Cholesterol

In this article:

1. Cholesterol functions
2. Foods high and low in cholesterol
3. Cholesterol absorption
4. Cholesterol transport in blood
5. Cholesterol clearance
6. Is cholesterol harmful?
7. High cholesterol levels (hypercholesterolemia)
8. Cholesterol tests (blood levels charts)
9. Low cholesterol levels (hypocholesterolemia)

Cholesterol Functions

In your body, cholesterol is ^[2]:

• A part of the cell membranes and myelin sheaths of the nerves
• A precursor for steroid hormones (cortisol, aldosterone, estrogens, progesterone, testosterone), bile acids (in the bile) and vitamin D

There seems to be NO CONVINCING EVIDENCE about the effect of cholesterol intake on the blood levels of adrenal hormones (epinephrine, cortisol) ^[42] or vitamin D ^[24].

Recommended Daily Cholesterol Intake

American Heart Association (AHA) and National, Heart, Lung and Blood Institute in the US, recommend limiting cholesterol intake to 300 mg per day for healthy adults with normal cholesterol levels and to 200 mg per day for individuals at high risk for coronary heart disease or diabetes type 2 ^[3,4].

Foods that Contain Cholesterol

Cholesterol is found mainly in organ meats, eggs and shrimps and, in lower amounts, in meat, fish and milk. The amount of cholesterol in foods does not necessary relate to the amount of fat: foods high in fat can be low in cholesterol and vice versa. Plant foods usually contain less than 1 mg of cholesterol per serving, which is insignificant for human nutrition and health ^[5]. Foods high in cholesterol can raise blood cholesterol levels in some people, but foods high in saturated fats and trans fats can raise it more.

Picture 2. Examples of foods high in cholesterol

Chart 1. List of Foods High in Cholesterol
FOOD	CHOLESTEROL (mg)
Veal brain (3 oz, 85 g)	2,600
Pork brain (3 oz, 85 g)	2,200
Beef or lamb brain (3 oz, 85 g)	1,700
Egg, goose (one, 144 g)	1,230
Egg, duck (one, 70 g)	620
Beef kidney (3 oz, 85 g)	610
Chicken/goose liver (3 oz, 85 g)	480
Fish, roe (3 oz, 85 g)	410
Beef liver (3 oz, 85 g)	340
Turkey liver (3 oz, 85 g)	330
Pork lungs (3 oz, 85 g)	330
Beef spleen (3 oz, 85 g)	300
Kielbasa (1 link, 370 g)	270
Biscuit with egg and sausage (160 g)	250
Squid (3 oz, 85 g)	220
Egg, chicken, whole (50 g) [all cholesterol is in the yolk]	210
Cuttlefish (3 oz, 85 g)	190
Chicken or beef heart (3 oz, 85 g)	180
Shrimps (3 oz, 85 g)	170
Veal (3 oz, 85 g)	100-130
Chicken, turkey, dark meat (back, leg) w/wo skin (3 oz, 85 g)	100-130
Beef, pork, fish and other seafood (3 oz, 85 g)	50-100
Poultry, light meat (breast, wing), w/wo skin: chicken, duck, goose, turkey meat (3 oz, 85 g)	50-80
Game meat: bison, boar, elk, goat, horse, moose (3 oz, 85 g)	50-70
Caviar (1 tbsp, 16 g)	95
Fish oil, menhaden (1 tbsp, 14 g)	70
Milk, sheep (1 cup, 237 mL)	70
Cheese (2 oz, 57 g)	~50
Milk, buffalo (1 cup, 237 mL)	50
Pate, goose (1 oz, 28 g)	40
Butter and clarified butter (ghee) (1 tbsp, 14 g)	30

Chart 1 source: USDA.gov ^[6]

