The carbon isotope ratios of nonessential amino acids identify sugar-sweetened beverage (SSB) consumers in a 12-wk inpatient feeding study of 32 men with varying SSB and meat exposures

Carbon stable isotope values in hair are associated with added sugar intake in adults but not young children: a cross-sectional study

BACKGROUND

Carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in tissues are proposed biomarkers for dietary intake, with δ13C values reflecting added sugar intake derived from corn and sugarcane, and δ15N values reflecting animal protein intake. Research in young children is limited.

OBJECTIVE

We examined associations between hair δ13C and δ15N values and dietary intake among children and also their mothers, to confirm associations found in other adults.

METHODS

Hair samples and 24-h dietary recalls were collected from children (aged 5.6 ± 0.2 y; n = 138) and adults (34.1 ± 0.7 y; n = 114) in a cross-sectional study in Philadelphia. Hair δ13C and δ15N values were determined by continuous-flow isotope ratio mass spectrometry. Intake assessments focused on foods with high δ13C values [e.g. sugar-sweetened beverages (SSB)], high δ15N values (e.g. meat), or both (e.g. cow's milk). Three analytical approaches-single- (δ13C), dual- (δ13C, δ15N) isotope regression models and, uniquely, k-means cluster analysis-were used to assess associations.

RESULTS

Among adults, regression models revealed positive associations of δ13C values with added sugar [β (95% confidence interval): single, 0.17 (-0.01, 0.36); dual, 0.31 (0.10, 0.53)] and SSB [single, 0.30 (0.12, 0.48); dual, 0.31 (0.09, 0.53)] intakes, confirming prior findings. Adults in the high δ13C-δ15N cluster drank more SSB than the low cluster (213 ± 23 compared with 109 ± 20 kcal/d, P = 0.03). Among children, no such associations were found. However, children in the high δ13C-δ15N cluster consumed more cow's milk (81 ± 9 compared with 31 ± 7 kcal/d, P = 0.009) and animal proteins (408 ± 33 compared with 272 ± 36 kcal/d, P = 0.04). Their cow's milk intake is significantly associated with δ13C and δ15N values.

CONCLUSIONS

Age-related dietary patterns, particularly higher cow's milk consumption in children, may mask δ13C-added sugar associations, highlighting the importance of accounting for age and dietary complexity in biomarker research. This study was registered at: Snacks, Smiles and Taste Preferences as registration number NCT03631992. Website: https://clinicaltrials.gov/study/NCT03631992; Added Sugar Intake, Sweet Taste Phenotypes and Biomarkers (SWBIO), NCT05047588. Website: https://clinicaltrials.gov/ct2/show/NCT05047588.

Associations of Food Group Intakes with Serum Carbon Isotope Ratio Values in Youth: Results from 2 Prospective Pediatric Cohort Studies

BACKGROUND

The carbon isotope ratio (CIR) is a candidate biomarker for sugar-sweetened beverage (SSB) intake in the United States. However, research specific to youth, who differ in their physiology and dietary patterns compared with adults, is lacking.

OBJECTIVES

We evaluated longitudinal associations of SSB intakes across childhood/adolescence with serum CIR. We also explored the relationship between other dietary intakes and serum CIR.

METHODS

Data were from participants in two longitudinal, pediatric cohorts in Colorado: Exploring Perinatal Outcomes among CHildren (EPOCH) study (visits at median 10 and 16 y, n = 150) and Healthy Start Study (visits at median 5 and 9 y, n = 166). Serum CIR was measured using isotope ratio mass spectrometry. Diet was assessed by food-frequency questionnaires (EPOCH) or 24-h diet recalls (Healthy Start). We assessed associations of longitudinal dietary intakes (log2-transformed, standardized) with serum CIR using linear mixed models adjusted for age, sex, and energy intake, and associations of change values between visits using linear regression models.

