Memory-based dietary assessment tools such as ‘fatally flawed’ NHANES

In a critical review * edited by Edward Archer PhD, MS (researcher at the University of Alabama at Birmingham), and published in the journal Proceedings of the Mayo Clinic, the authors argue that memory-based dietary assessment methods (such as 24-hour dietary recall surveys used in NHANES and food frequency questionnaires used in epidemiological studies) are “fundamentally and fatally flawed“and should not be used to inform public policy such as dietary guidelines for Americans.

NHANES data do not correlate with objective measures of energy and nutritional intake

The evidence is now overwhelming that NHANES 24-hour dietary recall data (collected by USDA researchers who ask Americans what they ate the night before) bear little relation to objective measures of energy intake. and actual nutritional values ​​of the same subjects, say the authors.

For example, the self-reported energy intakes reported in a high percentage of NHANES records are lower than the subjects’ actual energy needs (which are calculated using validated techniques based on basal metabolic rates), Dr Archer told FoodNavigator. -USA.

And that would mean that most people lose weight. Yet we know the opposite to be true.

Such contradictions are also evident in dozens of studies in which self-reported energy intakes by free-living subjects (based on food intake surveys and food frequency questionnaires) are consistently lower than their restenergy needs (for example. how many calories they need to maintain their current weight if they literally don’t do anything all day), But body weight data collected by the researchers shows the subjects in question are maintaining or gaining weight, proving that they are poorly reporting their energy intake, he said.

False claims are systemic

A 2013 studyled by Dr Archer and published in PLOS One found that over the 39-year history of NHANES, energy intake data for 67.3% of women and 58.7% of men was “not physiologically plausible“, he added.

And some groups – for example, obese women – underreport by up to 865 calories per day, making their dietary recall data so inaccurate it arguably is “completely valueless”Dr. Archer told FoodNavigator-USA.

But it’s not just a question of calories, he said. Self-reported dietary intake data is also used to estimate dietary intakes at the population level (e.g., are Americans getting enough calcium, iron, zinc?), Which then feeds into public policy, “so this policy is based on erroneous data “.

NHANES data is not “better than nothing”

But what does he say to researchers claiming that surveys like NHANES are a good enough approximationWhat Americans eat, as long as we take into account that respondents typically underreport calories by a certain percentage, for example?

“I would say that they are not” better than nothing ““Said Dr Archer. “They are worse than nothing because they give us the illusion of knowledge.

What’s more, “there is no typical underreporting,Added Dr Archer, who holds a doctorate in exercise science and a bachelor’s and master’s degree in psychology, and spends much of the article exploring why the recall data based on the memory is unreliable.

If we knew, for example, that everyone underreports calories by 10%, the data might be more useful, he said.

Nutrition research and policy are too dependent on self-reported dietary intake data which we know to be unreliable, says Dr Edward Archer

But he added: “The problem is that there is overreporting and underreporting in every category and in every population subgroup, and there is no consistent trend over time. [Misreporting also varies between countries and cultures, he said, citing data from 10 different countries]. “

There is a huge institutionalized inertia

Meanwhile, he said, “Physical activity, cardio-respiratory fitness, and exercise are major determinants of health and are largely ignored or poorly measured by federally-funded nutrition researchers.

Are Memory-Based Food Intake Surveys Really a Total Waste of Time? As a tool to accurately report what Americans eat, yes, he argued, “although they give an interesting insight into the perceptionson what they eat.

But if this misrepresentation is widely recognized (Dr. Archer cites dozens of articles to this effect), then why aren’t more people listening?

According to Dr. Archer: “There is a huge institutionalized inertia. If you’ve spent your entire career using this data, you’re not going to stop now.

Adam Drewnowski: “Everyone should just take a deep breath and relax.”

However, a researcher who has performed dozens of analyzes of NHANES data, told FoodNavigator-USA that “Everyone should just take a deep breath and relax”.

Dr Adam Drewnowski: “NHANES is a pretty good approximation of what people eat”

Adam Drewnowski, doctoral director, Center for Public Health Nutrition at the University of Washington, said: “First, NHANES is a pretty good approximation of what people eat, and a great tool for monitoring changes in the American diet over time.

“Second, the people who can’t remember what they ate yesterday are NOT the major problem. The problem is that what they ate yesterday may have nothing to do with what they ate the day before and the day before. So one intake day (or even two) doesn’t give you a complete picture of a particular individual – but provides a correct estimate for the population. There are modeling methods that estimate the “usual” diet from NHANES data. “

He also noted that dietary guidelines are not based exclusively on NHANES data (the DGAC report for example frequently refers to CDC data on biochemical indicators of nutrients).

USDA ARS: NHANES is designed to provide the population with means of average dietary intake

Meanwhile, David M. Klurfeld, Ph.D., head of the National Human Nutrition Program in the USDA Agricultural Research Department, told FoodNavigator-USA that there was “nothing new“In Dr. Archer’s article, which he claimed”ignored that NHANES is designed to provide population means of average food intake rather than their incorrect extrapolation to individual values ​​”.

He added: “The assumption used by Dr. Archer that we need 100% accuracy for individuals to arrive at the population mean is incorrect. Two recalls, as currently used in NHANES, of the USDA’s Automated Multiple Pass Method (AMPM) generate accurate energy reports for 78% of males and 74% of females. Knowing the degree of underreporting, mainly influenced by body mass index and sex, allows the population mean to be adjusted to approximate the actual intake.

Meanwhile, the USDA is validating his techniques, he said: “The USDA published the validation of AMPM in 2008 to estimate total energy in more than 500 subjects using double-labeled water, the gold standard, to estimate energy requirements. For the total sample, the underestimation was 11%; for people of normal weight, the error was only 3%.

“To conclude that memory cannot be used to assess food intake is to recommend that physicians no longer take their patients’ health histories. “

*Archer, E., Pavela, G., Lavie, CJ., Blair, SN. The ineligibility of “What We Eat in America” (WWEIA) and NHANES dietary data in nutrition and obesity research and the scientific formulation of national dietary guidelines.(Proceedings of the Mayo Clinic)

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