News & Analysis
Do Flawed Data on Caloric Intake From NHANES Present Problems for Researchers and Policy Makers? Mike Mitka, MSJ
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A
uthors of a recent study finding that underreporting of calorie intake by participants in observational studies based on surveillance data focusing on nutrition and obesity may present a problem to governments and scientists who use such flawed data to set health policy or to test hypotheses. But others disagree. At issue are the caloric intake data collected through the National Health and Nutrition Examination Survey (NHANES), an ongoing group of studies designed to assess the health and nutritional status of adults and children in the United States. Critics argue the data are flawed because they are based on 24-hour dietary recall, and people surveyed have a tendency to underreport their caloric intake or overstate the amount of the “good” foods (notably vegetables) or water they consume and to understate the amount of “bad” foods (pizza or sugared soda) they ingest. In responding, NHANES proponents acknowledge these biases and say that those conducting the survey use statistical methods to weigh responses that take into account participants’ biases in dietary recall. Fueling the debate is a recent study suggesting that about 67% of women and 59% of men who participated in NHANES provided caloric intake responses that were not physiologically plausible (Archer E et al. PLoS One. 2013;8[10]:e76632). The conclusion is based on the ratio of energy intake (food) to an estimated basal metabolic rate (the amount of energy expended daily by individuals at rest), as measured by kilocalories. The study authors, citing established norms, said the self-reported energy intake was implausible if the ratio was less than 1.35, as it was highly unlikely a normal, healthy freeliving person could habitually exist at a physical activity level below that number. Assessing data from 28 993 men and 34 369 women, aged 20 to 74 years from NHANES I (1971-1974) through NHANES 2009-2010, the authors found the historical ratio for women was 1.19 and 1.31 for men. These low ratios equate to an underreport-
ing of daily energy intake of 365 kcal a day for women and 281 kcal a day for men. The greatest disparities were seen in obese individuals (body mass index ⱖ30), with obese women underreporting an average of 856 kcal a day and obese men underreporting an average of 716 kcal a day. Lead author Edward Archer, PhD, a research fellow at the Arnold School of Health, University of South Carolina in Columbia, said that although underreporting among individuals who self-report their food and beverage intake has been known for years, few researchers have sought to improve the science. “The point of our study was to finally suggest to the scientific community to stop funding pseudoscience that tends to lead to ambiguous findings,” said Archer. “Food energy requirements should be determined by physical expenditure and exercise, and yet the vast amount of research ignores this.” Although conducting more rigorous science should be a goal, it is sometimes not achievable, said Marion Nestle, PhD, MPH, a professor of nutrition at New York University in New York City. “Every nutritionist knows people underreport what they eat and drink: I can’t tell you how old this news is [in the Archer study],” said Nestle. “The NHANES statisticians also recognize this underreporting and have done everything they can to correct for it. It’s imperfect but it’s the best we have.”
Agreeing with Nestle is NHANES’ Division of Health Examination Statistics (DHANES), which disseminated the data. “There is no perfect method for obtaining dietary intake information in surveys, and considerable research has been and continues to be undertaken to improve dietary assessment methodology,” DHANES officials said in a response to the article by Archer and colleagues. “NHANES dietary data are useful to examine populationlevel intakes by various groups, to examine trends over time, and to offer insights into nutrition monitoring programs,” DHANES officials added. Nestle also suggested other motives for Archer’s team to have produced such a study, noting that it was funded by an unrestricted research grant from the Coca-Cola Company. “Coca-Cola wants to undermine the data that links soda consumption to poor health,” Nestle said. “And yes, physical activity is important, but still the overwhelming evidence says that ‘calories in’ is more important than ‘calories out.’” Archer rejected the idea that his findings were biased by the grant. “I’m criticizing the federal government, and it’s not going to give us money for research, so I have to go outside,” said Archer. “Coke doesn’t know what we’re doing. I guess when you can’t attack the science, attack the scientist.”
People who respond to surveys based on 24-hour dietary recall have a tendency to overstate the amount of the “good” foods or water they consume and to understate the amount of “bad” foods they ingest.
jama.com
JAMA November 27, 2013 Volume 310, Number 20
Copyright 2013 American Medical Association. All rights reserved.
Downloaded From: http://jama.jamanetwork.com/ by a University of St. Andrews Library User on 05/16/2015
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News & Analysis
obese don’t eat much more than normal weight people, and so we thought they must have a metabolic issue,” Heymsfield said. “But we learned that people were clearly underreporting what they ate, and so the field is finally moving away from thinking about obesity as a metabolic problem to how food intake and energy expenditure are related to each other.” Although there are accurate tests that can precisely determine an individual’s energy intake, such testing is too expensive for use in large population studies. Heymsfield acknowledges the less-than-rigorous data found in NHANES will continue to be used. “So the scientific community is dying for an accurate way to assess food intake independent of what people tell you. It’s the holy grail, in a way.”