Picture 3. Examples of low-cholesterol foods

Chart 2. List of Foods Low in Cholesterol

All PLANT FOODS contain <1 mg cholesterol per serving

ANIMAL FOODS with <10 mg cholesterol/serving Nonfat milk (1 cup) Cottage cheese (2 oz, 57 g) Mayonnaise (1 tbsp, 14 g) Sour cream (1 tbsp, 12 g)

ANIMAL FOODS with 10-30 mg cholesterol/serving Seafood (3 oz, 85 g): monkfish, tuna (light, white), clams, crab (Alaska king), oysters (eastern), scallops Milk, cow’s (1 cup, 237 mL): whole (3.24% fat), reduced (2% fat) or low fat (1% fat); goat milk Ice cream (1/2 cup, 66 g) Goat cheese (2 oz, 57 g)

Chart 2 source: USDA.gov ^[6]

Cholesterol Absorption

In foods, cholesterol is in the form of free cholesterol or cholesterol esters (compounds made of cholesterol and fatty acids). After cholesterol ingestion, in the small intestine, the pancreatic enzyme cholesterol esterase cuts the fatty acids from cholesterol esters, and free cholesterol can be then, with the help of bile acids, absorbed into the small intestinal lining cells. There it is, together with triglycerides, packed into large fatty particles called chylomicrons, which enter the lymph–the fluid within the lymphatic vessels–and eventually the blood ^[7].

Cholesterol absorption efficiency among different individuals can vary from 20 to 80%, which mainly depends on genetic factors ^[18].

Cholesterol absorption can be decreased by viscous soluble fiber (oats, barley, psyllium husk), medications (cholesterol absorption inhibitors colestipol and colesevelam) and in certain intestinal diseases, like celiac disease.

Cholesterol Transport in the Blood

In the blood, cholesterol is transported within lipoproteins, which are compounds of lipids (triglycerides and cholesterol) and proteins. Low Density Lipoproteins (LDL) carry cholesterol from the liver to the tissues, including the arteries, and High Density Lipoproteins (HDL) pick cholesterol from the tissues, including the arteries, and carry it back to the liver for disposal. This way LDL can increase the cholesterol content of arterial plaques and has been hence named “bad cholesterol”, while HDL can remove some cholesterol from the plaques, so it has been named “good cholesterol” ^[8].

NOTE: HDL and LDL are often wrongly called “HDL cholesterol” and “LDL cholesterol,” while they actually mean High Density Lipoproteins and Low Density Lipoproteins, in which cholesterol represent only a small part.

Cholesterol Clearance

Cholesterol clearance means removal of cholesterol from the blood, mainly by the liver ^[86].

Is dietary cholesterol harmful?

Effect of Dietary Cholesterol on BLOOD CHOLESTEROL LEVELS:

• Dietary cholesterol increases blood cholesterol levels only in about 30% people (cholesterol responders) ^[9]; the effect does not depend on body weight ^[57].
• Consumption of eggs, which are high in cholesterol, can increase blood cholesterol levels in some people, but it increases both LDL and HDL cholesterol, so it does not significantly increase the Total/HDL cholesterol ratio ^[30,34]; besides that, dietary cholesterol increases mainly large LDL particles (“A pattern”), which are less plaque-forming, rather than small LDL particles (“B pattern”) ^[9,22].

* NOTE: In one study, palmitic acid, the most abundant saturated fatty acid in the human diet, increased blood cholesterol levels in individuals who already had increased total cholesterol levels (>225 mg/dL) and who were consuming more than 400 mg of cholesterol per day, but not in individuals with normal blood cholesterol levels were consuming less than 300 mg of cholesterol per day ^[67].

Effect of Dietary Cholesterol on CORONARY HEART DISEASE and STROKE

• According to several systematic reviews, in healthy people, eating up to seven eggs per week does not increase the risk of coronary heart disease and stroke ^{[10,11,12,13,23]} but may do so in individuals with diabetes ^[20,21,23].
• According to the Health Professionals Follow-Up Study (1986-1992), cholesterol intake was associated with increased risk of coronary heart disease only when it was associated with low dietary fiber intake.

