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Importance Breastfeeding has been suggested to protect against childhood cancers, particularly acute lymphoblastic leukemia (ALL). However, the evidence stems from case-control studies alone. Objective To investigate whether longer duration of exclusive breastfeeding is associated with decreased risk of childhood ALL and other childhood cancers. Design, Setting, and Participants This population-based cohort study used administrative data on exclusive breastfeeding duration from the Danish National Child Health Register. All children born in Denmark between January 2005 and December 2018 with available information on duration of exclusive breastfeeding were included. Children were followed up from age 1 year until childhood cancer diagnosis, loss to follow-up or emigration, death, age 15 years, or December 31, 2020. Data were analyzed from March to October 2023. Exposure Duration of exclusive breastfeeding in infancy. Main Outcomes and Measures Associations between duration of exclusive breastfeeding and risk of childhood cancer overall and by subtypes were estimated as adjusted hazard ratios (AHRs) with 95% CIs using stratified Cox proportional hazards regression models. Results A total of 309 473 children were included (51.3% boys). During 1 679 635 person-years of follow-up, 332 children (0.1%) were diagnosed with cancer at ages 1 to 14 years (mean [SD] age at diagnosis, 4.24 [2.67] years; 194 boys [58.4%]). Of these, 124 (37.3%) were diagnosed with hematologic cancers (81 [65.3%] were ALL, 74 [91.4%] of which were B-cell precursor [BCP] ALL), 44 (13.3%) with central nervous system tumors, 80 (24.1%) with solid tumors, and 84 (25.3%) with other and unspecified malignant neoplasms. Compared with exclusive breastfeeding duration of less than 3 months, exclusive breastfeeding for 3 months or longer was associated with a decreased risk of hematologic cancers (AHR, 0.66; 95% CI, 0.46-0.95), which was largely attributable to, IMPORTANCE: Breastfeeding has been suggested to protect against childhood cancers, particularly acute lymphoblastic leukemia (ALL). However, the evidence stems from case-control studies alone.OBJECTIVE: To investigate whether longer duration of exclusive breastfeeding is associated with decreased risk of childhood ALL and other childhood cancers.DESIGN, SETTING, AND PARTICIPANTS: This population-based cohort study used administrative data on exclusive breastfeeding duration from the Danish National Child Health Register. All children born in Denmark between January 2005 and December 2018 with available information on duration of exclusive breastfeeding were included. Children were followed up from age 1 year until childhood cancer diagnosis, loss to follow-up or emigration, death, age 15 years, or December 31, 2020. Data were analyzed from March to October 2023.EXPOSURE: Duration of exclusive breastfeeding in infancy.MAIN OUTCOMES AND MEASURES: Associations between duration of exclusive breastfeeding and risk of childhood cancer overall and by subtypes were estimated as adjusted hazard ratios (AHRs) with 95% CIs using stratified Cox proportional hazards regression models.RESULTS: A total of 309 473 children were included (51.3% boys). During 1 679 635 person-years of follow-up, 332 children (0.1%) were diagnosed with cancer at ages 1 to 14 years (mean [SD] age at diagnosis, 4.24 [2.67] years; 194 boys [58.4%]). Of these, 124 (37.3%) were diagnosed with hematologic cancers (81 [65.3%] were ALL, 74 [91.4%] of which were B-cell precursor [BCP] ALL), 44 (13.3%) with central nervous system tumors, 80 (24.1%) with solid tumors, and 84 (25.3%) with other and unspecified malignant neoplasms. Compared with exclusive breastfeeding duration of less than 3 months, exclusive breastfeeding for 3 months or longer was associated with a decreased risk of hematologic cancers (AHR, 0.66; 95% CI, 0.46-0.95), which was largely attributable to decrea

Vinding, Stokholm, Chaves, Bønnelykke and others, in the present issue of the American Journal of Clinical Nutrition, report potentially harmful offspring effects of taking supplements with long chain n-3 fatty acids, also known as n-3 polyunsaturated fatty acids (LCPUFAs) in pregnancy [1]. They examined the impact of maternal supplementation with fish oil during gestation, starting in week 24, on offspring growth and metabolic health assessed when the children were 10 y old. The study was based on follow-up from an influential trial in the field, the COPSAC2010 Study, which in 2016 provided evidence that fish oil could reduce offspring risk of persistent wheeze or asthma and infections of the lower respiratory tract, assessed up to age 5 y [2]. A number of additional studies focusing on a range of different outcomes in children have since been published based on this very same trial population. In the present work, the authors undertook physical examinations of the children at 10 y of age [1]. This publication succeeds 2 earlier publications from the trial cohort, where related outcomes were studied, one reporting increased birth weight for gestational age after maternal supplementation with n-3 LCPUFA, and the other reporting increased BMI during ages 1 to 6 y (several assessments were undertaken of BMI during this age span), as well as increased lean mass, bone mass, and fat mass (assessed by dual x-ray absorptiometry scan) at 6 y. Based on this new analysis, the authors infer that children of mothers receiving long chain n-3 fatty acids in pregnancy seem to have increased BMI, increased risk of being overweight, a tendency of increased fat percentage, and higher metabolic syndrome score at the age of 10

