It’s ‘Cholesterol Week’ here in the UK. It’s been accompanied inevitably with a rash of stories about the perils of cholesterol and how we should be more aware of our cholesterol levels and do something about them if they’re raised. This will all no doubt help to swell the coffers of the drug and food companies that sell ‘solutions’ to cholesterol, but let’s spend a moment analysing the basic premises on which the cholesterol hypothesis is based:
- cholesterol causes heart disease
- reducing cholesterol levels therefore reduces the risk of heart disease
Actually, studies show that taking dietary steps to reduce cholesterol does not bring broad benefits for health or save lives. We also have drugs that reduce cholesterol that also do not appear to improve health. What this means is that the second assumption above is on distinctly shaky ground. But what about the first?
The idea that cholesterol is a risk factor for heart disease is repeated loudly and often. However, there is at least some evidence that this ‘fact’ does not stand up to scrutiny.
By way of example, let’s take a look at the result of a recent study published in the journal Atherosclerosis [1]. In it, more that 82,000 adults in England, UK were followed for an average of over 8 years. The relationship between a range of lifestyle factors and health markers and risk of stroke and heart disease was assessed.
Some of the factors that were associated with an increased risk of both stroke and heart disease were smoking, raised blood pressure, diabetes and low levels of physical activity. What about cholesterol though? For all the talk about the perilous dangers of this substance you’d expect it to be associated with an increased risk of cardiovascular disease, right? Wrong.
- Higher total cholesterol levels were NOT associated with an increased risk of death due to heart disease.
- What is more, higher total cholesterol levels were actually associated with a REDUCED risk of death due to stroke.
Here’s what the authors of this study made of these results:
“Consistent with our findings, the existing evidence has generally shown that cholesterol is a stronger risk factor for coronary events than for stroke, whereas high blood pressure is a better predictor of stroke. We demonstrated an inverse association between total cholesterol and stroke risk, which is consistent with prior work particularly in relation to fatal hemorrhagic stroke.”
What the authors appear not to be able to say up front is that their mammoth study found that higher cholesterol levels are not a risk factor for heart disease, though they do admit to the fact that higher cholesterol levels are associated with lower stroke risk. But then they add this: ““Nevertheless lipid-lowering therapy with statins has shown to reduce the incidence of both thrombotic stroke and coronary disease.”
What they appear to be suggesting here is that we should gloss over their findings, because cholesterol-reduction with statins reduces the risk of stroke and heart disease, so cholesterol must cause these conditions after all.
But the thing about statins is that they don’t just reduce cholesterol, but have range of effects that might reduce risk of cardiovascular disease, including anti-inflammatory and blood-thinning properties. Here’s what I believe to be a more logical and honest appraisal of their studies findings.
1. higher cholesterol levels were not associated with heart disease and were associated with a reduced risk of stroke
2. statins reduce the risk of stroke and heart disease
3. any benefits of statins in this regard cannot be due to their cholesterol-reducing properties
Don’t be expecting much in the way of this sort of honest appraisal from the scientific establishment any time soon. For whatever reason, some seem keen to twist and turn in an effort to keep the cholesterol hypothesis alive.
References:
1. Hamer M, et al. Comparison of risk factors for fatal stroke and ischemic heart disease: A prospective follow up of the health survey for England. Atherosclerosis epub 22 August 2011.
