Colleen X. Munoz

Metabolic characteristics of keto-adapted ultra-endurance runners.

BACKGROUND Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations. METHODS Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n=10, %carbohydrate:protein:fat=59:14:25) diet, and the other a low-carbohydrate (LC; n=10, 10:19:70) diet for an average of 20 months (range 9 to 36 months). RESULTS Peak fat oxidation was 2.3-fold higher in the LC group (1.54±0.18 vs 0.67±0.14 g/min; P=0.000) and it occurred at a higher percentage of VO2max (70.3±6.3 vs 54.9±7.8%; P=0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21±0.02 vs 0.76±0.11 g/min; P=0.000) corresponding to a greater relative contribution of fat (88±2 vs 56±8%; P=0.000). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (-64% from pre-exercise) and 120 min of recovery (-36% from pre-exercise). CONCLUSION Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.

Hydration biomarkers and dietary fluid consumption of women.

Normative values and confidence intervals for the hydration indices of women do not exist. Also, few publications have precisely described the fluid types and volumes that women consume. This investigation computed seven numerical reference categories for widely used hydration biomarkers (eg, serum and urine osmolality) and the dietary fluid preferences of self-reported healthy, active women. Participants (n=32; age 20±1 years; body mass 59.6±8.5 kg; body mass index [calculated as kg/m(2)] 21.1±2.4) were counseled in the methods to record daily food and fluid intake on 2 consecutive days. To reduce day-to-day body water fluctuations, participants were tested only during the placebo phase of the oral contraceptive pill pack. Euhydration was represented by the following ranges: serum osmolality=293 to 294 mOsm/kg; mean 24-hour total fluid intake=2,109 to 2,506 mL/24 hours; mean 24-hour total beverage intake=1,300 to 1,831 mL/24 hours; urine volume=951 to 1,239 mL/24 hours; urine specific gravity=1.016 to 1.020; urine osmolality=549 to 705 mOsm/kg; and urine color=5. However, only 3% of women experienced a urine specific gravity <1.005, and only 6% exhibited a urine color of 1 or 2. Water (representing 45.3% and 47.9% of 24-hour total fluid intake), tea, milk, coffee, and fruit juice were consumed in largest volumes. In conclusion, these data provide objective normative values for hyperhydration, euhydration, and dehydration that can be used by registered dietitians and clinicians to counsel women about their hydration status.

Assessment of hydration biomarkers including salivary osmolality during passive and active dehydration

BACKGROUND/OBJECTIVES:Hydration state can be assessed via body mass change (BMΔ), serum and urine osmolality (Sosm, Uosm), urine-specific gravity (Usg) and urine volume (Uvol). As no hydration index has been shown to be valid in all circumstances, value exists in exploring novel biomarkers such as salivary osmolality (Vosm). Utilizing acute BMΔ as the reference standard, this research examined the efficacy of Sosm, Vosm, Uosm, Uvol and Usg, during passive (PAS) and active (ACT) heat exposure.SUBJECTS/METHODS:Twenty-three healthy men (age, 22±3 years; mass, 77.3±12.8 kg; height, 179.9±8.8cm; body fat, 10.6±4.5%) completed two randomized 5-h dehydration trials (36±1 °C). During PAS, subjects sat quietly, and during ACT, participants cycled at 68±6% maximal heart rate. Investigators measured all biomarkers at each 1% BMΔ.RESULTS:Average mass loss during PAS was 1.4±0.3%, and 4.1±0.7% during ACT. Significant between-treatment differences at −1% BMΔ were observed for Sosm (PAS, 296±4; ACT, 301±4 mOsm/kg) and Uosm (PAS, 895±207; ACT, 661±192 mOsm/kg). During PAS, only Uosm, Uvol and Usg increased significantly (−1 and −2% BMΔ versus baseline). During ACT, Vosm most effectively diagnosed dehydration ⩾2% (sensitivity=86%; specificity=91%), followed by Sosm (sensitivity=83%; specificity=83%). Reference change values were validated for Sosm, Usg and BMΔ.CONCLUSIONS:The efficacy of indices to detect dehydration ⩾2% differed across treatments. At rest (PAS), only urinary indices increased in concert with body water loss. During exercise (ACT), Sosm and Vosm exhibited the highest sensitivity and specificity. Sosm, Usg and BMΔ exhibited validity in serial measurements. These findings indicate hydration biomarkers should be selected by considering daily activities.

