Role of cholesterol in the development of cardiovascular diseases(Part 1)

Nature of cholesterol

Cholesterol is a form of fatty substance needed by your body for the maintenance of cell membranes,and production of bile acid and hormones[1]. With insufficient cholesterol, your cells will be adversely affected because the integrity of the cell membrane which encloses all its structures will be impaired. In addition, the quality of your bile acid which is one of the components of your bile and the different hormones that you need every minute of your life will deteriorate.

Cholesterol can be sourced from: (1) the foods and drinks that you take, and (2)the different chemical reactions taking place in your body. Because it is produced in your body, it has been postulated that probably you do not need the cholesterol coming from your foods and drinks! Hence, the cholesterol being produced in your body is enough to meet your needs[1]! However, it is not possible to totally remove all the cholesterol that is in your foods! It is impossible! Thus, if you want to control your dietary intake of it, you need to be choosy with your foods, selecting only those which are not rich in it (Consult Powertec 144). Examples of foods rich in cholesterol are meats, liver and other organ meats, dairy foods, egg yolks, and shellfish[2].

Transfer and elimination of cholesterol

When cholesterol is absorbed in your gastrointestinal tract, it travels in the bloodstream in the form of lipoproteins. It cannot travel as cholesterol; it has to be in the form of lipoproteins. There are two lipoproteins that carry cholesterol: (1) the low density lipoprotein (LDL) and the (2) high density lipoprotein (HDL). The LDLcarry the majority of cholesterol, around 75 to 85%, while the HDL carry approximately 15 to 25%[1]. Thus, they are called either LDL-cholesterol or HDL-cholesterol.

Aside from having different densities, the LDL-cholesterol and the HDL-cholesterol have different behavior when they are in the bloodstream. The LDL-cholesterol tends to bring the cholesterol away from the liver; that is, it brings its passengers to the far-flung structures of the body, such as in the blood vessels and peripheral tissues. Consequently, the cholesterol molecules are deposited in these organs. Specifically, when the cholesterol molecules are deposited in the inner lining of your medium to large blood vessels, these structures become inelastic, leading to the development of hypertension. When they are deposited in the small blood vessels of your heart, you will have heart disease and possible heart attack[3]. Since the LDL-cholesterol contributes to the development of cardiovascular diseases, such as hypertension and heart diseases, it is also known as the bad cholesterol.

The HDL-cholesterol, on the other hand, carries cholesterol molecules from the peripheral organs, such as the muscles and blood vessels, and brings them back to the liver—otherwise known as the reverse cholesterol transport—where they are taken up and incorporated as part of the bile. In a way, these cholesterol molecules were removed from the bloodstream, without inflicting any damage to the blood vessels and other organs of your body. Since the HDL-cholesterolhelped to remove cholesterol in the blood, it is also referred to as the good cholesterol.

Injury to the inner lining of blood vessels and cholesterol deposition

The innermost layer of your blood vessels is called the endothelium, and lately this structure has been receiving a lot of research attention because it has been becoming more clear that it is very much involved in the causation of atherosclerosis (deposition of fatty substances in the blood vessels) andhypertension. It has been postulated that the deposition of fatty substances is preceded by the injury of the endothelium.

(To be continued)

References:

  1. Sacher, Ronald A. and Richard A. McPherson. Widmann’s Clinical Interpretation of Laboratory Tests. F. A. Davis Company, Philadelphia, 2000.
  2. http://www.nhlbi.nih.gov/news/spotlight/fact-sheet/questions-and-answers-cholesterol-and-health-nhlbi-nutritionist-janet-de-jesus-ms-rd
  3. http://www.nhlbi.nih.gov/health/resources/heart/heart-cholesterol-hbc-what-html

Relationship between the intake of saturated fats and the development of cardiovascular problems

Nature of saturated fats

Saturated fats (SFs) are also known as saturated fatty acids. They are found in meats, coconut, palm oil, palm kernel oil, butter, egg yolks, milk, and milk products (except fat-free) [1] {Consult Powertec 63}.SFs come in different names, and examples are formic, acetic, propionic, butyric, valeric, caproic, caprylic (octanoic), capric (decanoic), lauric, myristic, palmitic, stearic, arachidic, behenic, and lignoceric[2]. Thus, if a food product that you are buying contains one or more of these, then you know that it contains SFs, and the best way to find out the SFsincorporatedin any grocery product is to look at the “Nutrition Facts” wherein the different substances contained in it are listed, including the quantity in terms of percent.

Relationship of saturated fats with cardiovascular diseases

It has been established from researches that if your diet is high in SFs, the level of your low-density lipoprotein(LDL) cholesterol is also high[3]. You should remember that LDL cholesterol is also known as the bad cholesterol, because it carries cholesterol away from yourliver and deposited them to far-away structures, such as the blood vessels. When LDL cholesterol is deposited in the internal lining of the blood vessels, atherosclerosis takes place, and the blood vessels become inelastic, leading to the development of hypertension.

Neutralizing the adverse effects of saturated fats

Substitution of saturated with polyunsaturated fats

One of the ways of counteracting the adverse health effects of SFsis to replace them with the polyunsaturated fats(PFs). If PFs are taken in instead of SFs, the LDL cholesterol decreases, and the ratio of total cholesterol with the high density lipoprotein (HDL) cholesterol, which is known as the good cholesterol, decreases, too [3],           implying that either the total cholesterol decreases, or the HDL cholesterol increases, or both scenario happen. When the LDL cholesterol decreases and the HDL cholesterol increases, the combination is a perfect recipe for the prevention of heart and blood vessel diseases.

