Can Your Cholesterol Be Too Low?

While most of us have been advised about the dangers of high cholesterol and the ways to avoid them, there are situations where your cholesterol may be too low. This includes "good" high-density lipoprotein (HDL) cholesterol and "bad" low-density lipoprotein (LDL). cholesterol.

By nature, having too little HDL is your blood is a bad thing, increasing the risk of hypertension and heart disease. While low HDL is typically associated with high-carbohydrate diets and obesity, there are also genetic and environmental factors that can cause levels to dip.

Similarly, while having too much LDL increases your risk of heart attack and stroke, having too little increases your risk of certain cancers, mood disorders, and cardiovascular diseases. While scientists are still not certain why this is, there appears to be a pretty clear threshold as to when a low LDL becomes problematic.

Despite its association with heart disease and obesity, cholesterol is essential to making certain vitamins and hormones and also plays a part in digestion and the metabolization of nutrients. The problem is that most Americans consume way too much through high-fat, high-carb diets. This only adds to the cholesterol that is already naturally produced by the liver.

A low-fat, low-carb diet, by contrast, can help maintain a higher concentration of HDL (which the body uses to excrete LDL from the body) and a lower concentration of LDL (which can clog arteries and form plaque).

We can measure HDL and LDL levels with a simple blood test. For the average American adult, the values, measured in milligrams per deciliter (mg/dL), can be interpreted as follows:

• HDL values of 40 or higher are considered "good," while anything less than 40 is considered "low."
• LDL values under 100 are considered "good," between 130 to 150 are "borderline," and 160 and over are "high."

Other blood tests are used to measure triglycerides, another form of fat, and total cholesterol, the total amount of LDL, HDL, and triglycerides in a blood sample.

From the standpoint of heart health, the total cholesterol level can never be too low. A problem, however, arises when the HDL drops below 40 mg/dL. Quite simply, the less HDL there is in your blood, the less you can clear LDL from the body. This, in turn, increase your risk of atherosclerosis (hardening of the arteries), heart attack, and stroke.

HDL also function as an antioxidant, preventing arterial damage caused by other fats and lipids. If the HDL levels are low (a condition referred to as hypoalphalipoproteinemia), the loss of this antioxidative effect may not only promote but accelerate plaque formation.

There are many reasons why your HDL may be low. Chief among these is a high-carbohydrate diet. A diet of this sort not only affects your blood sugar, increasing the risk of insulin resistance, it can lower your HDL while raising both your LDL and triglycerides by 30 percent to 40 percent.

Other factors associated with hypoalphalipoproteinemia include:

• Obesity and metabolic syndrome
• Type 2 diabetes
• Smoking
• Elevated triglycerides
• High-dose thiazide diuretics
• High-dose beta blockers
• Severe liver disease
• End-stage kidney disease
• Tangier Disease, a rare genetic disease associated with a severe, chronic reduction of HDL

While a low-fat diet is not seen to contribute significantly to chronically low HDL levels, malnutrition can.

While it would be fair to assume that a low LDL is a good thing, there are rare circumstances in which chronically low levels may increase your risk of certain diseases. And the sad part is that we really don't know why.

What we do know is that LDL is not all bad. LDL is what we call a carrier protein whose role it is to deliver chemicals to every cell in the body. It is also a critical component of cell membranes and serves as a brain antioxidant. It is also used by the body to create the hormones estrogen, progesterone, and testosterone.

Clearly, having chronically low levels can impair all of these function and may explain why chronic low LDL (hypobetalipoproteinemia) is associated with the following conditions:

• Hemorrhagic stroke
• Depression
• Anxiety
• Preterm birth and low birth weight
• Liver cirrhosis
• Cancer

These conditions can affect both sexes but tend to impact women with an LDL below 50 mg/dL. Men, by contrast, are more likely to be affected when their LDL dips below 40 mg/dL.

While there remains strong debate as to the associations, given the disparate nature of the conditions, it may be reasonable to assume that the loss of depletion of LDL may increase the oxidative stress on the brain, impacting both brain function and vascular integrity.

Similarly, abnormally low LDL levels during pregnancy may trigger hormonal imbalances that contribute, at least in part, to premature birth. We also know that low LDL is also associated with the dysregulation of a protein known as tumor necrotizing factor alpha (TNF-a), the condition of which may be associated with cancer, major depression, and Alzheimer disease.

With that being said, hypobetalipoproteinemia is often caused by cancer, liver disease, severe malnutrition, and other wasting disorders. As such, no one knows for sure if a chronically low LDL is necessarily the cause or consequence of a disease. It may be in some cases and in others not.

Hypobetalipoproteinemia is also believed associated with mutations of the so-called ANGPTL3 gene, causing abnormal drops in both LDL and HDL. Other likely genetic causes have been identified.

It is often difficult to manage low cholesterol with anything other than diet or lifestyle. There are currently no pharmacological agents able to raise HDL (with the exception of hormone replacement therapy in postmenopausal women). Vitamin supplementation, including high-dose vitamin E (100 to 300 mg/kg/day) and vitamin A (10,000 to 25,000 IUs daily), may help normalize LDL.

Beyond that, the best way your cholesterol within the normal limits is to:

• Exercise regularly
• Embark on a weight-loss plan if overweight
• Eat plenty of fruits, vegetables, whole-grain bread, and nuts
• Limit red meat, processed foods, sugar, and processed flour
• Avoid saturated fat and trans fat
• Take statin medications if indicated
• Stop smoking

The best plan of action is to keep your total cholesterol within the middle range, somewhere between 150 and 200 mg/dL, and to continue monitoring your levels as directed by your doctor.