What is LDL-Cholesterol?
Low-density lipoprotein (LDL) is a particle made of fats surrounded by proteins. Since fats do not mix with water, they are packaged inside proteins for delivery to cells. LDL is one of five such packages (lipoproteins) that transport fat throughout the body .
LDL has the highest cholesterol concentration of all lipoproteins. It is the major cholesterol carrier in the body. LDL contains:
Functions of LDL
- Transfers fat and cholesterol around the body for cells to use .
- Binds certain toxins, making them unable to trigger harmful immune responses. LDL binds toxins produced by bacteria (Staphylococcus) and the toxin lipopolysaccharide (LPS) [3, 4].
- Helps repair damaged blood vessels. When arteries become damaged, LDL binds to the artery wall to aid the healing process. This helps the artery in the short-term but can be harmful long-term .
When LDL gets inside the damaged artery wall to help the healing process, it undergoes a change and becomes oxidized. Oxidized LDL is toxic to artery wall cells. To remove oxidized LDL, inflammatory cells migrate to the artery wall .
Cholesterol, other fats, and more inflammatory cells can accumulate to form a fatty plaque in the artery. The plaque may grow large enough to restrict blood flow. For this reason, oxidized LDL contributes to heart disease .
In a meta-analysis (of 12 studies), those with oxidized LDL had a higher risk of heart disease .
LDL particles differ in size and density. Small, dense LDL particles are associated with higher heart disease risk than large, less dense particles. This is because small, dense LDL passes easily into blood vessels and becomes oxidized .
Lowering LDL is the primary goal for people with high cholesterol .
A fasting LDL blood test estimates the amount of cholesterol carried by all LDL particles. The following equation estimates LDL:
LDL-cholesterol = Total cholesterol – HDL-cholesterol – (Triglycerides/5) .
This equation can underestimate LDL if fat (triglycerides) levels are extremely high (> 400 mg/dL) .
LDL particles can also be directly measured in the blood, which is more accurate than the equation. However, this method is expensive and not widely available .
The main factors affecting blood LDL levels are the amount of cholesterol that is :
- Absorbed in the gut from food and bile
- Produced in the liver
- Used by cells
- Removed by the liver and HDL
The first two raise blood LDL, while the second two lower it.
Optimal, Normal, and Elevated LDL Levels
Below are LDL guidelines for people with low risk of heart disease .
- Normal < 100 mg/dL
- Borderline High: 100 – 129 mg/dL (still acceptable in healthy individuals)
- High: 130 – 190 mg/dL
- Very High: > 190 mg/dL
Recommendations encourage LDL levels < 70 mg/dL for individuals with high heart disease risk .
LDL vs. HDL
LDL and HDL work together to maintain cholesterol levels. LDL delivers cholesterol from the liver to organs that use it. HDL gathers unused cholesterol from organs and returns it to the liver for reuse .
Low LDL-Cholesterol Levels
Low LDL reduces heart disease risk. In a meta-analysis involving 38,153 adults with high cholesterol, very low LDL (< 50 mg/dL) was associated with lower heart disease risk than LDL 75 – 100 mg/dL .
However low LDL can contribute to health problems because cholesterol plays many roles in the body.
Causes of Low LDL-Cholesterol Levels
Cholesterol-lowering drugs (statins) are prescribed to people with high cholesterol. These drugs lower LDL 25 – 35% on average and can reduce LDL below 30 mg/dL .
Conditions Associated with Low LDL-Cholesterol Levels
In a study of 70,179 adults, LDL levels in the bottom 10% (< 87 mg/dL) were associated with a 43% increased risk of developing cancer .
2) Depression and Suicide
Depression symptoms were linked to low LDL in a study of 225 healthy young women .
In a study of 60 people, those with depression had lower LDL compared to healthy subjects .
In a meta-analysis (of 65 studies and over 500,000 participants), suicidal patients had lower LDL compared to both non-suicidal patients with a mental disorder and healthy patients .
