Welcome to Cardiovascular Disease (Unit AS 2: Diet, Lifestyle and Health)
Welcome to your study notes for Cardiovascular Disease (CVD). In this chapter of Unit AS 2, we will look at how the food we eat and the lifestyle choices we make directly affect the health of our heart and blood vessels.
Cardiovascular disease is one of the most important public health topics in the UK. By understanding the underlying biology and the key dietary recommendations, you will be well-prepared to tackle both short-answer questions and structured essays in your AS 2 exam.
Don't worry if the medical terms seem tricky at first! We will break every concept down into clear, manageable steps with simple memory tips along the way.
1. What is Cardiovascular Disease (CVD)?
Cardiovascular Disease (CVD) is an umbrella term used to describe any disease affecting the heart or blood vessels (the circulatory system).
The Four Main Types of CVD
The CCEA specification highlights four primary conditions under the CVD umbrella:
1. Coronary Heart Disease (CHD): Occurs when blood flow to the heart muscle is restricted. This can cause chest pain (known as angina) or a heart attack (myocardial infarction) if the blood supply is completely blocked.
2. Stroke: Occurs when the blood supply to part of the brain is cut off, depriving brain tissue of oxygen and nutrients.
3. Peripheral Arterial Disease (PAD): Occurs when there is a blockage or narrowing in the arteries carrying blood to the limbs, most commonly the legs.
4. Aortic Disease: Refers to conditions affecting the aorta (the main blood vessel carrying blood from the heart to the rest of the body), such as an aortic aneurysm (a bulge or weakness in the aortic wall).
The Underlying Process: Atherosclerosis
Most forms of CVD begin with a biological process called atherosclerosis.
• What is it? Atherosclerosis is the progressive narrowing and hardening of arteries caused by the accumulation of fatty deposits known as atheroma (or plaques) within the artery walls.
• What happens? As atheroma builds up over time, the lumen (the inside space of the blood vessel) becomes narrower, reducing blood flow and forcing the heart to work harder to pump blood. If a plaque ruptures, a blood clot can form, completely blocking the artery.
Everyday Analogy: Imagine your kitchen water pipes. Over time, grease and limescale can stick to the inside of the pipe, making the channel narrower and narrower until water can barely get through. That is exactly what atheroma does to your arteries!
Key Takeaway for Section 1: CVD covers four main conditions (CHD, Stroke, PAD, Aortic Disease), and the driving force behind arterial narrowing is atherosclerosis (the buildup of atheroma).
2. Understanding Risk Factors: Modifiable vs. Non-Modifiable
In your exam, you must clearly distinguish between factors an individual can change (modifiable) and those they cannot (non-modifiable).
Non-Modifiable Risk Factors (Things You Cannot Change)
• Age: Risk increases significantly as a person gets older, as arteries naturally lose elasticity and plaques have had decades to build up.
• Gender: Men generally have a higher risk of developing CVD at an earlier age than pre-menopausal women.
• Family History / Genetics: Having a close biological relative with early-onset heart disease increases personal risk.
• Ethnicity: People of South Asian and Sub-Saharan African descent have a statistically higher risk of developing CVD compared to other population groups.
Modifiable Risk Factors (Things You Can Change)
• Diet: Excessive intake of saturated and trans fats, high salt intake, and low intake of dietary fiber contribute directly to arterial damage and high blood pressure.
• Physical Inactivity: A sedentary lifestyle weakens cardiovascular fitness and contributes to weight gain.
• Smoking: Chemicals in tobacco damage the lining of arteries, raise blood pressure, and increase blood clotting tendencies.
• Alcohol Consumption: Excessive alcohol intake elevates blood pressure and adds surplus energy to the diet.
• Stress: Chronic, unmanaged stress can raise blood pressure and encourage negative coping mechanisms (like overeating or smoking).
Exam Warning — Causality vs. Correlation: Never state that CVD is caused only by eating fatty foods. CVD is a multifactorial condition, meaning it develops from a combination of multiple diet and lifestyle factors interacting with genetic predisposition.
Key Takeaway for Section 2: Risk factors split into non-modifiable (Age, Gender, Genetics, Ethnicity) and modifiable (Diet, Exercise, Smoking, Alcohol, Stress). Always present CVD as multifactorial.
3. UK Nutritional Thresholds and Dietary Guidelines
To score top marks in AS 2 essays, you must quote exact UK dietary reference values and official guidelines (SACN / NHS standards).
Key Quantitative Targets
• Total Fat: Total fat intake should not exceed \(\le 35\%\) of total food energy.
• Saturated Fat: Saturated fat should not exceed \(\le 11\%\) of total food energy.
• Trans Fatty Acids: Must not exceed \(\le 2\%\) of total food energy.
