What is cholesterol and why do we need it?
Cholesterol is a waxy, fat-like substance that is vital for our body to function correctly. It is not inherently bad. Cholesterol plays several essential roles, including:
- Building and maintaining cell membranes, ensuring their proper structure and function.
- Producing bile, which is necessary for digestion and the absorption of fat-soluble vitamins (A, D, E, and K).
- Creating hormones, such as estrogen, testosterone, and cortisol.
- Metabolizing vitamin D.
Because of its critical functions, having levels that are too low can be as problematic as having levels that are too high. The body produces all the cholesterol it needs, though we also get a small amount from our diet, specifically from animal products.
Potential risks associated with low cholesterol
Excessively low cholesterol levels, particularly very low LDL (low-density lipoprotein), have been associated with a number of potential health risks and complications, although ongoing research continues to clarify the specific causal relationships.
Neurological and mental health concerns
Several studies have explored the link between low cholesterol and neurological or psychological issues:
- Hemorrhagic stroke: Some long-term observational studies have found an association between very low LDL-cholesterol and an increased risk of hemorrhagic stroke, which is a type of stroke caused by bleeding in the brain.
- Mental health disorders: Low cholesterol has been linked to an increased risk of depression, anxiety, and mood instability. Some researchers theorize that cholesterol's role in brain cell function and serotonin production could be a factor.
Other serious health complications
Beyond neurological effects, low cholesterol is also tied to other significant health issues:
- Cancer: Observational studies have shown a connection between very low cholesterol and an increased risk of certain cancers, such as multiple myeloma, breast, and lung cancer. It is not clear whether the low cholesterol causes the cancer or is a marker of the underlying disease process.
- Immune function: A weakened immune response and increased susceptibility to infection have been observed in individuals with low cholesterol.
- Pregnancy complications: For pregnant women, low cholesterol may increase the risk of preterm birth or having a low birth weight baby.
- Critical illness: For hospitalized patients with critical illness, very low cholesterol levels can predict clinical deterioration.
Causes of low cholesterol
Low cholesterol, medically known as hypocholesterolemia, can be categorized by its cause: genetic or secondary.
Genetic causes (Primary Hypocholesterolemia)
Some rare genetic disorders can cause abnormally low cholesterol from birth:
- Abetalipoproteinemia: A rare inherited condition that prevents the body from absorbing fats and fat-soluble vitamins, resulting in extremely low LDL.
- Hypobetalipoproteinemia: Another rare genetic disorder where the body metabolizes LDL cholesterol very quickly.
- Smith-Lemli-Opitz syndrome: A genetic disorder affecting cholesterol synthesis, which can cause severe health and developmental abnormalities.
Medical conditions (Secondary Hypocholesterolemia)
More commonly, low cholesterol is a symptom of another underlying health problem:
- Liver disease: Since the liver produces cholesterol, diseases like hepatitis or cirrhosis can interfere with production and lower levels.
- Hyperthyroidism: An overactive thyroid gland increases metabolism, which can accelerate the breakdown of cholesterol.
- Malabsorption disorders: Conditions like Crohn's disease, celiac disease, or cystic fibrosis can prevent the body from properly absorbing fats and nutrients from food.
- Chronic infection or inflammation: Persistent infections like hepatitis C or sepsis can cause a temporary or long-term drop in cholesterol levels.
- Cancer: Certain cancers, particularly blood cancers like leukemia or lymphoma, are linked to low cholesterol.
- Malnutrition: Severe undernutrition from conditions like anorexia or alcohol abuse can lead to insufficient cholesterol.
Medication effects
For individuals on statins, cholesterol-lowering medication can sometimes lower levels more than intended. If this happens, a doctor may need to adjust the dosage.
How low is too low?
While there isn't a universally agreed-upon threshold, general guidelines define very low levels. Some experts consider total cholesterol below 120 mg/dL or LDL cholesterol below 50 mg/dL as very low, while others use a more aggressive LDL target. For most healthy people, having lower cholesterol is generally beneficial for heart health. The concern arises when levels drop for unexplained reasons or due to an underlying condition. An ideal LDL level for most people is below 100 mg/dL.
Low vs. High Cholesterol: A comparison
| Feature | Low Cholesterol (Hypocholesterolemia) | High Cholesterol (Hypercholesterolemia) |
|---|---|---|
| Associated Health Risks | Hemorrhagic stroke, mental health issues, pregnancy complications, increased infection risk, certain cancers. | Atherosclerosis, coronary artery disease, heart attack, ischemic stroke. |
| Primary Cause | Rare genetic disorders (e.g., abetalipoproteinemia). | Familial hypercholesterolemia (genetic). |
| Secondary Cause | Liver disease, hyperthyroidism, malnutrition, chronic infections. | Unhealthy diet (saturated/trans fats), sedentary lifestyle, smoking, obesity. |
| Common Symptoms | Can be asymptomatic, or symptoms may reflect the underlying cause (e.g., depression, fatigue). | Often called a "silent killer" because it has no noticeable symptoms until an event like a heart attack or stroke. |
Conclusion: Finding the right balance
While the public health conversation rightly focuses on the dangers of high cholesterol, it is important to remember that balance is key. Very low cholesterol levels are not a goal to be pursued but rather a potential red flag that can point to other, more serious health problems. For individuals whose low cholesterol is not a side effect of medication, identifying the underlying cause is the primary step for a healthcare provider. Addressing issues like malnutrition, treating infections, or managing conditions like hyperthyroidism is crucial. Maintaining a healthy lifestyle, including a balanced diet and regular exercise, supports overall health and helps regulate cholesterol levels, ensuring they remain in a safe, optimal range. Consulting a healthcare provider for a blood test is the only definitive way to know your cholesterol status and to receive the best course of action for your unique health profile. For more information on what your levels mean, visit the Mayo Clinic's expert Q&A on cholesterol levels.
