Thirty-nine years in medical practice, together with the many studies that have been published, have convinced me without a shadow of doubt that high blood cholesterol (hyperlipidaemia) is an important contributor to vascular disease (narrowing of blood vessels).
My youngest patient aged 18 had a total cholesterol of 600mg, and died in her early 20s because of the disease.
I emphatically disagree with some points brought up in the article The cholesterol myth, and am even more worried that the general public may misunderstand and interpret this article to mean that control of dietary intake of cholesterol and saturated fats, and treatment of hyperlipidaemia, is not important.
I am also concerned because foods that are rich in cholesterol and saturated foods generally also contribute to obesity – this is a major risk factor for the development of cardiovascular disease.
Malaysia has the most number of obese people in South-East Asia (WHO Non-Communicable Disease Country Profile, 2011). Our own National Cardiovascular Disease/Acute Coronary Syndrome database 2011-2013 data showed that 76% of patients with cardiovascular disease were overweight.
Do saturated fats and cholesterol in food contribute to hyperlipidaemia? Is dietary intake of cholesterol important?
There are controversies in the literature, with some authorities saying that dietary cholesterol does not contribute to blood cholesterol levels.
However, the latest guidelines from the United States Department of Agriculture (USDA), titled Dietary Guidelines for Americans 2015 – 2020, disagrees.
A summary of these guidelines advises us to “... eat a balanced diet of fruits and vegetables, wholegrains, seafood, lean meats, poultry, legumes, nuts and low-fat or fat-free dairy products. And as always, too much sodium and saturated fats are bad for you.”
In page 31 of this document under Saturated Fats, Trans Fats and Cholesterol, the reader will find several statements that contraindicate some points that were put forward in The cholesterol myth article.
For example, the article stated that “After many years, both the United States government and the American Heart Association have changed their policy and taken dietary cholesterol off the ‘Most Wanted List’.”
However, the USDA document states: “Intake of saturated fats should be limited to less than 10% of calories per day by replacing them with unsaturated fats.”
The document also states that “strong and consistent evidence shows that replacing saturated fats with unsaturated fats, especially polyunsaturated fats, is associated with reduced blood levels of cholesterol”.
The USDA document cautions that though the 2015 edition no longer limits consumption of dietary cholesterol to 300mgs/day, this change does not suggest that dietary cholesterol is no longer important to consider when building healthy eating patterns.
The document further states: “Strong evidence from mostly prospective cohort studies, but also randomised controlled trials, has shown that eating patterns that include lower intake of dietary cholesterol are associated with reduced risk of cardiovascular disease.”
Examples of saturated fats are animal meat such as beef, poultry and pork, and dairy products such as cheese, butter and milk.
Foods containing unsaturated fats include plant oils, nuts and fish.
We are the products of “nature and nurture” – our genes (nature) will decide many of the diseases we will develop, and nurture (how we are bought up, what we do and eat) will complement the former.
Does elevated blood cholesterol contribute to vascular disease?
Proof that elevated blood cholesterol contributes to the development of vascular disease comes from many epidemiological, animal and human studies.
In the famous MRFIT study (a randomised primary prevention trial to test the effect of a multifactor intervention programme on mortality from coronary heart disease), the risk of an individual developing coronary artery disease was directly proportional to his level of blood cholesterol.
Another famous study, The Lipid Research Clinics Prevalence Study, supported these findings.
Human studies include samples of plaques removed from diseased vessels, which have revealed cholesterol deposits.
The cholesterol myth article also quoted the recent BMJ Open article reporting a meta-analysis involving 68,094 patients and states that LDL cholesterol levels did not increase the chance of death caused by heart disease.
There’s a directly contrary view to this. The highly respected cardiologist Prof Eugene Braunwald (Brigham and Women’s Hospital, US) wrote an editorial in the July edition of the European Heart Journal entitled Reduction of LAD – cholesterol important at all ages, quoting several studies to support his argument.
In Van Oostrom’s 2005 paper published in the journal Cardiovascular Pathology, cholesterol deposits in blood vessels supplying the brain obtained from patients ages 39–89 years were analysed.
The study showed that with increasing age, the plaques showed increasing signs of instability, with increased risk of rupture and occlusion of the vessels – in the brain, the patient would suffer a stroke; in the heart, a heart attack.
Another study involving 763 patients by Wendorf published in the same journal supported this.
Prof Braunwald also quoted from the Prospective Studies Collaboration, involving 900,000 patients, including patients from East Asia and Australia.
This analysis showed that though elevated cholesterol was a more important risk factor for blockage of heart arteries in younger rather than older patients, it was still important in older patients.
The study showed that a reduction of total cholesterol by 1mmol/L increased the lifespan of people in the fifth to ninth decade of life, with theimprovement being more prominent in older patients.
In the last few paragraphs of the The cholesterol myth article, there was a question as to why billions of dollars worth of cholesterol-lowering drugs are still being sold when studies show that, for the most part, there is no link between dietary cholesterol and blood cholesterol.
The answer to this is simple. Dietary cholesterol only contributes about 10-20% of an individuals’ blood cholesterol – the remainder is manufactured by the body.
Cholesterol is a very important component of the body – it is an important part of our hormones, cell walls and the brain.
Some disease processes like diabetes, hypothyroidism and genetic deficiencies cause marked elevation of blood cholesterol levels – these abnormally-elevated levels contribute to “blocked arteries”, and thus, require to be lowered with treatment.
Many scientifically controlled and validated studies have shown that drug treatment of elevated cholesterol levels prevents the development/progression of blocked arteries in the brain (strokes) and heart arteries (heart attack).
Guidelines from our Health Ministry, the European Society of Cardiology and the American Heart Association help doctors decide who to treat, how much to treat and how to treat.
One important group of these drugs are the statins – they do have side effects, but when appropriately used, their benefits far outweigh their disadvantages.
Dr Kannan Pasamanickam is a consultant cardiologist with 39 years’ experience in medicine.