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Dietary fat intake and prevention of cardiovascular disease: systematic review

BMJ 2001; 322 doi: https://doi.org/10.1136/bmj.322.7289.757 (Published 31 March 2001) Cite this as: BMJ 2001;322:757

Fat myths and cardiovascular disease

In spite of the trivial findings Dr Hooper and his coworkers
concluded that their meta-analysis of the cholesterol-lowering dietary
trials supports ”a central role of dietary fat intake in the causation of
cardiovascular disease”.1 This surprising conclusion is based on a
borderline significant improvement of the combined cardiovascular events,
and a subgroup analysis showing a significant improvement of the same
outcome in five trials of more than two years duration. These effects may
rather be due to bias. Most of the trials reviewed by Dr. Hooper et al
were open or single-blind. It is widely acknowledged that such trials are
prey to bias, and had they been drug trials they would never have been
accepted by any major medical journal to-day. The only double-blind
dietary trial with a favourable outcome for cardiovascular events was the
Veterans Administration Trial, but that trial was biased by a
significantly larger number of heavy smokers in the control group.2
Another disquieting finding was the higher degree of atherosclerosis at
autopsy in the treatment group, certainly not in support of a beneficial
effect of dietary intervention.

The only outcome free of bias is total mortality. The mean weighted
rate ratio for that event was close to one in all subgroups, indicating
that dietary fat intake has no importance, and this conclusion is
supported by numerous epidemiological studies. Dynamic population studies
of more than hundred time periods in 35 countries found no association
between change of animal fat consumption and change of coronary mortality;
twenty-seven cohort and case-control studies including more than 150,000
participants did not find any difference between the character of dietary
fat in coronary patients and control individuals; and four cohort studies
found no supportive associations between dietary fat and degree of
atherosclerosis at autopsy.3 Add to that the numerous cross-sectional
studies, most of which found no or even contradictory associations between
fat consumption and the morbidity and mortality of cardiovascular
disease.3

Trans fat, a product of the industrial hardening of vegetable oils
with many unfortunate effects on experimental animals, is the only type of
fat that consistently has been found to be consumed more often by coronary
patients.4 It is time to tell the populations that the dietary advices
they have received since many decades are not only ineffective, they may
even have adverse health effects.5

Uffe Ravnskov. MD, PhD

Magle Stora Kyrkogata 9,
S-22350 Lund, Sweden

1. Hooper L, Summerbell CD, Higgins JPT, Thompson RL, Capps NE, Davey
Smith G, Riemersma RA, Ebrahim S. Dietary fat intake and prevention of
cardiovascular disease: systematic review. BMJ 2001;322:757-63 (31 March)

2. Dayton S, Pearce ML, Hashimoto S, Dixon WJ, Tomayasu U. A controlled
clinical trial of a diet high in unsaturated fat in preventing
complications of atherosclerosis. Circulation 1969;40,suppl II:1-63.

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

4. Oomen C, Ocké MC, Feskens EJM, van Erp-Baart MAJ, Kok FJ, Kromhout D.
Association between trans fatty acid intake and 10-year risk of coronary
heart disease in the Zutphen Elderly Study: a prospective population-based
study. Lancet 2001;357:746-51.

5. Ravnskov U. The Cholesterol Myths. Washington: New Trends Publishing,
2000.

Competing interests: No competing interests

31 March 2001
Uffe Ravnskov
Magle nStora Kyrkogata 9, S-22350, Lund
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