Dietary fat is not the villain
Zatonski and Professor Willett claim that a decrease of saturated fat and an
increase of polyunsaturated fat consumption explain the decrease of coronary
heart disease in Poland.1 However, ecological data are prey to bias
because they are rarely if ever adjusted for confounders. In this case they are
even contradicted by similar studies in the past. In
a review including 103 time periods in 35 countries I found that in 30 time
periods an increased intake of saturated fat was followed by increased heart
mortality, but after 29 other periods with increased saturated fat consumption
heart mortality was unchanged in six and decreased in 23.2Zatonski’s
and Willett´s statement that their finding is supported by epidemiological and
clinical evidence is not true either. In a review of all cohort and case-control studies coronary patients had
eaten more saturated fat than had healthy controls in three cohorts, but in one
cohort they had eaten less and in 22 cohorts and in 6 case-control studies no
difference was found.2 No cohort or case control study has found that
coronary patients have eaten less polyunsaturated fats either; on the contrary,
three cohort studies found that they had eaten more than had their heart-healthy
controls, and in 29 studies no difference was found.2 The absence of
an association between fat intake and coronary disease was recently confirmed in
a large Swedish population study.3 No association has been found
either between intake of dietary fats and degree of atherosclerosis at autopsy.2
Most important, two
meta-analyses of all
controlled, randomised dietary trials, in which the only type of intervention
was a lowering of dietary saturated fats and/or an increase of dietary
polyunsaturated fats found that the total number of deaths was identical in the
treatment and the control groups.2,4,5 As usual, epidemiological
studies are bad as proof, but excellent for falsification.
WA, Willett W. Changes in dietary fat and declining coronary heart disease
in Poland: population based study. BMJ 2005; 331:187-188
U. The questionable role of saturated and polyunsaturated fatty acids in
cardiovascular disease. J Clin Epidemiol1998;51: 443-460.
M, Nilsson PM, Nilssson JÅ, Månsson H, Berglund G. Dietary fat intake and
early mortality patterns – data from The Malmö Diet and Cancer Study. J
Intern Med 2005; 258: 153–165.
L, Summerbell CD, Higgins JPT, Thompson R, Capps NE, Davey Smith G, et al.
Dietary fat intake and prevention of cardiovascular disease: systematic
review. BMJ 2001; 322: 757-763
U. Diet-heart disease hypothesis is wishful thinking. BMJ 2002; 324: 238.
Competing interests: No competing interests