Welcome to your study guide for Diet Related Conditions or Disorders! In this unit, you will explore how the food we eat directly impacts our physical health. We will look at what causes specific conditions, how they affect the body (pathophysiology), common symptoms, and how following official dietary guidelines can prevent or manage them.

Don't worry if medical terms like atherosclerosis or polydipsia look intimidating at first. We will break down every term step by step with easy-to-remember explanations!

1. Cardiovascular Disease (CVD) and Hypertension

Cardiovascular Disease (CVD) is an umbrella term for conditions affecting the heart or blood vessels. Hypertension refers to chronically high blood pressure.

What Causes CVD and Hypertension?

• High intake of saturated fatty acids and trans fats: These fats raise levels of Low-Density Lipoprotein (LDL) cholesterol ("bad" cholesterol) relative to High-Density Lipoprotein (HDL) cholesterol ("good" cholesterol).
• Excess salt (sodium) intake: Eating too much salt causes the body to retain excess water, which increases blood volume and places extra strain on blood vessels, leading to hypertension.
• Excessive alcohol consumption: Contributes to elevated blood pressure and weight gain.

How It Affects the Body (Pathophysiology)

When there is excess LDL cholesterol in the bloodstream, it gradually builds up inside the walls of the arteries. This fatty plaque build-up is known as atherosclerosis.
As the plaques harden and enlarge, the arteries narrow and lose elasticity. This restricts blood flow:
• If blood flow to the heart muscle is restricted, it can cause chest pain (angina) or a heart attack (myocardial infarction).
• If blood flow to the brain is blocked, it leads to a stroke.

Dietary Management and UK Guidelines

• Salt reduction: Limit salt intake to a maximum of 6 g per day for adults.
• Fat substitution: Replace saturated and trans fats with monounsaturated and polyunsaturated fats (e.g., olive oil, vegetable oils, nuts, and oily fish).
• Adopt heart-healthy dietary patterns: Follow Mediterranean or DASH dietary principles rich in wholegrains, dietary fibre, and at least 5 portions of fruit and vegetables daily.

Key Takeaway: Excess saturated fat raises LDL cholesterol causing arterial plaque (atherosclerosis), while excess sodium (over 6 g/day) raises blood pressure (hypertension).

2. Obesity and Overweight

Obesity is a complex condition characterised by excessive accumulation of body fat that presents a risk to health.

How Obesity is Measured

Obesity is primarily assessed using the Body Mass Index (BMI) formula:

\(\text{BMI} = \frac{\text{weight in kg}}{(\text{height in m})^2}\)

According to UK and World Health Organization (WHO) standards, BMI is classified as follows:
• Normal range: \(18.5\text{–}24.9\text{ kg/m}^2\)
• Overweight: \(25.0\text{–}29.9\text{ kg/m}^2\)
• Obese: \(\ge 30.0\text{ kg/m}^2\)

Dietary Causes

Obesity results from a sustained positive energy balance — this means energy intake (calories eaten) consistently exceeds total energy expenditure (calories burned through basal metabolic rate and physical activity). Diets high in free sugars, ultra-processed foods, and dietary fats are energy-dense and make overconsumption easy.

Associated Health Risks

• Physical risks: Type 2 diabetes, coronary heart disease, stroke, osteoarthritic strain on weight-bearing joints (such as hips and knees), and certain cancers (e.g., colorectal/bowel cancer, breast cancer).
• Psychosocial impacts: Low self-esteem, social isolation, and depression.

Management Strategies

• Establish a caloric deficit (consuming fewer calories than expended).
• Practice portion control and reduce the calorie density of meals by cutting down on free sugars and saturated fats.
• Increase physical activity to raise energy expenditure.

Key Takeaway: Obesity develops from a chronic positive energy balance (\(\text{BMI} \ge 30.0\text{ kg/m}^2\)) and significantly elevates the risk of Type 2 diabetes, joint strain, and cardiovascular conditions.

3. Type 2 Diabetes Mellitus

Type 2 Diabetes is a metabolic disorder where the body cannot properly control blood glucose levels. It is closely linked to lifestyle, excess weight, and diet.

Causes and Mechanisms

• Insulin resistance: The pancreas produces the hormone insulin, but the body's cells no longer respond effectively to it.
• Relative insulin deficiency: Over time, the pancreas cannot produce enough extra insulin to overcome this resistance.
• Primary drivers: Excess adiposity (especially abdominal fat), physical inactivity, and regular consumption of refined carbohydrates and free sugars.

Symptoms and Long-Term Complications

• Key Symptoms:
— Polydipsia (excessive, unquenchable thirst)
— Polyuria (frequent urination)
— Lethargy and extreme fatigue
• Chronic Complications: If blood glucose remains uncontrolled, it damages small and large blood vessels, leading to retinopathy (eye damage/vision loss), nephropathy (kidney damage), peripheral neuropathy (nerve damage, often in feet), and increased risk of heart attacks and strokes.

Dietary Management

• Replace simple sugars with complex, low-glycaemic index (GI) carbohydrates that release glucose slowly into the bloodstream.
• Increase dietary fibre intake to slow glucose absorption.
• Avoid added/free sugars (such as sugary soft drinks, sweets, and pastries).
• Implement weight-management strategies to reduce abdominal body fat and improve insulin sensitivity.

Key Takeaway: Unlike Type 1 diabetes (an autoimmune condition), Type 2 diabetes is driven by insulin resistance linked to excess weight and refined sugars, requiring low-GI carbs and fibre for management.

4. Bone Health Disorders

Strong bones require adequate mineralisation throughout life. When key micronutrients are missing, two major disorders can develop: Osteoporosis and Rickets / Osteomalacia.

