Cardiovascular Health and Blood Pressure

This lesson covers the relationship between diet and cardiovascular disease (CVD) and high blood pressure (hypertension), as required by AQA GCSE Food Preparation and Nutrition specification 8585, section 3.2.3. You must understand the dietary factors that contribute to cardiovascular disease, how high blood pressure develops, and what dietary changes can reduce the risk.

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The Cardiovascular System

The cardiovascular system consists of the heart, blood, and blood vessels (arteries, veins, and capillaries). Its function is to transport oxygen, nutrients, hormones, and waste products around the body.

Cardiovascular disease (CVD) is a general term for conditions affecting the heart and blood vessels. It is the leading cause of death in the UK, responsible for approximately 25% of all deaths. The main types of CVD are:

Condition	Description
Coronary heart disease (CHD)	The coronary arteries (which supply blood to the heart muscle) become narrowed or blocked by a build-up of fatty deposits (atherosclerosis), reducing blood flow to the heart
Heart attack (myocardial infarction)	A complete blockage of a coronary artery, cutting off blood supply to part of the heart muscle, which can die
Stroke	A blood vessel in the brain becomes blocked or bursts, cutting off blood supply to part of the brain
Peripheral arterial disease	Narrowing of arteries that supply blood to the limbs (usually legs)

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Atherosclerosis: The Process

Atherosclerosis is the build-up of fatty deposits (called plaques or atheromas) on the inner walls of arteries. This is the underlying cause of most cardiovascular disease.

graph LR
    A["Healthy Artery<br/>(wide, clear lumen)"] --> B["Early Atherosclerosis<br/>(fatty streak on artery wall)"]
    B --> C["Advanced Atherosclerosis<br/>(plaque narrows the lumen)"]
    C --> D["Blood Clot (Thrombosis)<br/>(blocks the artery completely)"]
    D --> E["Heart Attack<br/>(if coronary artery)<br/>or Stroke<br/>(if brain artery)"]

    style A fill:#27ae60,color:#fff
    style B fill:#f39c12,color:#fff
    style C fill:#e67e22,color:#fff
    style D fill:#e74c3c,color:#fff
    style E fill:#c0392b,color:#fff

The process:

1. Damage occurs to the artery wall (caused by high blood pressure, smoking, or high cholesterol).
2. LDL cholesterol (low-density lipoprotein — "bad" cholesterol) deposits fat in the damaged area.
3. Over time, a plaque builds up, made of cholesterol, calcium, and fibrous tissue.
4. The artery becomes narrowed, reducing blood flow.
5. If the plaque ruptures, a blood clot (thrombus) forms, which can completely block the artery.
6. If the blocked artery supplies the heart = heart attack. If it supplies the brain = stroke.

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Dietary Factors That Increase CVD Risk

Dietary Factor	How It Increases CVD Risk
High saturated fat intake	Raises blood LDL cholesterol ("bad" cholesterol), which deposits fat in artery walls, promoting atherosclerosis
High trans fat intake	Raises LDL cholesterol and lowers HDL cholesterol ("good" cholesterol). Found in some processed and fried foods, hydrogenated vegetable oils
High salt (sodium) intake	Raises blood pressure (see below), which damages artery walls and increases the risk of heart attack and stroke
High free sugar intake	Contributes to obesity, which increases blood pressure and cholesterol levels
Low fruit and vegetable intake	Missing out on protective antioxidants (vitamins C and E, beta-carotene), fibre, and potassium
Low fibre intake	Soluble fibre helps to lower blood cholesterol. Insufficient fibre increases CVD risk
Excessive alcohol	Raises blood pressure, contributes to weight gain, can damage the heart muscle directly
Obesity	Increases blood pressure, blood cholesterol, and the risk of type 2 diabetes — all of which increase CVD risk

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Cholesterol: LDL vs HDL

Cholesterol is a fat-like substance found in the blood. It is essential for cell membranes, hormone production, and vitamin D synthesis, but too much of the wrong type is harmful.

Type	Full Name	Role	Effect on CVD
LDL	Low-density lipoprotein	Carries cholesterol from the liver to the cells	"Bad" — excess LDL deposits cholesterol in artery walls, forming plaques
HDL	High-density lipoprotein	Carries cholesterol from the cells back to the liver for disposal	"Good" — removes cholesterol from arteries, reducing plaque formation

Dietary Factors Affecting Cholesterol

Factor	Effect
Saturated fat	Raises LDL (bad) cholesterol
Trans fat	Raises LDL and lowers HDL cholesterol (worst combination)
Unsaturated fat (mono- and polyunsaturated)	Helps to lower LDL and raise HDL cholesterol
Soluble fibre (oats, beans, lentils, fruit)	Binds to cholesterol in the gut and removes it from the body, lowering blood cholesterol
Omega-3 fatty acids (oily fish, walnuts, flaxseeds)	Reduce triglycerides (another type of blood fat) and have anti-inflammatory effects on blood vessels
Plant sterols and stanols	Found naturally in small amounts in plants; also added to some spreads and yoghurts. Block cholesterol absorption in the gut

Exam Tip: Remember the simple rule: saturated fat raises LDL (bad), unsaturated fat lowers LDL (good). Oily fish provides omega-3, which reduces triglycerides and inflammation. Soluble fibre removes cholesterol from the body.

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High Blood Pressure (Hypertension)

What Is Blood Pressure?

Blood pressure is the force with which blood pushes against the walls of the arteries as the heart pumps it around the body. It is measured in millimetres of mercury (mmHg) and written as two numbers:

• Systolic pressure (the higher number) — the pressure when the heart beats and pushes blood out
• Diastolic pressure (the lower number) — the pressure between heartbeats when the heart is resting