Energy metabolism and hydration -
Theoretically, it can be evaluated that water loss through feces excretion is 25— g among people with a normal gastrointestinal function every day.
Water loss from feces excretion can be determined more accurately using the direct drying method. In this study, the primary objective was to determine the TEE of young adults using the doubly labeled water method. The secondary objective was to measure the water sources and losses of the human body.
These data could provide useful reference data for the development of recommendations on energy value and water intake. For the formula, α was set as 0.
A total of 25 young adults aged 18—23 years were recruited by offline campus propaganda from one college in Baoding, Hebei Province, China. The inclusion criteria were as follows: the age of participants was between 18 and 23 years; the participants were in a healthy state.
Females who were being in menstrual cycle or pregnant were also excluded. The study protocol and instruments were reviewed and approved by the Ethical Review Committee of Peking University.
The code of identification is IRB The study was registered on the website of Chinese clinical trial registry, and the code of identification is ChiCTR The study was conducted in accordance with the guidelines of the Declaration of Helsinki. Prior to the conduction of the study, all the participants read and voluntarily signed informed consent.
The cross-sectional study lasted 14 days. on the first day, the morning urine samples of the participants were collected and tested as baseline data. The height and weight of the participants were measured to calculate their body mass index BMI.
for isotope labeling. Then, 2 mL urine sample was collected 2 h, 4 h, 6 h, and 8 h after taking double-labeled water.
Over the next 13 days, 2 mL of urine was collected at a. every morning from day 2 to 14 to test isotopic abundance. In7 was used from day 1 to day 7, and the water-intake behaviors of the participants were evaluated and recorded using uniformly customized cup with scale to the nearest of 5 mL as reference.
All the participants' feelings of thirst were evaluated by the visual analog score questionnaire when water-intake behaviors happened. From day 5 to day 7, the weighing method combined with duplicate proportion method was used to weigh and record all foods taken by the participants, and the direct drying method was used to measure the water intake from food.
The corresponding chemical analysis method was used to determine the protein, fat, carbohydrate, and total ash in the food, respectively. The "3-day, h, real-time urine-excretion record" and "3-day, h, real-time fecal-excretion record" were used to record all the urine and feces excretion samples among the participants in real-time for 3 days.
All urine and feces excretion samples were weighed. The direct drying method was used to measure the water content in feces.
Cubital venous blood was collected on day 5, and plasma osmolality was determined. From day 1 to day 14, the physical activity record form was filled in to analyze the physical activity among the participants. In addition, data on the temperature, humidity, and wind speed of the environment where the participants located during these days were recorded in real-time.
In the whole process of the study, participants who failed to meet these requirements needed to let investigators know. Finally, all participants finished the study, and no one failed to meet the requirements. The indicators collected at different time points in the study are shown in Table 1.
The flow diagram was shown in Fig. Weight and height were measured by trained investigators according to relevant standards and procedures. Wearing light clothing and no footwear, height was measured twice with 0. In7 has been verified to be accurate and effective for evaluating fluid intake and used in this study [ 20 , 21 ].
The participants were trained to record all fluid intake behaviors for 7 consecutive days. The type, amount, time, and place of fluid intake were recorded in detail. For assisting the participants to evaluate the amount of fluid intake, uniformly customized cups with scale to the nearest of 5 mL were provided for every participant as reference.
All types of fluid, including tap water, bottled water, and other beverages, were counted. All food in 3 consecutive days, including two working days and one non-working day, was recorded and weighted using electronic balance YP, SPC, Shanghai, China.
The weight of each food before and after eating including inedible and inedible parts, such as bones was weighted, and then the actual amount was calculated g. Using the method of duplicate portion sampling, the same backup food samples were collected for testing of macronutrient intake and water intake from foods [ 22 ].
Test of water intake from foods: The water content in food was tested using the direct drying method according to the National Food Safety Standard GB Then, the percentage of water content in food and water intake from food were calculated [ 22 ].
Test of energy value from food: The protein content in food was tested using the Kjeldahl determination method according to the National Food Safety Standard GB The fat content in food was tested using the acid hydrolysis method according to the National Food Safety Standard GB The ash content in food was tested using the method according to the National Food Safety Standard GB The carbohydrate content in food was calculated by subtracting the total weight of the food sample from the weight of protein, fat, ash, and water in the food sample.
Measurement of water loss from urine excretion: Starting with the second voiding on one day and ending with the first voiding on next day, all urine samples were collected as total 24 h urine volume, which was calculated as water loss through urine excretion in a day.