3) Infectious Disease
Individuals with low LDL (< 70 mg/dL) had increased sepsis, a life-threatening complication of infections, and fever risk compared to those with LDL > 70 mg/dL in a study of 203 people .
In a study of more than 100,000 people, those with low total cholesterol were more likely to be admitted to the hospital for an infectious disease .
4) Type 2 Diabetes
In a study of over 400,000 people, lower LDL was associated with a higher risk of developing type 2 diabetes .
5) Risk of Dying
In studies including over 130,000 people, low LDL was associated with increased risk of death in many different populations. These include Danish adults, elderly adults, and heart attack, pneumonia and sepsis patients [36, 37, 38, 39, 40, 41].
6) Other Conditions
Low LDL due to genetic problems in creating cholesterol can lead to many different disorders. These conditions delay growth, behavior, and mental function in children .
Ways to Increase LDL-Cholesterol
1) Cholesterol Supplements
In a meta-analysis, taking DHA increased LDL 7.23 mg/dL on average compared to placebo .
High LDL-Cholesterol Levels
Causes of High LDL Cholesterol Levels
In obesity, the number of harmful (small, dense) LDL particles increases. Total LDL levels increase slightly .
Obesity also reduces the number of LDL receptors in the body, which reduces response to LDL and raises its levels in the blood .
2) High Cholesterol Diet
3) High Trans Fat and Saturated Fat Diet
A similar relationship exists between saturated fat intake and LDL. In a meta-analysis of 60 studies, replacing carbohydrates with saturated fat increased LDL .
Consuming a high-saturated fat diet for 3 weeks increased LDL and harmful (small, dense) LDL particles in a study of 53 adults .
4) Physical Inactivity
In a study of 1,331 adults, physical inactivity was linked to LDL .
5) Type 2 Diabetes
Patients with type 2 diabetes have elevated small, dense LDL particles and oxidized LDL. Total LDL levels remain normal or increase only slightly .
LDL particles remain in the blood longer for individuals with type 2 diabetes. This increases the likelihood of LDL depositing into blood vessels .
Insulin-resistant individuals, such as those with metabolic syndrome or type 2 diabetes, produce more LDL. These people respond better to cholesterol-lowering drugs (statins), which block cholesterol production .
LDL (including harmful small, dense LDL) is elevated during pregnancy, particularly in the second half of pregnancy. This increase is due to sex hormone (estrogen, progesterone) changes [63, 64, 65, 66, 67].
Animal studies suggest that mothers with high LDL in pregnancy deliver offspring with elevated heart disease risk .
7) Short Sleep
In a small study of 10 healthy older women, LDL increased after 3 consecutive nights of sleeping only 4 hours/night .
In a study of 14,257 youth, shorter sleep duration in adolescence increased the likelihood of high cholesterol in young adulthood, but only among females .
8) Kidney Disease
A low-functioning thyroid gland (hypothyroidism) can increase LDL .
In a study of 106 adults, patients with subclinical hypothyroidism had higher LDL than those with a healthy thyroid .
Many drugs raise LDL as a side effect. They include muscle building steroids, retinoids (often used for skin problems), anti-seizure drugs, corticosteroids and drugs that suppress the immune system [76, 77, 78, 79, 80, 81, 82, 79, 83, 84].
11) Alcohol Consumption
Alcohol intake may increase oxidized LDL but is also associated with lower overall LDL levels.
In a study of 587 adults, alcohol consumption was positively associated with oxidized LDL .
People who abused alcohol had higher oxidized LDL compared to moderate drinkers in a study of 530 Finnish men .
However, alcohol intake was associated with lower LDL in a study of 993 Japanese men .
Additionally, wine intake was linked to reduced oxidized LDL in a study of 551 older Italian adults .
12) Mental Stress
In one of the above studies of 199 middle-aged adults, those with greater LDL increases during the stressful task were more likely to have elevated LDL 3 years later .
In a study of 308 people, current cigarette smoking and tobacco waterpipe smoking were associated with elevated LDL .
