If you have high cholesterol should you eat eggs

Are eggs bad for the heart? This is a question patients frequently ask their doctors.

Until recently and for many years, the answer was yes because egg yolk contains a lot of cholesterol. However, recent research findings have changed this view.

Let us first understand some basic facts about cardiovascular disease and its risk factors.

Cardiovascular Disease (CVD)

Cardiovascular disease is a disease affecting the arteries, which are blood vessels that carry oxygen-rich blood to the heart and other parts of the body.

The commonest and most important CVD is atherosclerosis, in which plaques containing cholesterol, fibrous tissue and other cells build up in the walls of arteries. Atherosclerosis causes heart attacks (when it affects the arteries of the heart) and strokes (when the brain arteries are affected).

CVD Risk Factors

Cardiovascular disease risk factors are characteristics or conditions that increase the risk of developing CVD, due to atherosclerosis. It may be non-modifiable or modifiable.

Non-modifiable risk factors include age, family history and male gender.

The risk of atherosclerosis increases with age, in those with a history of heart attack or stroke in close relatives and is higher in men than women before menopause. Menopausal women have similar CVD risk to men.

Modifiable risk factors include high blood cholesterol, hypertension, diabetes, smoking, overweight, sedentary lifestyle and psychosocial stress.

Cholesterol

Cholesterol is a lipid (fatty substance) present in the bloodstream and in all of the body’s cells. It is important to the healthy functioning of our bodies. Most of the cholesterol in the body is made by the liver and does not come from cholesterol that we eat. It is needed to form cell membranes and hormones. It is also derived from certain foods like animal meat, milk and milk products such as butter and cheese, cakes, cookies, as well as in egg yolk.

Cholesterol is carried through our blood by particles called lipoproteins, consisting of low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Not all LDL particles are the same. Some LDL particles are less dense and less harmful than more dense LDL. High blood levels of LDL lead to deposition of cholesterol in the walls of arteries, causing atherosclerosis leading to heart attack and ischemic stroke.

HDL cholesterol, on the other hand, reduces the risk of CVD as it carries cholesterol away from the blood stream and from the walls of blood vessels.

A high blood LDL level can be inherited. The condition is known as familial hypercholesterolemia, in which a build-up of LDL cholesterol in the blood is present from birth. This can lead to coronary heart disease at an early age.

For many years, it was believed that cholesterol in the diet would significantly increase blood levels of cholesterol. Since egg yolk contains a significant amount of cholesterol (about 200mg), it was assumed that it would contribute to increased blood cholesterol levels. Many dietary guidelines hence recommended that eggs be eaten sparingly or not at all.

We now know from recent studies that dietary cholesterol increases blood cholesterol only slightly. In comparison, saturated fats and trans fats (made through the chemical process of hydrogenation of oils for example, in the manufacture of margarine) increase blood cholesterol more than dietary cholesterol.

Recent research has also established that dietary cholesterol increases the concentrations of both circulating LDL (bad) and HDL (good) cholesterol in individuals who absorb more dietary cholesterol. Hence, the ratio of bad to good cholesterol remains the same. In the majority of people who absorb less cholesterol from their diets, there is only a mild or no increase in blood cholesterol levels.

In addition, dietary cholesterol from egg intake has been shown to promote the formation of large LDL particles which are less harmful, and HDL particles which oppose the harmful small and dense LDL particles.

Large epidemiological and clinical studies indicate that for the general population, dietary cholesterol from eggs does not increase the risk of atherosclerotic cardiovascular disease.

Beneficial Constituents of Eggs

One average egg contains around 4.6g of fat, but only one quarter of this fat is saturated fat.

Egg yolk and the albumin in egg white contain many beneficial nutrients including lutein and zeaxanthin, which are good for the eyes; choline, which is good for the brain and nerves; various vitamins A, B (riboflavin, B12), folic acid and vitamin D. A single large egg contains roughly 6 g of protein and 72 calories.

Eggs are easy to prepare and serve and goes well with many other foods. So for most people that eat one or two eggs a day, this will not increase your blood cholesterol significantly and will provide many good nutrients. For a small percentage of people, including those who have diabetes and very high blood cholesterol levels due to genetic factors, they are more sensitive to eating dietary cholesterol than others. This means that when they eat food containing cholesterol, their LDL (bad) cholesterol levels will rise more than other people. For these people, it is important to discuss this issue with their doctors.

Of course, what you eat with your eggs matters greatly. The saturated fat in butter, cheese, bacon and sausage, for example, raises your blood cholesterol much more than the cholesterol in your egg.

By Dr Low Lip Ping, Chairman Emeritus of Singapore Heart Foundation

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