A. Osteoporosis ("Porous Bones")

• Definition: A condition characterised by low bone mineral density and structural deterioration of bone tissue, making bones brittle, fragile, and prone to fractures.
• Common fracture sites: Hip, spine (vertebrae), and wrist.
• High-risk groups: Post-menopausal women (due to declining oestrogen levels) and older adults.
• Dietary links: Inadequate lifelong intake of Calcium and Vitamin D.

B. Rickets (Children) and Osteomalacia (Adults)

• Definition: Inadequate mineralisation of the bone matrix leading to soft, weak, and painful bones.
• In children (Rickets): Results in skeletal deformities, such as bowed legs and curvature of the spine.
• In adults (Osteomalacia): Results in bone pain, muscle weakness, and an increased risk of fractures.
• Dietary/Environmental cause: Severe deficiency of Vitamin D (which is needed to absorb calcium) and/or dietary Calcium.

Dietary Prevention and Sources

• Calcium sources: Dairy products (milk, yoghurt, cheese), calcium-fortified plant-based drinks, tofu, and green leafy vegetables.
• Vitamin D sources: Oily fish (salmon, mackerel), egg yolks, fortified foods, and daily Vitamin D supplements where sunlight exposure is limited.

Memory Trick: Calcium is the brick; Vitamin D is the bricklayer. You cannot build strong bones with bricks alone if the bricklayer isn't there to put them into place!

Key Takeaway: Calcium and Vitamin D work together. Calcium provides the structural mineral, while Vitamin D enables its absorption. Deficiency leads to Rickets/Osteomalacia (soft bones) or Osteoporosis (brittle bones).

5. Iron-Deficiency Anaemia

Anaemia occurs when the concentration of haemoglobin or the number of red blood cells in the blood is lower than normal, reducing the blood's capacity to transport oxygen around the body.

Dietary Causes and Types of Iron

• Haem Iron: Found in animal tissues (red meat, poultry). It is readily and easily absorbed by the human digestive system.
• Non-Haem Iron: Found in plant sources (lentils, beans, dark green leafy vegetables, fortified cereals). It is less easily absorbed.
• The Role of Vitamin C: Consuming Vitamin C (ascorbic acid) alongside non-haem iron chemically converts it into a more soluble form, greatly enhancing its absorption.

Symptoms and High-Risk Groups

• Common Symptoms: Chronic fatigue, lethargy, breathlessness, pale skin (pallor), brittle nails, dizziness, and impaired immune function.
• High-Risk Groups: Menstruating women and adolescent girls (due to monthly blood loss), pregnant women (increased blood volume and foetal demand), and vegetarians or vegans who do not consume adequate iron-rich plant alternatives.

Management Strategies

• Eat rich sources of iron regularly: lean red meat, dark green leafy vegetables (spinach, kale), lentils, beans, and fortified breakfast cereals.
• Pair non-haem iron foods with Vitamin C-rich foods (e.g., having a glass of orange juice with fortified cereal or adding peppers to a lentil dish).

Key Takeaway: Iron is essential for haemoglobin production. Always remember to mention that Vitamin C enhances non-haem iron absorption in your exam answers!

6. Bowel Disorders and Gastrointestinal Health

The health of the digestive tract depends heavily on dietary fibre, also known as Non-Starch Polysaccharides (NSP), and adequate hydration.

Common Bowel Conditions Linked to Diet

• Constipation: Stools become hard, dry, and difficult to pass due to insufficient dietary fibre and low fluid intake.
• Diverticular Disease: Small bulges or pouches (diverticula) push outwards through weak spots in the colon wall due to high pressure from straining to pass small, hard stools. If these pouches become inflamed or infected, the condition is called diverticulitis.
• Colorectal (Bowel) Cancer: Long transit times allow waste products and potential carcinogens to remain in contact with the bowel lining for extended periods.

How Dietary Fibre Works

Insoluble fibre adds bulk to the stool and absorbs water, making waste softer, bulkier, and faster to pass through the intestine (reducing transit time and lowering pressure inside the colon).

UK Dietary Guidelines for Bowel Health

• Dietary Fibre (NSP): Adults should aim for 30 g of fibre per day.
• Sources of Fibre: Wholegrain breads and cereals, oats, brown rice, pulses (beans, lentils), seeds, fruits, and vegetables.
• Fluid Intake: Drink 6 to 8 glasses of fluid/water per day (fibre needs water to swell and work effectively).

Key Takeaway: A daily target of 30 g of fibre plus 6–8 glasses of fluid keeps waste moving smoothly, preventing constipation, diverticular disease, and lowering colorectal cancer risk.

Exam Pitfalls and Top Revision Tips

Make sure you avoid these common examiner-reported mistakes in your A2 7 exam:

• Mistake 1: Giving vague answers. Never just write "they eat unhealthy food". Specify the exact nutrient involved: e.g., "high intake of saturated fatty acids", "excess free sugars", or "insufficient non-starch polysaccharides".
• Mistake 2: Confusing Type 1 and Type 2 Diabetes. Remember that Type 1 is an autoimmune condition where the body cannot produce insulin. Type 2 is a metabolic condition linked to lifestyle, excess weight, and insulin resistance.
• Mistake 3: Forgetting exact UK numerical targets. Memorise these exact figures: maximum 6 g salt/day, target 30 g fibre/day, at least 5-a-day for fruit/vegetables, and BMI thresholds (25.0–29.9 for overweight, \(\ge 30.0\) for obese).
• Mistake 4: Missing the Vitamin C link. When writing about iron-deficiency anaemia, always state that Vitamin C enhances the absorption of non-haem iron from plant sources.