What? A Curved Relationship Between “Bad” Cholesterol and Longevity?

Low-density lipoprotein cholesterol (LDL-C), often called the “bad” cholesterol, is one of the most widely studied markers of heart and metabolic health (to keep things simple, we'll use the term 'heart health' throughout this article).

Many people have heard that lower LDL-C levels are generally related to better heart health.

A large body of research supports this relationship.[1]

However, some studies appear to show something different: people with higher LDL-C levels sometimes seem to live longer than those with lower LDL-C levels.[2],[3]

How can both be true?

Let's take a closer look.

The Relationship Between LDL-C and Longevity: The Danish Population Study

One study that attracted attention was a large Danish population study that followed more than 100,000 adults for approximately nine years.³

When researchers examined LDL-C levels across the population, they observed a curved relationship between LDL-C and longevity.

Individuals in the middle range appeared to have the most favorable outcomes, while outcomes were less favorable at both very low and very high LDL-C levels.

The illustrative figure below summarizes this relationship.

At first glance, findings like these may suggest that lower LDL-C is not always better for our health.

Some “experts” have even used studies like this to argue that higher LDL-C levels may be beneficial for longevity.

However, interpreting findings in isolation can sometimes lead to misleading conclusions.

To understand what these results really mean, it is important to understand what this type of study can—and cannot—tell us.

Let’s break this down.

Are Very Low LDL-C Levels Harmful?

Let's start with the simpler question.

Cholesterol plays important roles in the body.

It helps our bodies build cell membranes, certain hormones, and bile acids.

Given these important functions, it might seem logical that having too little cholesterol could be harmful.

However:

• It is practically impossible to eliminate cholesterol from our bodies completely
• In people with very low LDL-C levels (<30 mg/dL), no apparent organ dysfunction has been observed over the long term.[4]

This raises an important question:

If very low LDL-C does not appear to be inherently harmful, why do some studies report worse outcomes among people with low LDL-C levels?

LDL-C and Longevity: The "Chicken or Egg" Question

This is where study design becomes important.

The Danish study—and many similar studies—are observational studies.

Observational studies can identify relationships between factors, but they generally cannot determine which factor is causing the other.

In other words, they can tell us that low LDL-C levels and poorer health outcomes sometimes happen at the same time.

They cannot reliably tell us whether low LDL-C contributed to those outcomes, or whether underlying health conditions contributed to both.

This is often referred to as the "chicken or egg" problem.

Underlying health conditions, together with the limitations of observational studies, may help explain why some observational studies find higher mortality rates among people with very low LDL-C levels.

Let's take a look at some health conditions that may contribute to lower LDL-C levels.

Health Conditions That May Contribute to Lower LDL-C Levels

Cancer

• Some cancers can alter metabolism and increase energy demands.
• Cholesterol levels may decline before a cancer diagnosis is made.
• Cancer can result in increased risk of death.

Frailty and poor nutrition

• Severe undernutrition, muscle wasting, or disease-related weight loss (cachexia) can result in lower cholesterol levels.
• Over time, prolonged frailty or poor nutrition can contribute to poorer long-term health.

Chronic infection or inflammation

• Chronic infection or inflammation can lower cholesterol levels.
• Chronic infection or inflammation can increase the risk of death over time.

Liver diseases

• The liver plays a central role in cholesterol production.
• Advanced liver diseases can affect cholesterol production, lower LDL-C while also increasing health risks.

 

What Does Higher-Quality Evidence Show?

Not all studies provide the same ability to determine cause and effect.

Randomized controlled trials (RCTs) and meta-analyses of RCTs are generally considered among the strongest forms of clinical evidence for understanding cause-and-effect relationships.

In these studies, researchers ask people to take a medicine, supplement, follow a diet, or make another change, and then follow them over time to see what happens.

These studies help reduce many sources of bias that can affect observational research.

In contrast, observational studies can be influenced by factors such as underlying illness, frailty, nutritional status, and other factors that may affect both LDL-C levels and health outcomes.

Although researchers use various methods to reduce these biases, observational studies generally cannot determine cause and effect on their own.

A large body of RCTs and meta-analyses has examined the relationship between LDL-C and long-term health outcomes.

Overall, these studies suggest that maintaining healthy LDL-C levels contributes to better long-term heart health.

This includes studies that used dietary approaches to help maintain healthy LDL-C levels.[5]^,[6]

Final Words

LDL-C is more than just a number on a lab report.

When looking across available clinical research and separating signal from noise, the overall findings suggest that consistently maintaining healthy LDL-C levels over time can contribute to better long-term heart health.

If you have questions about your cholesterol levels or heart health, consult your healthcare provider for personalized guidance.

Stay well,

Derek Tang, PhD, MS, BSPharm

Truth Full Health

Your Trusted Supplement Partner

*Disclaimer: all blogged content is for informational purposes only and does not replace professional medical advice. These statements have not been evaluated by the Food and Drug Administration. This content is not intended to diagnose, treat, cure, or prevent any disease.

[1] American Heart Association. Lower your LDL. Accessed September 6, 2026. https://www.heart.org/en/health-topics/cholesterol/hdl-good-ldl-bad-cholesterol-and-triglycerides/lower-your-ldl

[2] Dean G. New study shows people with higher cholesterol live longer than people with lower cholesterol. NAD.com. Published March 20, 2025. Updated March 24, 2026. Accessed September 6, 2026. https://www.nad.com/news/new-study-shows-people-with-higher-cholesterol-live-longer-than-people-with-lower-cholesterol

[3] Title: Association between Low Density Lipoprotein and All Cause and Cause Specific Mortality in Denmark: Prospective Cohort Study. First author: CDL Johannesen. Journal: BMJ. Year of publication: 2020.

[4] Harvard Health Publishing. LDL cholesterol: How low can you (safely) go? Published January 20, 2020. Accessed November 9, 2025. https://www.health.harvard.edu/blog/LDL-Cholesterol-how-low-can-you-safely-go-2020012018638

[5] Title: Reduction in Saturated Fat Intake for Cardiovascular Disease. First author: L Hooper. Journal: Cochrane Database Syst Rev. Year of publication: 2020.

[6] Title: The Oslo Diet-Heart Study. Eleven-Year Report. First author: P Leren. Journal: Circulation. Year of publication: 1970.