Short-term changes in added sugar consumption by adolescents reflected in the carbon isotope ratio of fingerstick blood

Stable isotope ratios of nitrogen and carbon as biomarkers of a vegan diet

PURPOSE

Dietary biomarkers can potentially overcome the limitations of self-reported dietary data. While in ecology and archaeology, stable isotope ratios of carbon and nitrogen are widely used as biomarkers, this is not the case in nutrition research. Since the abundance of the 13C and the 15N isotope differ in food sources from plant and animal origin, stable isotope ratios of carbon and nitrogen (δ13C and δ15N) may differ in human biological material. Here, we investigated the stable isotope ratios of nitrogen and carbon in serum and urine from vegans and omnivores.

METHOD

Measurement of δ15N and δ13C in serum and 24 h urine was performed by Elemental Analyzer-Isotope Ratio Mass Spectrometer in the cross-sectional study "Risks and Benefits of a Vegan Diet". The study included 36 vegans and 36 omnivores with a median age of 37.5 years (matched for age and sex), who adhered to their diet for at least 1 year.

RESULTS

Both δ15N and δ13C were significantly lower in both the serum and 24 h urine of vegans compared to omnivores. δ15N either in serum or urine had 100% specificity and sensitivity to discriminate between vegans and omnivores. Specificity of δ13C was also > 90%, while sensitivity was 93% in serum and 77% in urine.

CONCLUSION

δ15N both in serum and urine was able to accurately identify vegans and thus appears to be a promising marker for dietary habits.

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.

Stable Isotope Abundance and Fractionation in Human Diseases

The natural abundance of heavy stable isotopes (¹³C, ¹⁵N, ¹⁸O, etc.) is now of considerable importance in many research fields, including human physiology. In fact, it varies between tissues and metabolites due to isotope effects in biological processes, that is, isotope discriminations between heavy and light isotopic forms during enzyme or transporter activity. The metabolic deregulation associated with many diseases leads to alterations in metabolic fluxes, resulting in changes in isotope abundance that can be identified easily with current isotope ratio technologies. In this review, we summarize the current knowledge on changes in natural isotope composition in samples (including various tissues, hair, plasma, saliva) found in patients compared to controls, caused by human diseases. We discuss the metabolic origin of such isotope fractionations and highlight the potential of using isotopes at natural abundance for medical diagnosis and/or prognostic.

Breath 13CO2-evidence for a noninvasive biomarker to measure added refined sugar uptake

Increased consumption of added sucrose and high-fructose corn syrup in the human diet has been associated with increasing incidence of obesity and metabolic disease. There are currently no reliable, objective biomarkers for added sugar intake that could be used in individuals or population settings. ¹³C is a stable isotope of carbon, and measurement of blood ¹³C content has been proposed as a marker of added sugar consumption. This study aimed to determine if breath ¹³CO₂ could represent an alternative, noninvasive biomarker to monitor added sugar intake. We undertook retrospective analyses of eight preclinical and human ¹³C-breath studies to define baseline breath ¹³CO₂ characteristics. All samples were analyzed using isotope ratio mass spectrometry, and breath ¹³CO₂ was expressed as the delta value, δ expressed as parts per thousand (‰). All data are expressed as mean ± SEM, with statistical significance considered at P < 0.05. Breath δ¹³CO₂ was significantly elevated in a cumulative manner in rats and mice that consumed a diet containing at least 15% sucrose. Mice fed an American rodent chow diet containing 50% sucrose and 15% corn starch had a significantly higher breath δ¹³CO₂ compared with rodents consuming an Australian rodent chow diet. Furthermore, breath δ¹³CO₂ was significantly increased in a dose-dependent manner in humans that ingested a bolus dose of sucrose. These findings suggest application for baseline breath δ¹³CO₂ as a noninvasive biomarker for added sugar consumption, with broad application for longitudinal assessment of population sugar intake and obesity management strategies.NEW & NOTEWORTHY We have found that breath ¹³CO₂ is increased in rats and mice consuming diets high in sucrose. We also found that human breath ¹³CO₂ is increased in humans consuming increasing amounts of sucrose. Our collective findings suggest that breath ¹³CO₂ represents a potential marker of added dietary sugar consumption.

