What Is Cholesterol & Why Our Bodies Need It

Article by Emilia Fish, BSC

Cholesterol was first identified in humans over 200 years ago1. Since then, it has been strongly associated with atherosclerosis and cardiovascular disease risk1. We have also discovered that we need cholesterol for several reasons, including:

• It provides rigidity, fluidity, and permeability to our cell membranes2,3.

• To make vitamin D and steroid hormones which are required to maintain the health of our bones, teeth and muscles4,5.

• To make bile, which helps to digest the fats we eat6.

So, while cholesterol can increase disease risk, the role of cholesterol is not all negative. It is actually needed by every cell of our body’s and plays a vital role in how our body’s function7.

What are cholesterol and triglycerides?

Cholesterol

Cholesterol is a fatty substance. The majority of cholesterol in our bodies is made endogenously, primarily the liver7,8,9, and some comes through our diets10,11. As blood is water-based and cholesterol is fat-based, two mediums that do not naturally mix, cholesterol is packaged into lipoproteins to circulate in the blood around the body7.

There are five different types of cholesterol which make up our total cholesterol. These are7,12:

1. Low-Density Lipoprotein Cholesterol (LDL-C).

2. Intermediate-Density Lipoprotein Cholesterol (IDL-C).

3. Very low-density lipoprotein (VLDL).

4. Chylomicrons (CM).

5. High-Density Lipoprotein Cholesterol (HDL-C).

Triglycerides

When talking about cholesterol, triglycerides are also often mentioned. Like cholesterol, they are a type of fat, packaged into lipoproteins and are similar to LDL-C and non-HDL cholesterol (non-HDL-C). Non-HDL-C is the figure when you take HDL from your total cholesterol. It includes IDL, VLDL, CM and their remnants12,13.

Factors potentially contributing to high cholesterol:

• Doing limited physical activity.

• Eating a diet high in saturated fats.

• Smoking.

• Having underlying conditions, such as diabetes or high blood pressure.

• Having a family history of cardiovascular disease (CVD).

• Having a rare genetic condition. This is called familial hypercholesterolaemia. You can read more about its diagnosis and treatment on the NICE website by searching for “Familial hypercholesterolaemia: identification and management”15.

What are some of the health risks of having high cholesterol?

• Atherosclerosis. The build-up of fatty deposits on the inner walls of the blood vessels that supply the heart or brain. It is an ongoing process which takes years to develop. It is a precursor of CVD14,16.

• Cardiovascular diseases. A broad term for conditions which affect the heart or blood vessels. This includes heart attack, stroke, transient ischaemic attacks and peripheral arterial diseases14,17.

How does cholesterol affect our health?

The type of cholesterol is important to consider when thinking about disease risk. Here is a very simplified explanation of the different types of cholesterol and why they have opposing effects on our health.

LDL-C and non-HDL-C (“bad” cholesterol).

• LDL-C and non-HDL-C are known as atherogenic cholesterol. They are associated with increased atherosclerosis and CVD risk12,18.

• They are more likely to bind in blood vessels, contribute to blockages, atherosclerosis, and CVD risk12,18.

• High LDL-C is a strong risk factor of CVD19.

HDL Cholesterol (“good” cholesterol).

• HDL-C is not atherogenic. In fact, it has an opposing effect12,18,19,20.

• HDL-C reverses the transport of atherogenic cholesterol from circulation back to the liver, where it can be degraded. Once degraded, it can no longer have the atherogenic effect20,21, 22.

• Low HDL-C is a strong risk factor of CVD23,24.

So, while LDL-C and non-HDL-C have a negative effect, HDL-C has a positive effect on our health.

Cholesterol level recommendations.

The guidelines for cholesterol levels are as follows25,26:

• Total cholesterol should be 5mmol/L or less for healthy adults; 4mmol/L or less for those at high risk.

• LDL-C should be 3mmol/L or less for healthy adults; 2mmol/L for those at high risk.

• Non-HDL should be 4mmol/L or less.

• Triglycerides should be 2.3mmol/L or less.

• HDL-C should be 1mmol/L or more.

Cholesterol in our diets:

In a typical Western diet, 55% of cholesterol comes from meat and fish, 25% from eggs and 20% from dairy products27.

Foods which raise our cholesterol. These are typically foods high in saturated and trans fats. Examples include26:

• Meat and dairy products including processed meats and cream.

• Cakes and biscuits.

• Hydrogenated fats, coconut, and palm oil.

Foods to replace saturated fats. You can add in small amounts of unsaturated fats which can help to reduce our cholesterol. Examples include26:

• Vegetable oils such as rapeseed oil.

• Nuts and seeds, including almonds and sunflower seeds.

• Oily fish such as salmon.

Foods that are high in dietary cholesterol. It is important to mention that these foods have a much smaller effect on blood cholesterol than saturated fats. Examples include26:

• Kidneys.

• Eggs.

• Prawns.

Dietary and lifestyle advice to reduce high cholesterol

1. Reduce our consumption of saturated and trans fats. This may be through swapping cooking methods from roasting or frying to steaming, poaching or microwaving26,28,29.

2. Reduce our alcohol consumption26,28,29.

3. Increase our movement26,28,29.

4. Increase our fibre intake. Foods high in fibre include wholegrain cereals, fruits, and vegetables26,28,29.

5. Consider consuming products high in plant sterols or stanols28. For example, Benecol products have been shown to reduce cholesterol levels by 7-10% within 3 weeks, as part of a balanced dirt30. However, no human studies show that consumption of these reduce the risk of coronary heart disease, and they should only be consumed by individuals aiming to lower their cholesterol levels31.

6. If you are concerned, talk to a registered nutritionist, dietitian, or your GP.

A final thought.

While having high levels of LDL-C and non-HDL-C can increase disease risk, it is important to remember that the role of cholesterol is not all negative. It is required by every cell of our body’s, plays an essential role in how our body’s work and HDL-C can reduce the levels of both LDL-C and non-HDL-C.

Resources to help us.

• National Health Service. What is high cholesterol26?

• British Dietetics Association. Cholesterol: Food Fact Sheet29.

• British Heart Foundation. High cholesterol – causes, symptoms and treatments32.

This blog post was written by Emilia Fish, a Food Science and Nutrition graduate and soon-to-be MSc Clinical and Public Health Nutrition student at UCL. She is part of the Nutrition Rocks intern team and enjoys sharing simple, evidence-based nutrition on @nutritionnourishment. Emilia has recently launched a podcast: Journeys in Food, Nutrition and Sustainability.

References:

(1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3108295/

(2) https://pubmed.ncbi.nlm.nih.gov/6301540/

(3) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5645210/

(4) https://www.ncbi.nlm.nih.gov/books/NBK22339/

(5) https://pubmed.ncbi.nlm.nih.gov/23356636/

(6) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2712638/

(7) https://www.ncbi.nlm.nih.gov/books/NBK279327/

(8) https://www.sciencedirect.com/science/article/pii/S1043276017301674#bib0080

(9) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2390860/

(10)https://www.sciencedirect.com/science/article/pii/B9780081003299000098

(11)https://link.springer.com/article/10.1007/BF01716251