More Evidence Emerges That Bats May Have Spread SARS Bridget M. Kuehn, MSJ
B
ats have long been among the prime suspects as carriers of the coronavirus that caused the 2003-2004 global outbreak of severe acute respiratory syndrome (SARS), but conclusive evidence has been hard to come by. Now a new study bolsters the case that bats may have directly transmitted the SARS virus to humans. The emergence of SARS in China and its rapid spread around the world drew attention to the public health importance of zoonotic diseases. Ultimately, the SARS pandemic grew to an estimated 8000 cases and 750 deaths. It also launched investigations into the source of the infection that continue to this day. In the months after the pandemic began, epidemiologists zeroed in on liveanimal markets in China as a likely site where the virus jumped from animals to humans. Some evidence suggested that the civet cat was a likely intermediate host for the virus. But many researchers suspected that bats were the true reservoir. In fact, in 2005 researchers published evidence that bats were a reservoir for SARS-like coronaviruses (Li W et al. Science. 2005;310[5748]:676-679).
2138
The new study demonstrates that Chinese horseshoe bats harbor a pair of SARSlike viruses that are very closely related to the strain that caused the 2003-2004 pandemic and that these strains have the capacity to directly infect human cells and civet cat cells as well as bat cells. These findings suggest that bats may have directly infected humans and that civet cats may have been incidentally infected. “Our discovery that bats may directly infect humans has enormous implications for public health control measures,” said Peter Daszak, PhD, president of EcoHealth Alliance and one of the report coauthors, in a statement released by EcoHealth Alliance. Daszak and his coauthors noted that their study demonstrates the public health importance of programs targeting wildlife that seek to identify previously unknown strains of viruses closely related to known pathogens. “These programs, focused on specific high-risk wildlife groups and hotspots of disease emergence, may be a critical part jof future global strategies to predict, prepare for, and prevent pandemic emergence,” they wrote.
.
news@JAMA FROM JAMA’S DAILY NEWS SITE
Education Makes a Difference When chronic health problems crop up in middle age, better-educated US adults appear more likely to make healthy lifestyle changes than their less-educated peers. Data from the Health and Retirement Study show that among adults in their 50s, those who hadn’t completed high school had a 15% to 20% likelihood of quitting smoking when faced with a new chronic condition. But those with a college education had more than a 30% chance of quitting. The latter had a 22% probability of starting exercise following diagnosis of a new chronic condition compared with 18% for those without a high school diploma. http://jama.md/1aPCwU4 Iron Supplements in Malaria-Endemic Regions Iron supplements are safe for children in malaria-endemic regions as long as they’re provided alongside malaria prevention and treatment efforts. Researchers studied 1958 children aged 6 to 35 months in rural Ghana. All received a powdered nutrient supplement; some contained iron and others did not. The malaria rate was significantly lower in the iron group, with 76.1 episodes of malaria per 100 child-years vs 86.1 episodes per 100 child-years in the group who did not receive iron. After adjusting for iron deficiency or anemia, there was no significant difference in malaria rates between the 2 groups. http://jama.md/17KKIVU Quick Detection of Acute Kidney Injury A simple blood test that diagnoses acute kidney injury within minutes might help reduce emergency department patients’ risk of permanent kidney damage. The test measures plasma neutrophil gelatinase–associated lipocalin (pNGAL), a protein that can indicate acute kidney injury in hospitalized patients after cardiac surgery or other invasive procedures. A study of 616 patients admitted to a hospital emergency department showed that the 21% of patients with acute kidney injury had the highest pNGAL levels. What’s more, those with more severe kidney injury had higher pNGAL levels than patients with milder injury. http://jama.md/16TCC8J
For more on these stories and other medical news, visit http://newsatjama.jama.com/.
JAMA November 27, 2013 Volume 310, Number 20
Copyright 2013 American Medical Association. All rights reserved.
