Charting the Chronology of Research on Added Sugars: A Scoping Review and Evidence Map.

The objective of this study was to conduct a scoping review and produce a publicly available database characterizing the design and reporting elements of the literature on dietary added sugars and select health outcomes. Relevant studies published from 1990 to 2021 were identified to create a database containing information on study and population characteristics, reported added sugars source and concentrations, dietary energy balance, total energy intake, and outcome measures related to body composition, obesity, cardiovascular disease, and diabetes mellitus. There were 245 publications identified, 22% of which describe interventions, and 78% describe observational studies. Publications pertaining to added sugars have risen dramatically since 2010, led by studies primarily assessing body composition (36%) or cardiovascular health (32%), including adults (65%), measuring liquid-only sources of added sugars (56%). Over 65% of studies reported total energy intake, 61% controlled for total energy intake in the design and analysis, and fewer than 5% of studies reported the energy balance of subjects. There has been a significant increase in research on added sugars since 2010, with substantial heterogeneity across all facets of methodology-study designs, exposures and outcomes of interest, terminology, and reporting of dietary intake data-thus limiting the ability to synthesize evidence in this scope of the literature. This evidence map highlights gaps and important areas for improvement to strengthen the state of research and better inform future policies and dietary recommendations on added sugars.

Intakes of Added Sugars, with a Focus on Beverages and the Associations with Nutrient Adequacy in US Adults (NHANES 2003-2018).

The Dietary Guidelines for Americans recommend adults increase their intake of nutrients that are under-consumed while limiting their intake of added sugars, sodium, and saturated fats. The purpose of this study was to examine the relationship between added sugars intake from specific types of beverages with added sugars (soft drinks, fruit drinks, sports and energy drinks, coffee and tea, and flavored milk) and nutrient adequacy among US adults (19+ y). Data from eight consecutive 2-y cycles of NHANES were combined (2003-2004 through 2017-2018), and regression analysis was conducted to test for trends in quantiles of added sugars intake from each beverage source and the rest of the diet (excluding those beverages) and nutrient adequacy. Results revealed significant associations that varied in direction according to the added sugars source, negative for some (i.e., soft drinks) in terms of greater percentages of adults not meeting a defined threshold of nutrient adequacy with higher added sugars intakes, and positive for others (i.e., fruit drinks, flavored milk, the rest of the diet) in terms of lower percentages of adults not meeting nutrient thresholds. In conclusion, the contribution of different added sugars sources to nutrient intakes is a critical consideration in developing population-based dietary recommendations.

Intakes of Added Sugars, with a Focus on Beverages and the Associations with Micronutrient Adequacy in US Children, Adolescents, and Teens (NHANES 2003-2018).

Added sugars intake from sweetened beverages among children, adolescents, and teens is a public health concern. This study examined the relationships between added sugars intake from specific types of beverages with added sugars and from the rest of the diet (excluding beverages with added sugars) and micronutrient adequacy among US children, adolescents, and teens. Data from eight consecutive 2 y cycles of NHANES were combined (2003-04 through 2017-18), and regression analysis was conducted to test for trends in quantiles of added sugars intake from each beverage source (soft drinks, fruit drinks, sport and energy drinks, coffee and tea, and flavored milk) and the rest of the diet (excluding those beverages) and micronutrient adequacy among children (2-8 y) and adolescents and teens (9-18 y). Among those aged 2-8 y, higher added sugars from flavored milk were associated with lower percentages below the estimated average requirement (EAR) for calcium. Among those aged 9-18 y, higher added sugars from soft drinks or coffee and tea were associated with higher percentages below the EAR for magnesium and vitamins A and C. In contrast, higher added sugars from fruit drinks or flavored milk were associated with lower percentages below the EAR (higher percentages above the adequate intake (AI)) for vitamin C (fruit drinks) and calcium, magnesium, phosphorus, vitamin A, and potassium (flavored milk). Regarding the rest of the diet, higher added sugars were associated with lower percentages below the EAR (higher percentages above the AI) for most micronutrients examined. The results suggest that the relationship between added sugars intake and micronutrient adequacy depends on the added sugar sources and their nutrient composition. Continued monitoring of sweetened beverage consumption, including beverage type, and the association with added sugars intake, micronutrient adequacy, and diet quality is warranted, given the changes in consumption and product development over time.

Trends in added sugars intake and sources among U.S. adults using the National Health and Nutrition Examination Survey (NHANES) 2001-2018.

