In
2009, the World Cancer Research Fund (WCRF)[1] conducted a
survey of 2,400 UK subjects to ascertain their views as to the evidence linking
diet and physical activity to cancer. WCRF argue that the advice linking diet
and physical activity to cancer is both robust and relatively unchanged in the
last decade. However, what they found was that in the 55+ group, 60% felt that
scientists were always changing their mind and that 30% thought that the best
advice was to avoid health advice and eat what you want. The figure for the
sample as a whole were marginally lower. A group of London scientists decided
to follow this up with a survey of material appearing in the UK press in one
week covering food and health and to examine this the media representation to
determine the accuracy or otherwise of the coverage. Their paper was published
in the journal “Public Understanding of Science”[2].The lead
authors were Professor Tom Sanders, a world authority on diet and
cardiovascular function and Dr Ben Goldacre, best known for his book “Bad
Science”, but he is also a research fellow at the London School of Hygiene and
tropical medicine. They were joined by Ben Cooper a medical student and William
Lee an MRC Training Fellow in Psychiatry.
Overall,
the top 10 best selling newspapers in the UK are read daily by about 10 million
people so print media has a very big audience. The study was carried out in the
first week of November and the focus was on articles that recorded an actual
health claim to a food in some way. Stories about GM or about waste or other
issues were excluded - the story had to involve a health claim as defined by
the European Food Standards Agency. A total of 111 such stories were reported
in the week. The next stage was to subject the reported new story to two
grading systems specifically designed to grade scientific evidence. The first
of these is called the Scottish Intercollegiate Guidelines Network (SIGN)[3]
and that of the WCRF. As the authors point out, each might have its flaws but
“..taken together, these tools represent robust and widely recognised measures
of relative evidence of quality”.
I
have averaged the scores of the two grading systems since they were generally
similar. The single most important figure was that only 10% fell into the
category “convincing”. All the rest fell into shades of doubt such as 15%
“probable and 7% “possible” or 4% “unclassifiable”. By far the biggest figure
of 64% is for “insufficient” evidence. In effect the general take home message
is that 1 in 10 media stories involving linking some aspect of diet to health
is true. For two thirds, the evidence is non-existent and the rest fall in
between. Where does the blame lie?
Journalists rely quite a lot on press
releases and the nature of press releases is that the releasing body, be it a
company, an NGO, a university or a trade organisation want the media to take up
the press release. Ideally, the journalist should use the press release as the
starting point to make contact with the researcher and to develop the story
from there. But quite often, it is the press release alone which makes it to
the print edition. One of the main culprits in this communication change in my
view are university communications units. They are constantly looking for press
coverage in an ever increasing academic environment and they have a captive
audience of academics who enjoy their moment of glory in the media.
I
would go further back in the communication chain to the actual research process
and bemoan the growth and dominance of unchallenged data on food and health.
Fine, I understand that certain associations between diet and health are not
readily amenable to testing in intervention studies. But these are few and far
between. What is exasperating is the rush to publicise the relationship observed
between serum whatever and some wonderful health attribute in some cross
sectional study without any direct evidence from human intervention studies
that the relationship stands up to this test. One area which is without doubt
the most culpable these days is the great news that “scientists have discovered
a link between some nutrient intake profile, a relevant common genetic
variation and some disease”. These triangular links of diet, phenotype and
disease (e.g. the gene for some lipoprotein, high blood cholesterol and olive
oil intake) are ten-a-penny and each worth more or less nothing without some
verification with an intervention study. So rapid is the expansion of this
unholy triangle that the funding to establish an intervention study is never likely
to be extensive. Which of the putative claims do you spend your money on?
An
exception is the work done by scientists at the University of Ulster and
Trinity College Dublin who showed that if low riboflavin status was corrected
in persons on medication for hypertension, those with a common (ca 30%) genetic
variation showed a dramatic reduction in blood pressure[4]. So they set
out to recruit equal numbers of the three genetic classes (the less common
genetic variation being absent or inherited from one parent or both) and they
carried out an intervention study (riboflavin supplement versus placebo) which
proved that those with the less common genetic variation responded very
positively with dramatically reduced blood pressure. They went back then four
years later and those that had been randomized to the placebo were now given
the riboflavin and vice versa and again they proved the association. This is
darn hard work but it is what is needed to take an “association” to a
“verification”. Sadly, the moment of glory in the media seems to satisfy most
scientists and most universities. It is easy to be critical of journalists for
not following press releases in more depth getting a second and their opinion
but those in glass houses......
[2]
Cooper BEJ et al (2011) The quality of
the evidence for dietary advice given in UK national newspapers. Public
Understanding of Science, May, 1-10
[4]
Wilson et al (2012) Riboflavin offers a
targeted strategy for managing hypertension in patients with the MTHFR 677TT
genotype: a 4-y follow-up. Am J Clin Nutr. Mar; 95(3):766-72. Epub 2012 Jan 25.
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