National dietary advice on fat consumption issued to
millions of US and UK citizens in 1977 and 1983, to
cut coronary heart disease incidence, lacked any
solid trial evidence to back it up, and "should not
have been introduced," concludes research published
in the online journal Open Heart.
Both sets of dietary guidelines recommended reducing
overall dietary fat consumption to 30% of total
energy intake, and specifically, saturated fat to
10% of total energy intake. Both acknowledged that
the evidence was not conclusive.
In the absence of any analysis of the evidence used
to corroborate the dietary recommendations, the
researchers carried out a systematic review and
meta-analysis of the randomised control trial data
that would have been available to the US and UK
regulatory committees at the time.
After a comprehensive search of research databases,
they found six relevant trials, covering seven
different dietary interventions, spanning an average
of five years, and involving 2467 men.
All the trials had been published before 1983 and
had looked at the relationship between dietary fat,
serum cholesterol, and the development of coronary
Five out of the six did not consider either the
overall or saturated fat recommendations. And all
but one focused on secondary rather than primary
The pooled data revealed a total of 740 deaths from
all causes, and 423 from coronary heart disease.
There was no difference in deaths from all causes
between the 'treatment' and comparison groups, with
370 deaths in both. And there was no significant
difference in deaths from coronary heart disease,
with 207 in the 'treatment' groups and 216 in the
The falls in serum cholesterol were significantly
greater in the 'treatment' groups, but this did not
seem to have any impact on the death rates from all
causes or from coronary heart disease, the analysis
The researchers highlight several caveats in the
evidence available at the time: no women were
included; no trial tested the dietary
recommendations; no trial concluded that dietary
guidelines should be drawn up.
"It seems incomprehensible that dietary advice was
introduced for 220 million Americans and 56 million
UK citizens, given the contrary results from a small
number of unhealthy men," write the researchers.
They go on to say: "The results of the present
meta-analysis support the hypothesis that the
available [randomised controlled trials] did not
support the introduction of dietary fat
recommendations in order to reduce [coronary heart
disease] risk or related mortality."
And they conclude: "Dietary advice not merely needs
review; it should not have been introduced."
But in a linked editorial, Rahul Bahl, of the Royal
Berkshire NHS Foundation Trust, sounds a note of
The most up to date review of the evidence also
concluded that the evidence on which current dietary
guidance is based was "very limited," but this doesn't
mean that the risk factor identified is not a true
risk factor, he says.
There is epidemiological and ecological evidence
suggesting a link between dietary fat and heart
disease, added to which public policies generally
don't require randomised controlled trial evidence,
"There is certainly a strong argument that an
overreliance in public health on saturated fat as
the main dietary villain for cardiovascular disease
has distracted from the risks posed by other
nutrients, such as carbohydrates," he writes.
"Yet replacing one caricature with another does not
feel like a solution," he insists.
For more information
Open Heart, an official journal of the British
Evidence from randomised controlled trials did not
support the introduction of dietary fat guidelines
in 1977 and 1983: a systematic review and