Advanced glycation end products, commonly abbreviated as AGEs, are a heterogeneous group of compounds that form naturally in the body when sugars react with proteins or fats, a process known as glycation. They also enter the body through the diet, particularly from foods exposed to high, dry heat — grilling, frying, roasting, and baking all accelerate their formation. Measured in the diet as dAGEs and typically expressed in kilounits per kilocalorie (kU/kcal), these compounds have been implicated in chronic inflammation and oxidative stress in adults. The receptor for advanced glycation end products, known as RAGE, can activate inflammatory signaling pathways such as nuclear factor kappa B (NF-κB), and previous research has suggested that high dietary AGE intake could influence sleep quality through several different mechanisms, including inflammatory and metabolic pathways.

Despite growing interest in how AGEs affect adult health, almost nothing has been known about their impact on young children, whose developing nervous systems and sleep architecture may be especially vulnerable. To address that gap, a team of nutrition and dietetics researchers — Gökçen Doğan of Lokman Hekim University, Büşra Demirer of Karabuk University, and Nurcan Yabanci Ayhan of Ankara University — designed an observational cross-sectional study to evaluate whether dietary AGE intake is associated with sleep disorders in preschool-aged children. The study was retrospectively registered as NCT07062640 and received ethics approval from Karabuk University in accordance with the Declaration of Helsinki, with written and verbal informed consent obtained from a parent for each participant.

The researchers enrolled 304 children between the ages of three and five, a group that was 46.05 percent female and 53.95 percent male. Parents completed a detailed questionnaire administered through face-to-face interviews, covering sociodemographic information, the child’s eating habits, and a 24-hour diet record form that allowed the team to calculate the average daily dAGE intake in kU/kcal. Sleep problems were assessed with the Sleep Disorders Scale for Children, a validated instrument known as the SDSC that screens for a range of sleep difficulties in young children. This combination of tools allowed the investigators to quantify both sides of the equation — how much dietary AGE each child consumed and how disturbed their sleep actually was.

The results were striking. According to the SDSC, 67.4 percent of the participating children had sleep disorders, a prevalence that underscores how common sleep problems are in the preschool years. When the researchers compared dietary intake between the two groups, they found that children with sleep disorders consumed an average of 6.22 ± 1.88 kU/kcal of dietary AGEs, while children with normal sleep consumed 4.79 ± 1.32 kU/kcal. That difference was statistically significant, with a p-value below 0.001. Average intake was nearly identical across the sexes — 5.76 ± 1.81 kU/kcal in girls and 5.74 ± 1.87 kU/kcal in boys — indicating that the association was not simply a matter of one sex eating differently from the other.

To make sure the association was not being driven by confounding factors, the team built a logistic regression model adjusted for the child’s age, sex, body mass index, and the age at which complementary foods were first introduced. Even after accounting for those variables, higher dietary AGE intake remained independently associated with sleep disorders: each increase in intake corresponded to 1.76-fold higher odds of having a sleep disturbance (odds ratio 1.763; 95 percent confidence interval 1.418–2.117; p < 0.001). In practical terms, children eating the most AGE-rich diets had nearly twice the odds of disrupted sleep compared with those eating the least, a substantial effect for a single dietary factor in an observational study.

Why would compounds created by cooking heat affect a child’s sleep? The authors point to several plausible mechanisms. Dietary AGEs can promote systemic inflammation and oxidative stress, and chronic low-grade inflammation has been repeatedly linked to disrupted sleep regulation. The interaction of AGEs with RAGE triggers NF-κB signaling, a master switch of inflammation that could, in theory, perturb the neural and hormonal systems that govern sleep-wake cycles. Metabolic disturbances are another candidate pathway, since sleep quality is tightly entwined with glucose metabolism and hormonal balance. The study’s related subject areas — including orexin, a neuropeptide central to arousal and wakefulness — hint at the broader neurobiological territory where diet and sleep may intersect, though the cross-sectional design of this study cannot confirm which mechanisms are actually at work.

The researchers themselves are careful about what the findings do and do not prove. Because the study is cross-sectional, it captures a single moment in time and cannot establish whether high AGE intake causes sleep problems, whether children who sleep poorly gravitate toward certain foods, or whether some third factor influences both. The authors conclude that the findings highlight the potential clinical relevance of dietary AGE exposure as a modifiable dietary factor in relation to sleep health among preschool children, and they suggest that dietary assessment — including consideration of cooking practices — may be relevant when evaluating children with sleep disturbances. But they explicitly note that longitudinal and intervention studies are needed to clarify the direction and causality of the association. No funding was received for the research, and the authors declare no competing interests.

