Why High LDL Levels May Not be a Good Predictor of Heart Disease

The adverse effects of cholesterol on your health are well-known – or at least, most people would agree that high levels of cholesterol aren’t good for your heart. However, the role of cholesterol as the bad guy in causing heart disease is more complicated than it first appears. In fact, recent studies claim that having high cholesterol might not be the sure-fire way of predicting heart attacks that conventional medical advice would have you believe.

What is cholesterol?

Cholesterol is a substance that exists naturally in tissues and blood all around your body. It consists of a combination of steroids, alcohol, and lipids (fats). Although it has an extremely poor reputation, cholesterol is actually vital for good health. You need cholesterol to stabilize cell membranes, synthesize Vitamin D, and create hormones like cortisol, oestrogen, and testosterone. Cholesterol also supports your immune system and brain function.

If cholesterol is so important, why has it got such a bad name?

It’s because there are different types of cholesterol. High-density lipoprotein (HDL) is the one that performs many essential functions, so it’s known as the “good” cholesterol. Low-density lipoprotein (LDL) is the one that builds up and could cause atherosclerosis (hardened arteries). Many studies indicate that atherosclerosis is a primary cause of heart disease, so LDL is known as the “bad” cholesterol.

Measuring the level of LDL in your blood is a standard approach to calculating your risk of developing heart disease. If you have high LDL, your doctor is likely to advise you to take medication to reduce your risk. Increasingly, health care professionals are encouraging people to take steps to improve their diet, do more exercise, reduce stress, and cut out activities like smoking and excessive alcohol consumption, to help clear your arteries and minimize the risk of heart disease.

Does LDL really cause heart disease?

There’s no simple answer to this question. There’s certainly plenty of published evidence that seems to confirm a link between LDL and heart disease. However, as our understanding of cholesterol and what it does in our bodies improves, this evidence becomes less concrete.

For example, a study examined statistics showing that around 75% of people who suffer a heart attack don’t have dangerously high LDL levels. LDL isn’t a single substance – there are three subclasses: A, B, and I. The study’s researchers found that the proportion of each class of LDL is more significant than having a high overall LDL, with subclass B being most closely associated with damage to the heart. So, if you have a high total LDL but a low level of subclass B LDL, your risk of heart disease is likely to be lower than you think.

In 2015, the BMJ (British Medical Journal) published a paper that showed 92% of older people who have high levels of LDL live as long or even longer than those who have low LDL. The study was a comprehensive review that looked at data from 19 previous studies and over 68,000 people in total. The authors not only concluded that high LDL levels don’t indicate an increased risk of heart disease in the over-60s, but that the value of conventional treatments such as the use of statins is in doubt.

A large study published in Expert Review of Clinical Pharmacology in 2018 goes even further, claiming LDL doesn’t cause heart disease at all. A collaboration between medical professionals and researchers around the world examined the evidence base on LDL and heart disease and called much of the research into question. They claim that previous LDL studies have serious flaws, with research papers excluding clinical trials that didn’t show a link between LDL and heart disease. They further argue that LDL could have significant beneficial qualities.

The history of medicine is notorious for the reluctance of people to question accepted wisdom when new evidence takes an entirely contrary view, and such is the case with LDL. For 50 years, high levels of LDL have been blamed as a leading cause of heart disease, but more recent research is starting to question the facts behind this assertion. There needs to be more research done to confirm these new ideas about LDL, but there’s good reason to believe high LDL levels may not be a predictor of heart disease after all.

Written by Miles Price

References:

1. National Center for Biotechnology Information. PubChem Database. Cholesterol, CID=5997, https://pubchem.ncbi.nlm.nih.gov/compound/cholesterol
2. Hua J, Malinski T. Variable Effects Of LDL Subclasses Of Cholesterol On Endothelial Nitric Oxide/Peroxynitrite Balance – The Risks And Clinical Implications For Cardiovascular Disease. Int J Nanomedicine. 2019;14:8973-8987. doi:10.2147/IJN.S223524
3. Ravnskov U, Diamond DM, Hama R, et al. Lack of an association or an inverse association between low-density-lipoprotein cholesterol and mortality in the elderly: a systematic review. BMJ Open 2016;6:e010401. doi:10.1136/bmjopen-2015-010401
4. Ravnskov U, Lorgeril M, Diamond D, et al. LDL-C does not cause cardiovascular disease: a comprehensive review of the current literature. Expert Review of Clinical Pharmacology, 2018;11:10, 959-970, doi: 10.1080/17512433.2018.1519391