LIPIDS – Separating Fats from Fiction

Ampath Diagnostic Guide | Pathology solutions are in our DNA

🧬 What Are Lipids?

Lipids (fats) are essential for many biological functions, despite the common misconception that they’re bad for health.

Two main forms in the bloodstream:

1. Triglycerides – The primary storage form of energy
   • High levels increase risk for:
     • Diabetes
     • Cardiovascular disease (CVD)
     • Pancreatitis
2. Cholesterol – A key component in:
   • Hormone production (e.g. cortisol, oestrogen, testosterone)
   • Cell membrane integrity
   • Absorption of fat-soluble vitamins

The liver produces most cholesterol, while some comes from animal-based foods (poultry, dairy, red meat).

🧪 Lipoproteins & Transport

Because lipids are fat-soluble, they’re transported in blood by lipoproteins (fat + protein molecules).

Key lipoproteins:

• VLDL (Very-Low-Density Lipoproteins) – carry triglycerides
• LDL (Low-Density Lipoproteins) – carry cholesterol
• HDL (High-Density Lipoproteins) – carry cholesterol back to the liver

📊 Lipogram – Laboratory Measurement & Interpretation

A lipogram measures:

• Total cholesterol
• Triglycerides
• HDL cholesterol
• LDL cholesterol

HDL ("Good" Cholesterol):

• Removes unused cholesterol from cells
• Returns cholesterol to the liver for disposal
• Has anti-inflammatory effects
• Higher levels are cardio-protective
• Can be increased through exercise and lowering carbohydrate intake

LDL ("Bad" Cholesterol):

• Transports cholesterol through the bloodstream
• More prone to oxidation → can damage arteries
• High levels increase risk for:
  • Coronary artery disease
  • Stroke (cerebrovascular disease)
  • Peripheral vascular disease

Reducing LDL levels decreases the risk of CVD.
LDL levels are key to guiding treatment decisions.

🎯 Target Levels for Lipids

1. Total & LDL Cholesterol Targets

• Very High Risk (e.g. atherosclerosis, diabetes with microalbuminuria, familial hypercholesterolaemia, chronic kidney disease, Framingham risk >30%):
  • Total cholesterol: < 4.0 mmol/l
  • LDL cholesterol: < 1.8 mmol/l
• High Risk (15–30%):
  • Total cholesterol: < 4.5 mmol/l
  • LDL cholesterol: < 2.5 mmol/l
• Moderate/Low Risk (<15%):
  • Total cholesterol: < 5.0 mmol/l
  • LDL cholesterol: < 3.0 mmol/l

2. Other Optimal Lipid Targets

• HDL cholesterol:
  • ≥ 1.0 mmol/l in men
  • ≥ 1.2 mmol/l in women
• Triglycerides:
  • < 2.0 mmol/l

🍽️ Is Fasting Required?

Fasting is not always required. Non-fasting samples are suitable for:

• First-line screening
• Most patients

Fasting is required if:

• Triglyceride levels are > 8.0 mmol/l
• Patient is recovering from pancreatitis
• Patient is on medications that raise triglycerides (e.g. steroids, oestrogen, retinoic acid)

🔎 Screening Guidelines

When to Start:

• Men: Age 35
• Women: Age 45
• Start at age 20 if any of the following apply:
  • Diabetes
  • Family history of heart disease or high cholesterol
  • Personal history of coronary risk factors (e.g. smoking, high BP)

Frequency:

• Every 5 years if normal
• More frequently if risk factors are present
• Continue until age 65
• Follow up 6-monthly for lifestyle changes and 2 months after changing medication

💊 Treatment Considerations

Treatment is based on:

• LDL cholesterol level
• Risk factors
• Risk calculations (e.g. Framingham score)

Automatically high-risk if:

• Atherosclerosis
• Diabetes (Type 2 > 40 years old, or Type 1 with microalbuminuria)
• Genetic lipid disorders (e.g. familial hypercholesterolaemia)
• Chronic kidney disease

Others require formal risk scoring using:

• Total and HDL cholesterol
• Blood pressure, age, sex, smoking status
• Online tools (e.g. Framingham risk calculator)

🚶 Lifestyle & Medication

Lifestyle Changes (first-line treatment):

• Reduce saturated fat and total fat intake
• Lose weight if overweight
• Perform regular aerobic exercise
• Increase intake of:
  • Fruits and vegetables
  • Fibre-rich foods (e.g. oats, beans)

Medications:

• Statins (e.g. atorvastatin, simvastatin):
  • Lower LDL by 20–60%
  • Also reduce triglycerides and raise HDL
  • Prevent plaque rupture in blood vessels
• Fibrates (e.g. gemfibrozil, fenofibrate):
  • Lower triglycerides
  • Raise HDL
  • Often used with statins

📉 Secondary Causes of High Lipid Levels

Causes of High LDL Cholesterol:

• Obesity
• Insulin resistance
• Type 2 diabetes
• Underactive thyroid
• Kidney or liver disease
• Medications:
  • Corticosteroids
  • Androgens
  • Diuretics
  • Antiretrovirals
  • Retinoids
  • Progestogens

Causes of High Triglycerides (include the above plus):

• Alcohol abuse
• HIV infection
• Oral contraceptives
• Oestrogen therapy

🥑 Can Food Lower Cholesterol?

Yes — focus on type of fat, not just total fat.

Better choices:

• Replace saturated fats (red meat, butter, cheese) with monounsaturated fats (olive oil, avocado)
• Avoid trans fats (found in some margarines, fried foods, baked goods)
• Eat more:
  • Oily fish (omega-3s): salmon, tuna, herring
  • Nuts (walnuts, pistachios) – watch calories
  • High-fibre foods: fruits, vegetables, beans, oats

🥚 Eggs are good protein sources and don’t raise cholesterol significantly.

🧠 Final Thoughts

• Aim to improve overall health, not just cholesterol levels
• A healthy diet includes:
  • Milk and dairy
  • Limited sweets and refined carbs (e.g. white bread, pasta, white rice)
• These reduce risk of obesity, insulin resistance, and diabetes