Does dietary cholesterol actually raise levels in your body?

Diet

Think you know where cholesterol actually comes from? Think again!

10/10/2019


Alex Hesketh

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What is cholesterol?


Cholesterol is a fatty substance which is produced naturally by the liver and is found is every cell in the body. It can also be found in some foods, namely animal products. Cholesterol is vital for the maintenance of cell membranes and the production of vitamin D and bile acid. It is also important in the production of many key hormones such as testosterone and oestrogen. 


As cholesterol travels around the body in the blood, it is bound to small proteins called lipoproteins. High-density lipoproteins (HDL), remove cholesterol from our tissues, take it back to the liver where the cholesterol is recycled. Because of their role in the body, HDL is often referred to as the “good cholesterol” and offer a protective role. In contrast, low-density lipoproteins (LDL) are commonly known as ‘bad cholesterol’ because they carry cholesterol from the liver to our tissues, depositing it on our artery walls. This eventually leads to fatty plaques developing which block the blood vessels and increase the risk of cardiovascular disease and stroke. 


What causes high cholesterol?


There are several factors that can increase your risk of bad cholesterol including;

  • Smoking – the walls of your blood vessels can become damaged from cigarette smoking which makes them more prone to building up fatty deposits. 
  • Obesity – having a body mass index (BMI) of 30 or greater puts you at higher risk of high cholesterol.  
  • Lack of exercise – exercise helps boost your body’s HDL, or “good”, cholesterol while increasing the size of the particles that make up your LDL, or “bad” cholesterol, making them less harmful. 
  • Age – as you age, your liver becomes less able to remove LDL cholesterol, increasing the likelihood of having high cholesterol.
  • Genetics – high cholesterol levels can be passed down through families in the genes and can lead to Familial hypercholesterolaemia (FH for short) which is an inherited condition. If left untreated FH can result in heart disease at a very young age. 

As well as diet and lifestyle, our cholesterol levels can also be affected by having certain conditions such as thyroid disease. Hormones produced by our thyroid gland play a major role in the regulation of metabolism and aid the breakdown of fats including cholesterol. If the thyroid gland is underactive or overactive, the body’s ability to process cholesterol can be affected. Hypothyroidism, in particular, can lead to hypercholesterolemia, which is the increase of LDL cholesterol in the body.


How does dietary cholesterol affect blood cholesterol?


Although it may seem logical that consuming foods high in cholesterol would raise blood cholesterol levels, it has been suggested that this is not the case for everyone.


It is believed that foods high in dietary cholesterol have very little impact on blood cholesterol levels in most people (1,2). This is because the body tightly regulates the amount of cholesterol in the blood by controlling the amount it produces. When you consume less dietary cholesterol, your body naturally produces more, whereas, when you increase the amount of dietary cholesterol you consume, your body makes less.


However, in some people, dietary cholesterol does raise cholesterol levels. These people are referred to as “hyperresponders” and this tendency is often considered to be genetic (3, 4). Several studies classify a hyperresponder as someone with a response to dietary cholesterol >2.2 mg/dL for each additional 100mg of dietary cholesterol (3,4). 


While some people respond to dietary cholesterol, it is believed that saturated fats play an important role in raising cholesterol levels. This is because saturated fats affect how the liver handles cholesterol. A study found that consuming saturated fats raised LDL cholesterol levels (bad cholesterol), which in turn raises cardiovascular risk (5). 


With that said, new research has shown that a raise in LDL cholesterol might not necessarily be as bad as it seems, as there are two types of LDL cholesterol (6, 7, 8); 

  • Small, dense LDL: These are small lipoproteins that can penetrate the arterial wall easily, which drives heart disease.
  • Large LDL: These lipoproteins are large and fluffy and don't easily penetrate the arteries.

It has been found that people with mostly small, dense LDL particles have three times greater risk of heart disease compared to those with mostly large LDL particles (9). Therefore, if we want to reduce our risk of heart disease, we need to have mostly large LDL particles and less of the small, dense LDL particles. 


Even though saturated fats can raise LDL cholesterol levels, it has been identified that they change the LDL particles from small, dense to large (10, 11). This then changes the LDL to a benign subtype that is associated with a reduced risk of heart disease. 


