The French paradox is the observation of low coronary heart disease (CHD) death rates despite high intake of dietary cholesterol and saturated fat.The French paradox concept was formulated by French epidemiologists in the 1980s. France is actually a country with low CHD incidence and mortality. The mean energy supplied by fat was 38% in Belfast and 36% in Toulouse in 1985–86.4 More recently, in 1995–97, the percentage of energy from fat was 39% in Toulouse according to a representative population survey.
THE FRENCH PARADOX AND CAUSES OF DEATH
The first source of error could come from an underestimated CHD mortality. According to this hypothesis, French physicians may not declare all the CHD deaths as CHD. If standardised data—for example those provided by the MONICA (monitoring of trends and determinants in cardiovascular disease) project—are used, the results concerning CHD attack and mortality rates show that France is at a low risk for CHD. Under certification of CHD deaths in France is a possible bias, but after correction, it remains a low bias. Thus, validated data on CHD mortality and incidence show that France is characterised by CHD risk, corroborating the first part of the French paradox definition.
THE FRENCH PARADOX AND SATURATED FAT
In correlation studies, measures that represent characteristics of an entire population (consumption of animal fat, daily milk, and alcohol) are used to describe disease (CHD mortality). Limitations of correlational studies are the inability to link exposure with disease in particular individuals, the lack of ability to control the effects of potential confounding factors, and the use of average exposure levels rather than actual individual values. Numerous correlation studies have been carried out in various countries concerning the relation between consumption of fat and CHD mortality. In one of the most interesting ones, Artaud-Wild and colleagues examined the relation of CHD mortality to the intake of foodstuffs and nutrients in 40 countries. After having defined a cholesterol–saturated fat index (CSI), they studied the relation between the CSI and CHD mortality (per 100 000 men aged 55–64 years) for all 40 countries. France had a CSI of 24 per 1000 kcal and a CHD mortality rate of 198, whereas Finland had a CSI of 26 per 1000 kcal and a CHD mortality rate of 1031.
In the seven countries study, 12763 men from 16 cohorts in seven countries were examined for CHD risk factors in 1958. Information on diet was collected by use of seven day food records. The average consumption of animal food groups, with the exception of fish, was positively associated with 25 year CHD mortality rates. Furthermore, the average population intake of saturated fat was strongly related to 10 and 25 year CHD mortality rates.
It is interesting to compare the World Health Organization dietary recommendations for saturated fat (< 10% of total energy) with actual intakes in France. In representative cross sectional surveys of the French population performed in 1986–87 and 1995–97, the saturated fat intake was 15% of the total energy intake in the first survey and 16% in the latter survey. This high consumption of saturated fatty acids is such that French subjects are exposed to a high risk of CHD. Why a high consumption of saturated fatty acids does not lead to a high CHD risk in France (and maybe elsewhere) is a central question behind the French paradox concept. The French paradox is a way of presenting provocative results from epidemiological studies and does not take into account causality between risk factors and CHD mortality.
THE FRENCH PARADOX AND THE VARIABILITY OF CHD
The MONICA project has provided an overview of CHD event rates in 37 populations from 1985 to 1993 and these data show a large variability in CHD event rates depending on persons, place, and time. Some countries present low or high CHD incidence and dissimilar CHD mortality trends. Analysis shows that France has low CHD incidence, but not very dissimilar to that observed in other countries such as Belgium (Ghent) or Spain (Barcelona). Moreover, analysis shows that countries exhibit different CHD mortality trends. Some regions with rather low CHD attack rates show a significantly declining trend in CHD mortality (Ghent, Toulouse, Strasbourg) or a more limited decrease (Augsburg, Lille) or even an increase (Barcelona). Some regions with high CHD attack rates present dissimilar trends in CHD mortality, a significant decrease (Belfast), a more limited decrease (Glasgow), or even a significant increase (Kaunas, Tarnobrzeg). In a recent study in Oxfordshire, the CHD attack rates in men were 273 per 100 000, much lower than rates reported by MONICA centres in Glasgow and Belfast and similar to rates reported by MONICA centres in France and northern Italy. France has actually low CHD incidence and, in reality, it is very close to Germany, Italy or Spain. New paradoxes may emerge in CHD mortality and in CHD case fatality trends or in epidemiological situations within each country. In any case, whatever the terms—French paradox, North-South paradox, or Mediterranean paradox—the most difficult issue is not the description but the explanation.
Recently, the Framingham risk function has been tested on other populations. In these studies, it has overestimated absolute coronary risk in diverse populations: Japanese, Hispanic males living in the USA; Italian males in Italy; Danish and French males and females. The general conclusion was that the Framingham models should not be used to predict absolute CHD risk in populations with different incidences. A more appropriate CHD risk function could be produced locally. However, a single risk function derived in one place at a particular time may not be applicable elsewhere and must be adjusted for geographical and temporal factors. Furthermore, the contribution of classical risk factors to the trends in CHD over 10 years across the WHO MONICA project populations has been studied: variability of CHD event rates have been explained by trends of major risk factors in only 15% in women and 40% in men. These results suggest that other CHD risk factors should be measured or discovered, particularly in countries with a low CHD incidence.