RESULTS

In linear mixed models, higher SSB intake across visits was associated with higher serum CIR in both cohorts [β (95% confidence interval (CI)): 0.11 (0.06, 0.15) in EPOCH and 0.14 (0.07, 0.21) in Healthy Start]. Higher meat intake and a higher dietary animal protein ratio were also positively associated with serum CIR in both cohorts [β (95% CI): 0.08 (0.05, 0.12) and 0.18 (0.13, 0.23) in EPOCH; 0.08 (0.01, 0.16) and 0.28 (0.21, 0.35) in Healthy Start]. In change analyses, there were positive associations for changes in the dietary animal protein ratio between visits with changes in serum CIR in both cohorts, but not for changes in SSB intake.

CONCLUSIONS

Our findings support serum CIR as a potential biomarker of SSB intake in youth cross-sectionally; however, there was not a strong link between change values over longer-term follow-up. Meat/animal protein intake was also consistently and, at times, more strongly associated with serum CIR.

Optimising Growth, Immunity, and Gene Expression in Broiler Chickens Through Dietary Threonine Levels and Oil Inclusion

BACKGROUND

The inclusion of synthetic amino acids in poultry nutrition plays a crucial role in both enhancing the synthesis of immunoglobulins and elevating the overall comprehensiveness of the amino acid profile.

OBJECTIVES

This research examined the effects of consuming threonine (Thr) in various forms levels with low or high oil on broiler chickens' growth and immunity.

METHODS

We investigate the growth performance, feed efficiency, immune response, intestinal morphology, absorptive capacity, and expression of some genes related to the feed intake (Pro-opiomelanocortin [POMC]), fatty acid synthesis (Acetyl-CoA Carboxylase [ACC]), immunity (lipopolysaccharide-induced tumour necrosis like alpha factor [LITAF]), and heat shock protein 70 (HSP70). Eight groups of chicks were used, including four dietary Thr levels (100%, 115%, 130%, or 145%) with two oil levels (mixture of sunflower 50% and soybean oils 50%): (control) and high.

RESULTS

The higher dietary Thr level (145%) with high oil inclusion significantly increased ACC and POMC gene expression, resulting in the lowest feed intake, body weight gain (BWG), and liver fat content. Combining high oil with 115% Thr was the optimum for the broilers. The birds have significant (p ≤ .05) growth performance, immune parameters, and intestinal health, as well as the lowest expression of ACC, POMC, HSP70, and LITAF, which was reflected in better feed conversion ratio and lower incidence of fatty liver, thermo-resistance, and immune status of the birds.

CONCLUSIONS

The combination of high oil and 115% Thr levels optimises broiler health and productivity, enhancing growth, immune function, and gut health. This diet lowers the expression of genes associated with fatty liver and stress, leading to better feed efficiency, thermo-resistance, and overall well-being. Adopting these dietary adjustments can improve broiler performance and economic viability in poultry farming by enhancing essential productivity metrics.

The carbon isotope ratio of breath is elevated by short-term and long-term added sugar and animal protein intake in a controlled feeding study

BACKGROUND

The breath carbon isotope ratio (CIR) was recently identified as a noninvasive candidate biomarker of short-term added sugars (AS) intake.

OBJECTIVES

This study aimed to better understand the potential of the breath CIR as a dietary biomarker. We evaluated the effects of short-term and long-term intakes of AS, animal protein (AP), and related variables on breath CIR, in the context of typical dietary intake patterns.

METHODS

We conducted a 15-d controlled feeding study of 100 adults (age 18-70 y, 55% females) in Phoenix, AZ. Participants were provided individualized diets that approximated habitual food intakes and recorded the timing of food consumption. Three breath samples (fasting, midday, and evening) were collected on each of 3 nonconsecutive study days. We modeled the effects of dietary intake in each of 8 h preceding collection of the breath sample on breath CIR with a linear mixed model, which also included 15-d mean intakes, sex, age, and BMI.