Downloaded From: http://jama.jamanetwork.com/ by a University of St. Andrews Library User on 05/16/2015
jama.com
Thomas_EyeDesign/iStock.com
Regardless of the funding source, Archer said his findings also suggest this underreporting is getting worse. “What we’re doing is training the public to tell us what they’re eating, and if we tell them fat is bad, they will report eating less fat,” Archer said. “We’re teaching people to lie better.” Some researchers argue that if the underreporting is roughly consistent, it can show dietary trends that could be associated with the effects of various modifying tools, such as taxing certain foods. Steven Heymsfield, MD, a professor of nutrition, Pennington Biomedical Research Center, Louisiana State University in Baton Rouge, said such trends can also mislead scientists. “Many years ago, we saw the NHANES data showing the
Do Flawed Data on Caloric Intake From NHANES Present Problems for Researchers and Policy Makers? Mike Mitka, MSJ
swilmor/iStock.com
A
uthors of a recent study finding that underreporting of calorie intake by participants in observational studies based on surveillance data focusing on nutrition and obesity may present a problem to governments and scientists who use such flawed data to set health policy or to test hypotheses. But others disagree. At issue are the caloric intake data collected through the National Health and Nutrition Examination Survey (NHANES), an ongoing group of studies designed to assess the health and nutritional status of adults and children in the United States. Critics argue the data are flawed because they are based on 24-hour dietary recall, and people surveyed have a tendency to underreport their caloric intake or overstate the amount of the “good” foods (notably vegetables) or water they consume and to understate the amount of “bad” foods (pizza or sugared soda) they ingest. In responding, NHANES proponents acknowledge these biases and say that those conducting the survey use statistical methods to weigh responses that take into account participants’ biases in dietary recall. Fueling the debate is a recent study suggesting that about 67% of women and 59% of men who participated in NHANES provided caloric intake responses that were not physiologically plausible (Archer E et al. PLoS One. 2013;8[10]:e76632). The conclusion is based on the ratio of energy intake (food) to an estimated basal metabolic rate (the amount of energy expended daily by individuals at rest), as measured by kilocalories. The study authors, citing established norms, said the self-reported energy intake was implausible if the ratio was less than 1.35, as it was highly unlikely a normal, healthy freeliving person could habitually exist at a physical activity level below that number. Assessing data from 28 993 men and 34 369 women, aged 20 to 74 years from NHANES I (1971-1974) through NHANES 2009-2010, the authors found the historical ratio for women was 1.19 and 1.31 for men. These low ratios equate to an underreport-
ing of daily energy intake of 365 kcal a day for women and 281 kcal a day for men. The greatest disparities were seen in obese individuals (body mass index ⱖ30), with obese women underreporting an average of 856 kcal a day and obese men underreporting an average of 716 kcal a day. Lead author Edward Archer, PhD, a research fellow at the Arnold School of Health, University of South Carolina in Columbia, said that although underreporting among individuals who self-report their food and beverage intake has been known for years, few researchers have sought to improve the science. “The point of our study was to finally suggest to the scientific community to stop funding pseudoscience that tends to lead to ambiguous findings,” said Archer. “Food energy requirements should be determined by physical expenditure and exercise, and yet the vast amount of research ignores this.” Although conducting more rigorous science should be a goal, it is sometimes not achievable, said Marion Nestle, PhD, MPH, a professor of nutrition at New York University in New York City. “Every nutritionist knows people underreport what they eat and drink: I can’t tell you how old this news is [in the Archer study],” said Nestle. “The NHANES statisticians also recognize this underreporting and have done everything they can to correct for it. It’s imperfect but it’s the best we have.”
Agreeing with Nestle is NHANES’ Division of Health Examination Statistics (DHANES), which disseminated the data. “There is no perfect method for obtaining dietary intake information in surveys, and considerable research has been and continues to be undertaken to improve dietary assessment methodology,” DHANES officials said in a response to the article by Archer and colleagues. “NHANES dietary data are useful to examine populationlevel intakes by various groups, to examine trends over time, and to offer insights into nutrition monitoring programs,” DHANES officials added. Nestle also suggested other motives for Archer’s team to have produced such a study, noting that it was funded by an unrestricted research grant from the Coca-Cola Company. “Coca-Cola wants to undermine the data that links soda consumption to poor health,” Nestle said. “And yes, physical activity is important, but still the overwhelming evidence says that ‘calories in’ is more important than ‘calories out.’” Archer rejected the idea that his findings were biased by the grant. “I’m criticizing the federal government, and it’s not going to give us money for research, so I have to go outside,” said Archer. “Coke doesn’t know what we’re doing. I guess when you can’t attack the science, attack the scientist.”
People who respond to surveys based on 24-hour dietary recall have a tendency to overstate the amount of the “good” foods or water they consume and to understate the amount of “bad” foods they ingest.
jama.com
JAMA November 27, 2013 Volume 310, Number 20
Copyright 2013 American Medical Association. All rights reserved.
Downloaded From: http://jama.jamanetwork.com/ by a University of St. Andrews Library User on 05/16/2015
2137
News & Analysis
obese don’t eat much more than normal weight people, and so we thought they must have a metabolic issue,” Heymsfield said. “But we learned that people were clearly underreporting what they ate, and so the field is finally moving away from thinking about obesity as a metabolic problem to how food intake and energy expenditure are related to each other.” Although there are accurate tests that can precisely determine an individual’s energy intake, such testing is too expensive for use in large population studies. Heymsfield acknowledges the less-than-rigorous data found in NHANES will continue to be used. “So the scientific community is dying for an accurate way to assess food intake independent of what people tell you. It’s the holy grail, in a way.”