Effect of Dietary Cholesterol on DIABETES MELLITUS 2

• There is LITTLE EVIDENCE that high cholesterol intake increases the risk of diabetes 2 ^[11,22].

Effect of Dietary Cholesterol on GALLSTONE formation

• There is CONFLICTING EVIDENCE about the effect of dietary cholesterol on the formation of cholesterol gallstones: from no to some effect ^[15,16].

Effect of Dietary Cholesterol on CANCER

• According to several studies and reviews, there in LACK OF CONVINCING EVIDENCE about the association between high cholesterol intake and increased risk of lung, prostate, breast and colorectal cancer ^[18-p.568] or pancreatic cancer ^[19].

Blood Cholesterol and Other Risk Factors for Coronary Heart Disease

The following factors increase the risk of coronary heart disease ^{[4; 35-II4-19; 113]}:

• High levels of LDL cholesterol (LDL-C), especially small dense LDL particles (LDL-P) ^[98,131] and oxidized LDL (oxLDL) ^[103,104]
• Low levels of HDL cholesterol
• High total/HDL cholesterol ratio, for example, in polygenic ^[47] and familial hypercholesterolemia ^[51]
• Diabetes mellitus type 1 or 2 ^[144]
• Obesity
• Cigarette smoking ^[145]
• Previous heart attack or stroke, blockage of the arteries in the neck, arms or legs
• Family history of heart disease
• High blood pressure
• High triglyceride levels ^[14,148]
• High levels of C-reactive protein (CRP) ^[146]
• High levels of homocysteine ^[147]
• Age >45 for men or >55 for women

High Blood Cholesterol Levels (Hypercholesterolemia)

Definition

Blood levels of total cholesterol >240 mg/dL (6.2 mmol/L) are considered high ^[28].

Causes:

Nutrients and foods that can increase cholesterol levels:

• Trans fats (hard margarines, processed meats) ^[47,56]
• Saturated fats (beef, pork) ^[4,33,34,56]
• Cholesterol (organ meats, egg yolk, shrimps) increases blood cholesterol only in some people ^[9,57]

Life style associated with increased cholesterol levels:

• Obesity, especially abdominal obesity ^[107,149]

Genetic disorders with increased cholesterol levels:

• Polygenic hypercholesterolemia ^[50]:
  • LDL: >190 mg/dL
  • Symptoms are usually absent
• Familial hypercholesterolemia ^[17,50,51]:
  • Heterozigous: LDL: 190-350 mg/dL
    • Symptoms, usually only in adults: fatty nodules (xanthomas) in the skin and Achilles tendons; small yellowish nodules around the eyes (xanthelasma)
  • Homozygous: LDL: 400-1,000 mg/dL
    • Symptoms: xanthomas, xanthelasma, greyish ring in the eye cornea (arcus senilis), death often before 30

Drugs that can increase cholesterol levels:

• Anabolic steroids can raise LDL and severely lower HDL cholesterol ^[60,61].
• Corticosteroids can raise total and HDL cholesterol ^[58,59].

Treatment

A Cholesterol-Lowering Diet

Cholesterol-lowering diet may lower your LDL levels by 5-15% ^[48].

Cholesterol-lowering diet consists of ^[4]:

• Only enough calories to maintain a healthy weight
• Replacing saturated fats (<7% of daily calories or <15 g saturated fat/day in a 2,000 Cal diet) with unsaturated fats
• Avoiding trans fats (hard margarines, cakes, crackers, frostings)
• Cholesterol intake <200 mg or <100 mg/day
• Soluble fiber, 10-25 g per day:
  • Beta-glucan can lower total and LDL cholesterol by 1.55 mg/dL per gram of fiber ^[66]. In one meta-analysis, adding 2 cups of cooked oatmeal (3 g of beta glucan) to a diet was associated with a drop of total and LDL cholesterol by about 5 mg/dL ^[66]. Other meta-analyses that evaluated the effect of beta-glucan from oats and barley have shown similar results ^[62].
  • Psyllium husk soluble fiber in doses 3-16 g/day (6-32 g psyllium husk powder/day) was associated with a drop of total cholesterol by 8 mg/dL and LDL cholesterol by 9 mg/dL in average, according to several meta-analyses ^[62].
  • Soluble fiber does not lower HDL cholesterol ^[66].
  • According to Electronic Code of Federal Regulations in the US, adding at least 3 g of beta-glucan from whole barley or oats (at least 1 cup of cooked oat bran, or 2 cups of cooked oatmeal, or 1.2 cup of cooked barley), or at least 7 g of soluble fiber from psyllium husk (at least 14 g of psyllium husk powder) may reduce the risk of coronary heart disease ^[63].
  • There is insufficient evidence about the cholesterol lowering effect of guar gum, gum arabic, inulin or fructooligosaccharides (FOS).
• Phytosterols (plant sterols and stanols), at least 2 g per day, may also reduce cholesterol absorption and decrease LDL levels by 6-15% ^{[141,142,143]}.

Life Style Changes

• Weight loss (if obese) of even few pounds can lower blood LDL levels regardless of the diet composition ^[99].
• Exercise, for example at least 30 minutes of brisk walking per day, may increase your HDL levels. Exercise does not appear to significantly affect LDL levels, though ^[94].
• Reference: ^[4,48]

Drugs That Lower Cholesterol Levels

• Statins: most potent are rosuvastatin and atorvastatin, which can reduce LDL cholesterol levels by up to 60% ^[49].
• Ezetimibe (cholesterol absorption inhibitor) inhibits the absorption of cholesterol from foods and bile and can lower LDL-cholesterol levels by about 20% without lowering HDL cholesterol ^[26,27,49].
• Vitamin B3 (nicotinic acid, niacin) in high doses (2-3 g/day) can slightly decrease LDL cholesterol and lipoprotein (a), and increase HDL cholesterol by up to 18% ^[49] or, according to one review, by 20-40% ^[159]
• Fenofibrate lowers LDL ^[25]
• Bile acid resins (sequestrants) cholestyramine, colesevelam and colestipol bind cholesterol-containing bile acids in the intestine and prevent their reabsorption; they can lower LDL cholesterol levels by 15-30% ^[4-p.15].

Treatment options for homozygous familial hypercholesterolemia:

• Medications lomitapide and mipomersen can reduce LDL levels by about 50% ^[17].
• LDL apheresis–a dialysis-like procedure to remove excessive LDL from the blood–from 5th year of age, can reducle LDL levels by about 50% ^[54].
• Portacaval anastomosis can reduce LDL levels by about 30% ^[52].
• Liver transplantation can normalize LDL levels ^[53].

Tests for Blood Cholesterol and Triglyceride Levels

Blood test called lipid panel or lipid profile includes tests for HDL and LDL cholesterol, total cholesterol (HDL, LDL and other types of cholesterol) and triglyceride levels.

Chart 5. Lipid Panel or Profile
Total cholesterol (TC)
Below 200 mg/dL (5.2 mmol/L)*	Desirable
200-239 mg/dL (5.2-6.2 mmol/L)	Borderline high
240 mg/dL (6.2 mmol/L) and above	High
LDL cholesterol (LDL-C)
Below 70 mg/dL (1.8 mmol/L)	Ideal for people at very high risk of heart disease
Below 100 mg/dL (2.6 mmol/L)	Ideal for people at risk of heart disease
100-129 mg/dL (2.6-3.3 mmol/L)	Near ideal
130-159 mg/dL (3.4-4.1 mmol/L)	Borderline high
160-189 mg/dL (4.1-4.9 mmol/L)	High
190 mg/dL (4.9 mmol/L) and above	Very high
HDL cholesterol (HDL-C)
Below 40 mg/dL (1 mmol/L) (men)Below 50 mg/dL (1.3 mmol/L) (women)	Poor
40-49 mg/dL (1-1.3 mmol/L) (men)50-59 mg/dL (1.3-1.5 mmol/L) (women)	Better
60 mg/dL (1.6 mmol/L) and above	Best
Triglycerides (TG)
Below 150 mg/dL (1.7 mmol/L)	Desirable
150-199 mg/dL (1.7-2.2 mmol/L)	Borderline high
200-499 mg/dL (2.3-5.6 mmol/L)	High
500 mg/dL (5.6 mmol/L) and above	Very high