Research on trends over time in added sugars intake is important to help gain insights into how population intakes change with evolving dietary guidelines and policies on reducing added sugars. The purpose of this study was to provide an analysis of dietary trends in added sugars intakes and sources among U.S. adults from 2001 to 2018, with a focus on variations according to the sociodemographic factors, age, sex, race and ethnicity and income, and the health-related factors, physical activity and body weight. Data from nine consecutive 2 year cycles of the National Health and Nutrition Examination Survey (NHANES) were combined and regression analyses were conducted to test for trends in added sugars intake and sources from 2001 to 2018. Trends were examined in the whole sample (19+ years) and in subsamples stratified by age (19-50, 51+ years), sex, race and ethnicity (Asian, Black, Hispanic, White), household income (poverty income ratio low, medium, high), physical activity level (sedentary, moderate, vigorous) and body weight status (normal, overweight, obese). From 2001 to 2018, added sugars intake (% kcal) decreased significantly (P < 0.01), from 16.2 to 12.7% among younger adults (19-50 years), mainly due to declines in added sugars from sweetened beverages, which remained the top source. There were no changes in intake among older adults, and by 2018, the 23% difference in intake between younger and older adults that existed in 2001 almost disappeared. Declines in added sugars intake were similar among Black and White individuals, and all income, physical activity and body weight groups. Population-wide reductions in added sugars intake among younger adults over an 18 year time span coincide with the increasing public health focus on reducing added sugars intake. With the updated Nutrition Facts label now displaying added sugars content, it remains to be seen how added sugars intake trends carry forward in the future.

Trends in Added Sugars Intake and Sources Among US Children, Adolescents, and Teens Using NHANES 2001-2018.

BACKGROUND: Over the past 2 decades, there has been an increased emphasis on added sugars intake in the Dietary Guidelines for Americans (DGA), which has been accompanied by policies and interventions aimed at reducing intake, particularly among children, adolescents, and teens. OBJECTIVES: The present study provides a comprehensive time-trends analysis of added sugars intakes and contributing sources in the diets of US children, adolescents, and teens (2-18 years) from 2001-2018, focusing on variations according to sociodemographic factors (age, sex, race and ethnicity, income), food assistance, and health-related factors (physical activity level, body weight status). METHODS: Data from 9 consecutive 2-year cycles of the NHANES were combined and regression analyses were conducted to test for trends in added sugars intake and sources from 2001-2018 for the overall age group (2-18 years) and for 2 age subgroups (2-8 and 9-18 years). Trends were also examined on subsamples stratified by sex, race and ethnicity (Hispanic, non-Hispanic Asian, non-Hispanic Black, non-Hispanic White), income (household poverty income ratio), food assistance, physical activity level, and body weight status. RESULTS: From 2001-2018, added sugars intakes decreased significantly (P < 0.01), from 15.6% to 12.6% kcal among children (2-8 years) and from 18.4% to 14.3% kcal among adolescents and teens (9-18 years), mainly due to significant declines in added sugars from sweetened beverages, which remained the top source. Declines in added sugars intakes were observed for all strata, albeit to varying degrees. CONCLUSIONS: Declines in added sugars intakes were observed among children, adolescents, and teens from 2001-2018, regardless of sociodemographic factors, food assistance, physical activity level, or body weight status, but variations in the magnitudes of decline suggest persistent disparities related to race and ethnicity and to income. Despite these declines, intakes remain above the DGA recommendation; thus, continued monitoring is warranted.

Sources of Added Sugars Intake Among the U.S. Population: Analysis by Selected Sociodemographic Factors Using the National Health and Nutrition Examination Survey 2011-18.

Recent estimates of added sugars intake among the U.S. population show intakes are above recommended levels. Knowledge about the sources of added sugars contributing to intakes is required to inform dietary guidance, and understanding how those sources vary across sociodemographic subgroups could also help to target guidance. The purpose of this study was to provide a comprehensive update on sources of added sugars among the U.S. population, and to examine variations in sources according to sociodemographic factors. Regression analyses on intake data from NHANES 2011-18 were used to examine sources of added sugars intake among the full sample (N = 30,678) and among subsamples stratified by age, gender, ethnicity, and income. Results showed the majority of added sugars in the diet (61-66%) came from a few sources, and the top two sources were sweetened beverages and sweet bakery products, regardless of age, ethnicity, or income. Sweetened beverages, including soft drinks and fruit drinks, as well as tea, were the largest contributors to added sugars intake. There were some age-, ethnic-, and income-related differences in the relative contributions of added sugars sources, highlighting the need to consider sociodemographic contexts when developing dietary guidance or other supports for healthy eating.