Introduction The number of people adhering to plant-based diets has been increasing dramatically in recent years, fueled by both environmental and animal welfare concerns. Beneficial or possible adverse consequences of such diets, particularly the most restrictive forms during pregnancy, have been minimally explored. The aim of this prospective observational study was to examine associations between different forms of plant-based diets during pregnancy with birth outcomes and pregnancy complications. Material and methods The Danish National Birth Cohort included 100 413 pregnancies to 91 381 women in 1996–2002. The population consisted of 66 738 pregnancies, about which sufficient dietary data were available and included in the study. Dietary and supplemental intake was assessed by Food Frequency Questionnaire in gestational week 25 and women were characterized as fish/poultry-vegetarians, lacto/ovo-vegetarians, vegans or omnivorous, based on their self-report in gestational week 30. Main outcome measures were pregnancy and birth complications, birth weight and small for gestational age. Results A total of 98.7% (n = 65 872) of participants were defined as omnivorous, whereas 1.0% (n = 666), 0.3% (n = 183) and 0.03% (n = 18) identified themselves as fish/poultry vegetarians, lacto/ovo-vegetarians or vegans, respectively. Protein intake was lower among lacto/ovo-vegetarians (13.3%) and vegans (10.4%) than among omnivorous participants (15.4%). Intake of micronutrients was also considerably lower among vegans, but when dietary supplements were taken into consideration, no major differences were observed. Compared with omnivorous mothers, vegans had a higher prevalence of preeclampsia and their offspring had on average −240 g (95% confidence interval −450 to −30) lower birth weight. Conclusions The women reporting that they adhered to vegan diets during pregnancy had offspring with lower mean birth weight and higher risk of pr, Introduction: The number of people adhering to plant-based diets has been increasing dramatically in recent years, fueled by both environmental and animal welfare concerns. Beneficial or possible adverse consequences of such diets, particularly the most restrictive forms during pregnancy, have been minimally explored. The aim of this prospective observational study was to examine associations between different forms of plant-based diets during pregnancy with birth outcomes and pregnancy complications. Material and methods: The Danish National Birth Cohort included 100 413 pregnancies to 91 381 women in 1996–2002. The population consisted of 66 738 pregnancies, about which sufficient dietary data were available and included in the study. Dietary and supplemental intake was assessed by Food Frequency Questionnaire in gestational week 25 and women were characterized as fish/poultry-vegetarians, lacto/ovo-vegetarians, vegans or omnivorous, based on their self-report in gestational week 30. Main outcome measures were pregnancy and birth complications, birth weight and small for gestational age. Results: A total of 98.7% (n = 65 872) of participants were defined as omnivorous, whereas 1.0% (n = 666), 0.3% (n = 183) and 0.03% (n = 18) identified themselves as fish/poultry vegetarians, lacto/ovo-vegetarians or vegans, respectively. Protein intake was lower among lacto/ovo-vegetarians (13.3%) and vegans (10.4%) than among omnivorous participants (15.4%). Intake of micronutrients was also considerably lower among vegans, but when dietary supplements were taken into consideration, no major differences were observed. Compared with omnivorous mothers, vegans had a higher prevalence of preeclampsia and their offspring had on average −240 g (95% confidence interval −450 to −30) lower birth weight. Conclusions: The women reporting that they adhered to vegan diets during pregnancy had offspring with lower mean birth weight and higher risk of preeclampsia compared with omnivorous

