Cholesterol: Good vs. Bad and the Latest Insights - Cardiology

Dr. He Dongjin reply Cardiology

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Currently, low-density lipoprotein (LDL) cholesterol remains a major culprit in atherosclerosis.
Dietary restrictions on cholesterol have been relaxed compared to the past because approximately 80% of cholesterol is produced by the body, with only 20% coming from dietary sources.
For more details, please refer to Dr.
Huang Rui-Ren's health education article at http://www.twhealth.org.tw/index.php?option=com_zoo&task=item&item_id=1029&Itemid=19.

The "Dietary Guidelines for Americans" are established by the U.S.
Department of Health and Human Services (HHS) and the U.S.
Department of Agriculture (USDA), and are updated every five years.
Although the latest version of the guidelines no longer specifies that cholesterol intake should be limited to less than 300 mg per day, it still explicitly recommends that individuals "should minimize the intake of high-cholesterol foods." This is because foods high in cholesterol often also contain higher levels of saturated fats, which are detrimental to health.
Furthermore, the guidelines note that while eggs and shellfish contain higher levels of cholesterol, they are low in saturated fats and can be included in protein choices in moderation.
The rationale behind these recommendations is twofold: first, dietary control has limited effectiveness in lowering cholesterol levels, and second, there are effective cholesterol-lowering medications available.
In fact, about 80% of the total cholesterol in the blood is produced by the body, meaning it is largely independent of dietary intake.
The liver produces 80% of cholesterol, with only 20% influenced by the consumption of high-cholesterol foods, which in turn affects blood cholesterol levels.
This implies that even with strict dietary control, the maximum impact on total blood cholesterol levels is around a 20% reduction.
For example, if the total cholesterol level is 250 mg/dL, strict dietary control may only reduce it to about 200 mg/dL.
Thus, while it is still advisable to reduce the intake of high-cholesterol foods, the effectiveness of dietary control is limited.
There are now effective cholesterol-lowering medications available, which are convenient to take—typically one to two pills a day can achieve ideal cholesterol reduction.
These medications are known as statins, which have revolutionized the management of cardiovascular diseases over the past twenty years.
For individuals with existing cardiovascular diseases, those who have had stents placed, high-risk groups, or diabetic patients, taking statins as prescribed can help maintain LDL cholesterol levels in the ideal range (below 100 mg/dL) and reduce mortality rates by one-third, demonstrating significant efficacy.
Even though the U.S.
Dietary Guidelines have undergone some changes regarding cholesterol intake recommendations, it remains essential for the population to reduce cholesterol intake to lower the risk of cardiovascular diseases and avoid metabolic syndrome.
In Japan, the term "lifestyle diseases" is often used to describe conditions related to high blood pressure, high blood sugar, and high cholesterol, indicating a strong correlation between these conditions and poor lifestyle habits.
Therefore, appropriate dietary control and lifestyle changes remain important.
Regarding egg consumption, it is recommended to eat one egg yolk every two days.
One egg yolk contains about 250 mg of cholesterol, and since the previous recommendation was to limit daily cholesterol intake to no more than 300 mg, consuming one egg yolk per day would leave little room for other cholesterol-containing foods, making it easy to exceed the limit.
Although there is debate about whether cholesterol intake should be strictly limited, from a cardiovascular disease prevention standpoint, it is still advisable to consume one egg yolk every two days, while there is no need to restrict egg white intake.
However, for individuals aged 80 and above, who are considered elderly and long-lived, there is less need for dietary restrictions, as at this age, "not wanting to eat" is a greater concern than "restricting what to eat."
Low-density cholesterol is a primary cause of atherosclerosis.
Cholesterol is synthesized by the liver and is an essential component of cell membranes.
The levels of total cholesterol and LDL cholesterol are parallel; as total cholesterol increases, LDL cholesterol also rises.
The reason for closely monitoring cholesterol, particularly LDL cholesterol, is that it is a health hazard.
Conditions such as cerebrovascular occlusion, angina, and coronary artery atherosclerosis, collectively referred to as cardiovascular atherosclerosis, are primarily caused by LDL cholesterol, which accumulates on the inner walls of blood vessels.
The body's physiological response to oxidized LDL leads to atherosclerosis.
Initially, fatty streaks can be seen in the blood vessels, which gradually accumulate and form atherosclerotic plaques; in severe cases, these can become calcified.
Therefore, the presence of calcification in blood vessels indicates long-term atherosclerosis.
A more alarming situation arises when an atherosclerotic plaque suddenly ruptures or develops a crack, leading to platelet aggregation and the formation of a thrombus, which can obstruct blood vessels.
The timing of such ruptures is unpredictable; for instance, a person with only 50% narrowing of a coronary artery may suddenly experience plaque rupture, resulting in a thrombus that completely blocks the artery, leading to a myocardial infarction.

So, what types of individuals are more likely to experience plaque rupture? Can it be predicted? Is the plaque stable or unstable? Currently, medicine cannot predict this.
Therefore, patients with existing atherosclerotic plaques are advised to undergo medication treatment to reduce the risk of heart attacks.

The commonly used medications fall into two categories:
1.
Antiplatelet medications, with aspirin being the most commonly used.
A low dose (75 to 150 mg) is typically sufficient.
If a coronary artery plaque suddenly ruptures and causes a thrombus, aspirin can prevent platelet aggregation, allowing for medical intervention.
2.
Statins, which can lower the concentration of "bad cholesterol" in coronary artery plaques, stabilizing the plaques and reducing the risk of rupture.
Statins have few side effects, but it is generally recommended to monitor liver function (ALT) for the first 3 to 6 months after starting treatment, as less than 1% of patients may experience elevated liver function.
Additionally, monitoring muscle enzymes (CK or CPK) is advised, as some medications can cause rhabdomyolysis, although this is not common.
Some patients may experience muscle soreness, such as in the arms or thighs, and a small number may have lower back pain.
If any of these side effects occur, patients should consult their physician for possible dosage adjustments or medication changes.

It is important to note that statins should not be combined with red yeast rice or supplements containing red yeast rice, as red yeast rice also contains small amounts of statin-like compounds, which can lead to overdose and cause rhabdomyolysis, kidney disease, or even be fatal if not handled carefully.

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Reply Date: 2016/05/29