Comparison of Various Methods to Determine Added Sugars Intake to Assess the Association of Added Sugars Intake and Micronutrient Adequacy.

Different methods for determining the effect of added sugars intake among children and adults on meeting recommended nutrient intakes were compared using 24 h dietary recall data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. Four methods were used to determine deciles of added sugars intake (as the percentage of total calories): 1 day intake, 2 day average intake, and individual usual intake (UI) determined with the National Cancer Institute (NCI) and the multivariate Markov Chain Monte Carlo methods. Percentages of the population below the Estimated Average Requirement (EAR) for calcium and vitamin D/above the Adequate Intake (AI) for potassium and dietary fiber for each decile of added sugars intake were assessed with the NCI method. Using regression analyses, added sugars intake deciles (by any method) in children were inversely associated (p < 0.001) with percentages below the EAR/above the AI of vitamin D, calcium, potassium, and fiber. In adults, added sugars intake deciles were inversely associated with meeting recommendations for vitamin D, potassium, and fiber. There were no significant between-method differences for regression coefficients for any nutrients investigated. Overall, these methods showed a similar association of added sugars intake with nutrient inadequacy/adequacy; therefore, method preference may depend more on practical reasons.

Micronutrient Dilution and Added Sugars Intake in U.S. Adults: Examining This Association Using NHANES 2009-2014.

There is inconsistent evidence regarding the impact of added sugars consumption on micronutrient dilution of the diet. We examined the associations between added sugars intake deciles and nutrient adequacy for 17 micronutrients in U.S. adults 19+ (n = 13,949), 19-50 (n = 7424), and 51+ y (n = 6525) using two days of 24 hour dietary recall data from the National Health and Nutrition Examination Survey (NHANES) 2009-2014 and regression analysis. Added sugars intake deciles ranged from <3.8 to >23.3% of calories among adults 19+ y, with a median intake of 11.0% of calories. Significant associations (p ≤ 0.01) between added sugars intake deciles and percentage of the population below the Estimated Average Requirement (EAR) were found for magnesium, vitamin C, vitamin D, and vitamin E; only the association with magnesium remained significant after dropping the two highest and lowest deciles of intake, suggesting a threshold effect. Intakes below approximately 18% of calories from added sugars were generally not associated with micronutrient inadequacy. However, even at the lower deciles of added sugars, large percentages of the population were below the EAR for these four micronutrients, suggesting that adequate intakes are difficult to achieve regardless of added sugars intake.

Association of Added Sugars Intake with Micronutrient Adequacy in US Children and Adolescents: NHANES 2009-2014.

BACKGROUND: A concern about the excessive consumption of added sugars is the potential for micronutrient dilution, particularly in children and adolescents; however, the evidence is inconsistent. OBJECTIVE: We examined the associations between added sugars intake and micronutrient adequacy in US children and adolescents using data from NHANES 2009-2014. METHODS: Children and adolescents aged 2-18 (n = 7754), 2-8 (n = 3423), and 9-18 y (n = 4331) were assigned to deciles of added sugars intake based on the average of 2 d of dietary recall. Usual intake of micronutrients was determined using 2 dietary recalls and the National Cancer Institute method. Within each age group, regression analyses were used to assess the relationship between added sugars intake decile and percentage of the population below the estimated average requirements (EARs) for 17 micronutrients. RESULTS: Deciles of added sugars intake (percentage of calories) ranged from <6.4 to >22.8 among children and adolescents aged 2-18 y, with a median intake of 13.3% of calories. Significant positive associations (P < 0.01) between added sugars intake and percentage of the population (aged 2-18 y) below the EAR were found only for calcium, magnesium, and vitamin D. These associations virtually disappeared after dropping the 2 highest and lowest deciles of intake, suggesting a threshold effect; intakes below approximately 19% of calories from added sugars were generally not associated with micronutrient inadequacy. CONCLUSIONS: As added sugars intake increased, there was a threshold above which an increase in the prevalence of inadequate intakes for calcium, magnesium, and vitamin D among US children and adolescents was observed. However, even at the lower deciles of added sugars, large percentages of the population were below the EAR for these nutrients, suggesting that adequate intakes of these nutrients are difficult to achieve independent of added sugars intake.