RESULTS

Median (IQR) intakes of AS and AP in our study were 65 (38) and 67 (33) g/d, respectively. Midday and evening breath CIRs correlated strongly with each other (0.80) and with fasting breath CIR (0.77 and 0.68, respectively). In our linear mixed models, breath CIR increased by AS consumed 1-4 h before sample collection, AP consumed 3-6 h before sample collection, and 15-d intakes of AS and AP, all with similar effect sizes. The breath CIR was also inversely associated with 15-d intakes of intrinsic sugars and plant protein; thus, associations with 15-d intakes were particularly strong when expressed proportionally as the AS ratio (added sugars/total sugars) and AP ratio (animal protein/total protein).

CONCLUSIONS

The breath CIR is a promising measure of long-term intakes of AS and AP, especially as proportional intakes. Approaches to increase specificity would benefit the further development of this biomarker.

The Carbon Isotope Ratio as an Objective Biomarker of Added Sugar Intake: A Scoping Review of Current Evidence in Human Nutrition

Objective biomarkers of dietary intake are needed to advance nutrition research. The carbon isotope ratio (C13/C12; CIR) holds promise as an objective biomarker of added sugar (AS) and sugar-sweetened beverage (SSB) intake. This systematic scoping review presents the current evidence on CIRs from human studies. Search results (through April 12, 2024) yielded 6297 studies and 24 final articles. Studies were observational (n = 12), controlled feeding (n = 10), or dietary interventions (n = 2). CIRs were sampled from blood (n = 23), hair (n = 5), breath (n = 2), and/or adipose tissue (n = 1). Most (n = 17) conducted whole tissue (that is, bulk) analysis, 8 used compound specific isotope analysis (CSIA), and/or 2 studies used methods appropriate for analyzing breath. Studies were conducted in 3 concentrated geographic regions of the United States (n = 7 Virginia; n = 5 Arizona; n = 4 Alaska), with only 2 studies conducted in other countries. Studies that used CSIA to examine the CIR from the amino acid alanine (CIR-Ala; n = 4) and CIR analyzed from breath (n = 2) provided the most robust evidence for CIR as an objective biomarker of AS and SSBs (R2 range 0.36-0.91). Studies using bulk analysis of hair or blood showed positive, but modest and more variable associations with AS and SSBs (R2 range 0.05-0.48). Few studies showed no association, particularly in non-United States populations and those with low AS and SSB intakes. Two studies provided evidence for CIR to detect changes in SSB intake in response to dietary interventions. Overall, the most compelling evidence supports CIR-Ala as an objective indicator of AS intake and breath CIR as an indicator of short-term AS intake. Considering how to adjust for underlying dietary patterns remains an important area of future work and emerging methods using breath and CSIA warrant additional investigation. More evidence is needed to refine the utility and specificity of CIRs to measure AS and SSB intake.

Carbon Isotope Ratios of Plasma and RBC Fatty Acids Identify Meat Consumers in a 12-Week Inpatient Feeding Study of 32 Men

BACKGROUND

Molecular stable isotope ratios are a novel type of dietary biomarker with high sensitivity and specificity for certain foods. Among these, fatty acid carbon isotope ratios (CIRs) have strong potential but have not been investigated as dietary biomarkers.

OBJECTIVES

We evaluated whether fatty acid CIRs and mass proportions were associated with meat, fish, and sugar-sweetened beverage (SSB) intake.

METHODS

Thirty-two men [aged 46.2 ± 10.5 y; BMI (kg/m2): 27.2 ± 4.0] underwent a 12-wk inpatient dietary intervention at the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona. Men were randomly assigned to 1 of 8 dietary treatments varying the presence/absence of dietary meat, fish, and SSBs in all combinations. Fatty acid CIRs and mass proportions were measured in fasting blood samples and adipose tissue biopsies that were collected pre- and postintervention. Dietary effects were analyzed using multivariable regression and receiver operating characteristic AUCs were calculated using logistic regression.

