Cholesterol and its relationship with health is a hugely complicated topic. To date, the exact function and optimum level of cholesterol is not comprehensively understood.
What's more, renowned researchers still debate over the specific dietary recommendations to "optimise" cholesterol levels in the body.
This week's article, the first of a two-part series, will focus on defining cholesterol and the consequences of cholesterol imbalance.
WHAT IS CHOLESTEROL?
Cholesterol is a tiny organic molecule that presents as a soft, waxy substance in the body. It can be consumed through the diet, but the vast majority of cholesterol present in the body is produced mainly by the liver (approximately 75pc).
Cholesterol is required for numerous functions, including cell protection, hormone production and the making of bile. In fact, cholesterol is so important that if you didn't eat any cholesterol-containing foods, your body would still produce enough of it to carry out these vital functions.
A huge number of factors such as genetics, nutrition, exercise and other lifestyle factors can influence the type and amount of cholesterol in the body.
GOOD AND BAD CHOLESTEROL
Part of the confusion surrounding cholesterol in diet and health is that there are many types of cholesterol with different functions and different meaning in terms of disease risk.
High-density lipoprotein (HDL) cholesterol is often referred to as "good" cholesterol, and so having higher amounts is suggested to help protect the cardiovascular system.
Low-density lipoprotein (LDL) cholesterol is considered the "bad" cholesterol, with very-low-density lipoprotein (VLDL) cholesterol linked to a greater risk of arteriosclerosis and cardiovascular disease.
Because of their hydrophobic nature (resistance to water), cholesterol cannot freely travel in the bloodstream by itself and must be transported in tiny packages called lipoproteins (lipid and protein).
When cholesterol is measured in the blood, a measurement is usually taken of the total cholesterol being transported by HDL or LDL.
However, when assessing the health-risk-associated cholesterol levels in the body, it is not just the amount (number) of cholesterol present that is important but also the size (density) of the molecules.
For this reason, it is important that your doctor offers comprehensive feedback on cholesterol test results and not just a "total" cholesterol measurement.
People with a large number of VLDL cholesterol are suggested to have a greater potential health risk than those with a high total cholesterol or LDL cholesterol level.
If you want to prevent or lower the risk of developing atherosclerosis, you must aim to reduce the number of LDL cholesterol and, in particular, VLDL particles circulating in the blood.
WHAT'S THE PROBLEM?
As I have already stated, cholesterol is vitally important for multiple functions in the body, so when or why does the problem occur?
Our arteries are lined by a one-cell layer called the endothelium. Blood that contains cholesterol and many other components is in constant contact with the inner lining of our arteries.
The problem occurs when the LDL particles attach to the arterial wall and elicit an inflammatory immune response. Our immune system responds to this attached LDL particle by producing immune cells that go to the site and try to remove the LDL particle.
If there are only a small number of particles, then the immune response can remove them efficiently, but if there are a large number of LDL particles attached to the endothelium, then the immune cells are unable to dislodge the particles.
As a result, a plaque builds up, narrowing the arterial space. This can lead to reduced blood flow and a myriad of health issues, such as pain, an increased risk of heart attacks and stroke.
HDL cholesterol, on the other hand, is said to offer protection to the body's cardiovascular system by helping to remove LDL cholesterol that builds up as arterial plaque.
Multiple studies have illustrated that having high HDL cholesterol levels can reduce the risk of cardiovascular and heart disease, even when LDL levels are high.
It is, therefore, strongly recommended that not only should someone with sub-optimal cholesterol levels seek to reduce LDL cholesterol, but they should also aim to increase the level of HDL cholesterol.
Improving the overall ratio of HDL cholesterol to LDL cholesterol is most likely the most effective strategy for those aiming to reduce the risk of cardiovascular-related diseases.
CHOLESTEROL AND DIET
The type and level of cholesterol in the body is affected by a multitude of factors, including genetics, dietary components such as the presence of refined carbohydrates or a lack of fibre, and a lack of physical activity.
Historically, people with high cholesterol would have been told to avoid all fats and increase their intake of dietary carbohydrates. This kind of blanket advice can easily lead to increased intake of all carbohydrates, including foods with added sugars, and removing many of the healthy sources of fat within the diet.
We now know that this approach can worsen cholesterol imbalances by increasing LDL cholesterol levels further and doing nothing to increase HDL cholesterol.
It is simply not true that all dietary cholesterol, fat and even certain saturated fats are "bad" for your health.
The commonly held opinion that cholesterol and fats found in foods such as butter, whole milk, eggs and coconut oil are foods that should be avoided at all costs again is simply not true.
For example, research published in the American Journal of Clinical Nutrition in 2010 found no association between saturated fat and heart disease.
Rather than increasing the body's cholesterol levels, much of the cholesterol we eat is actually excreted by the body and not stored at all.
That dietary cholesterol contributes very little to total cholesterol levels in the blood provides just another example of how genuinely healthy and nutrient-rich foods can mistakenly get a bad name.
Check back next week to discover the key dietary considerations for balancing cholesterol levels with the aim of reducing the risk of cardiovascular disease.
Daniel Davey BSc MSc, CSCS, NEHS is a performance nutritionist