French paradox

The French paradox is an apparently paradoxical epidemiological observation that French people have a relatively low incidence of coronary heart disease (CHD), while having a diet relatively rich in saturated fats, in apparent contradiction to the widely held belief that the high consumption of such fats is a risk factor for CHD. The paradox is that if the thesis linking saturated fats to CHD is valid, the French ought to have a higher rate of CHD than comparable countries where the per capita consumption of such fats is lower.

It has also been suggested that the French paradox is an illusion, created in part by differences in the way that French authorities collect health statistics, as compared to other countries, and in part by the long-term effects, in the coronary health of French citizens, of changes in dietary patterns that were adopted years earlier.

In 1991, Serge Renaud [fr], a scientist from Bordeaux University, France—considered today the father of the phrase—presented the results of his scientific study into the term and actual scientific data behind the perception of the phrase. This was followed by a public documentary broadcast on the American CBS News television channel, 60 Minutes.^{[citation needed]}

In 1991, Renaud extended his studies in partnership with then junior researchers, cardiologist Michel de Lorgeril [fr] and dietician Patricia Salen [fr]. The three enhanced Renaud's study, with their paper concluding that: a diet based on southwestern Mediterranean cuisine (which is high in omega-3 oils, antioxidants and includes "moderate consumption" of red wine) created lower cases of cancer, myocardial infarction and cardiovascular disease; partly through increasing HDL cholesterol whilst reducing LDL cholesterol.

In 1999, Malcolm Law and Nicholas Wald published a study in the British Medical Journal, using data from a 1994 study of alcohol and diet to explain how the French paradox might actually be an illusion, caused by two statistical distortions.

First, Law and Wald attributed about 20% of the difference in the observed rates of CHD between France and the United Kingdom to the under-certification of CHD in France, relative to the UK.

Second, Law and Wald presented a time-lag hypothesis: if there is a delay between increasing serum cholesterol concentrations and any subsequent increase in ischaemic heart disease mortality, then the current rate of mortality from CHD is more likely to be linked to past levels of serum cholesterol and fat consumption than to current serum cholesterol levels and patterns of fat consumption. They wrote,

We propose that the difference is due to the time lag between increases in consumption of animal fat and serum cholesterol concentrations, and the resulting increase in mortality from heart disease—similar to the recognised time lag between smoking and lung cancer. Consumption of animal fat and serum cholesterol concentrations increased only recently in France, but did so decades ago in Britain.