It’s about time someone said this:
Diet research built on a ‘house of cards’?
The next time a headline about diet and disease catches your eye, check the fine print of the study.
If it is based on a food questionnaire — and there’s a good chance it will be — then the conclusions should be handled with caution.
That’s because people don’t tell the truth, not even to scientists.
Scientists know this. Research has proven it. It’s been an awkward problem in nutrition science for more than 40 years.
And that’s long enough, according to an international group of nutrition researchers. They’ve launched a campaign to end the use of one of the most common research tools in nutrition science.
“All of these studies, if they are based on self-report estimates of energy intake, really don’t contain scientifically meaningful information,” said David Allison, a prominent obesity researcher at the University of Alabama at Birmingham and lead author on a report signed by 45 scientists from around the world.
This matters, the expert group warned, because the flawed data could result in public health policies that are not science-based, but built on a “house of cards,” Allison said.
“We’re talking about hundreds if not thousands of papers published every year.“
Is a high-fat diet linked to breast cancer? Do fruit and vegetables protect against Alzheimer’s disease? How much of obesity can be explained by eating too many calories?
To get those answers, scientists need to gather data about who ate what, and when. So they ask research subjects to self-report, to think back, sometimes over months and years, and fill in a detailed food questionnaire about what they ate.
Other studies ask people to keep food diaries. And sometimes the researchers do random spot checks, calling subjects and asking them to remember everything they’ve eaten for the last 24 hours.
But because humans are very bad at admitting or remembering what they ate, all the self-reported methods have shown evidence of bias.
I’ve been saying something like this for ages. And it applies to tobacco ‘research’ as well, of course. Nothing is measured accurately. The numbers are all fuzzy. All ‘research’ done using questionnaires should be regarded as unscientific. It should never be used as the underpinning for research conclusions or policy decisions.
He admits the group is taking a controversial stand that has sparked mixed reaction from the nutrition science community.
“It varies a lot with who you ask,” Allison said. “Much of the scientific community applauds us and says it’s a refreshing point of view.”
“And as you might expect, some individuals who have based much of their research career and program on the use of these methods say we can’t abandon them because in part we don’t have anything better.”
Marian Neuhouser of the Fred Hutchinson Cancer Research Centre in Seattle, who has done some of the research that has exposed the bias in self-reported data, agrees the data is flawed. But she says if researchers perform a backup biomarker study they can correct for some of those biases.
Biomarker studies using urinalysis are accepted methods of accurately measuring energy intake. But that requires research subjects to be brought into a lab for a urine test. Researchers say that’s too expensive and impractical for large-population studies.
Considering the obesity epidemic and the level of chronic disease, surprisingly little work is being done to improve methods, said Ross Prentice, a professor of biostatistics at the Hutchinson Centre.
Technical solutions being considered include chin-mounted “chew monitors,” or wrist monitors that measure hand-to-mouth movements. Some have suggested using smart phones to take photographs of food.
Allison prefers a biologically based approach, perhaps a test of breath or urine for products of digestion, which does not depend on the honour system and the fallibility of human memory.
I can see a problem with wrist monitors that measure hand-to-mouth movements: Smokers would come out way ahead of everyone.
And chew monitors would call out people who like to chew gum.
And let’s suppose that biomarker studies using urinalysis accurately measure energy intake. They won’t, however, measure energy expenditure. And if people are only eating what they need to balance intake with expenditure, then a lumberjack cutting down trees with a hand axe in the depths of winter will be expending far more energy than someone sitting quietly in a warm room, and will need to have an energy intake to match it. You only know if someone is over-eating or under-eating if you also know their energy expenditure as well.
Basically, the whole field is wall-to-wall bad science, and probably always will be. And the best thing that could happen would be for the funding for all of it to be terminated. Because if you can’t do good research, you’d best not do any at all.
If you haven’t got a telescope with sufficient resolution to be able to see the canals on Mars, you shouldn’t be trying to draw maps of them. And, who knows, there might not be any canals at all on Mars.
For a time in the late 19th and early 20th centuries, it was erroneously believed that there were canals on Mars. These were a network of long straight lines in the equatorial regions from 60° N. to 60° S. Lat. on the planet Mars. They were first described by the Italian astronomer Giovanni Schiaparelli during the opposition of 1877, and confirmed by later observers. Schiaparelli called these canali, which was translated into English as “canals”. The Irish astronomer Charles E. Burton made some of the earliest drawings of straight-line features on Mars, although his drawings did not match Schiaparelli’s. By the early 20th century, improved astronomical observations revealed the “canals” to be an optical illusion, and modern high resolution mapping of the Martian surface by spacecraft shows no such features.
Sciaparelli’s map of Martian canals
Just as a matter of interest, I got hold of another more recent NASA/JPL map of Mars (click to enlarge). I found Tharsis. Chryse, Eden, Arabia, and Hellas in both of them.
More at Science Daily.