Smoking was also associated with increased oxidized LDL in a study of 28 adults .
14) Elevated Ferritin
In studies of over 11,000 people, those with higher blood ferritin levels were more likely to have increased LDL. It is not known whether elevated ferritin is a cause or result of elevated LDL [95, 96].
Conditions Associated with High LDL-Cholesterol Levels
1) Heart Disease
By far the biggest problem with elevated LDL is its accumulation in arteries. This can create fatty plaques that restrict blood flow and harden the blood vessels. Clogged arteries can become completely blocked, causing a stroke or heart attack, while hardened arteries lead to high blood pressure [97, 98, 99].
Even at very low levels, LDL was associated with artery hardening in a study of 1,779 adults .
2) Chronic Obstructive Pulmonary Disease (COPD)
In a study of 48 COPD patients and 32 healthy adults, those with COPD had higher oxidized LDL. Oxidized LDL was linked with poor lung function and inflammation .
LDL levels were linked with poor lung function in a study of 82 COPD patients and 43 healthy participants 
In a study of 60 people, LDL was 3 times higher among those with anxiety compared to those without anxiety .
4) Gum Disease
In a meta-analysis (of 19 studies), patients with gum disease had higher LDL than individuals without gum disease .
Ways to Lower LDL-Cholesterol
1) Weight Loss
In a study of 35 young women, weight loss lowered the creation of new cholesterol .
2) Low Cholesterol Diet and Low Saturated Fat Diet
With low-cholesterol diets, the liver rapidly clears both LDL and VLDL, so LDL levels in the blood remain low .
In a study of 155 adults, replacing saturated fats with polyunsaturated fats for eight weeks reduced LDL by 10% .
Reducing saturated fat intake lowered LDL in children in a meta-analysis .
In a study of 8,433 people, a “healthy” diet was associated with lower LDL. This diet included high intake of whole grains, fruit, dairy, vegetables, and unsaturated oil, and low intake of fast food, sugary beverages, poultry, processed meat, and flavored rice .
4) High Monounsaturated Fat (MUFA) Diet
In a study (DB-RCT) of 22 healthy adults, consuming any of three high-MUFA diets (using either olive oil, peanut oil, or peanuts and peanut butter) lowered LDL by 14% on average. These diets also reduced LDL oxidation compared to a standard American diet [122, 123].
Consuming a moderate-MUFA diet (10% of calories from MUFAs) and high-MUFA diet (14% of calories from MUFAs) both lowered LDL in a study of 35 participants with high cholesterol. The high-MUFA diet produced the greatest benefits .
In a study of over 80,000 young adults, more days per week of either aerobic or strength exercise were associated with lower LDL .
A meta-analysis (of 51 studies and 4,700 adults) found that exercises such as jogging, running, and biking decreased LDL by 5% .
In a study of 20 overweight women, 12 weeks of combined aerobic and strength exercise reduced oxidized LDL .
6) Red Yeast Rice Extract
Red yeast rice is an Asian food and traditional medicine. Some red yeast rice products contain a chemical (monacolin K) identical to the active ingredient in a cholesterol-lowering drug (lovastatin) .
In a meta-analysis (6,663 patients), red yeast rice (3 – 24 mg/day) decreased LDL by an average of 39 mg/dL .
Red yeast rice is well-tolerated but is not approved by the FDA as a drug. More large-scale studies must confirm its safety and effectiveness .
Red yeast rice extract supplements contain a yeast toxin (citrinin) harmful to the liver and kidneys at high doses. Because companies rarely report the amount of citrinin in these products, users should be careful when purchasing red yeast rice supplements [130, 129].
7) Soluble Fiber
In a study of 30 adults, taking 3 grams of soluble fiber supplements daily for 12 weeks decreased LDL by 18% .
A meta-analysis showed that beta-glucan consumption of more than 3g/day reduces LDL by 8 mg/dL in people with high cholesterol .