RESULTS

CIRs of the several abundant SFAs, MUFAs and arachidonic acid (20:4n-6) in plasma were strongly associated with meat, as were a subset of these fatty acids in RBCs. Effect sizes in plasma ranged from 1.01‰ to 1.93‰ and were similar but attenuated in RBCs. Mass proportions of those fatty acids were not associated with diet. CIRs of plasma dihomo-γ-linolenic acid (20:3n-6) and adipose palmitic acid (16:0) were weakly associated with SSBs. Mass proportions of plasma odd-chain fatty acids were associated with meat, and mass proportions of plasma EPA and DHA (20:5n-3 and 22:6n-3) were associated with fish.

CONCLUSIONS

CIRs of plasma and RBC fatty acids show promise as sensitive and specific measures of dietary meat. These provide different information from that provided by fatty acid mass proportions, and are informative where mass proportion is not. This trial is registered at www.clinicaltrials.gov as NCT01237093.

Evaluating a Model of Added Sugar Intake Based on Amino Acid Carbon Isotope Ratios in a Controlled Feeding Study of U.S. Adults

Previous studies suggest that amino acid carbon stable isotope ratios (CIRAAs) may serve as biomarkers of added sugar (AS) intake, but this has not been tested in a demographically diverse population. We conducted a 15-day feeding study of U.S. adults, recruited across sex, age, and BMI groups. Participants consumed personalized diets that resembled habitual intake, assessed using two consecutive 7-day food records. We measured serum (n = 99) CIRAAs collected at the end of the feeding period and determined correlations with diet. We used forward selection to model AS intake using participant characteristics and 15 CIRAAs. This model was internally validated using bootstrap optimism correction. Median (25th, 75th percentile) AS intake was 65.2 g/day (44.7, 81.4) and 9.5% (7.2%, 12.4%) of energy. The CIR of alanine had the highest, although modest, correlation with AS intake (r = 0.32, p = 0.001). Serum CIRAAs were more highly correlated with animal food intakes, especially the ratio of animal to total protein. The AS model included sex, body weight and 6 CIRAAs. This model had modest explanatory power (multiple R2 = 0.38), and the optimism-corrected R2 was lower (R2 = 0.15). Further investigations in populations with wider ranges of AS intake are warranted.

Amino Acid Nitrogen Isotope Ratios Respond to Fish and Meat Intake in a 12-Week Inpatient Feeding Study of Men

BACKGROUND

The natural abundance nitrogen stable isotope ratio (NIR) of whole tissue correlates with animal protein intakes, including meat and fish. Amino acid (AA) NIRs (NIRAAs) are more variable than the whole-tissue NIRs and may thus better differentiate among foods.

OBJECTIVES

We evaluated whether NIRAAs were associated with intakes of fish and meat and whether these dietary associations were larger than with whole-tissue NIRs.

METHODS

Men were recruited at the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona, and randomly assigned to one of eight 12-wk inpatient dietary interventions, which varied the presence/absence of fish, meat, and sugar-sweetened beverages (SSBs) in all possible combinations. Fasting blood was drawn pre- and postintervention and plasma and RBC NIRAAs (free and protein-bound) were measured as secondary outcomes in 32 participants. Multivariable regression was used to determine responses of postintervention NIRAAs to dietary variables, and logistic regression was used to calculate receiver operating characteristic AUCs.

RESULTS

Most plasma NIRAAs increased with fish and meat intakes, but to a greater extent with fish intake. The largest increase in response to fish intake was plasma NIRLeucine (β = 2.19, SE = 0.26). The NIRThreonine decreased with both fish and meat intakes. Fewer RBC NIRAAs increased with fish intake, and only RBC NIRProline increased with meat intake. No plasma or RBC NIRAA responded to SSB intake. We identified fish intake with a high degree of accuracy using plasma NIRLeucine (corrected AUC, cAUC = 0.96) and NIRGlutamic acid/glutamine (cAUC = 0.93), and meat intake to a lower degree using plasma NIRProline (cAUC = 0.80) and RBC NIRProline (cAUC = 0.85).

