Dietary fat intake and risk of stroke: Authors' reply

He
et al maintain that saturated fat is bad and polyunsaturated fat is good for the
cardiovascular system.¹ They reject a large number of contradictory
epidemiologic and experimental studies² by the argument that they are
inconsistent and inadequate. Instead they refer to a previous study from their
group.³ In that study the authors had calculated that a replacement
of 5% of energy from saturated fat^{with the same amount of
polyunsaturated fat should be followed by a 50% lower risk of coronary heart
disease. They claimed that this calculation was supported by Sacks and Katan’s
review4 of four allegedly successful dietary trials.5-8
However, these authors had ignored four similar trials with a less favourable
outcome.9-12}

Relevant
data from all eight trials are shown in the table (see below). As seen, the
accumulated relative risk of death in the four trials cited by Sacks and Katan
decreased by eight percent, but in the four trials that they had ignored, it
increased by nine percent, and the figures for coronary mortality was not much
better.^2,13  Another
contradictory finding was that complicated atherosclerosis was significantly
more pronounced in the treatment group of the only trial that included a
post-mortem.⁸

This
way of reviewing the literature is not unique. In a meta-analysis of all
controlled, randomised cholesterol lowering trials I found that trials
considered supportive were cited on average 40 times, but unsupportive trials
only seven times per year.¹⁴  Also,
in three of the most influential American reviews of the diet-heart idea, half
of a large selection of contradictory studies were ignored; 
the rest were quoted irrelevantly; or insignificant findings in favour of
the hypothesis were inflated; or unsupportive results were quoted as if they
were supportive.¹⁵ And in a recent letter in Science Scott Grundy,
one of the main figures in the cholesterol campaign, claimed that saturated
fatty acids are the main dietary cause of coronary heart disease, but the many
studies he used as support either had not addressed this question, or they were
inconclusive, or directly contradictory.¹⁶

No
statistical operations are able to explain away the fact that an exchange of
saturated with polyunsaturated fats has no effect on mortality. This is also in
accordance with the findings of He et al. that intake of dietary fats are not
associated with the risk of stroke,¹⁷ and this is also what we should
expect because the idea that atherosclerosis in the coronary arteries should
have a different cause than atherosclerosis in the cerebral ones are highly
unlikely.

 References

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