Even with those caveats, the study lands at a moment when parents and pediatricians are increasingly worried about both childhood sleep and the ubiquity of heat-processed foods in young children’s diets. Sleep disturbances in preschoolers are associated with behavioral problems, impaired learning, and metabolic risk later in life, and the new finding that two-thirds of a typical preschool sample screened positive for sleep disorders is itself a sobering data point. If the AGE-sleep link holds up in future research, it would suggest that something as simple as cooking method — swapping fried and heavily roasted foods for steamed, boiled, or stewed alternatives, which generate far fewer AGEs — could become a low-cost lever for improving children’s sleep. The study, published open access in BMC Pediatrics on 8 October 2026, offers no prescriptions yet, but it opens an intriguing line of investigation into how the chemistry of cooking may reach all the way into a child’s bedroom at bedtime.

For now, the practical takeaway is one of awareness rather than alarm. The study does not identify specific foods to banish from the family table, and its authors stop short of any clinical recommendation. What it does provide is a measurable, testable hypothesis: that dAGE intake, quantified in kU/kcal from a 24-hour diet record, tracks with sleep health in children as young as three. With odds ratios approaching twofold and a highly significant p-value, the signal is strong enough to warrant serious follow-up. Whether the culprit is inflammation, oxidative stress, metabolic disruption, or some combination of the three, the idea that a modifiable dietary factor might influence preschool sleep is a compelling target for the longitudinal and intervention studies the researchers say must come next — studies that could eventually transform advice about children’s dinners into advice about their dreams.

Subject of Research: The association between dietary advanced glycation end products and sleep disturbances in preschool children

Article Title: Association between dietary advanced glycation end products and sleep disturbances in preschool children: a cross-sectional study

Article References: Doğan, G., Demi̇rer, B., & Ayhan, N. Y. (2026). Association between dietary advanced glycation end products and sleep disturbances in preschool children: a cross-sectional study. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07811-5

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07811-5

Keywords: advanced glycation end products, sleep disturbances, preschool children, pediatric nutrition, cross-sectional study, dietary assessment, inflammation, oxidative stress, cooking methods, processed foods, sleep disorders scale for children, BMC Pediatrics

The new analysis, published as a systematic review and meta-analysis in Food Science & Nutrition, was conducted by a team at the University of Catanzaro in Italy. The researchers combed through three major bibliographic databases, PubMed, Web of Science, and Scopus, covering publications from January 2000 through February 2026. From 5,247 initially identified papers, they narrowed the field through duplicate removal, title and abstract screening, and full-text assessment to 43 validation studies encompassing 8,467 healthy adults. Every included study had tested a food frequency questionnaire against an established reference method, either repeated 24-hour dietary recalls or prospective food records, and reported Pearson or Spearman correlation coefficients for nutrient intake.

The restrictions were deliberate and methodologically significant. The team limited inclusion to studies conducted in Europe, the United States, Canada, Australia, and New Zealand, regions that share mature, harmonized food composition databases such as the USDA nutrient tables, the UK’s McCance and Widdowson compilations, and the EuroFIR and FSANZ systems. They also excluded studies with fewer than 50 participants, questionnaires designed for single nutrients, and populations with specific diseases or physiological states such as pregnancy. The goal was not to assume that people in these countries eat the same food, but to ensure that the measurement infrastructure behind each validation study was broadly comparable, reducing a major source of statistical noise before the numbers were ever pooled.

The pooled results tell a story of moderate but meaningful validity. Against 24-hour recalls, the correlation coefficient for total energy was 0.454, rising to 0.501 when food records served as the reference. Carbohydrates fared better at roughly 0.52 against both comparators, and dietary fiber emerged as the standout performer, with correlations of 0.593 against recalls and 0.598 against records. Protein and lipids landed in the 0.41 to 0.48 range. Among micronutrients, riboflavin and magnesium showed some of the strongest associations, reaching 0.633 and 0.573 respectively against food records, while vitamin C, calcium, and zinc performed solidly. At the other end of the spectrum, iodine was the clear weak point, with a correlation of just 0.103 against recalls, and vitamin A and sodium also lagged behind.

Why does fiber shine while iodine stumbles? The answer lies in the psychology and physiology of dietary recall. Fiber comes bundled with foods that people recognize and count easily: whole grains, legumes, fruits, vegetables. Iodine, by contrast, hides in iodized salt, dairy, and seafood in amounts that vary enormously and that few respondents can estimate. Sodium poses a similar problem, since discretionary salt added at the table or during cooking is nearly invisible to any self-report instrument. The researchers also noted that monounsaturated and polyunsaturated fats correlated more weakly than saturated fat, likely because participants struggle to identify the types of oils and spreads they use, a well-documented blind spot in self-reported diet.

