Cholesterol is an essential substance for humans and all animals, as it builds and repairs cell membranes and also plays a role in vitamin D production, cell communication and other biochemical processes. In fact, cholesterol is so important that the body on its own produces about one gram of it every day in addition to absorbing cholesterol through the diet. Cells in the liver produce most of the body’s own cholesterol (a process called cholesterol synthesis), which then is supplied to the digestive system via the gallbladder and bile.
The body responds to dietary cholesterol intake by decreasing or raising its own production. Dietary sources of cholesterol are meats and animal fats, as well as eggs (in particular egg yolk). This includes butter, milk and animal-based oils, such as fish oil. Vegetables and fruits hardly contain any cholesterol, but processed vegetable products, like margarine, baking shortenings and vegetable oil, are rich in “trans fats” that generally are thought to have a cholesterol-raising effect.
A person’s blood cholesterol levels typically are a combination of genetic factors, lifestyle (especially dietary choices), and other medical conditions. The body’s own cholesterol synthesis differs from person to person, and some people have elevated blood control levels even though they are on a vegetarian diet and otherwise healthy. About 2 out of 1,000 people have a clinically high blood cholesterol level (greater than 240mg/dL) entirely because of genetic reasons. Even if these people adjust their diets, the body’s own synthesis will make up for the reduced cholesterol intake.
Given the human body’s cholesterol adaptability, experts aren’t still entirely sure to what extent dietary cholesterol intake affects blood levels. Some scientists say that dietary cholesterol intake has little effect on blood levels. However, the current medical mainstream opinion still believes that if the body constantly is flooded with cholesterol through meat and fat-rich diet, there will be an impact on blood levels.
Lack of physical exercise, smoking, obesity, stress, and certain conditions, such as diabetes or kidney problems also are thought to raise cholesterol levels.
Often it’s not the overall cholesterol level, but the concentration of low-density lipoprotein (LDL) cholesterol that’s the main focus when assessing somebody’s cholesterol levels. As you’ve probably noticed before, blood test results typically show two values for cholesterol: LDL and HDL (high-density lipoprotein). It’s the LDL (often called “bad cholesterol”) that doctors worry about. An LDL level of higher than 160 mg/dL is considered dangerously high.
It’s even worse when the LDL is high and the HDL (the “good cholesterol”) is too low. The afore-mentioned trans fats have exactly this effect. They lower HDL while raising LDL levels. The good cholesterol earns its nickname from its ability to channel excessive cholesterol back to the liver, i.e., it helps the body recycle cholesterol. If you have too little HDL, too much cholesterol stays in your blood vessels, instead of being recycled.
How dangerous is hypercholesterolemia?
The problem with cholesterol is that high levels in your blood don’t cause any visible symptoms right away. The waxy substance silently accumulates in your arteries in the form of fatty deposits. This accumulation along your arterial walls is called atherosclerosis. As these deposits (cholesterol plaque) grow in size, in the long run, it narrows the space available for blood to flow through, which in turn raises your blood pressure.
More dangerously yet, if large deposits break apart, chunks of that plaque can clot blood vessels and — if it reduces or blocks the flow of blood to the heart — trigger a heart attack. Some 75% of heart attacks are caused by such cholesterol plaque ruptures. Similarly, an artery blockage that lowers the blood supply to the brain will cause a stroke. Both heart attack and stroke can be fatal and are the leading causes of death in the US population. About 1 in every 4 deaths is due to heart disease and often high cholesterol is one of the factors behind it, given that 33% of Americans are estimated to have cholesterol levels of greater than 200 mg/dL.
Since high cholesterol levels don’t produce any early symptoms, checking cholesterol levels (the test is called “screening lipid panel”) in many countries it’s part of standard health screenings for people older than age 35. For example, if you belong to the 60% of Americans who get an annual physical, your cholesterol levels likely will be part of that and any worrisome trends can be spotted early on.
What can you do to lower cholesterol levels?
Once you notice elevated cholesterol levels — in particular high LDL levels — you’ll need to do something about it right away. There’s no procrastination when it comes to cholesterol levels because once the plaque is on your artery walls it’s not easy to remove again.
You can’t change your genetics, but your dietary cholesterol intake is fully under your control. For starters, entirely avoid trans fats and, in general, pay more attention to what sort of fats and oils your favourite processed and restaurant foods use.
Eating more vegetables also helps to lower LDL levels, as plants produce phytosterols, which is a substance that competes with cholesterol for absorption in the intestinal tract. The more phytosterols you eat, the more cholesterol won’t have a chance to be absorbed into your bloodstream.
It’s not just your diet. Getting more aerobic exercise can raise HDL levels and, by virtue of body fat loss, lower LDL levels too. Quitting smoking also can go a long way to improve cholesterol levels. This is because smoking damages the artery walls, creating a surface that’s easier for cholesterol deposits to form on.
If lifestyle changes aren’t enough to bring down your LDL levels, doctors will resort to medications, where the typical choice are statins. They can lower total cholesterol by about 50% in most people and thus reduce the risk of cardiovascular diseases. Other treatment options include fibrates and cholestyramine, but these are used more rarely, such as for pregnant women and when patients are allergic to statins. If you think you require cholesterol treatment medication, talk to your doctor about available options and what could be right for you.
- Grundy, Scott M., et al. “2018 AHA/ACC Guideline on the Management of Blood Cholesterol.” Circulation, 10 Nov. 2018, professional.heart.org/idc/groups/ahamah-public/@wcm/@sop/@smd/documents/downloadable/ucm_502856.pdf, 10.1161/cir.0000000000000625. Accessed 8 Sept. 2020.
- Bhatnagar, D., et al. “Hypercholesterolaemia and Its Management.” BMJ, vol. 337, no. aug21 1, 21 Aug. 2008, pp. a993–a993, 10.1136/bmj.a993. Accessed 8 Sept. 2020.
- Hooper, Lee, et al. “Reduction in Saturated Fat Intake for Cardiovascular Disease.” Cochrane Database of Systematic Reviews, 19 May 2020, 10.1002/14651858.cd011737.pub2. Accessed 8 Sept. 2020.
- Vincent, Melissa J, et al. “Meta-Regression Analysis of the Effects of Dietary Cholesterol Intake on LDL and HDL Cholesterol.” The American Journal of Clinical Nutrition, vol. 109, no. 1, 8 Sept. 2020, pp. 7–16, 10.1093/ajcn/nqy273. Accessed 8 Sept. 2020.