Received opinion is that having high levels of cholesterol in your blood-stream increases your risk of heart disease and stoke. However, a recent reliable Scandinavian study has found that higher levels of cholesterol may be linked with a reduced risk of death overall. What exactly is going on here? And what are the implications for type 2 diabetics?
If you are a type 2 diabetic and are in control of your diabetes, you are most likely eating a low-fat diet. However, there is an 85 percent chance that you also have issues with the level of cholesterol in your blood and your low-fat diet is also helping you reduce your risk of cardiac diseases.
Cholesterol is a type of fat found in your bloodstream which, when present in excessive amounts, can cling to the walls of your arteries to form plaque. An excessive build-up of plaque may block an artery, triggering a heart attack or stroke.
Cholesterol is an essential structural component of your cell membranes. It also has a role in the workings of the brain, along with many other uses.
In short, cholesterol is vital for the functioning of the body and the recent study, which was published in the Scandinavian Journal of Healthcare and reported in the Irish Times Health supplement on the 15th October 2013, throws new light on how cholesterol levels relate to aspects of health other than heart disease.
Unfortunately the general public only seems to be aware of the role cholesterol plays in depositing plaque in arteries and thus being a primary cause of heart attacks and strokes. Why might this be so?
Perhaps the reasons for this ‘knowledge bias’ might be commercial. Take functional foods for example.
Functional foods are foods that offer additional benefits beyond basic nutrition. A good example is oatmeal as it contains soluble fibre that helps the digestive process.
Some foods can be modified to improve the health benefits of eating or drinking them. Orange juice, for example, may be fortified with calcium for bone health.
The global market for all functional foods exceeded US$25 billion in 2011. It is growing rapidly.
Some particular functional foods, such as yoghurts containing probiotics and spreads with added plant sterols, are publicised as ‘helping to lower cholesterol’.
The market for these foods is also growing rapidly, which is not surprising as cholesterol-lowering foods are promoted heavily using advertisements that tap into our fear of heart attacks and strokes.
These ads however tend to limit our view of cholesterol to the effects cholesterol can have on our vascular system and ignore the other functions of this fat. Hence they create knowledge bias, ie a one-sided view of cholesterol.
Medical practise also, but inadvertently, tends to give cholesterol a bad name and restrict our view of its function. Medicines such as statins are increasingly being prescribed to lower cholesterol.
Indeed, the use of statins rose by 17% worldwide between 2007 and 2012, and statins are now being prescribed in more than 214 million monthly prescriptions according to IMS Health, a consulting firm that tracks drug prescriptions at pharmacy level.
Again the subliminal effect is that the dangers of cholesterol are emphasised while the fat’s healthful functions are ignored.
What the study found
The medical profession in Europe recommends that levels of cholesterol in the blood should not exceed 5.0mmol/l (about 190mg/d). Anything above this level is said to increase the risk of heart disease or stroke.
The Scandinavian study sampled 120,000 adults in Denmark and looked at both types of cholesterol (HDL and LDL) together. Researchers found that people with higher levels of cholesterol (ie above the 5.0 mark) had reduced rates of cancer and many other illnesses, ie a reduced risk of death.
For instance, men aged between 60 and 70 with total cholesterol levels ranging from 5.00 to 5.99 mmol/l had a 32% reduced risk of death compared to men with total cholesterol levels of less than 5.00. For men with levels between 6.00 and 7.99mmol/l, the risk of death was 33% lower.
Even in individuals with very high levels of cholesterol (more than 8.00mmol/l), the risk of death was no higher than it was for those with levels of less than 5.00mmol/l.
In the women surveyed, results were similar. In women aged 60 to 70, levels of 5.00 to 5.99 and 6.00 to 7.99 were associated with a 43% and 41% reduced risk of death respectively.
Do the results of this research suggest that we should not lower cholesterol levels if we’re not at risk of cardiac disease? I don’t think so.
It’s only one study, albeit a very well conducted one, among many cholesterol studies. The weight of research still points to high cholesterol being a risk.
Now read on!
In a related Scandinavian study, published in the Journal of Psychiatric Research, individuals with reduced cholesterol levels were found to be more at risk of death from suicide, accidents and violence.
In this study, the researchers compared the violent behaviour of nearly 80,000 men and women with their cholesterol levels, and concluded that ‘low cholesterol is associated with increased criminal violence.’ Several studies worldwide have tracked the same connection.
What’s unclear is exactly why low cholesterol is linked to negative behaviour. It has been suggested that low cholesterol levels have an impact on normal brain function.
It may be that low cholesterol levels suppress the production or availability of neurotransmitters such as serotonin which is said to contribute to feelings of well-being and happiness.
In 2011, a wide-ranging Cochrane review of the outcomes for patients on cholesterol-lowering medication stirred controversy when it recommended the need for further analysis on whether the health benefits of statins outweigh their disadvantages.
A Cochrane Review is a form of meta-research or systematic review of all published trials that seeks to collate all evidence concerning a specific research question in healthcare. Systematic reviews use explicit, systematic methods to minimise bias.
The review found that, for persons who have suffered a heart attack or stroke, the benefits from taking cholesterol-lowering medication are beyond question. The researchers said, however, that the effect of cholesterol-lowering medication in people who have not yet had a heart attack or stroke is not large enough to justify the cost, effort and risk of adverse effects.
A recent study by Irish researchers at Galway University Hospital found that using statins to prevent strokes or heart attacks in otherwise healthy people can actually increase cardiovascular risk in women, people with diabetes and the young.
This review found that statins can increase the risk of diabetes, cataracts and erective dysfunction in young users and cause a significant increase in the risk of cancer and neurodegenerative disorders in the elderly.
Thus, it seems that if you’re not in a high risk group, meaning that you have not already had a heart attack or stroke, the disadvantages of taking cholesterol-lowering medications might outweigh the benefits.
What to do?
So, what should those of us with type 2 diabetes do, especially if we have issues with our cholesterol levels? Let’s summarise.
Health scientists and the medical profession believed that excess cholesterol is a risk factor for heart attacks and strokes. This view has not been contradicted by recent studies which suggest that higher levels of cholesterol actually lower the overall risk of death from all causes, ie the increased risk of heart attacks and strokes is outweighed by lower risks of all other health-related causes of death.
In addition, lower cholesterol levels have been associated with fatal violence. Further studies suggest that medications used to lower cholesterol successfully may have adverse effects on other aspects of our health.
My view is that, given that heart attacks and strokes are caused by the build-up of plaque in arteries, due to excessive cholesterol, controlling the level of cholesterol floating around in the blood-stream would seem to be the wise thing to do. I’ll continue to take my statins daily until my doctor advises me otherwise.