Does Low Levels of ‘Bad’ Cholesterol Have Downside?
A new study suggests it may be possible for cholesterol levels to be too low.
The study researchers found that low levels of “bad” cholesterol, known as LDL cholesterol, were tied to an increased risk of hemorrhagic stroke, which occurs when a blood vessel bursts in the brain.
The findings suggest that, “as is true with many things in nutrition, moderation and balance is key when deciding the optimal target level of LDL cholesterol,” study senior author Dr. Xiang Gao, an associate professor of nutritional sciences at Penn State, said in a statement. “You can’t go to either extreme — too high or too low.” [ Cholesterol Levels: High, Low, Diagnosis, Treatment & Prevention ]
The authors said the findings, which were published (July 2) in the journal Neurology, might help further refine recommendations for healthy cholesterol levels. For example, people who are at high risk for hemorrhagic stroke, because of risk factors such as having a family history of the condition, might be better off aiming for cholesterol targets that aren’t quite as stringent as would otherwise be recommended.
Although the new study was large, involving nearly 100,000 people, all of the participants lived in a single city in China, and it’s unclear how well the findings apply to other populations.
Effects Of Cholesterol On The Body
Cholesterol is a waxy substance found in your blood and in your cells. Your liver makes most of the cholesterol in your body. The rest comes from foods you eat. Cholesterol travels in your blood bundled up in packets called lipoproteins.
Cholesterol comes in two forms:
- Low-density lipoprotein (LDL)
- High-density lipoprotein (HDL).
- Low-density lipoprotein (LDL) is the “bad,” unhealthy kind of cholesterol. LDL cholesterolcan build up in your arteries and form fatty, waxy deposits called plaques and increase the risk of heart disease and ischemic stroke, which occurs when a clot blocks blood flow to part of the brain.
For healthy adults, LDL cholesterol should stay below 100 milligrams per deciliter (mg/dL), according to the National Institutes of Health. However, recent guidelines recommend that people who are at very high risk of heart problems should aim to get their LDL cholesterol even lower, below 70 mg/dL.
Still, some previous studies have found a link between low LDL cholesterol levels and an increased risk of hemorrhagic stroke. However, most of these studies were small and measured cholesterol levels at a single point in time, which means they couldn’t take into account fluctuations in cholesterol levels over time, the authors said.
In addition, your body’s hormone-producing glands use cholesterol to make hormones such as estrogen, testosterone, and cortisol. Hormones can also have an effect on your body’s cholesterol levels. Research has shown that as estrogen levels rise during a woman’s menstrual cycle, HDL cholesterol levels also go up, and LDL cholesterol levels decline. This may be one reason why a woman’s risk for heart disease increases after menopause, when estrogen levels drop.
Lowered production of thyroid hormone (hypothyroidism) leads to an increase in total and LDL cholesterol. Excess thyroid hormone (hyperthyroidism) has the opposite effect. Androgen deprivation therapy, which reduces levels of male hormones to stop prostate cancer growth, can raise LDL cholesterol levels. A deficiency of growth hormone can also raise LDL cholesterol levels.
According to the Centers for Disease Control , over 31 percent of Americans have high LDL cholesterol. You may not even know it because high cholesterol doesn’t cause noticeable symptoms.
The only way to find out if your cholesterol is high is through a blood test that measures cholesterol in milligrams per deciliter of blood (mg/dL). When you get your cholesterol numbers checked, you’ll receive results for:
- Total blood cholesterol: This includes your HDL, LDL, and 20 percent of your total triglycerides.
- Triglycerides: This number should be below 150 mg/dL. Triglycerides are a common type of fat. If your triglycerides are high and your LDL is also high or your HDL is low, you’re at risk of developing atherosclerosis.
- HDL: The higher this number, the better. It should be at least higher than 55 mg/dL for females and 45 mg/dL for males.
- LDL: The lower this number, the better. It should be no more than 130 mg/dL if you don’t have heart disease, blood vessel disease, or diabetes. It should be no more than 100 mg/dL if you have any of those conditions or high total cholesterol.
- High-density lipoprotein (HDL)is the “good,” healthy kind of cholesterol. It transports excess cholesterol out of your arteries to your liver, which removes it from your body.
According to the National Institutes of Health (NIH), HDL levels of 60 mg/dL and higher are considered protective, while those under 40 mg/dL are a risk factor for heart disease.
According to a 2013 review, smokers typically have lower HDL cholesterol than nonsmokers. Research shows quitting smoking can increase HDL. If you smoke, talk to your doctor about smoking cessation programs or other methods you can use to quit smoking.
Keeping Cholesterol Numbers In Check
There are several things that influence your cholesterol numbers — some of which you have control over. While heredity may play a role, so too do diet, weight, and exercise.
Eating foods that are low in cholesterol and saturated fats, getting regular exercise, and managing your weight are all associated with lower cholesterol levels and lower risks of cardiovascular disease.