Are People Consuming the Diets They Say They Are? Self-Reported vs Estimated Adherence to Low-Carbohydrate and Low-Fat Diets: National Health and Nutrition Examination Survey, 2007-2018.

BACKGROUND: Mischaracterization of dietary intake by patients and study participants is a common problem that presents challenges to clinical and public health approaches to improve diet quality, identify healthy eating patterns, and reduce the risk of chronic disease. OBJECTIVE: This study examined participants' self-reported adherence to low-carbohydrate and low-fat diets compared with their estimated adherence using up to 2 24-hour recalls. DESIGN: This cross-sectional study acquired data on dietary intake from respondents in the National Health and Nutrition Examination Survey, 2007-2018. PARTICIPANTS/SETTING: This study included 30 219 respondents aged 20 years and older who had complete and reliable dietary data and were not pregnant or breastfeeding. MAIN OUTCOME MEASURES: The main outcome was prevalence of self-reported and estimated adherence to low-carbohydrate or low-fat diet patterns. STATISTICAL ANALYSES PERFORMED: Self-reported adherence to low-carbohydrate or low-fat diets was evaluated using responses to questionnaires. Estimated adherence to these diets was assessed using data from up to 2 24-hour recalls and usual intake methodology developed by the National Cancer Institute. RESULTS: Of the 1.4% of participants who reported following a low-carbohydrate diet, estimated adherence (<26% energy from carbohydrates) using 24-hour recalls was 4.1%, whereas estimated adherence among those that did not report following a low-carbohydrate diet was <1% (P value for difference = .014). Of the 2.0% of participants who reported following a low-fat diet, estimated adherence (<30% energy from fat) was 23.0%, whereas estimated adherence among those who did not report following a low-fat diet was 17.8% (P value for difference = .048). CONCLUSIONS: This research demonstrates that most individuals mischaracterized their diet pattern when compared with up to 2 24-hour recalls. These findings emphasize the need for clinicians and public health professionals to be cautious when interpreting individuals' self-reported diet patterns, and should aim to collect more detailed dietary data when possible.

Restricted carbohydrate diets below 45% energy are not associated with risk of mortality in the National Health and Nutrition Examination Survey, 1999-2018.

Introduction: Cardiometabolic diseases (CMD) are the leading causes of death for people living in the United States. Dietary strategies, such as restricting carbohydrate intake, are becoming popular strategies for improving health status. However, there is limited and often contradictory evidence on whether restricting carbohydrate intake is related to all-cause, CMD, or cardiovascular disease (CVD) mortality. Methods: The objective of the present study was to evaluate the association between restricted carbohydrate diets (<45%en) and mortality from all-causes, CMD, and CVD, stratified by fat amount and class. Data were acquired using the National Health and Nutrition Examination Survey (1999-2018) linked with mortality follow-up until December 31, 2019 from the Public-use Linked Mortality Files. Multivariable survey-weighted Cox proportional hazards models estimated hazard ratios for 7,958 adults (≥20 y) that consumed <45%en from carbohydrates and 27,930 adults that consumed 45-65%en from carbohydrates. Results: During the study period a total of 3,780 deaths occurred, including 1,048 from CMD and 1,007 from CVD, during a mean follow-up of 10.2 y. Compared to individuals that met carbohydrate recommendations (45-65%en), those that consumed carbohydrate restricted diets (<45%en) did not have significantly altered risk of mortality from all-causes (HR: 0.98; 95% CI: 0.87, 1.11), CMD (1.18; 0.95, 1.46), or CVD (1.20; 0.96, 1.49). These findings were maintained when the restricted carbohydrate diet group was stratified by intake of total fat, saturated fat (SFA), monounsaturated fat (MUFA), and polyunsaturated fat (PUFA). Discussion: Carbohydrate restriction (<45%en) was not associated with mortality from all-causes, CVD, or CMD. Greater efforts are needed to characterize the risk of mortality associated with varied degrees of carbohydrate restriction, e.g., low (<26%en) and high (>65%en) carbohydrate diets separately.

Fat Intake Modifies the Association between Restricted Carbohydrate Diets and Prevalent Cardiometabolic Diseases among Adults in the United States: National Health and Nutrition Examination Survey, 1999-2018.

Background: Cardiometabolic diseases (CMDs), which include heart disease, stroke, and diabetes, account for over one-third of the mortality burden in the United States annually. Nearly one-half of all deaths from CMD are attributable to suboptimal diet quality, and many Americans are turning to special diets for general health improvement. Among the most popular of these diets restrict daily carbohydrate intake to <45% of energy, yet their association with CMD is not well understood. Objectives: This study evaluated the association between restricted carbohydrate diets and prevalent CMD, stratified by fat intake. Methods: Dietary and CMD data were retrieved from 19,078 participants aged ≥20 y in the National Health and Nutrition Examination Survey, 1999-2018. The National Cancer Institute methodology was used to assess usual dietary intake. Results: Compared to participants that met recommendations for all macronutrients, those that consumed restricted carbohydrate diets were 1.15 (95% CI: 1.14, 1.16) times as likely to have CMD; and those that met recommendations for carbohydrates, but not all macronutrients, were 1.02 (95% CI: 1.02, 1.03) times as likely to have CMD. Higher intakes of saturated and polyunsaturated fat were associated with greater prevalence of CMD in restricted and recommended carbohydrate intake groups. Higher intake of monounsaturated fat was associated with lower prevalence of CMD among participants that met carbohydrate, but not all macronutrient, recommendations. Conclusions: To our knowledge, this is the first nationally representative study to evaluate the relationship between carbohydrate restriction and CMD, stratifying by fat intake. Greater efforts are needed to understand longitudinal relationships between carbohydrate restriction and CMD.

