Cholesterol

Cholesterol is a waxy substance produced by your liver and found in some of the food you eat. Although cholesterol plays a critical role in the development of problems in your heart and blood vessels, your body needs it, because it is part of your cell membrane. Cholesterol is required to build and maintain membranes. It modulates membrane fluidity over the range of physiological temperatures. Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling and nerve conduction. Within cells, cholesterol is the precursor molecule in several biochemical pathways. In the liver, cholesterol is converted to bile, which is then stored in the gallbladder. Bile contains bile salts, which solubilize fats in the digestive tract and aid in the intestinal absorption of fat molecules as well as the fat-soluble vitamins, Vitamin A, Vitamin D, Vitamin E, and Vitamin K. Cholesterol is an important precursor molecule for the synthesis of Vitamin D. Moreover, cholesterol level is linked to your hormones-- the steroid hormones, including the adrenal gland hormones cortisol and aldosterone as well as the sex hormones progesterone, estrogens, and testosterone, and their derivatives. Some research indicates that cholesterol may act as an antioxidant.

It is important to keep your total cholesterol level at less than 200 mg per deciliter of blood, and maintain a favorable ratio of good (HDL) to bad (LDL) cholesterol. Your LDL should be low (less than 100), and your HDL should be high (60 or higher). Exercise and a balanced diet can increase your HDL .

We should know sources of cholesterol, and maintain our optimal cholesterol level. Foods with animal fat contain cholesterol to varying extents. Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry, and shrimp. Human breast milk also contains significant quantities of cholesterol. The amount of cholesterol present in plant-based food sources is generally much lower than animal based sources. In addition, plant products such as flax seeds and peanuts contain cholesterol-like compounds called phytosterols, which are suggested to help lower serum cholesterol levels.

Total fat intake, especially saturated fat and trans fat, plays a larger role in blood cholesterol than intake of cholesterol itself. Saturated fat is present in full fat dairy products, animal fats, several types of oil and chocolate. Trans fats are typically derived from the partial hydrogenation of unsaturated fats, and do not occur in significant amounts in nature. Trans fat is most often encountered in margarine and hydrogenated vegetable fat, and consequently in many fast foods, snack foods, and fried or baked goods.

What is the optimal cholesterol level? How can we reduce blood cholesterol?

In the 1987 report of National Cholesterol Education Program, Adult Treatment Panels suggested the total blood cholesterol level should be less than 200 mg/dL (normal blood cholesterol). 200–239 mg/dL is borderline-high, and more than 240 mg/dL is very high cholesterol.

However, as today's testing methods determine LDL ("bad") and HDL ("good") cholesterol separately, this simplistic view has become somewhat outdated. The desirable LDL level is considered to be less than 100 mg/dL (2.6 mmol/L), although a newer upper limit of 70 mg/dL (1.8 mmol/L) can be considered in higher risk individuals based on some of the above-mentioned trials. A ratio of total cholesterol to HDL—another useful measure—of far less than 5:1 is thought to be healthier. Of note, typical LDL values for children before fatty streaks begin to develop is 35 mg/dL.

A change in diet in addition to other lifestyle modifications may help reduce blood cholesterol. Avoiding animal products may decrease the cholesterol levels in the body not only by reducing the quantity of cholesterol consumed but also by reducing the quantity of cholesterol synthesized. Those wishing to reduce their cholesterol through a change in diet should aim to consume less than 7% of their daily calories from saturated fat and fewer than 200 mg of cholesterol per day. The view that a change in diet (to be specific, a reduction in dietary fat and cholesterol) can lower blood cholesterol levels, and thus reduce the likelihood of development of, among others, coronary artery disease (CAD) leading to coronary heart disease (CHD) has been challenged. An alternative view is that any reductions to dietary cholesterol intake are counteracted by the organs such as the liver, which will increase or decrease production of cholesterol to keep blood cholesterol levels constant. Another view is that although saturated fat and dietary cholesterol also raise blood cholesterol, these nutrients are not as effective at doing this as is animal protein.

What is HDL?

High-density lipoprotein (HDL) is one of the five major groups of lipoprotein which enable lipids like cholesterol and triglycerides to be transported within the water-based bloodstream. In healthy individuals, about thirty percent of blood cholesterol is carried by HDL. High concentrations of HDL (over 60 mg/dL) have protective value against cardiovascular diseases such as ischemic stroke and myocardial infarction. Low concentrations of HDL (below 40 mg/dL for men, below 50 mg/dL for women) increase the risk for atherosclerotic diseases.

How can we raise our HDL ?

A link has been shown between level of HDL and onset of dementia. Those with high HDL were less likely to have dementia. Low HDL-C in late-middle age has also been associated with memory loss.
You can raise your HDL with healthy and balanced diet and lifestyle
Certain changes in lifestyle can have a positive impact on raising HDL levels:
· Aerobic exercise
· Weight loss
· Smoking cessation
· Removing trans fatty acids from the diet
· Mild to moderate alcohol intake
· Adding soluble fiber to diet
· Using supplements such as omega 3 fish oil or flax oil
· Increasing intake of cis-unsaturated fats and cholesterol.

What is LDL?

Low-density lipoprotein (LDL) is one of the five major groups of lipoproteins that enable lipids like cholesterol and triglycerides to be transported within the water-based bloodstream.
Because LDL particles can also transport cholesterol into the artery wall, retained there by arterial proteoglycans and attract macrophages which engulf the LDL particles and start the formation of plaques, increased levels are associated with atherosclerosis. Over time vulnerable plaques rupture, activate blood clotting and produce arterial stenosis, which if severe enough results in heart attack, stroke, and peripheral vascular disease symptoms and major debilitating events.

How can we lower our LDL?

In the USA, the American Heart Association, NIH, and NCEP provide a set of guidelines for fasting LDL-Cholesterol levels, estimated or measured, and risk for heart disease. As of about 2005, these guidelines were based on a goal of presumably decreasing death rates from cardiovascular disease to less than 2% to 3% per year or less than 20% to 30% every 10 years. Note that 100 is not considered optimal; less than 100 is optimal, though it is unspecified how much less.

Sources:
Dr. Laurie Steelsmith. Natural Choices for Women’s Health (New York: Three Rivers Press, 2005).
http://en.wikipedia.org/wiki/Cholesterol
http://en.wikipedia.org/wiki/High-density_lipoprotein
http://en.wikipedia.org/wiki/LD