Understanding cholesterol: beyond the basics

Cholesterol has long been a prominent focus in discussions about heart health and disease prevention. Yet, it’s a complex and essential substance with vital roles in our bodies. Here, we’ll delve into what cholesterol is, how it functions, its different types, its connection to heart disease, and ways we can manage cholesterol through diet and lifestyle choices. Finally, we’ll explore the evolving scientific evidence that challenges some long-held beliefs around cholesterol and heart health.

What is cholesterol?

Cholesterol is a waxy, fat-like substance produced by the liver and found in all cells throughout the body. Although often associated with negative health implications, cholesterol is crucial to numerous bodily functions:

1. Hormone production: cholesterol is a building block for sex hormones like oestrogen and testosterone
2. Bile acid production: it aids in digesting fats through the production of bile acids
3. Vitamin absorption: it’s essential for absorbing fat-soluble vitamins (A, D, E, and K)
4. Vitamin D synthesis: cholesterol plays a role in synthesising vitamin D, which is crucial for bone health
5. Cell structure: it supports cell membrane structure and integrity

Without cholesterol, survival would be impossible, as it’s integral to these fundamental processes.

How does cholesterol work?

Despite its critical roles, cholesterol can’t function in isolation within our bloodstream. Since it’s a fat, cholesterol doesn’t dissolve in blood and requires transport via molecules called lipoproteins:

• LDL (low-density lipoproteins): often termed “bad” cholesterol, LDL carries cholesterol from the liver to cells, but high levels can lead to artery-clogging plaque buildup
• HDL (high-density lipoproteins): known as “good” cholesterol, HDL helps transport cholesterol away from arteries back to the liver for excretion
• VLDL (very low-density lipoproteins): these lipoproteins transport triglycerides, another type of fat that contributes to energy but, when elevated, can pose heart health risks

While dietary cholesterol only contributes about 20% to blood cholesterol levels, saturated fats in the diet have a notable influence on how the liver regulates cholesterol. This is why dietary choices are crucial in managing cholesterol levels and supporting heart health.

Types of cholesterol and their functions

Each type of cholesterol-carrying lipoprotein plays a distinct role in the body’s lipid management system:

1. LDL (low-density lipoproteins): often referred to as “bad” cholesterol, LDL can accumulate within arterial walls. This buildup can lead to the formation of plaques, narrowing and hardening arteries – a condition known as atherosclerosis – which increases the risk of heart attacks and strokes.
2. HDL (high-density lipoproteins): HDL aids in transporting cholesterol away from the arteries and back to the liver, where it can be broken down and excreted. High levels of HDL are generally associated with lower risk for heart disease.
3. VLDL (very low-density lipoproteins): VLDL carries triglycerides, contributing to energy storage, but when triglycerides are elevated, they can heighten heart disease risk, particularly if accompanied by abnormal LDL or HDL levels.
4. Triglycerides: although not a type of cholesterol, triglycerides are part of the lipid profile and a significant marker for heart health. Elevated levels can increase cardiovascular risk, especially when paired with high LDL or low HDL.

The role of cholesterol in heart disease

Medical science traditionally holds that high levels of LDL cholesterol are linked to an increased risk of heart disease. When LDL cholesterol deposits in the arterial walls, it forms plaques that lead to atherosclerosis. Over time, this narrows the arteries, restricting blood flow and potentially leading to cardiovascular events like heart attacks and strokes.

The association between LDL cholesterol and heart disease forms the basis for many cardiovascular health strategies, including cholesterol-lowering medications like statins. However, as we’ll see in recent evidence, this relationship may not be as straightforward as previously thought.

Reviewing the evidence: is LDL always “bad”?

The complexity of cholesterol’s role in health has led to differing scientific perspectives. Here are some landmark studies that shaped our understanding of cholesterol and heart disease:

• Framingham heart study (1948): this pioneering study identified high cholesterol as a major risk factor for heart disease, alongside smoking, high blood pressure, and diabetes. It laid the foundation for cholesterol management in cardiovascular health.
• Ware et al. (2009): challenged the notion that LDL cholesterol directly correlates with heart disease, suggesting that high LDL may not be the only factor driving atherosclerosis or heart attacks.
• Ravnskov et al. (2016): found no strong link between LDL cholesterol and heart disease in individuals under 60, indicating that cholesterol’s role in heart disease may be influenced by age and other factors.
• DuBroff et al. (2020): questioned the mortality reduction benefits of cholesterol-lowering drugs, calling for a reassessment of these medications in heart health management.
• Johannesen et al. (2020): suggested an optimal LDL level of around 3.6 mmol/L, indicating that previous cholesterol targets may need revision based on age, genetics, and individual health profiles.

These studies highlight the evolving nature of our understanding of cholesterol and heart disease, suggesting that personalised approaches may be more effective than a one-size-fits-all approach.

Dietary strategies for cholesterol management

While dietary cholesterol has a limited impact on blood cholesterol levels, diet still plays a significant role in managing cholesterol. This is because certain foods affect how our body handles cholesterol, influencing LDL and HDL levels.

Here are some dietary strategies for optimising cholesterol levels:

1. Reduce saturated and trans fats: saturated fats, found in red meat and full-fat dairy products, can raise LDL cholesterol. Trans fats, often found in processed and fried foods, are particularly harmful and should be avoided.
2. Increase unsaturated fats: foods rich in unsaturated fats, such as avocados, nuts, and olive oil, can help lower LDL cholesterol.
3. High-fibre foods: soluble fibre, found in oats, beans, and whole grains, can help reduce LDL levels by binding cholesterol in the digestive tract and preventing its absorption.
4. Incorporate plant sterols: certain foods, like fortified margarine and orange juice, contain plant sterols that block cholesterol absorption.
5. Emphasise whole foods: fruits, vegetables, and whole grains provide essential nutrients without the added fats and sugars of processed foods, supporting overall heart health.

Lifestyle strategies for cholesterol management

Beyond diet, lifestyle changes are fundamental to cholesterol management and heart health:

• Regular physical activity: aerobic activities like brisk walking, cycling, and swimming can boost HDL cholesterol while lowering LDL levels
• Quit smoking: smoking cessation can increase HDL cholesterol and reduce the risk of heart disease
• Moderate alcohol intake: if consumed, alcohol should be in moderation, as excessive drinking can increase triglycerides and affect heart health
• Stress management: chronic stress may contribute to higher cholesterol levels, so incorporating relaxation techniques, such as mindfulness or yoga, can be beneficial
• Prioritise sleep: quality sleep is essential for overall health, including heart health, as poor sleep has been linked to higher cholesterol levels and cardiovascular disease risk

Concluding thoughts: a personalised approach to cholesterol management

Research on cholesterol and heart disease is continually evolving. While cholesterol remains an essential factor in cardiovascular health, the relationship between cholesterol levels and heart disease is more nuanced than once believed. Recent evidence suggests that factors like age, genetics, and lifestyle play significant roles in how cholesterol affects our health.

As a result, a personalised approach to cholesterol management, considering individual health profiles and risk factors, is becoming increasingly important. Consulting healthcare professionals for tailored advice and regular monitoring can help optimise cholesterol levels, supporting heart health in a way that aligns with individual needs and goals.

By focusing on balanced nutrition, regular exercise, and healthy lifestyle habits, we can take proactive steps toward maintaining cholesterol levels that support overall well-being, helping us thrive without unnecessary limitations.