Correlation coefficients, however, only capture one dimension of questionnaire quality: the ability to rank individuals correctly. The team therefore also calculated standardized mean differences to detect systematic bias in absolute intake levels. Here a familiar pattern emerged. Compared with 24-hour recalls, questionnaires tended to overestimate the intake of several nutrients, with significantly elevated differences for fiber, potassium, vitamin E, and polyunsaturated fats. The overestimation was smaller when food records were the reference, and for many nutrients the differences were not statistically significant. This bias likely reflects a combination of difficulty in judging average portion sizes and a well-known tendency to overreport foods perceived as healthy. Crucially, the authors note that such bias can be partially corrected statistically, and that for most nutrients the standardized mean differences remained below 0.50, a threshold suggesting acceptable agreement.

One of the most valuable contributions of the analysis is its set of subgroup comparisons, which function as a practical design guide for the next generation of questionnaires. Interviewer-administered versions outperformed self-administered ones for energy, carbohydrates, protein, and lipids, presumably because a trained interviewer reduces misinterpretation of questions and improves portion-size estimation. Questionnaires with more food items, above the median of 128 in this dataset, showed slightly higher correlations than shorter instruments, consistent with the idea that a longer food list better captures the true variability of habitual diets, though at the cost of greater respondent burden. Studies rated as very good on the Serra-Majem quality scale reported stronger agreement, and European studies edged out those from other regions. Notably, sample size above the recommended minimum of about 50 participants did not materially change validity, although larger studies displayed far greater heterogeneity.

That heterogeneity is the elephant in the room. The I-squared statistic, which quantifies the share of variability across studies that cannot be explained by chance, exceeded 75 percent for most nutrients and approached or surpassed 90 percent for several, including energy and fiber. Even after restricting the analysis to methodologically homogeneous Western countries, the inconsistency persisted, leading the authors to conclude that instrument-level factors, questionnaire length, administration mode, reference period, and nutrient-specific measurement error, drive variability more than cultural or population differences do. This finding echoes the largest previous meta-analysis of food frequency questionnaire validity, published by Cui and colleagues in 2023, which pooled 130 studies and 21,494 participants globally and reported validity coefficients ranging from roughly 0.17 to 0.77. The new study extends that work by adding Scopus as a third database, pushing the search window six years forward to capture the growing wave of digital and web-based questionnaires, and sharpening the geographic focus for interpretability in Western epidemiological contexts.

The practical implications are considerable. For researchers designing cohort studies, the message is that overall-diet questionnaires are well suited to their classic epidemiological role: ranking individuals by habitual intake of energy, macronutrients, carbohydrates, and fiber, and characterizing broad dietary patterns. They are a weaker choice when the exposure of interest is a specific micronutrient with high day-to-day variability or hidden dietary sources, such as iodine or sodium; in those cases, targeted validation, repeated recalls, or objective biomarkers remain essential. The authors also caution that their findings concern relative validity, the ability to rank people, rather than absolute agreement, since the eligibility criteria required correlation coefficients and excluded studies reporting only complementary measures such as Bland-Altman analyses.

Looking forward, the transition from paper to digital formats looms large. Web-based questionnaires promise standardized administration, integrated portion-size images, automated nutrient calculation, and better acceptability among digitally fluent participants, and several such tools appeared among the studies included here. Yet the authors are clear-eyed about the limits of technology: systematic underreporting and memory bias are intrinsic to self-report, and digitization alone cannot eliminate them. Their conclusion is a measured endorsement. The food frequency questionnaire remains irreplaceable for large-scale nutrition research because of its low cost, low burden, and unique ability to capture long-term habitual intake, but its results should be read with an understanding of what it measures well and what it does not. Future work, they argue, should focus on identifying the conditions under which these instruments deliver the most informative estimates, so that the humble checklist continues to earn its central place in the science of diet and disease.

Subject of Research: Relative validity of food frequency questionnaires for assessing dietary intake in adult populations

Article Title: Relative Validity of Food Frequency Questionnaires in Adult Populations: A Systematic Review and Meta‐Analysis

Article References: Pujia, C., Ferro, Y., Placanica, A., Bruno, R., Guadagni, F., Malaguarnera, G., Mazza, E., Montalcini, T., & Pujia, A. (2026). Relative Validity of Food Frequency Questionnaires in Adult Populations: A Systematic Review and Meta‐Analysis. Food Science &amp; Nutrition, 14(10), Article e72381. https://doi.org/10.1002/fsn3.72381

Image Credits: AI Generated

DOI: 10.1002/fsn3.72381

Keywords: food frequency questionnaire, dietary assessment, nutritional epidemiology, meta-analysis, systematic review, validation studies, 24-hour recall, food records, macronutrients, micronutrients, measurement error, diet-disease risk