Background N-nitroso compounds (NOCs) can be formed by endogenous reactions between nitrosatable drugs and nitrite. Animal studies have found that several NOCs are teratogenic, and epidemiological studies report associations between prenatal exposure to nitrosatable drugs and adverse birth outcomes. It is unknown whether prenatal exposure to nitrosatable drugs is harmful to the child's reproductive health, including pubertal development. Objectives We investigated whether prenatal exposure to nitrosatable drugs was associated with timing of puberty and whether nitrate, nitrite and antioxidant intake modified any association. Methods The population-based Danish National Birth Cohort (DNBC) Puberty Cohort, which includes 15,819 children, was used to investigate the association between prenatal exposure to nitrosatable drugs and timing of puberty. Around gestational week 11 and gestational week 18, mothers provided information about drug use during pregnancy. The children's self-reported information on onset of pubertal milestones was collected every six months from 11 years of age and throughout puberty. To investigate potential effect modification by nitrite, nitrate and antioxidant intake, information on these factors was obtained from a food frequency questionnaire completed by the mothers in gestational week 25, and information on nitrate concentration in maternal drinking water at her residential address was obtained from monitoring data from public waterworks. Data were analysed using a multivariable regression model for interval-censored data estimating difference in months in timing of puberty between exposure groups. Results A total of 2,715 children were prenatally exposed to nitrosatable drugs. We did not find an association between prenatal exposure to nitrosatable drugs and timing of puberty. This finding was supported by null-findings in the following sub-analyses investigating: 1. subtypes of nitrosatable drugs, Background: N-nitroso compounds (NOCs) can be formed by endogenous reactions between nitrosatable drugs and nitrite. Animal studies have found that several NOCs are teratogenic, and epidemiological studies report associations between prenatal exposure to nitrosatable drugs and adverse birth outcomes. It is unknown whether prenatal exposure to nitrosatable drugs is harmful to the child's reproductive health, including pubertal development. Objectives: We investigated whether prenatal exposure to nitrosatable drugs was associated with timing of puberty and whether nitrate, nitrite and antioxidant intake modified any association. Methods: The population-based Danish National Birth Cohort (DNBC) Puberty Cohort, which includes 15,819 children, was used to investigate the association between prenatal exposure to nitrosatable drugs and timing of puberty. Around gestational week 11 and gestational week 18, mothers provided information about drug use during pregnancy. The children's self-reported information on onset of pubertal milestones was collected every six months from 11 years of age and throughout puberty. To investigate potential effect modification by nitrite, nitrate and antioxidant intake, information on these factors was obtained from a food frequency questionnaire completed by the mothers in gestational week 25, and information on nitrate concentration in maternal drinking water at her residential address was obtained from monitoring data from public waterworks. Data were analysed using a multivariable regression model for interval-censored data estimating difference in months in timing of puberty between exposure groups. Results: A total of 2,715 children were prenatally exposed to nitrosatable drugs. We did not find an association between prenatal exposure to nitrosatable drugs and timing of puberty. This finding was supported by null-findings in the following sub-analyses investigating: 1. subtypes of nitrosatable drugs (secondary and tertiary amines and

OBJECTIVE It has been hypothesized that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children can increase risk of developing type 1 diabetes. RESEARCH DESIGN AND METHODS We undertook a prospective, register-based analysis of children in Denmark by investigating the association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes. During the pandemic, Denmark had one of the highest test rates per capita in the world, and 90% of all Danish children were tested. RESULTS Compared with children with a history of only negative SARS-CoV-2 tests, we did not observe a higher risk of first-time diagnosis of type 1 diabetes in children 30 days or more after a positive SARS-CoV-2 test (hazard ratio 0.85; 95% CI 0.70–1.04). CONCLUSIONS Our data do not support that SARS-CoV-2 infection is associated with type 1 diabetes or that type 1 diabetes should be a special focus after a SARS-CoV-2 infection in children., OBJECTIVE: It has been hypothesized that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children can increase risk of developing type 1 diabetes. RESEARCH DESIGN AND METHODS: We undertook a prospective, register-based analysis of children in Denmark by investigating the association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes. During the pandemic, Denmark had one of the highest test rates per capita in the world, and 90% of all Danish children were tested. RESULTS: Compared with children with a history of only negative SARS-CoV-2 tests, we did not observe a higher risk of first-time diagnosis of type 1 diabetes in children 30 days or more after a positive SARS-CoV-2 test (hazard ratio 0.85; 95% CI 0.70-1.04). CONCLUSIONS: Our data do not support that SARS-CoV-2 infection is associated with type 1 diabetes or that type 1 diabetes should be a special focus after a SARS-CoV-2 infection in children.