Interpreting common hydration biomarkers on the basis of solute and water excretion

Background/Objectives:This investigation evaluated 12 hydration biomarkers, to determine which represent 24-h whole-body water balance (that is, measured as water retention or clearance (WR-C) by the kidneys).Subjects/Methods:Healthy males (n=59; body mass, 75.1±7.9 kg; height, 178±6 cm; age, 22±3 years; body mass index, 23.9±2.4 kg/m2) met with a registered dietitian each morning (days 1–11) to optimize completeness and accuracy of food and fluid records, then went about ordinary daily activities. These men visited the laboratory for blood samples and collected all urine produced on days 1, 3, 6, 9 and 12. The reference standard (WR-C) was calculated using 24-h urine volume, 24-h urine osmolality, and serum osmolality (single morning venous sample).Results:Statistical regression analyses indicated that, among the 12 hydration biomarkers, only 24-h urine osmolality (r2=0.60, P<0.0001) and 24-h urine specific gravity (r2=0.52, P<0.0001) strongly predicted WR-C. The 24-h fluid intake, 24-h body mass change, 24-h urine color and 24-h urine volume were weak (P>0.05) predictors of WR-C, similar to serum osmolality and other single measurements (range of r2 values, 0.19–0.0001).Conclusions:These observations of healthy, active young men demonstrate that WR-C is strongly related to the 24-h concentration of urine, which in turn reflects the excretion of total solids in the diet. Although morning urine assessments provided information about a single time point, 24-h urine osmolality and 24-h urine specific gravity were the best predictors of 24-h body water balance.

Effects of theobromine and caffeine on mood and vigilance.

Abstract Like caffeine, theobromine crosses the blood-brain barrier and binds to adenosine receptors, suggesting it might share caffeine’s beneficial effects on mood and vigilance. Therefore, the purpose of this study was to assess the effect of theobromine doses commonly found in foods on mood and vigilance parameters sensitive to caffeine. Caffeine was tested as a positive control. Twenty-four men (age, 23 [3] years) completed 6 double-blind trials during which they consumed experimental beverages, assessed their mood using standardized self-report questionnaires, and completed a 2-hour visual vigilance task. Three experimental doses (100, 200, and 400 mg theobromine) were delivered in a cocoa-based beverage; 3 matched control treatments (0 mg theobromine, 400 mg theobromine, and 100 mg caffeine) were delivered in a non–cocoa beverage. Mean salivary concentrations of theobromine exhibited significant dose-dependent differences (400 mg trials > 200 mg trial > 100 mg trial > 0 mg trials; P < 0.005). At every dose tested, theobromine failed to consistently affect mood state or vigilance (P > 0.05), but 100-mg caffeine significantly decreased lethargy/fatigue and increased vigor (P = 0.006 and 0.011, respectively). These findings indicate theobromine does not influence mood and vigilance when administered in nutritionally relevant doses, despite sharing many of caffeine’s structural characteristics.

Habitual total water intake and dimensions of mood in healthy young women

Acute negative and positive mood states have been linked with the development of undesirable and desirable health outcomes, respectively. Numerous factors acutely influence mood state, including exercise, caffeine ingestion, and macronutrient intake, but the influence of habitual total water intake remains unknown. The purpose of this study was to observe relationships between habitual water intake and mood. One hundred twenty healthy females (mean ± SD; age = 20 ± 2 y, BMI = 22.9 ± 3.5 kg⋅m(-2) ) recorded all food and fluids consumed for 5 consecutive days. Investigators utilized dietary analysis software to determine Total Water Intake (TWI; total water content in foods and fluids), caffeine, and macronutrient consumption (i.e. protein, carbohydrate, fat). On days 3 and 4, participants completed the Profile of Mood State (POMS) questionnaire, which examined tension, depression, anger, vigor, and confusion, plus an aggregate measure of Total Mood Disturbance (TMD). For comparison of mood, data were separated into three even groups (n = 40 each) based on TWI: low (LOW; 1.51 ± 0.27 L/d), moderate (MOD; 2.25 ± 0.19 L/d), and high (HIGH; 3.13 ± 0.54 L/d). Regression analysis was performed to determine continuous relationships between measured variables. Group differences (p < 0.05) were observed for tension (MOD = 7.2 ± 5.4, HIGH = 4.4 ± 2.9), depression (LOW = 4.5 ± 5.9, HIGH = 1.7 ± 2.3), confusion (MOD = 5.9 ± 3.4, HIGH = 4.0 ± 2.1), and TMD (LOW=19.0 ± 21.8, HIGH=8.2 ± 14.2). After accounting for other mood influencers, TWI predicted TMD (r(2) = 0.104; p = 0.050). The above relationships suggest the amount of water a woman consumes is associated with mood state.

An empirical method to determine inadequacy of dietary water

OBJECTIVES The physiological regulation of total body water and fluid concentrations is complex and dynamic. The human daily water requirement varies because of differences in body size, dietary solute load, exercise, and activities. Although chronically concentrated urine increases the risk of renal diseases, an empirical method to determine inadequate daily water consumption has not been described for any demographic group; instead, statistical analyses are applied to estimate nutritional guidelines (i.e., adequate intake). This investigation describes a novel empirical method to determine the 24-h total fluid intake (TFI; TFI = water + beverages + moisture in food) and 24-h urine volume, which correspond to inadequate 24-h water intake (defined as urine osmolality of 800 mOsm/kg; U800). METHODS Healthy young women (mean ± standard deviation; age, 20 ± 2 y, mass, 60.8 ± 11.7 kg; n = 28) were observed for 7 consecutive days. A 24-h urine sample was analyzed for volume and osmolality. Diet records were analyzed to determine 24-h TFI. RESULTS For these 28 healthy young women, the U800 corresponded to a TFI ≥2.4 L/d (≥39 mL/kg/d) and a urine volume ≥1.3 L/d. CONCLUSIONS The U800 method could be employed to empirically determine 24-h TFI and 24-h urine volumes that correspond to inadequate water intake in diverse demographic groups, residents of specific geographic regions, and individuals who consume specialized diets or experience large daily water turnover. Because laboratory expertise and instrumentation are required, this technique provides greatest value in research and clinical settings.