It seems that there isn’t one clear-cut cause of high cholesterol, and it might not be as simple as consuming foods high in cholesterol or saturated fats raising the levels in our bodies. What is important is ensuring you live a healthy lifestyle, avoid smoking, heavy drinking and processed food and exercise regularly. This way you will be putting yourself in good stead to keep your cholesterol levels healthy throughout your life. Research has found that the Mediterranean diet is associated with reductions in cardiovascular disease, check out one of our previous articles for more information. 


High cholesterol is very common, yet most people don’t know they have it as there are no obvious signs or symptoms. In order to know whether you have high cholesterol it is necessary to have a cholesterol check. Our cholesterol check gives a thorough breakdown of your cholesterol levels in your blood including your HDL, LDL and triglyceride levels, as well as your heart disease risk. In aid of National Cholesterol Month, we have our Cholesterol Check down to only £29, from £39. 


Check your cholesterol levels this October!


References
 

1.    ML, F. (2012). Rethinking dietary cholesterol. - PubMed - NCBI. [online] Ncbi.nlm.nih.gov. Available at: https://www.ncbi.nlm.nih.gov/pubmed/22037012 [Accessed 10 Oct. 2019].
2.    Jones, P., Pappu, A., Hatcher, L., ZC, L., Lllingworth, D. and Connor, W. (1996). Dietary cholesterol feeding suppresses human cholesterol synthesis measured by deuterium incorporation and urinary mevalonic acid levels. - PubMed - NCBI. [online] Ncbi.nlm.nih.gov. Available at: https://www.ncbi.nlm.nih.gov/pubmed/8857917 [Accessed 10 Oct. 2019].
3.    Herron, K., Vega-Lopez, S., Conde, K., Ramjiganesh, T., Roy, S., Shachter, N. and Fernandez, M. (2002). Pre-Menopausal Women, Classified as Hypo- or Hyper-Responders, do not Alter their LDL/HDL Ratio Following a High Dietary Cholesterol Challenge. Journal of the American College of Nutrition, 21(3), pp.250-258.
4.    Herron, K., Vega-Lopez, S., Conde, K., Ramjiganesh, T., Shachter, N. and Fernandez, M. (2003). Men Classified as Hypo- or Hyperresponders to Dietary Cholesterol Feeding Exhibit Differences in Lipoprotein Metabolism. The Journal of Nutrition, 133(4), pp.1036-1042.
5.    Greene, C., Waters, D., Clark, R., Contois, J. and Fernandez, M. (2006). Plasma LDL and HDL characteristics and carotenoid content are positively influenced by egg consumption in an elderly population. Nutrition & Metabolism, 3(6).
6.    BMJ (2014). Saturated fat is not the major issue. BMJ, 348(may15 1), pp.g3332-g3332.
7.    Krauss, R. (1994). Heterogeneity of plasma low-density lipoproteins and atherosclerosis risk. Current Opinion in Lipidology, 5(5), pp.339-349.
8.    Erbey, J., Robbins, D., Forrest, K. and Orchard, T. (1992). Low-density lipoprotein particle size and coronary artery disease in a childhood-onset type 1 diabetes population. Metabolism, 48(4), pp.531-534.
9.    St-Pierre, A., Cantin, B., Dagenais, G., Maurie?ge, P., Bernard, P., Despre?s, J. and Lamarche, B. (2005). Low-Density Lipoprotein Subfractions and the Long-Term Risk of Ischemic Heart Disease in Men. Arteriosclerosis, Thrombosis, and Vascular Biology, 25(3), pp.553-559.
10.    Ivanova, E., Myasoedova, V., Melnichenko, A., Grechko, A. and Orekhov, A. (2017). Small Dense Low-Density Lipoprotein as Biomarker for Atherosclerotic Diseases. Oxidative Medicine and Cellular Longevity, 2017, pp.1-10.
11.    Dreon, D., Fernstrom, H., Campos, H., Blanche, P., Williams, P. and Krauss, R. (1998). Change in dietary saturated fat intake is correlated with change in mass of large low-density-lipoprotein particles in men. The American Journal of Clinical Nutrition, 67(5), pp.828-836.

 


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