he food frequency questionnaire (FFQ) is designed to capture an individual’s habitual dietary intake and is the most applied method in nutritional epidemiology. Our aim was to assess the relative validity and reproducibility of the FFQ used in the Diet, Cancer, and Health—Next Generations cohort (DCH-NG). We included 415 Danish women and men aged 18–67 years. Spearman’s correlations coefficients, Bland–Altman limits of agreement and cross-classification between dietary intakes estimated from the FFQ administered at baseline (FFQbaseline), and the mean of three 24-h dietary recalls (24-HDRs) and the FFQ administered after 12 months (FFQ12 months) were determined. Nutrient intakes were energy-adjusted by Nutrient Density and Residual methods. Correlation coefficients ranged from 0.18–0.58 for energy and energy-adjusted nutrient intakes, and the percentage of participants classified into the same quartile ranged from 28–47% between the FFQbaseline and the 24-HDRs. For the FFQ12 months compared with FFQbaseline, correlation coefficients ranged from 0.52–0.88 for intakes of energy, energy-adjusted nutrients, and food groups, and the proportion of participants classified into the same quartiles ranged from 43–69%. Overall, the FFQ provided a satisfactory ranking of individuals according to energy, nutrient, and food group intakes, making the FFQ suitable for use in epidemiological studies investigating diet in relation to disease outcomes. Keywords: food frequency questionnaire; 24-h dietary recall; web-based; relative validity; reproducibility; epidemiology; nutrition; diet; cancer, The food frequency questionnaire (FFQ) is designed to capture an individual’s habitual dietary intake and is the most applied method in nutritional epidemiology. Our aim was to assess the relative validity and reproducibility of the FFQ used in the Diet, Cancer, and Health—Next Generations cohort (DCH-NG). We included 415 Danish women and men aged 18–67 years. Spearman’s correlations coefficients, Bland–Altman limits of agreement and cross-classification between dietary intakes estimated from the FFQ administered at baseline (FFQbaseline), and the mean of three 24-h dietary recalls (24-HDRs) and the FFQ administered after 12 months (FFQ12 months) were determined. Nutrient intakes were energy-adjusted by Nutrient Density and Residual methods. Correlation coefficients ranged from 0.18–0.58 for energy and energy-adjusted nutrient intakes, and the percentage of participants classified into the same quartile ranged from 28–47% between the FFQbaseline and the 24-HDRs. For the FFQ12 months compared with FFQbaseline, correlation coefficients ranged from 0.52–0.88 for intakes of energy, energy-adjusted nutrients, and food groups, and the proportion of participants classified into the same quartiles ranged from 43–69%. Overall, the FFQ provided a satisfactory ranking of individuals according to energy, nutrient, and food group intakes, making the FFQ suitable for use in epidemiological studies investigating diet in relation to disease outcomes.

INTRODUCTION: Worldwide infertility is highly prevalent, and lifestyle factors, such as food intake, could have an essential role in the success of a fertility treatment. The literature is not consistent and adequate for recommendations to the increasing number of women and men of reproductive age who ask for lifestyle guidance. Therefore, the aims of the Food & Fertility Study will be to investigate the possible association between food intake and semen quality in men, and pregnancy and live birth rates in women undergoing intrauterine insemination or assisted reproductive technology treatment.METHODS AND ANALYSIS: The Food & Fertility Study is a multicentre prospective cohort study which plans to enrol a total of 4000 women and men between 2022 and 2024. Data collection will take place in four fertility clinics through a web-based Food Frequency Questionnaire. Data on sperm quality and pregnancy and live birth rates will be obtained from medical records and national registers.ETHICS AND DISSEMINATION: The study is registered with and approved by the Danish Data Protection Agency, the North Denmark Region (j.nr: 2019-055298). Further, a Statement of Work and a Master Collaboration Agreement have been submitted and approved by the regional legal departments (AGR-2019-731-9667). Dissemination of the results will be through national and international conferences, in scientific environments, in the form of lectures to the broader public, and by peer-reviewed publications in international scientific journals.TRIAL REGISTRATION NUMBER: NCT05454046.