New research from the Monell Chemical Senses Center and Temple University about nutritional biomarkers using carbon and nitrogen stable isotope ratios showed very different results in children versus adults, which points the way to better understanding the role of added sugars in overall dietary patterns across the lifespan.
Overall, added sugar intake by Americans well exceeds amounts recommended by the federal government. This is concerning because excess intake is associated with chronic diseases such as diabetes and obesity. Having an accurate way to measure dietary intake of added sugar is imperative for monitoring dietary health in both children and adults. Since most of the added sugar in the United States comes from corn-based sweeteners (for example, high fructose corn syrup) and cane sugar, which both use a unique photosynthesis process compared to other plants, carbon stable isotope ratios (δ13C) are an emerging way to monitor added sugar intake.
Stable isotope ratios are found in body tissues such as blood and hair, and provide insights into what a person eats. For example, in hair, which grows at a rate of 1 cm per month, a 3 cm segment from the scalp can reveal dietary patterns over the past three months. Past studies have focused on adults living in Alaska and Virginia, and the majority have found that higher δ13C values in body tissues such as hair and blood were associated with higher intake of foods with added sugars, particularly sugar-sweetened beverages, or SSBs. Some studies have found that the relationship between δ13C and added sugar is strengthened when the nitrogen stable isotope (δ15N), a proposed biomarker for protein, is also evaluated.
However, similar research has been limited in young children under the age of five. A new Monell-Temple study in the American Journal of Clinical Nutrition that focused on young children found that the δ13C biomarker did not predict added sugar consumption among children, yet saw a positive association of δ13C values with dietary added sugar in adults. First author Alissa D. Smethers, PhD, RD , Monell Research Associate and Assistant Professor of Instruction at Temple University, also presented this work at the American Society for Nutrition annual meeting held May 31 - June 3, 2005.
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, noted senior author Julie A. Menella, PhD , Monell Member.
Hair Samples Tell the Story
In the present study, hair samples and 24-hour dietary recalls were collected from 138 children aged 3-11 years and their mothers (114 total). Intake of foods and beverages high in added sugars were assessed along with all other aspects of their diets (for example, fruits, vegetables, dairy, and protein).
The team used an analytical approach previously employed in wildlife research, but not yet applied to humans, which involved a cluster analysis of δ13C and δ15N values to identify broad dietary patterns. They used three statistical models to determine whether hair δ13C values were associated with added sugar or SSBs. The first two were a simple (δ13C) and dual (δ13C & δ15N) regression model and the third - the cluster analysis - used δ13C and δ15N values to determine how the isotopes naturally aggregate in individuals and relate to dietary patterns as a whole.
Surprisingly, the δ13C in hair did not predict added sugar intake among young children, but did predict added sugar consumption among the mothers, which replicates findings of prior research in adults.
Combining the finding that children in the high δ13C–δ15N cluster drank more cow's milk than the low cluster and that consumption of cow's milk (but not SSBs) was associated with both δ13C and δ15N values, the authors suggest that the greater prevalence and higher consumption of plain, unsweetened cow's milk relative to SSBs during childhood compared to adulthood may have obscured the association between δ13C values and SSBs consumption in the children.
However, the team suggests that as children enter adolescence and their dietary patterns start to resemble those of adults, the relationship between added sugar/SSBs and δ13C values will likely emerge. Overall, the cluster analysis of stable isotopes suggests that it may be useful not only to identify differences in person-to-person consumption but also to identify age-related differences.
"Added sugars are linked to a host of unfavorable health outcomes, and while carbon stable-isotope biomarkers of added sugar intake have shown great promise for understanding links with health outcomes in adults, our findings call into question the interpretation of carbon stable-isotope values in hair among children," said coauthor Jennifer O. Fisher, PhD, Associate Director of the Center for Obesity Research and Education at Temple University. "This suggests that values may not yield as straightforward of results as have been reported in adults."
The robust statistical analysis used by the team allowed them to take a holistic approach to understand individual differences in the diets of children and adults. Nevertheless more research is warranted to explore δ13C and δ15N as biomarkers during the early, sensitive periods of childhood.
"We need more studies in children paired with controlled feeding studies," said Smethers, who is also a registered dietitian. "We need to pay more attention to the whole dietary pattern in children, not just the amount of added sugar they consume. "
This research was supported by grants R01DC016616 and 1F32DC018710 from the National Institute of Deafness and Other Communications Disorders.
Temple co-authors also include Elizabeth M. Carney and Donna L. Coffman, PhD.