CONCLUSIONS

Plasma and RBC NIRAAs were associated with fish and meat intakes but were not superior to whole-tissue stable isotope biomarkers in identifying these intakes in a US diet. This trial is registered at www.clinicaltrials.gov as NCT01237093.

OUP accepted manuscript

Stable isotope analysis of teeth and bones is regularly applied by archeologists and paleoanthropologists seeking to reconstruct diets, ecologies, and environments of past hominin populations. Moving beyond the now prevalent study of stable isotope ratios from bulk materials, researchers are increasingly turning to stable isotope ratios of individual amino acids to obtain more detailed and robust insights into trophic level and resource use. In the present article, we provide a guide on how to best use amino acid stable isotope ratios to determine hominin dietary behaviors and ecologies, past and present. We highlight existing uncertainties of interpretation and the methodological developments required to ensure good practice. In doing so, we hope to make this promising approach more broadly accessible to researchers at a variety of career stages and from a variety of methodological and academic backgrounds who seek to delve into new depths in the study of dietary composition.

A Systematic Review of Metabolomic Biomarkers for the Intake of Sugar-Sweetened and Low-Calorie Sweetened Beverages

Intake of added sugars (AS) is challenging to assess compared with total dietary sugar because of the lack of reliable assessment methods. The reliance on self-reported dietary data in observational studies is often cited as biased, with evidence of AS intake in relation to health outcomes rated as low to moderate quality. Sugar-sweetened beverages (SSBs) are a major source of AS. A regular and high intake of SSBs is associated with an overall poor diet, weight gain, and cardiometabolic risks. An elevated intake of low-calorie sweetened beverages (LCSBs), often regarded as healthier alternatives to SSBs, is also increasingly associated with increased risk for metabolic dysfunction. In this review, we systematically collate evidence and provide perspectives on the use of metabolomics for the discovery of candidate biomarkers associated with the intake of SSBs and LCSBs. We searched the Medline, Embase, Scopus, and Web of Science databases until the end of December 2020. Seventeen articles fulfilled our inclusion criteria. We evaluated specificity and validity of the identified biomarkers following Guidelines for Biomarker of Food Intake Reviews (BFIRev). We report that the ¹³C:¹²C carbon isotope ratio (δ¹³C), particularly, the δ¹³C of alanine is the most robust, sensitive, and specific biomarker of SSBs intake. Acesulfame-K, saccharin, sucralose, cyclamate, and steviol glucuronide showed moderate validity for predicting the short-term intake of LCSBs. More evidence is required to evaluate the validity of other panels of metabolites associated with the intake of SSBs.

UK Nutrition Research Partnership (NRP) workshop: Forum on advancing dietary intake assessment

The development of better and more robust measures of dietary intake in free living situations was identified as a priority for advancing nutrition research by the Office of Strategic Coordination for Health Research (OSCHR) Review of Nutrition and Human Health Research in 2017. The UK Nutrition Research Partnership (NRP) sponsored a workshop on Dietary Intake Assessment methodology alongside its series of ‘Hot Topic’ workshops designed to accelerate progress in nutrition research by bringing together people from a range of different disciplines. The workshop on Dietary Intake Assessment methodology took place via Zoom over two half‐days in January 2021 and included 50 scientists from a wide range of disciplines. The problems with current methods of dietary assessment and how emerging technologies might address them were set out in pre‐recorded presentations and explored in panel discussions. Participants then worked in breakout groups to discuss and prioritise the research questions that should be addressed to best further the field and lead to improvements in dietary assessment methodology. Five priority research questions were selected. Participants were asked to brainstorm potential approaches for addressing them and were then asked to focus on one approach and develop it further. At the end of these sessions, participants presented their project ideas to the rest of the workshop and these will be reported back to the Medical Research Council. It is hoped that potential collaborative projects arising from these discussions will be taken forward in response to future funding calls.