While we are consistently encouraged to keep our cholesterol levels in check for the sake of our heart health, common sense dictates that we should be somewhat cautious here. After all, cholesterol is an essential element in the body and, for instance, is integral to the structure and function of all our cells, including those in the brain.
The great majority of cholesterol in the bloodstream does not come from our diets, but is made in the liver. One wonders if, somehow, the body is intent on some sort of slow suicide, or if its manufacturing of cholesterol reflects its need for this substance.
Studies have linked low levels of cholesterol with worse outcomes in certain, specific aspects of health. There has been, for instance, previous evidence linking cholesterol-reducing interventions with deaths due to accidents, suicide and violence (e.g. murder).
Recently, I came across a British Medical Journal study dating from 1990 that made for interesting reading [1]. This study aggregated the results of 6 cholesterol-lowering trials in people without a prior history of cardiovascular disease (e.g. heart attack or stroke).
The individual interventions were either a drug or dietary change. Each trial was well-conducted, and had a comparison group which was not exposed to the intervention.
Overall, the intervention groups in whom cholesterol levels were reduced were:
- At no reduced risk of death overall
- At no reduced risk of death due to heart disease
- At a significantly increased risk (43 per cent) of death due to cancer
- At a significantly increased risk (76 per cent) of death due to accidents, suicide and violence
The increased risk of death due to cancer seemed to be due to the findings of one specific trial, in which individuals were treated with the fibrate drug clofibrate. If this trial was removed from the analysis, the risk of death from cancer was not significantly raised.
However, the increased risk of death from accidents, suicide and violence was a consistent finding, and it held true even when the researchers split their analysis into studies of diet-alone or drug therapy-alone interventions. In other words, dietary intervention to lower cholesterol increased the risk accidents, suicide and violence, and so did medication.
This consistency in the results does suggest something real is going on, and specifically that lowering cholesterol increases the risk of these issues. Accidents, suicide and violence may not appear very connected, but one could all argue they are all going to be more likely in individuals whose brains are prone to, say, impulsivity or aggression.
The authors of the review speculated as to how cholesterol reduction might cause the increase in death rates due to accidents, suicide and violence seen across the individual studies.
They wrote:
There is some experimental evidence that modifying the fat in the diet has both neurochemical and behavioural consequences. In laboratory rats these include altered fluidity and cholesterol content of cell membranes within the central nervous system and effects on maze learning, pain threshold, and physical activity. Monkeys fed a diet low in saturated fat and cholesterol (modelled on American Heart Association recommendations) were significantly more aggressive than control animals consuming a diet high in fat and cholesterol.
But the authors went on to say that similar studies are entirely lacking in humans. They do, however, point our attention to studies which show low blood cholesterol levels are more common in, say, criminals, individuals with history of violence or conduct disorder, and murderers with a history of violence.
While this evidence is old, I think it adds to the current body of evidence which supports the role of cholesterol in healthy brain function. There has been at least some acknowledgement in the scientific literature that cholesterol-reducing treatments can impair brain function.
Cholesterol reduction is presented to us by most health agencies and health professionals as a ‘no-brainer’: why wouldn’t you want to bring your cholesterol level down (you’d be mad not to, almost)? Well, one reason for perhaps not wanting to lower cholesterol levels is that it can have unforeseen consequences (which can be devastating).
References:
1. Muldoon MF, et al. Lowering cholesterol concentrations and mortality: a quantitative review of primary prevention trials. BMJ 1990;301:309-14 [hr]
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