Must share this. The authors (Archer et al.) of an article just published in Mayo Clinic Proceedings are claiming:
… that the main source of dietary information used by the U.S. Government’s 2015 Dietary Guidelines Advisory Committee (DGAC) is scientifically flawed because the underlying data are primarily informed by memory-based dietary assessment methods (M-BMs) (eg, interviews and surveys).
The Inadmissibility Of What We Eat In America And NHANES Dietary Data In Nutrition And Obesity Research And The Scientific Formulation Of National Dietary Guidelines, Mayo Clinic Proceedings, 9 June 2015
Are The Data Underlying The U.s. Dietary Guidelines Flawed? Opposing Views Regarding The Validity Of Widely-cited What We Eat In America And Nhanes Dietary Data Presented In Mayo Clinic Proceedings, Mayo Clinic Press Release, 9 June 2015
Flawed. There’s that word. My red flags are up. As you know, there’s no such thing as not-flawed. All studies lie along a continuum from well-done to not well-done, but they are all flawed to some degree. When you hear this word being used to discredit someone or something, there’s usually an agenda behind it. It’s more political than evidence-based.
Every researcher knows the limitations of recall. It’s not a “well-kept open secret.” So, you validate your tool. You do studies that measure what people actually ate and compare it to what they say they ate. You compare food frequency questionnaires to diet records. You repeat recalls and measure the deviations. You compare what people say they ate to their biomarkers. The US Dietary Guidelines, it must be said, don’t depend solely on epidemiological studies. There are randomized controlled trials that dole out food and measure exactly what people ate. All of this science is evaluated together to come up with the guidelines, at least it should be.
Archer et al.’s use of hyperbole is another red flag:
- Not just evidence but “unequivocal evidence.”
- Not just limited empirical support but “no empirical support.”
- Not just little examination but “no examination.”
- Researchers who use M-BMs have “uncritical faith.” Uncritical? Then why go through validation?
- Not just flawed but “fundamentally and fatally flawed.”
- Not just false but “indisputably false.” There’s no disputing!
- Not just a misuse but a “major misuse.”
This is just from the abstract. Real scientists don’t speak this way. Well, they do if they are young or if they want to sway public opinion without a body-of-evidence. But even then an editor would catch it. I’ve learned the hard way that hyperbole doesn’t get you anywhere.
A rebuttal by Drs. Davy and Estabrooks appeared in the same issue:
The Validity Of Self-Reported Dietary Intake Data: Focus On The “What We Eat In America” Component Of The National Health And Nutrition Examination Survey Research Initiative, Mayo Clinic Proceedings, 9 June 2015
Where Archer et al. claim there is “no empirical support” for memory-based dietary assessment methods (M-BMs), Davy and Estabrooks give examples of empirical support. (That’s why using an absolute such as “no” gets you in trouble.)
Davy and Estabrooks also note that more objective measurements (other than M-BMs) are not without their drawbacks … expense, logistics for use on large populations, error, inability to match the biomarker with the food eaten:
Biomarkers could provide information on specific dietary factors (eg, energy intake [doubly labeled water], protein intake [urinary nitrogen excretion], or fruit/vegetable intake [blood carotenoid concentrations]) but not specific foods consumed (eg, carrots, cantaloupe) or overall diet quality.
Finally, Davy and Estabrooks note that Archer et al. cite studies in defense of their argument that use the same type of participant recall that they say is flawed. To do so is “scientific doublespeak”:
The commentary by Archer et al asserts that the use of memory-based assessment methods by NHANES and others “constitutes the single greatest impediment to actual scientific progress in the fields of obesity and nutrition research.”
To argue that these data represent a waste of resources, while concurrently citing scientific findings where those same data collection methods were used to demonstrate the importance of diet and activity in health, is scientific doublespeak — and an impediment to scientific progress in obesity and nutrition research.
Somebody is afraid that the US Dietary Guidelines are going to deflate their bottom line.