Carbohydrate Intakes Below Recommendations With a High Intake of Fat Are Associated With Higher Prevalence of Metabolic Syndrome.

BACKGROUND: More than one-third of adults in the United States have metabolic syndrome, and dietary carbohydrate intake may modify the likelihood of developing this condition. Currently, there is a lack of consistent evidence demonstrating the relationship between carbohydrate intake that falls below recommendations and metabolic syndrome. Not accounting for the differences in fatty acid classes of these dietary patterns may be a reason for inconsistent findings. OBJECTIVE: This study evaluated the association between a carbohydrate intake below recommendations and metabolic syndrome stratified by fat quantity and fatty acid classes in a nationally representative sample of US adults. DESIGN: This cross-sectional study acquired data on food and nutrient intake and markers of metabolic syndrome from respondents in the National Health and Nutrition Examination Survey 1999-2018. PARTICIPANTS/SETTING: This study included 19,078 respondents who were aged 20 years or older, had reliable and complete data on food and nutrient intake and markers of metabolic syndrome, and were not pregnant or breastfeeding. MAIN OUTCOME MEASURES: The main outcome was prevalence of metabolic syndrome. STATISTICAL ANALYSES PERFORMED: Usual dietary intake was estimated using the National Cancer Institute's usual intake methodology. Multivariable logistic regression models assessed the relative odds of prevalent metabolic syndrome between those who had a carbohydrate intake below recommendations and those who met carbohydrate recommendations. RESULTS: Those who had a carbohydrate intake below recommendations had 1.067 (95% CI 1.063 to 1.071) times greater odds of having metabolic syndrome compared with those who met carbohydrate recommendations (P < 0.001). High intake of fat of any class was associated with higher odds of metabolic syndrome (total fat: 1.271, 95% CI 1.256 to 1.286; saturated fatty acid: 1.072, 95% CI 1.060 to 1.085; monounsaturated fatty acid: 1.317, 95% CI 1.300 to 1.333; polyunsaturated fatty acid: 1.056, 95% CI 1.047 to 1.066; P < 0.001 for all comparisons) in those who had a carbohydrate intake below recommendations. CONCLUSIONS: The odds of prevalent metabolic syndrome were higher among individuals who had a carbohydrate intake below recommendations compared with individuals who met carbohydrate recommendations.

Quality of Popular Diet Patterns in the United States: Evaluating the Effect of Substitutions for Foods High in Added Sugar, Sodium, Saturated Fat, and Refined Grains.

Background: Many Americans have adopted popular diet patterns for general health improvement that restrict specific foods, macronutrients, or eating time. However, there is limited evidence to characterize the quality of these diet patterns. Objectives: This study 1) evaluated the quality of popular diet patterns in the United States and 2) modeled the effect of targeted food substitutions on diet quality. Methods: Dietary data from 34,411 adults ≥20 y old were acquired from the NHANES, 2005-2018. Dietary intake was assessed using the National Cancer Institute's usual intake methodology, and the Healthy Eating Index-2015 was used to evaluate diet quality. A diet model was used to evaluate the effect of targeted food substitutions on diet quality. Results: A pescatarian diet pattern had the highest diet quality (65.2; 95% CI: 64.0, 66.4), followed by vegetarian (63.0; 95% CI: 62.0, 64.0), low-grain (62.0; 95% CI: 61.6, 62.4), restricted-carbohydrate (56.9; 95% CI: 56.6, 57.3), time-restricted (55.2; 95% CI: 54.8, 55.5), and high-protein (51.8; 95% CI: 51.0, 62.7) diet patterns. Modeled replacement of ≤3 daily servings of foods highest in added sugar, sodium, saturated fat, and refined grains with alternative foods led to an increase in diet quality and a decrease in energy intake for most diet patterns. Conclusions: Low diet quality was observed for all popular diet patterns evaluated in this study. Modeled dietary shifts that align with recommendations to choose foods lower in added sugar, sodium, saturated fat, and refined grains led to modest improvements in diet quality and larger reductions of energy intake. Greater efforts are needed to encourage the adoption of dietary patterns that emphasize consumption of a variety of high-quality food groups.

Diet Sustainability Analyses Can Be Improved With Updates to the Food Commodity Intake Database.

Diet sustainability analyses inform policymaking decisions and provide clinicians and consumers with evidence-based information to make dietary changes. In the United States, the Food Commodity Intake Database (FCID) provides a crosswalk for integrating nationally representative data on food intake from the National Health and Nutrition Examination Survey (NHANES) with data on sustainability outcomes from other publicly available databases. However, FCID has not been updated since 2010 and does not link with contemporary NHANES data, which limits further advancements in sustainability research. This study fills this research gap by establishing novel linkages between FCID and NHANES 2011-2018, comparing daily per capita food intake with and without these linkages, and making these data publicly available for use by other researchers. To update FCID, two investigators independently established novel data linkages, a third investigator resolved discrepancies, and a fourth investigator audited linkages for accuracy. Dietary data were acquired from nearly 45,000 adults from 2001 to 2018, and food intake was compared between updated vs. non-updated FCID versions. Total food intake from 2011 to 2018 was 5-23% higher using the updated FCID compared to the non-updated version, and intake was over 100% higher in some years for some food categories including poultry, eggs, legumes, starchy vegetables, and tropical oils (P < 0.001 for all comparisons). Further efforts may be needed to create new food composition data to reflect new products and reformulations that enter the food supply over time. This study removes a barrier to further diet sustainability analyses by establishing a data crosswalk between contemporary NHANES and other publicly available databases on agricultural resource use, environmental impacts, and consumer food expenditures.