Eating saturated fat can cause blood cholesterol levels to rise. This fact, as well as the belief that cholesterol causes heart disease, is at the basis of the advice we’re often given to avoid saturated fat.

One piece of evidence that is sometimes cited in support of the idea that saturated fat causes heart disease is commonly referred to as the ‘North Karelia Project’. This project, which started in 1972, was an attempt to reduce the risk of heart disease in individuals living in the province of North Karelia in Finland. This intervention employed, among other things, a diet lower in saturated fat. Risk of heart disease declined and the intervention was deemed a success. The approach was subsequently adopted on a country-wide basis.

The first thing to note about the North Karelia Project, though, is that it was multiple intervention in nature. In addition to attempts to have people eat less saturated fat, it also aimed to reduce smoking and blood pressure. It employed a number of strategies including health education, screening and intensification of treatment in those already being treated for cardiovascular disease. Because of the multiple intervention nature of the project, it is simply impossible to gauge which element(s) of it might have been responsible for any benefits seen from the interventions.

And a closer look at the project itself revealed some other issues that have been highlighted by researchers [1]. For example, other parts of Finland also saw reductions in risk of death from heart disease and, overall, death rates were the same elsewhere as in North Karelia. Interestingly, one of the original North Karelia investigators subsequently wrote to the Lancet medical journal to express his own doubts regarding the ‘success’ of the project [2]. He expressed the opinion that he did not think it was possible to draw the positive conclusions that had been presented in the original paper.

So, while the North Karelia experience is sometimes used to support the idea of people eating a low saturated fat diet and getting their cholesterol levels down, it’s simply not fit for this purpose. Not only does the multiple-intervention nature of the study limit its usefulness, but there’s considerable doubt about how effective the intervention was too.

If we really want to know if eating less saturated fat or taking dietary steps to reduce cholesterol is beneficial to health, then these things needed to be studied in isolation. And when they are, what the evidence as a whole reveals is there is no reduction in risk of heart disease or overall risk of death.

These facts can come as a shock, bearing in mind how much talk there is regarding the supposed hazards of cholesterol. The widespread belief that cholesterol is hazardous to health does not chime with the notion that cholesterol reduction per se does not improve health or save lives.

But let us not forget that cholesterol is an essential constituent of the body and that there is evidence linking ‘raised’ levels of cholesterol with enhanced health, particularly in the elderly.

By way of example, let’s take a look at a study published last year which assessed the relationship between cholesterol levels and overall risk of death in the elderly over a six-year period [3]. Compared to individuals with cholesterol levels of less than 5.0 mmol/l, those with cholesterol levels of 5.0-5.9 mmol/l were 38 per cent less likely to die. In those with cholesterol levels of 6.0 mmol/l or more, risk of death was lowered by 41 per cent.

I’ve chosen to highlight this study because it was actually performed in Finland – which spawned the flawed North Karelia Project.

The evidence should really cause us to reconsider the wisdom of cutting back on saturated fat and lowering cholesterol levels through dietary means. The next time someone suggests you eat less saturated fat, ask for the evidence that this prevents disease and saves lives. Don’t be too surprised, though, that what turns up doesn’t amount to a hill of beans.

Here's to a healthy heart,

Dr John Briffa
for The Cholesterol Truth

References:

1. Shah Ebrahim and George Davey Smith Editor’s Response - exporting failure. International Journal of Epidemiology 2001;30:1496-1497

2. Salonen JT. Did the North Karelia project reduce coronary mortality? Lancet 1987;2:269

3. Tuikkala P, et al. Serum total cholesterol levels and all-cause mortality in a home-dwelling elderly population: a six-year follow-up. Scand J Prim Health Care. 2010;28(2):121-7.