* Units in US: mg/dL; in Canada and EU: mmol/L
Chart 5 source: Mayo Clinic ^[28]

Total/HDL Cholesterol Ratio

According to several reviews of studies, total/HDL cholesterol ratio is considered one of the best predictors of coronary heart disease and associated mortality; the higher the ratio, the greater the risk ^[35,55,64]. The effect of total/HDL cholesterol ratio has not been evaluated in controlled clinical trials, so it should be interpreted with caution ^[56].

Trans fats intake is associated with unfavorable increase of total/HDL ratio ^[56].

Replacing saturated fats with unsaturated fats ^[33,34,56], soluble fiber intake ^[66] and weight loss ^[56] is associated with favorable decrease of total/HDL ratio.

LDL-P Test

LDL-P (LDL Particles) test measures the number of LDL cholesterol particles in the blood rather than the concentration of LDL cholesterol (LDL-C) measured by most current tests. The results of LDL-P test should be compared with the results of LDL-C test; when the results do not match (high LDL-P/normal LDL-C or normal LDL-P/high LDL-C), then, according to some authors, the LDL-P test results are considered a better predictor of the risk of cardiovascular disease (heart attack and stroke) than LDL-C results ^[29,37]. According to other authors, LDL-P test does not give better information about the coronary heart disease risk than total/HDL cholesterol ratio ^[65].

LDL-P is measured by nuclear magnetic resonance (NMR) spectroscopy.

Chart 6. LDL Particles Number (LDL-P)
<1,000	Optimal
1,000-1,299	Near or above optimal
1,300-1,599	Borderline-high risk
1,600-2,000	High risk
>2,000	Very high risk
Small LDL-P Number
700	Safe maximum

Chart 6 source: Novant Health ^[40]

Studies about LDL-P:

• In one large prospective study in women (1995-2008), small LDL and small HDL particles were associated with increased risk of diabetes 2 ^[38].
• In one study in adolescents, losing weight resulted in a decreased number and increased size of LDL particles ^[39].

Small, Dense LDL Particles

Small, dense LDL particles (“pattern B”) are considered greater risk for coronary heart disease than large LDL particles (“pattern A”) ^[98,131]. Small dense LDL particles are more prone to become oxidized and thus even more harmful for the arteries ^[133].

Increased levels of small dense LDL particles are associated with:

• Abdominal obesity ^[97,98,131]
• High triglyceride levels ^[98,110,154]
• Diabetes type 2 ^[130,131]
• High blood pressure ^[131]
• Trans fat intake ^[151]

Levels of small dense LDL particles can be decreased by:

• Weight loss ^[131,156]
• Diet high in both fat and saturated fat ^{[153,154,155]} and low in carbohydrates ^[157]
• Treatment of diabetes with acarbose or troglitazone ^[131] or insulin ^[129]
• Decreasing triglyceride levels by statins and fibrates ^[131,32]

Oxidized LDL Cholesterol

Oxidized LDL cholesterol has been associated with increased risk of artery hardening (atherosclerosis) and coronary heart disease ^{[103,104,113]}.

