Louis Roller takes a look at cholesterol, its types and the risks posed by LDL-C

Cholesterol is a fatty substance that is carried around the body in the blood. The body produces most cholesterol naturally, and it is found in some foods. Lipoproteins carry cholesterol in the blood. The two main types that carry cholesterol to and from cells are called low density lipoproteins (LDL-C) and high density lipoproteins (HDL-C).

The lower the density of the lipoproteins the more fats it contains. HDL-C is called the ‘good cholesterol’ because it helps to keep cholesterol from building up in the arteries.

LDL-C cholesterol is called the ‘bad cholesterol’ because it is the main source of cholesterol build-up and blockage in the arteries. Statin medications work to reduce this LDL-C and to a lesser extent, increase HDL-C. They will also reduce triglycerides (TG).

Total cholesterol is a reading of the HDL-C and LDL-C.

Triglycerides are another form of fat in the blood that can also raise the risk of heart disease. High triglycerides are often associated with low HDL cholesterol increasing risk, even though total cholesterol levels in the blood appear normal. When there is too much LDL-cholesterol in the blood, it builds up in the walls of the arteries (plaque).

About three-quarters of the cholesterol in our bodies is made in the liver and the rest may come from the types of fats we eat. Our genes will also partly determine what our blood cholesterol levels are as will our diet and lifestyle. Cholesterol itself in food has only a very small effect on blood cholesterol. However eating too much saturated fat may lead to excess cholesterol in the blood stream.

Hyper-cholesterolaemia (high blood cholesterol) is one risk factor for coronary artery disease If our cholesterol level is 6.5 mmol/L or greater the risk of heart disease is about four times greater than that of a person with a cholesterol level of 4 mmol/L.

About 30% of the community will die from heart disease and most of these will be over 65 years old.

Modifiable risk factors for cardiovascular disease

  • smoking
  • high blood pressure
  • elevated cholesterol (total or low density lipoprotein)
  • decreased high density lipoprotein cholesterol
  • diabetes
  • obesity (large waist measurement – males >90cm; female>80cm;  high body mass index- >25kg/m2)
  • sleep apnoea
  • lifestyle (minimal exercise, poor nutrition, high stress, excess alcohol)

The most effective way to lower LDL cholesterol is to reduce the amount of saturated fat and follow a healthy diet.

  • limiting cakes, biscuits, pastries 
  • choosing reduced fat milks 
  • using polyunsaturated or monounsaturated margarine or oils instead of butter 
  • choosing lean cuts of meat and remove visible fat 
  • removing fat from chicken  
  • including more fish and beans in meals 
  • losing weight if overweight.

By making a number of changes to diet, cholesterol can fall by 10 per cent. About 15 per cent of people will see no change and another 15 per cent will see changes of 20-30 per centThe CSIRO Healthy Heart Program has been shown to effectively lower LDL cholesterol levels by 15 per cent and includes comprehensive diet and lifestyle information for heart health.

How high is high cholesterol?

If the cholesterol level is between 5.5 and 6.5, risk of heart disease is only increased by a small amount. A few moderate changes to diet might be sufficient. However if heart disease is present, or one parent had developed heart disease at an early age (< 55 years of age), then larger changes need to be made

If the cholesterol level is higher than 6.5 then more changes need to be made.

If despite changes to diet cholesterol levels remains above 6.5, medication should be considered.

Triglycerides are a stored energy source. Most of the triglyceride in blood is found in the very large particles, the VLDL. Under some circumstances high blood triglyceride can be a risk factor for heart disease. If cholesterol levels are high, 6.5 and above is considered a high cholesterol level, and HDL cholesterol is low (less than 0.9) then triglycerides can increase the risk of heart disease if they are greater than 1.7. 

Triglycerides can be lowered by: reducing excess weight, increasing exercise, drinking  alcohol moderately (as alcohol is very efficient at elevating triglycerides) and reducing the amount of refined starchy foods and sugary drinks in the diet. 

Target lipid levels for patients on lipid-modifying therapy

Lipid Component                                                                        Target level

Low-density lipoprotein cholesterol (LDL-C)                          < 2.0 mmol/L

Non-high-density lipoprotein cholesterol (non-HDL-C)       < 2.5 mmol/L

Total cholesterol (TC)                                                                 < 4.0 mmol/L

High-density lipoprotein cholesterol (HDL-C)                        > 1.0 mmo/L

Triglycerides (TG)                                                                        < 2.0 mmol/L                          

The Heart Foundations Absolute Cardiovascular Disease Risk Calculator is a very powerful tool for pharmacist to use when counselling patients It takes into account: gender, age, systolic blood pressure, smoking status, total cholesterol, HDL cholesterol, presence of diabetes and ECG LVH (left ventricular hypertrophy).

http://www.cvdcheck.org.au/

Therapeutic Guidelines Cardiovascular Version 7, Therapeutic guidelines, Melbourne, 2018.

Associate Professor Louis Roller, from the Faculty of Pharmacy and Pharmaceutical Sciences Monash University, was the 2014 recipient of the PSA Lifetime Achievement Award.