High cholesterol? it might not be what you think.

High cholesterol? it might not be what you think.

Cholesterol, heart disease
It has been blamed for heart disease. Eggs and saturated fat have been crucified because of it. Yet our body needs cholesterol so much that nearly all cells make it. What do we do if our levels are high?

Luckily eggs are off the forbidden food list. Saturated and trans fats still take the spotlight for dietary advice. But this might not be the full picture. A recent paper reported evidence that scientists were paid to downplay links between sugar and heart disease, and point the finger at fat instead. Understanding how heart disease occurs and why cholesterol is made in our body might shine some light on this conundrum.

Heart disease, the modern scourge, is the leading cause of death globally. It is mainly caused by atherosclerosis, a buildup of plaque in blood vessels commonly referred to as ‘hardening of the arteries’. This plaque can cause inflammation, resulting in clogged blood vessels and restricted blood flow to the heart. When this happens, oxygen can’t reach the heart muscle, which can lead to coronary heart disease and ultimately a heart attack.

What causes the plaque? Cholesterol is believed to be one of the culprits that cause fatty streaks which gradually build up to form plaques. It is less clear where the cholesterol comes from. Two main forms of cholesterol are found in the blood, known as LDL (low density lipoprotein) and HDL (high density lipoprotein). HDL is a healthy cholesterol, produced in small amounts, while LDL is associated with hardening of the arteries.

Cholesterol is an insoluble molecule, similarly to fat. It is created within most body cells (but mainly the liver) to help with digestion, and make bile, vitamin D and hormones. Cholesterol is an important component of cell membrane structure. It also has another role.

One of the hardworking liver’s many important jobs is to convert glucose—broken down from sugar and carbohydrates, and protein when needed—to energy. It stores glucose as glycogen (as do muscles), a compound molecule that can be easily broken down for energy when needed, like when fasting or exercising. If there are more calories from food than can be used for energy and other important roles in our body, the excess needs to go somewhere. This is where fat cells come in.

The liver converts excess food to fat. Fat cannot enter the bloodstream on its own, so the liver packages this excess fat into a transport protein called VLDL. The role of VLDL is to transport the fat to fat cells. When VLDL empties itself of the fat, it becomes like LDL cholesterol. When too much of this LDL cholesterol is bumping around our blood vessels, that is when it can start sticking to blood vessel walls and create atherosclerosis.

This means that cholesterol from dietary sources like eggs and saturated fat is not the problem. Scientists now agree that dietary cholesterol does not raise blood cholesterol levels. Recent research has also shown that replacing saturated fat with polyunsaturated fats like vegetable oil and margarine does not lead to reduced risk of heart disease as previously thought. Some saturated fats might not even be so bad.

Eating too much sugar and carbohydrates is an important, under-appreciated contender for atherosclerosis–and potentially heart disease. Although lifestyle changes like quitting smoking and exercising more can lower heart disease risk, we can also reduce cholesterol levels and be kind to our heart by avoiding excess calories from sugar, white bread, pasta, cakes, biscuits and doughnuts.


Australian Heart Foundation, URL www.heartfoundation.org.au.
Whitney E, Rolfes S R (2013). Understanding Nutrition. Belmont: Wadsworth.
Biochemistry II: Metabolism, the University of Adelaide.
Ramsden CE, Zamora D, Majchrzak-Hong S, et al. (2016). Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment. BMJ, 353:i1246.
Ramsden C E, Zamora D, Leelarthaepin B, et al. (2013). Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ, 346:e8707 doi: 10.1136/bmj.e8707.
Siri-Tarino PW, Sun Q, Hu FB, Krauss RM (2010). Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. The American Journal of Clinical Nutrition, doi: 10.3945/ajcn.2009.27725.
Kearns CE, Schmidt LA, Glantz SA (2016). Sugar industry and coronary heart disease research: a historical analysis of internal industry documents. JAMA internal medicine, 176(11), 1680-1685.
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