Sources of Added Sugars in Young Children, Adolescents, and Adults with Low and High Intakes of Added Sugars.

High intake of added sugars is associated with excess energy intake and poorer diet quality. The objective of this cross-sectional study (n = 16,806) was to estimate usual intakes and the primary food sources of added sugars across the range of intakes (i.e., deciles) among U.S. children (2-8 years), adolescents and teens (9-18 years), and adults (≥19 years) using the National Health and Nutrition Examination (NHANES) data from 2009-2012. The percent energy contributed by added sugars was 14.3 ± 0.2% (2-8 years), 16.2 ± 0.2% (9-18 years), and 13.1 ± 0.2% (≥19 years), suggesting the highest intakes are among adolescents and teens. However, the primary foods/beverages that contribute to added sugars were remarkably consistent across the range of intakes, with the exception of the lowest decile, and include sweetened beverages and sweet bakery products. Interestingly across all age groups, even those in the lowest decile of added sugars exceed the 10% guidelines. Additional foods contributing to high intakes were candy and other desserts (e.g., ice cream) in children and adolescents, and coffee and teas in adults. Tailoring public health messaging to reduce intakes of these identified food groups may be of utility in designing effective strategies to reduce added sugar intake in the U.S.

Trans fatty acids and cholesterol levels: An evidence map of the available science.

High intakes of industrial trans fatty acids (iTFA) increase circulating low density lipoprotein cholesterol (LDL-C) levels, which has implicated iTFA in coronary heart disease (CHD) risk. Published data on iTFA and LDL-C, however, represent higher intake levels than the U.S. population currently consume. This study used state-of-the-art evidence mapping approaches to characterize the full body of literature on LDL-C and iTFA at low intake levels. A total of 32 independent clinical trials that included at least one intervention or control group with iTFA at ≤3%en were found. Findings indicated that a wide range of oils and interventions were used, limiting the ability to determine an isolated effect of iTFA intake. Few data points were found for iTFA at <3%en, with the majority of low-level exposures actually representing control group interventions containing non-partially hydrogenated (PHO) oils. Further, it appears that few dose-response data points are available to assess the relationship of low levels of iTFA, particularly from PHO exposure, and LDL-C. Therefore, limited evidence is available to determine the effect of iTFA at current consumption levels on CHD risk.

Recommendations on reporting requirements for flavonoids in research.

Numerous observational and intervention-based human studies support the notion of a beneficial role for dietary flavonoids in human health. Despite these studies, it is not yet possible to make dietary recommendations with regard to the types and amounts of flavonoids to be consumed. The inherent diversity of flavonoid structure, chemistry, and natural distribution in foods lends itself to errors in reporting the types and/or amounts of flavonoids consumed, as well as incomplete recognition of requirements for intervention studies that aim to assess their benefits in a clinical setting. A need exists for guidelines that facilitate the design and reporting of flavonoid research. With a focus on clinical studies, this article 1) outlines limitations commonly encountered in the field of flavonoid research, including the inconsistent use of nomenclature, inappropriate analytic methods, inconsistent use of existing flavonoid databases, and the lack of full consideration in the design of test materials for intervention trials, and 2) provides guidance for future studies with a focus on clinical intervention trials. Adoption of this guidance will facilitate more accurate and interpretable research that will support the development of dietary recommendations regarding the intake of flavonoids.

Fortification and health: challenges and opportunities.

Fortification is the process of adding nutrients or non-nutrient bioactive components to edible products (e.g., food, food constituents, or supplements). Fortification can be used to correct or prevent widespread nutrient intake shortfalls and associated deficiencies, to balance the total nutrient profile of a diet, to restore nutrients lost in processing, or to appeal to consumers looking to supplement their diet. Food fortification could be considered as a public health strategy to enhance nutrient intakes of a population. Over the past century, fortification has been effective at reducing the risk of nutrient deficiency diseases such as beriberi, goiter, pellagra, and rickets. However, the world today is very different from when fortification emerged in the 1920s. Although early fortification programs were designed to eliminate deficiency diseases, current fortification programs are based on low dietary intakes rather than a diagnosable condition. Moving forward, we must be diligent in our approach to achieving effective and responsible fortification practices and policies, including responsible marketing of fortified products. Fortification must be applied prudently, its effects monitored diligently, and the public informed effectively about its benefits through consumer education efforts. Clear lines of authority for establishing fortification guidelines should be developed and should take into account changing population demographics, changes in the food supply, and advances in technology. This article is a summary of a symposium presented at the ASN Scientific Sessions and Annual Meeting at Experimental Biology 2014 on current issues involving fortification focusing primarily on the United States and Canada and recommendations for the development of responsible fortification practices to ensure their safety and effectiveness.