Accuracy of Urine Color to Detect Equal to or Greater Than 2% Body Mass Loss in Men.

CONTEXT Clinicians and athletes can benefit from field-expedient measurement tools, such as urine color, to assess hydration state; however, the diagnostic efficacy of this tool has not been established. OBJECTIVE To determine the diagnostic accuracy of urine color assessment to distinguish a hypohydrated state (≥2% body mass loss [BML]) from a euhydrated state (<2% BML) after exercise in a hot environment. DESIGN Controlled laboratory study. SETTING Environmental chamber in a laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty-two healthy men (age = 22 ± 3 years, height = 180.4 ± 8.7 cm, mass = 77.9 ± 12.8 kg, body fat = 10.6% ± 4.6%). INTERVENTION(S) Participants cycled at 68% ± 6% of their maximal heart rates in a hot environment (36°C ± 1°C) for 5 hours or until 5% BML was achieved. At the point of each 1% BML, we assessed urine color. MAIN OUTCOME MEASURE(S) Diagnostic efficacy of urine color was assessed using receiver operating characteristic curve analysis, sensitivity, specificity, and likelihood ratios. RESULTS Urine color was useful as a diagnostic tool to identify hypohydration after exercise in the heat (area under the curve = 0.951, standard error = 0.022; P < .001). A urine color of 5 or greater identified BML ≥2% with 88.9% sensitivity and 84.8% specificity (positive likelihood ratio = 5.87, negative likelihood ratio = 0.13). CONCLUSIONS Under the conditions of acute dehydration due to exercise in a hot environment, urine color assessment can be a valid, practical, inexpensive tool for assessing hydration status. Researchers should examine the utility of urine color to identify a hypohydrated state under different BML conditions.

Hormonal and Thirst Modulated Maintenance of Fluid Balance in Young Women with Different Levels of Habitual Fluid Consumption.

Background: Surprisingly little is known about the physiological and perceptual differences of women who consume different volumes of water each day. The purposes of this investigation were to (a) analyze blood osmolality, arginine vasopressin (AVP), and aldosterone; (b) assess the responses of physiological, thirst, and hydration indices; and (c) compare the responses of individuals with high and low total water intake (TWI; HIGH and LOW, respectively) when consuming similar volumes of water each day and when their habitual total water intake was modified. Methods: In a single-blind controlled experiment, we measured the 24 h total water intake (TWI; water + beverages + food moisture) of 120 young women. Those who consumed the highest (HIGH, 3.2 ± 0.6 L·day−1, mean ± SD) and the lowest (LOW, 1.6 ± 0.5 L·day−1) mean habitual TWI were identified and compared. Outcome variables were measured during two ad libitum baseline days, a four-day intervention of either decreased TWI (HIGH) or increased TWI (LOW), and one ad libitum recovery day. Results: During the four-day intervention, HIGH and LOW experienced differences in thirst (p = 0.002); also, a statistically significant change of AVP occurred (main effect of TWI and day, p < 0.001), with no effect (TWI or day) on aldosterone and serum osmolality. Urine osmolality and volume distinguished HIGH from LOW (p = 0.002) when they consumed similar 24 h TWI.

Hydration status affects mood state and pain sensation during ultra-endurance cycling.

Abstract Laboratory-based studies indicate mild dehydration adversely affects mood. Although ultra-endurance events often result in mild to moderate dehydration, little research has evaluated whether the relationship between hydration status and mood state also exists in these arduous events. Therefore, the purpose of this study was to evaluate how hydration status affected mood state and perceptual measures during a 161 km ultra-endurance cycling event. One hundred and nineteen cyclists (103 males, 16 females; age = 46 ± 9 years; height = 175.4 ± 17.9 cm; mass = 82.8 ± 16.3 kg) from the 2011 and 2013 Hotter’N Hell events participated. Perceived exertion, Thermal, Thirst, and Pain sensations, Brunel Profile of Mood States, and urine specific gravity (USG) were measured pre- (~1 h before), mid- (~97 km), and post-ride. Participants were classified at each time point as dehydrated (USG ≥ 1.022) or euhydrated (USG ≤ 1.018). Independent of time point, dehydrated participants (USG = 1.027 ± 0.004) had decreased Vigour and increased Fatigue, Pain, Thirst, and Thermal sensations compared to euhydrated participants (USG = 1.012 ± 0.004; all P < 0.01). USG significantly correlated with Fatigue (r = 0.36), Vigour (r = −0.27), Thirst (r = 0.15), and Pain (r = 0.22; all P < 0.05). In conclusion, dehydrated participants had greater Fatigue and Pain than euhydrated participants. These findings indicate dehydration may adversely affect mood state and perceptual ratings during ultra-endurance cycling.