• Salt (Sodium): Adults should consume no more than \(6\text{g}\) of salt per day (which is equivalent to \(2.4\text{g}\) of sodium).
• Dietary Fiber: Adults should aim for \(30\text{g}\) of dietary fiber per day (SACN 2015 recommendations).
• Omega-3 Fatty Acids: The UK recommendation is to eat at least two portions of fish per week, one of which should be oily fish (e.g., salmon, mackerel, sardines), providing Long Chain n-3 Polyunsaturated Fatty Acids (n-3 PUFA).
Common Pitfall Alert: Salt vs. Sodium
Do not use the words "salt" and "sodium" interchangeably in calculations or definitions. Remember the formula:
\(\text{Salt} = \text{Sodium} \times 2.5\)
The daily limit for an adult is \(6\text{g}\) of salt, which equals \(2.4\text{g}\) of sodium.
Key Takeaway for Section 3: Memorise the figures: \(\le 35\%\) total fat, \(\le 11\%\) saturated fat, \(\le 2\%\) trans fat, \(6\text{g}\) salt (\(2.4\text{g}\) sodium), \(30\text{g}\) fiber, and 2 portions of fish weekly (1 oily).
4. Key Dietary Mechanisms
Examiners look for your ability to explain how specific nutrients influence heart health at a physiological level.
Cholesterol: LDL vs. HDL
Cholesterol is transported in the bloodstream bound to proteins (lipoproteins):
• Low-Density Lipoprotein (LDL): Often termed "bad cholesterol". LDL transports cholesterol from the liver to the body's cells. When LDL levels are excessively high, it deposits cholesterol into the walls of the arteries, accelerating atheroma formation.
• High-Density Lipoprotein (HDL): Known as "good cholesterol". HDL collects surplus cholesterol from the bloodstream and body tissues and carries it back to the liver for excretion or recycling, thus protecting against plaque buildup.
Memory Trick: Remember LDL = Lethal / Lowdown (keep it low!) and HDL = Healthy / Heroic (keep it high!).
Replacing vs. Reducing Fats
Crucial Exam Tip: Do not simply write "people need to reduce fat". Mark schemes demand that you explain replacing saturated fats with unsaturated fats (Monounsaturated Fatty Acids - MUFA, and Polyunsaturated Fatty Acids - PUFA). Replacing saturated fats with unsaturated oils (such as olive or rapeseed oil) lowers circulating LDL cholesterol without negatively lowering HDL.
Dietary Fiber: The Importance of Soluble Fiber
While the overall adult target is \(30\text{g}\) per day, soluble fiber (found in foods like oats, barley, pulses, beans, and lentils) plays a specific role in lowering CVD risk. Soluble fiber forms a gel-like substance in the digestive tract that binds to bile acids and cholesterol, preventing them from being reabsorbed and encouraging their elimination from the body. In contrast, insoluble fiber primarily adds bulk to stools and aids digestive transit.
Antioxidants and Phytochemicals
• The Nutrients: Antioxidant vitamins include Vitamin A (beta-carotene), Vitamin C, and Vitamin E, alongside natural phytochemicals found in colourful fruits and vegetables.
• The Mechanism: Oxidation of LDL cholesterol inside artery walls is a critical trigger that causes white blood cells to engulf it, forming foam cells and accelerating plaque growth. Antioxidants neutralise harmful free radicals, helping to prevent the oxidation of LDL cholesterol.
Alcohol Consumption
Excessive alcohol consumption raises blood pressure (hypertension), which damages arterial walls and creates rough patches where atheroma can stick. Furthermore, alcohol provides high energy (\(7\text{kcal/g}\)), contributing to positive energy balance, weight gain, and obesity.
Key Takeaway for Section 4: Soluble fiber binds cholesterol; MUFA/PUFA should replace saturated fat to lower LDL; antioxidants prevent LDL oxidation; and excess alcohol drives up blood pressure.
5. Quick Summary & Exam Checklist
Before sitting your AS 2 exam, make sure you can answer the following questions with confidence:
• Can you define atherosclerosis and name the 4 types of CVD?
• Can you list 4 non-modifiable and 5 modifiable risk factors?
• Can you state the exact numerical targets for total fat (\(\le 35\%\)), saturated fat (\(\le 11\%\)), trans fat (\(\le 2\%\)), salt (\(6\text{g}\)), sodium (\(2.4\text{g}\)), and fiber (\(30\text{g}\))?
• Can you explain the physiological difference between LDL and HDL?
• Did you explain that saturated fat should be replaced by MUFA/PUFA, rather than just saying "cut all fat"?
• Can you describe how soluble fiber and antioxidants (A, C, E) protect the circulatory system?