In a meta-analysis of 21 studies and 1,717 people with high cholesterol, psyllium (3 – 20.4 g/day) reduced LDL by an average of 11 mg/dL .
In a study of 68 adults, adding 15 g of psyllium to cholesterol-lowering medication was as effective as taking more medication without psyllium .
10) Black and Green Tea
In a meta-analysis of 39 studies with 2,298 subjects with high cholesterol, consuming garlic for at least 2 months decreased LDL 9 mg/dL on average .
Most studies used garlic powder (600 – 5,600 mg/day), while some used garlic oil (9–18 mg/day), garlic extract (1000 – 7200 mg/day), and raw garlic (4 – 10g/day). Aged garlic extract had the strongest effects .
In a study of 40 older adults, daily consumption of a beverage made up of various berries lowered LDL .
In a study of 30 type 2 diabetes patients, cranberry extract lowered LDL .
Berries can also lower oxidized LDL. Frozen berries (bilberries, lingonberries, black currants) lowered oxidized LDL in a study of 60 healthy adults .
In a study of 21 healthy men, drinking cranberry juice daily for 2 weeks lowered oxidized LDL .
In a study of 58 diabetic patients, consuming 320 mg/day of anthocyanins for 24 weeks decreased LDL by 8% compared to placebo .
Anthocyanins did not lower LDL in studies of healthy participants .
14) Dark Chocolate
Consuming a diet high in cocoa powder and dark chocolate lowered oxidized LDL in a study of 23 healthy people .
15) Plant Sterols
The average effective dose is 1.6 g/day, with the largest effects at around 3 g/day .
Soy mildly reduced LDL (by 4.8 mg/dL) in a meta-analysis with 2,670 participants. Soy lowered LDL more effectively for those with high cholesterol than in healthy subjects. The average soy intake was 30 g/day .
In a study of 30 patients with high cholesterol, 500 mg of soy lecithin taken daily for 2 months lowered LDL by an impressive 56% .
19) Vitamin C
According to a meta-analysis, taking at least 500 mg/day of vitamin C for at least 4 weeks lowered LDL by 7.9 mg/dL on average .
In a meta-analysis, eating 2 to 3 servings of nuts (including walnuts, almonds, macadamias, pistachios, hazelnuts, peanuts, and pecans) per day decreased LDL by an average of 10.2 mg/dL .
Eating half a cup of legumes per day reduced LDL cholesterol by an average of 6.6 mg/dL, according to a meta-analysis .
Glucomannan is another type of plant fiber extracted from the konjac root, also known as the elephant yam. It decreases LDL in adults and children, according to meta-analyses (of RCT studies) [170, 171, 172].
23) Coenzyme Q10
Taking 150 mg of coenzyme Q10 daily for 2 weeks lowered LDL by 12.7% in a study of 53 healthy men. Importantly, coenzyme Q10 also reduced unhealthy (small, dense) LDL particles .
In a study of 100 healthy adults, taking 200 mg/day of coenzyme Q10 for 1 week removed cholesterol from immune cells (macrophages). This improves blood flow by shrinking the fatty plaques in the arteries .
As a supplement to standard therapy, 1 g/day of curcumin lowered LDL in a study (RCT) of 100 patients with high heart disease risk .
Because estrogen helps to lower LDL, the decline in estrogen levels after menopause makes older women prone to elevated LDL. In studies two studies conducted in postmenopausal women, estrogen replacement therapy lowered LDL 14-27% [178, 179].
In studies including 74 overweight adults, 27 participants with high cholesterol, and 57 patients with hardening of the arteries, grapefruit lowered LDL. In one of the studies, red grapefruit was more effective than white [180, 181, 182].
28) Black Cumin
Black cumin (Nigella sativa) lowered LDL by an average of 22 mg/dL according to a meta-analysis .
30) Artichoke Leaf Extract
Consuming artichoke leaf extract decreased LDL by 15 mg/dL, according to a meta-analysis (of 9 studies including 702 subjects, most of whom had high cholesterol). The only side effect was rare, mild stomach pain .