Considerations on an approach for establishing a framework for bioactive food components.

Bioactive food components have shown potential health benefits for more than a decade. Currently there are no recommended levels of intake [i.e., Dietary Reference Intakes (DRIs)] as there are for nutrients and fiber. DRIs for essential nutrients were based on requirements for each specific nutrient to maintain normal physiologic or biochemical function and to prevent signs of deficiency and adverse clinical effects. They were later expanded to include criteria for reducing the risk of chronic degenerative diseases for some nutrients. There are many challenges for establishing recommendations for intakes of nonessential food components. Although some nonessential food components have shown health benefits and are safe, validated biomarkers of disease risk reduction are lacking for many. Biomarkers of intake (exposure) are limited in number, especially because the bioactive compounds responsible for beneficial effects have not yet been identified or are unknown. Furthermore, given this lack of characterization of composition in a variety of foods, it is difficult to ascertain intakes of nonessential food components, especially with the use of food-frequency questionnaires designed for estimating intakes of nutrients. Various intermediary markers that may predict disease outcome have been used as functional criteria in the DRI process. However, few validated surrogate endpoints of chronic disease risk exist. Nonvalidated intermediary biomarkers of risk may possibly predict clinical outcomes, but more research is needed to confirm the associations between cause and effect. One criterion for establishing acceptable intermediary outcome indicators may be the maintenance of normal physiologic function throughout adulthood, which presumably would lead to reduced chronic disease risk. Multiple biomarkers of outcomes that demonstrate the same health benefit may also be helpful. It would be beneficial to continue to refine the process of setting DRIs by convening a workshop on establishing a framework for nonessential food components that would take into consideration intermediary biomarkers indicative of optimal health.

Fortification: new findings and implications.

This article reviews the current landscape regarding food fortification in the United States; the content is based on a workshop sponsored by the North American Branch of the International Life Sciences Institute. Fortification of the food supply with vitamins and minerals is a public health strategy to enhance nutrient intakes of the population without increasing caloric intake. Many individuals in the United States would not achieve recommended micronutrient intakes without fortification of the food supply. The achievement and maintenance of a desirable level of nutritional quality in the nation's food supply is, thus, an important public health objective. While the addition of nutrients to foods can help maintain and improve the overall nutritional quality of diets, indiscriminate fortification of foods could result in overfortification or underfortification in the food supply and nutrient imbalances in the diets of individuals. Any changes in food fortification policy for micronutrients must be considered within the context of the impact they will have on all segments of the population and of food technology and safety applications and their limitations. This article discusses and evaluates the value of fortification, the success of current fortification efforts, and the future role of fortification in preventing or reversing nutrient inadequacies.

Are dietary bioactives ready for recommended intakes?

Research has shown that numerous dietary bioactive components that are not considered essential may still be beneficial to health. The dietary reference intake (DRI) process has been applied to nonessential nutrients, such as fiber, yet the majority of bioactive components await a recommended intake. Despite a plethora of new research over the past several years on the health effects of bioactives, it is possible that the field may never reach a point where the current DRI framework is suitable for these food components. If bioactives are to move toward dietary guidance, they will likely require an alternative path to get there.

Strategies to optimize the impact of nutritional surveys and epidemiological studies.

The development of nutrition and health guidelines and policies requires reliable scientific information. Unfortunately, theoretical considerations and empirical evidence indicate that a large percentage of science-based claims rely on studies that fail to replicate. The session "Strategies to Optimize the Impact of Nutrition Surveys and Epidemiological Studies" focused on the elements of design, interpretation, and communication of nutritional surveys and epidemiological studies to enhance and encourage the production of reliable, objective evidence for use in developing dietary guidance for the public. The speakers called for more transparency of research, raw data, consistent data-staging techniques, and improved data analysis. New approaches to collecting data are urgently needed to increase the credibility and utility of findings from nutrition epidemiological studies. Such studies are critical for furthering our knowledge and understanding of the effects of diet on health.