More Evidence Emerges That Bats May Have Spread SARS Bridget M. Kuehn, MSJ
B
ats have long been among the prime suspects as carriers of the coronavirus that caused the 2003-2004 global outbreak of severe acute respiratory syndrome (SARS), but conclusive evidence has been hard to come by. Now a new study bolsters the case that bats may have directly transmitted the SARS virus to humans. The emergence of SARS in China and its rapid spread around the world drew attention to the public health importance of zoonotic diseases. Ultimately, the SARS pandemic grew to an estimated 8000 cases and 750 deaths. It also launched investigations into the source of the infection that continue to this day. In the months after the pandemic began, epidemiologists zeroed in on liveanimal markets in China as a likely site where the virus jumped from animals to humans. Some evidence suggested that the civet cat was a likely intermediate host for the virus. But many researchers suspected that bats were the true reservoir. In fact, in 2005 researchers published evidence that bats were a reservoir for SARS-like coronaviruses (Li W et al. Science. 2005;310[5748]:676-679).
2138
The new study demonstrates that Chinese horseshoe bats harbor a pair of SARSlike viruses that are very closely related to the strain that caused the 2003-2004 pandemic and that these strains have the capacity to directly infect human cells and civet cat cells as well as bat cells. These findings suggest that bats may have directly infected humans and that civet cats may have been incidentally infected. “Our discovery that bats may directly infect humans has enormous implications for public health control measures,” said Peter Daszak, PhD, president of EcoHealth Alliance and one of the report coauthors, in a statement released by EcoHealth Alliance. Daszak and his coauthors noted that their study demonstrates the public health importance of programs targeting wildlife that seek to identify previously unknown strains of viruses closely related to known pathogens. “These programs, focused on specific high-risk wildlife groups and hotspots of disease emergence, may be a critical part jof future global strategies to predict, prepare for, and prevent pandemic emergence,” they wrote.
.
news@JAMA FROM JAMA’S DAILY NEWS SITE
Education Makes a Difference When chronic health problems crop up in middle age, better-educated US adults appear more likely to make healthy lifestyle changes than their less-educated peers. Data from the Health and Retirement Study show that among adults in their 50s, those who hadn’t completed high school had a 15% to 20% likelihood of quitting smoking when faced with a new chronic condition. But those with a college education had more than a 30% chance of quitting. The latter had a 22% probability of starting exercise following diagnosis of a new chronic condition compared with 18% for those without a high school diploma. http://jama.md/1aPCwU4 Iron Supplements in Malaria-Endemic Regions Iron supplements are safe for children in malaria-endemic regions as long as they’re provided alongside malaria prevention and treatment efforts. Researchers studied 1958 children aged 6 to 35 months in rural Ghana. All received a powdered nutrient supplement; some contained iron and others did not. The malaria rate was significantly lower in the iron group, with 76.1 episodes of malaria per 100 child-years vs 86.1 episodes per 100 child-years in the group who did not receive iron. After adjusting for iron deficiency or anemia, there was no significant difference in malaria rates between the 2 groups. http://jama.md/17KKIVU Quick Detection of Acute Kidney Injury A simple blood test that diagnoses acute kidney injury within minutes might help reduce emergency department patients’ risk of permanent kidney damage. The test measures plasma neutrophil gelatinase–associated lipocalin (pNGAL), a protein that can indicate acute kidney injury in hospitalized patients after cardiac surgery or other invasive procedures. A study of 616 patients admitted to a hospital emergency department showed that the 21% of patients with acute kidney injury had the highest pNGAL levels. What’s more, those with more severe kidney injury had higher pNGAL levels than patients with milder injury. http://jama.md/16TCC8J
For more on these stories and other medical news, visit http://newsatjama.jama.com/.
JAMA November 27, 2013 Volume 310, Number 20
Copyright 2013 American Medical Association. All rights reserved.
Downloaded From: http://jama.jamanetwork.com/ by a University of St. Andrews Library User on 05/16/2015
jama.com
Thomas_EyeDesign/iStock.com
Regardless of the funding source, Archer said his findings also suggest this underreporting is getting worse. “What we’re doing is training the public to tell us what they’re eating, and if we tell them fat is bad, they will report eating less fat,” Archer said. “We’re teaching people to lie better.” Some researchers argue that if the underreporting is roughly consistent, it can show dietary trends that could be associated with the effects of various modifying tools, such as taxing certain foods. Steven Heymsfield, MD, a professor of nutrition, Pennington Biomedical Research Center, Louisiana State University in Baton Rouge, said such trends can also mislead scientists. “Many years ago, we saw the NHANES data showing the