PFs are abundantly found in safflower oil, soybean oil, sunflower oil, soybeans, tofu, and fish[1]{Consult Powertec 63}. In simpler terms, what you will do is to replace meat with fish, and replace animal-based cooking oil with the ones taken and derived from plants.

 

Avoidance of replacing saturated fats with carbohydrates

When carbohydrates are used to replace SFs, it was found out that the level of both the triglycerides (another form of fat) andLDL cholesterol are elevated in the blood while the HDL cholesterol decreases. These consequences are all the more pronounced if the carbohydratesare refined and added with sugar[3]. This is bad for the heart and the blood vessels. Thus, it should be avoided.

Dietary cholesterol should be avoided if significant saturated fats have been in the diet

Based on animal researches, it was determined that if the dietary cholesterol has been increased,   the tendency of saturated fat to increase the LDL cholesterol level in the blood is also increased. This means that working alone, saturated fats increase the LDL cholesterol level in the blood. If the intake of dietary cholesterol is increased, it will aggravate the LDL cholesterol-raising effect of saturated fats. Therefore, as much as possible, the simultaneous intake of significant amount of dietary cholesterol and saturated fats should be avoided [3].

Foods rich in cholesterol are the following: eggs, roast beef, leg lamb (lean), leg lamb (lean and fat), pork chop (lean), chicken leg (fried, meat and skin), crabmeat (canned), salmon (canned), shrimp (canned) [1]. You need to avoid taking these foods if you have been taking a lot of saturated fats.

References:

  1. Roth, Ruth A. Nutrition and Diet Therapy. Singapore: Delmar Learning, 2007.
  2. Murray, Robert K., Daryl K. Granner, Peter A. Mayes, and Victor W. Rodwell. Harper’s Biochemistry. Appleton and Lange: Stamford, Connecticut, 2000.

Siri-Tarino, P., et. al. (2010). Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. http://www.ncibi.nlm.nih.gov/pmc/articles/pmc2943062/

Obesity as a risk factor for chronic diseases

Obesity is one of the most common disorders in medical practice. In the United States about 60 million people are now obese (more than 30%) and 68% of population is overweight.  It is alarming that overweight rates among children have doubled and among adolescents even tripled, increasing the number of years they are exposed to the health risks of obesity. Obesity is defined as an excess of body fat. The best way to classify obesity is to use body mass index (BMI). It closely correlates with excess fat tissue, and it’s calculated by dividing measured body weight in kilograms by the height in meters squared.  A normal BMI is defined as 18.5 – 24.9. Overweight is defined as BMI 25-29, 9 and obesity is BMI over 30. Class I obesity is 30-34.9, class II obesity 35-39, 9 and extreme obesity, or class III is over 40. Obesity is a risk factor for developing type 2 diabetes, cardiovascular diseases, especially coronary disease, hypertension, obstructive sleep apnea , knee osteoarthritis, hyperlipidemia (high blood cholesterol levels) and even cancer.  It is also an important risk factor for stroke, abdominal angina, obesity hypoventilation syndrome (Pickwickian syndrome) and deep vein thrombosis (which is a risk factor for developing pulmonary embolism).  For example, except the fact that diabetes is the risk factor for developing coronary disease it is also the leading cause of amputation of the lower limbs throughout the world.

The main cause of obesity in the most of cases is sedentary life and chronic ingestion of excess calories. But, nowadays, it has been discovered that genetic influences are very important, to even 40-70 %. Most probably is that obesity develops from the interactions of multiple genes, environmental factors and behavior. Since there is a rapid increase in obesity in the last 30 years it is obvious that environmental factors have the most important role in the development of this disease. Upper body obesity (excess fat around waist and flank) is much more dangerous than lower body obesity (fat in the thighs and buttocks) and it is a greater risk for developing diabetes mellitus, stroke, coronary artery disease and early death. Of course, it is important to know  that obesity itself leads to hyperlipidemia, which leads to atherosclerosis, and that’s the most important risk factor for developing cardiovascular and cerebrovascular disease, and they are the leading cause of death in the Western World. Of course atherosclerosis will develop even if people have low cholesterol levels and if they are slim, but the process will be slower and the stenosis of the arteries probably won’t be significant.  Also, some studies have shown that being only 10 pounds overweight increases the force on the knee by 30-60 pounds with each step. Overweight women have nearly 4 times the risk of knee osteoarthritis; for overweight men the risk is 5 times greater. For a woman of normal height, for every 11 lb weight loss (approximately 2 BMI units), the risk of knee osteoarthritis dropped > 50%. Conversely, a comparable weight gain was associated with an increased risk of later developing knee OA. It is obvious that obesity plays an important role in the development of the most important chronic diseases today and by controlling our weight we can significantly decrease the risk of sudden and early death as well as the disability caused by stroke, heart attack, osteoarthritis or diabetes.

References:

1. Role of Body Weight in osteoarthritis, http://www.hopkinsarthritis.org/patient-corner/disease-management/role-of-body-weight-in-osteoarthritis/

2. Maxine A.Papadakis, Current Medical Diagnosis and Treatment 2014, Visceral Artery Insufficiency (Intestinal Angina), p 453-454

3. Diabetes and Amputation, http://www.diabetes.co.uk/diabetes-and-amputation.html

4. Kumar and Clark, Clinical Medicine, 2005, 6th edition, Obesity p.252-257

5.Robert B.Baron, MD, MS, Nutritional Disorders, Obesity, , Current Medical Diagnosis and Treatment 2014, 53rd edition p.1213-1215

6. Robert F.Kushner, Evaluation and Management of Obesity, Harrison’s Principles of Internal Medicine (18th edition), p 629-634