Habitual consumption of eggs does not alter the beneficial effects of endurance training on plasma lipids and lipoprotein metabolism in untrained men and women.

Changes in plasma lipid and apolipoprotein profiles were evaluated in 12 healthy, unfit subjects (VO(2peak) 39.1+/-2.8 ml.kg(-1).min(-1); 5 women, 7 men) at baseline and following endurance exercise training. The exercise protocol consisted of a 6-week endurance exercise training program (4-5 days week(-1); 60 min.session(-1); > or =65% HR(max)). Subjects were randomly assigned to consume an egg- (n=6; 12 eggs.week(-1)) or no-egg (n=6; 0 eggs.week(-1))-based, eucaloric, standardized diet for 8 weeks. Both diets were macronutrient balanced [60% carbohydrate, 30% fat, 10% protein (0.8 g.kg(-1).day(-1))] and individually designed for weight maintenance. Plasma lipids were measured twice within the same week at baseline and following exercise training. At baseline, subjects were normolipidemic with values of 163.9+/-41.8, 84.8+/-36.7, 60.6+/-15.4 and 93.1+/-52 mg dl(-1) for total cholesterol, LDL cholesterol and HDL cholesterol and triglyceride concentrations, respectively. A two-way ANOVA was used to analyze diet and exercise effects and interactions. In both groups, endurance exercise training resulted in a significant 10% increase in HDL-C (P<.05), a 19% decrease in Apo B concentrations (P<.05) and reductions in plasma CETP activity (P<.05). Plasma LDL-C decreased by 21% (P=.06). No main effects of diet or interactions with plasma lipids or Apo B concentrations were observed. These data demonstrate that endurance training improved the plasma lipid profiles of previously unfit, normolipidemic subjects independent of dietary cholesterol intake from eggs.

Gender impacts the post-exercise substrate and endocrine response in trained runners.

BACKGROUND: Although several studies have investigated gender differences in the substrate and endocrine responses during and following endurance exercise, few have studied sex differences during a more prolonged recovery period post endurance exercise. The purpose of this study was to compare and characterize the endocrine and substrate profiles of trained male and female adult runners during the three-and-a-half hour recovery period from an endurance run. METHODS: After consuming a euenergetic diet (1.8 g.kg-1.d-1 protein, 26% fat, 58% carbohydrates, 42.8 +/- 1.2 kcal/kg body weight) for 8 days, blood was collected from trained male (n = 6, 21 yrs, 70 kg, 180 cm, 9% body fat, VO(2peak) 78.0 +/- 3.4 mL.kg FFM-1.min-1) and female (n = 6, 23 y, 66 kg, 170 cm, 29% body fat, VO(2peak) 71.6 +/- 4.5 mL.kg FFM-1.min-1) endurance runners at rest and during recovery from a 75 min run at 70% VO(2peak). Circulating levels of glucose, lactate, free fatty acids (FFAs), insulin, cortisol, growth hormone (GH), and free insulin-like growth factor I (IGF-I) were measured. RESULTS: During the recovery period, females experienced increases in glucose, lactate and insulin while no changes were noted in men (P < 0.05). Males experienced increases in GH and decreases in IGF-I levels respectively (P < 0.05) while no changes were observed in females. FFA levels increased during recovery from endurance exercise, but changes were not different between genders. CONCLUSION: These data further document gender differences in substrate and endocrine changes during a prolonged recovery period following endurance exercise. Future studies are needed to evaluate the effect of differing diets and nutritional supplements on these gender-specific post-exercise substrate and endocrine differences.

The effects of nutritional supplementation throughout an endurance run on leucine kinetics during recovery.

This study determined the effect of nutritional supplementation throughout endurance exercise on whole-body leucine kinetics (leucine rate of appearance [Ra], oxidation [Ox], and nonoxidative leucine disposal [NOLD]) during recovery. Five trained men underwent a 2-h run at 65% VO(2max), during which a carbohydrate (CHO), mixed protein-carbohydrate (milk), or placebo (PLA) drink was consumed. Leucine kinetics were assessed during recovery using a primed, continuous infusion of 1-13C leucine. Leucine Ra and NOLD were lower for milk than for PLA. Ox was higher after milk-supplemented exercise than after CHO or PLA. Although consuming milk during the run affected whole-body leucine kinetics, the benefits of such a practice for athletes remain unclear. Additional studies are needed to determine whether protein supplementation during exercise can optimize protein utilization during recovery.