997).
These plus other studies reveled a strong link existed between diet and heart health. In particular it highlighted the relevance of specific types of fat in our diet not just all fats.
Not all fats are bad, in fact some are essential.
It is a common misconception that all dietary fats are harmful to our health. In reality, certain types of fats are actually beneficial and play an important role in maintaining optimal health.
While it is true that heart disease and stroke are leading causes of death worldwide, blaming dietary fat alone for these conditions is oversimplifying the issue. Other factors, such as smoking, obesity, and physical inactivity, also contribute to the risk of heart disease.
However, making smart choices about the types of fats you consume is a key strategy for preventing heart disease and maintaining good health.
By incorporating healthy fats such as monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs omega 6 & 3), into your diet and avoiding unhealthy saturated ones can help to reduce harmful LDL cholesterol levels and increase the beneficial HDL cholesterol levels. This can lead to a lower risk of heart disease and stroke.
Prof. Walter Willett from Harvard University suggests that the most compelling evidence for the benefits of omega-3 fat is its ability to prevent or treat heart disease and stroke. (Willett, 2017). Omega-3 fats aid in maintaining a regular heartbeat, which is essential for good cardiovascular health. If the heart's electrical rhythm is significantly disrupted, it can lead to serious complications such as ventricular fibrillation (also known as arrhythmia) or cardiac arrest.
The process of atherosclerosis, an irregular local thickening and loss of elasticity of the arterial wall can lead to cardiac arrest. Figure 2 illustrates the process of CHD and cardiac arrest and possible involvement of lipids.
Figure 2 Possible processes involved in the development of ischaemic heart disease and myocardial infarction. Shaded boxed indicate points where lipids may be involved.
Conclusion
In conclusion, cardiovascular disease (CVD) is a serious health condition that encompasses various disorders affecting the heart and blood vessels. Atherosclerosis, the buildup of cholesterol-laden plaques in the arteries, is a common underlying factor in these conditions and can lead to severe consequences like heart attacks, strokes, and limb ischemia.
Research has established a strong link between diet and heart disease, particularly concerning the types of fats consumed. Studies such as the Seven Countries Study and the Framingham Heart Study have highlighted the relationship between serum cholesterol concentration, saturated fatty acid consumption, and the prevalence of coronary heart disease.
Further investigations, such as the Nurse's Health study, have shown that excessive intake of saturated and trans fats increases the risk of heart disease, while monounsaturated and polyunsaturated fats, found in foods like nuts, hemp seed and fish, are associated with a lower risk.
However, it is important to note that not all fats are detrimental to health. Certain fats, such as omega-3 fatty acids, have been shown to have significant benefits in preventing and treating heart disease and stroke. Incorporating healthy fats into the diet, while avoiding unhealthy saturated fats, can help reduce harmful LDL cholesterol levels and increase beneficial HDL cholesterol levels, thereby reducing the risk of cardiovascular disease.
While dietary fat is not the sole cause of heart disease and stroke, making informed choices about the types of fats consumed is a crucial strategy in maintaining cardiovascular health. By adopting a balanced and nutritious diet that includes beneficial fats, individuals can take proactive steps towards preventing cardiovascular disease and promoting overall well-being.
References
de Lorgeril, M. (1999). Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications After Myocardial Infarction: Final Report of the Lyon Diet Heart Study. Circulation, 779-85.
Willett, W. C. (2017). Eat, Drink and be Healthy. The Harvard Medical School Guide to Healthy Eating. New York: Simon & Schuster.
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