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Why heart disease mortality is low in France: the time lag explanationCommentary: Alcohol and other dietary factors may be importantCommentary: Intrauterine nutrition may be importantCommentary: Heterogeneity of populations should be taken into accountAuthors' response

BMJ 1999; 318 doi: (Published 29 May 1999) Cite this as: BMJ 1999;318:1471

Rapid Response:

A stillborn hypothesis

The idea of a lag time between increases in consumption of saturated
fatty acids (SFA) and an increase in mortality from coronary heart disease
(CHD), presented by Law and Wald1 has since long been falsified. First, a
host of confounding variables may explain an association between a
population´s consumption of SFA at a certain time and heart mortality.2
More reliable are their secular trends. If the amount of SFA in the diet
has importance changes of their consumption should sooner or later be
followed by similar changes in heart mortality even if the initial
correlation is false. In a recent review3 I presented the results from the
four most comprehensive studies of the secular trends including 103 time
periods in 36 countries. In 30 time periods consumption of SFA had
increased as had CHD mortality. But in 33 periods where the consumption
had increased CHD mortality was unchanged in ten (+ 5%) and had decreased
in 23 periods. Of particular interest for the Law-Wald hypothesis is one
of the studies where the changes of CHD mortality were correlated with the
changes of SFA consumption during 24 years. In that study an increase of
SFA consumption and CHD mortality followed each other in seven countries.
In eleven countries, however, where the consumption had increased between
15 and 190% (mean 54%), CHD mortality was unchanged in three and had
decreased between 6 and 27% (mean 15%) in eight countries.

This should not surprise because the combined results from eight
ecological, 41 cross-sectional, 25 cohort, and six case-control studies
as well as a meta-analysis of nine, controlled, randomised trials also
contradict any influence of dietary SFA on atherosclerosis or coronary
heart disease.3 There is no French paradox either. Anyone who cares to
plot the data from the MONICA study will find that the French data just
happen to be situated at the extreme corner of a scatter diagram that
includes most combinations of SFA consumption or serum cholesterol, and
CHD mortality.

Uffe Ravnskov, MD, PhD

Independent researcher

1. Law M, Wald N. Why heart disease mortality is low in France: the
time lag explanation. BMJ 1999;318:1471

2. Yerushalmy J, Hilleboe HE. Fat in the diet and mortality from heart
disease. A methodologic note. NY State J Med 1957;57:2343-54.

3. Ravnskov U. The questionable role of saturated and polyunsaturated
fatty acids in cardiovascular disease. J Clin Epidemiol 1998;51:443-60.

Competing interests: No competing interests

04 June 1999
Uffe Ravnskov
Independent researcher
RÕbygatan 2, Lund, Sweden