Cholesterol is a waxy substance. Technically a sterol (modified steroid), cholesterol is an essential structural component of all animal cell membranes. It maintains both the membrane structural integrity and fluidity. The vast majority of cholesterol in the body is produced in the liver, while the rest is absorbed from the diet.
Cholesterol is the basic raw material that your body uses to make Vitamin D; sex hormones such as estrogen, progesterone, and testosterone; and the bile acids needed for digestion. Cholesterol travels around the body in particles called lipoproteins, the most common of which are high-density lipoproteins (HDL) and low density lipoproteins (LDL). Traditionally HDL’s have been considered good cholesterol and LDL’s bad cholesterol.
Research has now categorised 5 types of cholesterol
1 – HDL-2: Particles are large and buoyant and the most protective. They are anti-inflammatory and anti-atherogenic (atherosclerosis being the condition in which an artery wall thickens from the accumulation of fatty materials, called plaque, induced by inflammation, inhibiting blood flow from the heart).
2 – HDL – 3: Particles are small, dense and may be inflammatory. At present HDL-3 is poorly understood.
3- LDL-A: A buoyant, fluffy molecule that does no harm as long as it is not damaged by oxidation (a process caused by free radicals that enables cholesterol to form plaque).
4 – LDL-B: A small, hard, dense molecule that promotes atherosclerosis.
5 – Lp(a): a very small, highly inflammatory particle that is thrombogenic (blood clotting).
How cholesterol contributes to atherosclerosis
Your arteries and heart have a lining called the endothelium. LDL floats around the blood stream delivering cholesterol to the cells that need it. When doing this some of the LDL’s are damaged by oxidation (LD-B’s are most likely to be damaged and oxidised). The LDL sticks to the endothelium which begins the process of inflammation. The immune system responds sending white blood cells (WBC’s). The artery wall thickens as a result of the invasion and accumulation of WBC’s, and proliferation of intimal-smooth-muscle cell creating a fibro fatty plaque.
Why we measure cholesterol levels
In 1953 a biologist named Ancel Keys proposed a theory that heart disease was caused by too much fat in the diet. At the time fat in the diet and cholesterol in the blood were believed to be linked. Keys looked at data on fat consumption and heart disease from various countries and published the results, the Seven Countries Study, which supposedly demonstrated a clear link between the amount of dietary fat consumed and the incidence of heart disease. Many researches criticised Keys for omitting data that didn’t support his theory. Keys had food consumption data from 22 countries and only used 7. When the data for all 22 countries was analysed by Dr John Yudkin from the University of London, instead of confirming Keys hypothesis, it found that the correlation between fat, cholesterol, and heart disease literally vanished. Furthermore the single dietary factor that had the strongest association with coronary heart disease was sugar.
In the 1970’s the argument, cholesterol verse sugar, raged in the scientific community. The end result was that the powers that be deemed cholesterol to be the culprit for causing heart disease.
What should my cholesterol level be
A difficult question to answer as 50% of people who suffer a heart attack have normal or low cholesterol levels, and the other 50% have high levels.
Some things we do know:
– Cholesterol is a critical component in the structure of all our cells, and performs a number of important functions in the body.
– People who have heart disease or a family history of heart disease need to monitor and manage their cholesterol levels closely.
– An elevation of your cholesterol, either high or low, indicate serious health concerns.
– Higher cholesterol levels post menopause is normal.
– Extremes of cholesterol levels, either high or low, indicate serious health concerns.
– Higher cholesterol levels is predictive of a longer life span in those of us over 85 years of age.
– Despite 50 years of medical research, treatment, and dietary advice based on cholesterol being a major cause of heart disease, heart attacks remain the number 1 cause of death in Australia today.
There are many non-invasive and invasive tests to determine your risk of heart attack. Ask your doctor if you are concerned. The National Heart, Lung, and Blood Institute publishes a list of available tests online at www.nhibi.nih.gov
By Simon Ayling