Natural abundance carbon isotope ratio analysis and its application in the study of diet and metabolism

Due to differences in carbon assimilation pathways between plants, there are subtle but distinct variations in the carbon isotope ratios of foods and animal products throughout the food supply. Although it is well understood that the carbon isotope ratio composition of the diet influences that of the consumers' tissues, the application of natural abundance carbon isotope ratio analysis in nutrition has long been underappreciated. Over the past decade, however, several studies have investigated the utility of carbon isotope ratio analysis for evaluation of nutritional biomarker status, primarily focusing on its application as an objective indicator of sugar and animal protein intake. More recently, research investigating the application of natural abundance measurements has been extended to study fatty acid metabolism and has yielded encouraging results. Collectively, data from large-scale observational studies and experimental animal studies highlight the potential for carbon isotope ratio analysis as an additional and effective tool to study diet and metabolism. The purpose of this review is to provide an overview of natural abundance carbon isotope ratio analysis, its application to studying nutrition, and an update of the research in the field.

Methodology for the assessment of added/free sugar intake in epidemiological studies

PURPOSE OF REVIEW

High-sugar intake has been linked to increased risk of diseases but an accurate assessment of added/free sugar intake has always been a challenge in research. This review summarizes the methodologies for assessing added/free sugar intake reported in recent literature.

RECENT FINDINGS

Four different methods for added/free sugar-intake assessment are discussed, including the carbon isotope ratio (δC) method, Food Patterns Equivalent Database, disaggregation method and the 10-step systematic method. These methods have different strengths and limitations in terms of requirement for background knowledge, flexibility to sugar definition, level of subjectivity, accuracy and needs for recalculation/modification when used in different countries or food products.

SUMMARY

Although advances have been made in the methodologies for assessing added/free sugar intake, accurate assessment continues to be difficult. Of the methods reviewed, the 10-step systematic method could be a simpler method to provide relatively accurate estimation of added/free sugar intake. Further improvements or combining with other methods may allow more accurate and flexible estimation. Development of a completely objective biomarker for added/free sugar intake is unlikely to be achievable, therefore future research may need to focus on developing correction equations for use with biomarkers such as δC to improve their specificity to added/free sugar intake.

Association of free sugar intake with blood pressure and obesity measures in Australian adults

PURPOSE

This study examined the association of free sugar (FS) intake with obesity measures and blood pressure (BP) among a nationally representative sample of Australian adults.

METHODS

Data from adults (weighted n = 5136) who completed 2 × 24-h recalls and had complete data for BP, waist circumference (WC), waist-to-height ratio (WHtR), and body mass index (BMI) were analyzed. Associations between percentage energy of FS from all food sources (%EFS_total), beverages only (%EFS_beverages), and non-beverages sources only (%EFS_{non-beverages}) and obesity measures and BP were examined using linear and non-linear regressions. Logistic regression was used to calculate the odds ratios (OR) of being classified as overweight and/or obese, having increased cardiometabolic risks, and elevated BP per 5% point increase in %EFS_total, %EFS_beverages, and %EFS_{non-beverages}. All regression analyses were adjusted for known socio-economic and lifestyle confounders.

RESULTS

%EFS_beverage was positively associated with BMI, WC, and WHtR (all p < 0.05), while %EFS_non-beverage was inversely associated with these outcomes. Increases in odds of having an undesirable WC/WHtR were found with increasing %EFS_beverages (OR per 5% point increase in %EFS_beverages: 1.19 for WC; 1.23 for WHtR, both p < 0.001). %EFS_total and %EFS_{non-beverages} were weakly and negatively associated with diastolic BP. A 5% point increase in %EFS_total and %EFS_non-beverage was associated with a 10-25% reduction in odds of having elevated BP.

CONCLUSIONS

Our results suggested that only a higher FS intake from beverages may be associated with obesity, and higher FS intake was associated with reduced odds of having elevated BP.