Health disorders and other factors associated with increased levels of oxidized LDL:

• High triglyceride levels ^{[103,114,126]}
• Low HDL levels ^[103,126]
• Increased glucose levels (hyperglycemia) ^{[103,114,124,128]}
• Diabetes mellitus type 1 ^[121], diabetes type 2 ^{[103,115,128]} and its duration ^[127], insulin resistance with hyperinsulinemia ^{[106,112,128]}
• Obesity ^{[107,109,117]}, especially abdominal obesity ^{[106,108,111,114]}
• Metabolic syndrome (a combination of above factors) ^[112,114]
• High LDL levels ^[126]
• Smoking ^[117,118]

Factors that can decrease oxidized LDL levels:

• Weight loss (in obese individuals) ^[107]
• Replacement of some of the saturated fats by unsaturated fats decreased oxidized LDL in one study ^[135] but increased it in another one ^[136].
• Insulin treatment in diabetes type 1 ^[121] and diabetes type 2 ^[123]
• Metformin treatment in diabetes 2 ^[125]
• Prolonged, moderate exercise (walking) ^[134]
• Cocoa powder ^[105], cocoa powder with milk ^[138], cocoa extract high in flavanols (polyphenols) in a low-calorie diet ^[137]
• Statins: (cerivastatin) ^[116]
• L-carnitine supplements (in individuals with diabetes 2) ^[122]

The levels of oxidized LDL cholesterol do not seem to be associated with consumption of trans fats ^[140] or antioxidant potential of the blood ^[126], which explains why antioxidants, like vitamin C ^[119] and E have only little effect on oxidized LDL levels.

Atherogenic Dyslipidemia

Dyslipidemia is a combination of ^[75,76]:

• Low levels of large HDL particles
• High levels of small HDL particles
• High levels of small dense LDL particles
• High triglyceride levels

Atherogenic dyslipidemia refers to a combination of blood lipid concentrations associated with increased risk of artery hardening and narrowing (atherosclerosis) and thus with coronary heart disease ^[76]. Dyslipidemia is commonly found in obese individuals and in those with insulin resistance (diabetes type 2) ^[76].

Metabolic syndrome, which represents even greater risk for coronary heart disease than dyslipidemia, includes 3 or more of the following ^[77,112]:

• Abdominal obesity (waist circumference ≥40 inches or 102 cm in men or ≥35 inches or 88 cm in women)
• Increased blood pressure: systolic (upper) ≥130 mm Hg, or diastolic (lower) ≥85
• Triglyceride levels ≥150 mg/dL
• HDL ≤40 in men and ≤50 in women
• Fasting glucose ≥100 mg/dL

Low Blood Cholesterol Levels (Hypocholesterolemia)

Hypocholesterolemia means blood levels of total cholesterol lower than 150 (3.9 mmol/L) or 120 mg/dL (3.1 mmol/L); cut-off values vary among different authors ^[42].

Causes ^[41,42]:

• High catabolic states: critical illness (cancer, leukemia ^[45], sepsis, burns, trauma), infections (malaria, tuberculosis, hepatitis C), parasitic infestations (leishmaniasis), chronic liver disease (cirrhosis), anorexia, hyperthyroidism
• Chronic inflammation: inflammatory bowel disease (IBD), rheumatoid arthritis
• Chronic anemia (thalassemia, sickle-cell anemia, aplastic anemia, sideroblastic anemia)
• Malabsorption (celiac disease, chronic pancreatitis, HIV/AIDS), starvation
• Drugs that lower cholesterol (statins)
• Rare genetic disorders: abetalipoproteinemia (ABL), familial hypobetalipoproteinemia (FHBL), and chylomicron retention disease (CRD)
• Phenylketonuria (an inherited disorder of the metabolism of the amino acid phenylalanine) ^[46]

Symptoms are often absent but may include loos white stools (steatorrhea) and neurological symptoms (impaired vision, etc.) ^[42,43].

Treatment depends on the cause. Hypocholesterolemia in critically ill patients is a bad prognostic sign ^[42,44].

There seems to be LACK OF EVIDENCE that hypocholesterolemia would result in adrenal insufficiency with decreased production of steroid hormones (cortisol, corticosterone, aldosterone) ^[42].