How does diet affect cholesterol levels?

In 1913, the results of experiments were published in which a diet rich in cholesterol caused a significant increase in blood cholesterol levels and changes in the arterial walls in rabbits. This was one of the first pieces of experimental evidence linking diet, cholesterol and the development of atherosclerotic changes, although the animal model did not allow the results to be directly extrapolated to humans. Subsequent studies showed that the lipid profile is influenced not only by the amount of cholesterol present in food, but above all by the overall composition of the diet.

1. Characteristics of cholesterol
2. Diet and cholesterol
3. Cholesterol test
4. FAQ

Characteristics of cholesterol

Cholesterol is a fatty substance that occurs naturally in the human body. It does not provide energy, but is necessary for the formation of cell membranes, the production of steroid hormones, bile acids and vitamin D. Most cholesterol is produced by the body, mainly in the liver, whilst some comes from animal products such as eggs, meat, offal and dairy products.

LDL cholesterol and HDL cholesterol

Cholesterol is not soluble in water, which is why it is transported in the blood in particles called lipoproteins. The terms "LDL cholesterol" and "HDL cholesterol" do not describe two different types of cholesterol, but rather the amount of the same substance carried by different particles. LDL primarily transports cholesterol from the liver to the tissues, and a higher concentration of LDL indicates a greater amount of cholesterol circulating in low-density lipoproteins. HDL is involved, amongst other things, in collecting cholesterol from the tissues and transporting it to the liver.

Estimated cholesterol content in certain foods

Diet and cholesterol

Diet affects cholesterol levels by altering lipoprotein production in the liver, the absorption of lipids in the gut, and the rate at which LDL is removed from the blood. A high intake of saturated fatty acids may limit the uptake of LDL by the liver, which is why blood levels of LDL may rise.

Dietary factors

Replacing some saturated fats with mono- and polyunsaturated fats, found in olive oil, rapeseed oil, nuts, seeds and fish, usually helps to lower LDL levels. Soluble, viscous fibre from oats, barley, pulses, vegetables and fruit reduces the reabsorption of bile components and increases their excretion, causing the liver to use more cholesterol to produce bile acids. In addition, specific plant-based active compounds can "compete" with cholesterol for absorption in the intestine.

Current EFSA guidelines

On the other hand, an energy surplus, high intakes of added sugars and alcohol may increase the liver’s production of triglycerides and very low-density lipoproteins. Dietary cholesterol may also raise LDL levels, but the response varies, and the EFSA (European Food Safety Authority) identifies saturated fats as a more significant dietary factor influencing its concentration.

According to the EFSA, fats should provide 20–35 per cent of an adult’s total dietary energy intake. For a 2,000 kcal diet, this corresponds to approximately 44–78 g of fat per day. The adequate intake for linoleic acid (an omega-6 fatty acid) has been set at 4% of energy, and for alpha-linolenic acid (an omega-3 fatty acid) at 0.5% of energy (these acids are found mainly in plants). In a 2,000 kcal diet, this amounts to approximately 8.9 g and 1.1 g per day, respectively. For adults, an adequate intake of 250 mg of eicosapentaenoic acid and docosahexaenoic acid combined, i.e. EPA and DHA (mainly from fish), has also been established.

Cholesterol test

A total cholesterol level below 190 mg/dl (4.9 mmol/l) is considered the target level for adults. The target LDL cholesterol level depends on cardiovascular risk and is below 115 mg/dl for low risk, below 100 mg/dl for moderate risk, below 70 mg/dl for high risk, and below 55 mg/dl for very high risk.

The result depends on cholesterol production in the liver, its absorption in the gut, its removal from the blood, its use in the synthesis of bile acids, and its excretion in bile. The liver constantly adjusts its own synthesis to the supply of cholesterol and the body’s requirements, but the extent of this compensation varies between individuals. Genes, body weight, physical activity, thyroid function, co-existing conditions and medications also play a role.

"Cholesterol levels are not influenced solely by the amount of cholesterol in the diet. The overall diet is far more important – particularly the type of fats consumed, an adequate intake of fibre and maintaining a healthy body weight." Łukasz Domeracki – Dietitian

FAQ

Is high cholesterol always caused by a poor diet?

No. Diet is one of the key factors, but cholesterol levels are also influenced by genetics, age, body weight, physical activity, medical conditions (e.g. hypothyroidism) and certain medicines.

Do eggs raise cholesterol?

Eggs contain a lot of cholesterol, but for most healthy people, moderate consumption has less of an impact on LDL levels than an excess of saturated fats in the diet. It is the overall diet that matters.

Which foods help to lower LDL cholesterol?

Foods rich in soluble fibre, such as porridge, barley, pulses, vegetables and fruit, as well as nuts, seeds, olive oil, rapeseed oil and oily fish, can have a beneficial effect.

Do you need to completely cut out fats from your diet?

No. Fats are an essential part of the diet. However, it is advisable to limit saturated fats and replace them with monounsaturated and polyunsaturated fats.

Can diet replace cholesterol-lowering medication?

For some people, lifestyle changes can significantly improve their lipid profile. However, if a doctor prescribes medication, diet should complement it, not replace it.

How often should you have your cholesterol checked?

The frequency of testing depends on your age, state of health and individual cardiovascular risk. In healthy adults, it is advisable to have a lipid profile carried out periodically as recommended by your doctor, and more frequently in those at increased risk.

Does physical activity affect cholesterol levels?

Yes. Regular physical activity helps maintain a healthy weight, can improve the lipid profile and is one of the key elements in the prevention of cardiovascular disease.

Sources:

• Asbaghi, O., Choghakhori, R., Ashtary-Larky, D., & Abbasnezhad, A. (2020). Effects of the Mediterranean diet on cardiovascular risk factors in non-alcoholic fatty liver disease patients: A systematic review and meta-analysis. Clinical nutrition ESPEN, 37, 148–156. https://doi.org/10.1016/j.clnesp.2020.03.003
• Koch, C. A., Kjeldsen, E. W., & Frikke-Schmidt, R. (2023). Vegetarian or vegan diets and blood lipids: a meta-analysis of randomized trials. European heart journal, 44(28), 2609–2622. https://doi.org/10.1093/eurheartj/ehad211
• Chawla, S., Tessarolo Silva, F., Amaral Medeiros, S., Mekary, R. A., & Radenkovic, D. (2020). The Effect of Low-Fat and Low-Carbohydrate Diets on Weight Loss and Lipid Levels: A Systematic Review and Meta-Analysis. Nutrients, 12(12), 3774. https://doi.org/10.3390/nu12123774