31) Rice Bran Oil
A meta-analysis showed that rice bran oil lowered LDL by 7 mg/dL on average in healthy participants and those with high cholesterol .
Spirulina consumption greatly reduced LDL — by 41 mg/dL on average — according to one meta-analysis. The Spirulina doses were between 1 – 10 g/day, taken for 2-12 months. Longer supplementation, but not dose, was linked with reduced LDL .
The bergamot orange is a citrus fruit from Italy. Bergamot extract (500 – 1500 mg/day) reduced LDL between 23% and 39% in a study of 237 patients with high cholesterol .
In a study of 80 people with high cholesterol, bergamot extract (150 mg/day) lowered LDL and harmful (small, dense) LDL particles .
34) Olive Oil
In a study of 25 healthy adults, adding 10 g of olive oil to a meal reduced LDL and oxidized LDL (compared to a meal with no olive oil or with corn oil) .
Consuming 50 g/day of olive oil for 4 weeks was associated with lower LDL compared to consuming the same amount of butter in a study of 91 older adults .
35) Fish and EPA
In another study of 36 patients with type 2 diabetes, taking EPA slightly reduced LDL .
36) Conjugated Linoleic Acid
In a meta-analysis, consumption of foods or supplements enhanced with conjugated linoleic acid was associated with reduced LDL .
37) Alpha-Lipoic Acid
In a study of 22 obese subjects, taking 600 mg/day of alpha-lipoic acid decreased LDL over 2 weeks .
In a study of 6 patients with polycystic ovary syndrome, taking 1.2 g/day of alpha-lipoic acid shifted LDL from smaller (more harmful) to larger (less harmful) particles .
In a study of 42 healthy elderly subjects, those who regularly consumed guarana had lower oxidized LDL compared to those who had never consumed guarana .
40) African Mango
In a 4-week study of 40 obese individuals, African mango consumption decreased LDL .
41) LDL Apheresis
A procedure called LDL apheresis removes LDL from the blood. It is an option for people who don’t respond to drugs and have very high cholesterol levels. LDL apheresis takes 2-4 hours and must be performed every few weeks .
LDL apheresis reduces LDL by more than 60% in patients with high cholesterol due to genetics (familial hypercholesterolemia) .
A study of 45 patients with high cholesterol resistant to drugs found that LDL apheresis lowered LDL by 56%. Quality of life improved in most patients .
In another study of 14 patients with high cholesterol, LDL apheresis was safe long-term (over 10 years), and lowered LDL by 82% on average .
LDL levels are influenced by your genes. If you’ve gotten your genes sequenced, SelfDecode can help you determine if your levels are high or low as a result of your genes, and then pinpoint what you can do about it.
If you’re sick and tired of guessing about your health, SelfDecode can help you find specific answers that conventional doctors/diagnostics may never uncover.
Here’s a breakdown of some genes that can influence LDL levels:
- Abetalipoproteinemia is a rare disease where LDL is almost absent. This is due to a poor ability to absorb fat (caused by a mutation in the microsomal transfer protein (MTP) gene) .
- Familial hypobetalipoproteinemia is another rare condition where LDL levels are below 50 mg/dL. The cause is a mutation of the apoprotein B (APOB) gene .
- Some people have reduced activity of genes that break down cholesterol (ATP-binding cassette (ABC) transporters). This can increase LDL levels and lower response to cholesterol medication .
- In a study of 599 patients with elevated LDL, carrying an apolipoprotein 5 (APOA5) SNP was associated with smaller LDL particle size and higher oxidized LDL levels .
- Proprotein convertase subtilisin/kexin type 9 (PCSK9) breaks down the LDL receptor, resulting in the accumulation of LDL in the blood. Variants of PCSK9 can cause either elevated or low cholesterol .
These mutations cause problems in removing LDL from the blood, resulting in elevated LDL .
Irregular LDL Levels?
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