Urine volume was measured with the accuracy of 0. Cubital venous blood was also used to test plasma osmolality, which can reflect the hydration status.
Plasma osmolality was determined using osmolality meter SMC 30C, Tianhe, Tianjin, China. Measurement of water loss from feces excretion: Feces samples were measured with an accuracy of 0.
Additionally, the water content in feces was tested using the direct drying method according to the National Food Safety Standard GB The difference between the original weight of fecal sample and the constant weight after drying was the water content of fecal sample. A stable isotope mass spectrometer MAT plus; Thermo Fisher Scientific; Massachusetts, USA and multi-purpose on-line gas preparation and introduction device Gas BenchII; Thermo Fisher Scientific; Massachusetts, USA were used to determine the isotopic abundance in the urine of the participants [ 19 , 27 ].
Analysis of hydrogen isotopes using H 2 -H 2 O equilibrium method: The chromatographic column temperature was set at 70 °C. The procedure was as follows: 0. After inflation, the bottle stood at 25 °C for 1 h.
Then, after the isotopic exchange between gas H 2 and hydrogen, gas H 2 and miscellaneous gas were separated through the chromatographic column before entering the stable isotope mass spectrometer for testing. Three national reference samples, including QYTB Beijing water , QYTB1 seawater , and QYTB2 Tibet water , were used in the test.
The accuracy of hydrogen isotope analysis of standard samples reached 0. Analysis of oxygen isotopes by CO 2 -H 2 O equilibrium method: The chromatographic column temperature was set at 70 °C. After inflation, 0. After the isotopic exchange between oxygen in gas CO 2 and oxygen in samples, gas CO 2 and miscellaneous gas were separated through the chromatographic column before entering the stable isotope mass spectrometer for testing.
The accuracy of oxygen isotope analysis of standard samples reached 0. The determination on subjective thirst sensation and urinary urgency, physical activity, temperature, humidity, and wind speed is described in the Additional file 1.
Unification of study procedure and training: Standardized training was conducted for investigators to make them familiar with all procedures of each step.
Unified training was conducted for the participants to make them understand how to fill in the corresponding questionnaires, how to collect relevant samples, and be familiar with the procedures that they need to participate in.
After the study began, the whole process was strictly supervised and quality controlled by special quality-control researchers. At a. on day 1, the participants were required to measure their weight after emptying morning urine. The amount of double-labeled water for each participant was calculated accurately according to the weight.
At the same time, mL of distilled water for mouthwash was weighed for each participant. The participants drank and swallowed the double-labeled water within the specified time and rinsed their mouths according to the specified process. The method of determination on isotopic abundance was accurate.
During the test, when the internal accuracy was lower than 0. The external accuracy of the data and the stability of the instrument were tested for the parallel samples every 10 samples.
SAS 9. The mean and standard deviation SD were used to describe the quantitative parameters in line with the normal distribution, and a T-test was used to analyze the indexes of different groups of participants.
The median and interquartile were used to describe the quantitative parameters not in line with the normal distribution, and Mann—Whitney U test was used to analyze these indexes of different groups of participants.
Count data were presented as n percentage , and the method of Chi-square test was used to analyze these indexes of different groups of participants. The significance levels were set at 0. The formulas on the indexes related to the determination of doubly labeled water, the calculation on the metabolic water, water loss through skin evaporation, and respiration are described in the Additional file 2.
All participants finished the study. The average age of these 25 young adults was The height, weight, BMI, body surface area, and physical activity were The average temperature indoors and outdoors of the dormitory and classroom, canteen, and playground from day 1 to 14 was The average humidity indoors and outdoors of the dormitory and classroom, canteen, and playground was The average wind speed of the dormitory, classroom, canteen, and playground was 0.
According to the corresponding table of absolute humidity and relative humidity atmospheric pressure: 1 bar , the absolute humidity was calculated as 8. Among 25 participants, the median number of 24 h fluid intake was 5 2. The percentage of no sensation of thirst, initial sensation of thirst, a strong sensation of thirst, and super sensation of thirst was 5.
The median 24 h urination was 6 2. The percentage of no sensation to urinate, initial sensation or urge to urinate, strong urge to urinate, and super urge to urinate was 6. The average plasma osmolality was No statistically significant difference was found in plasma osmolality between females and males Among 25 participants, the median protein, fat, and carbohydrate intake was The energy provided by protein, fat, and carbohydrate accounted for The median energy value and TEE were There was a statistical difference in the energy value and TEE between females and males The amount of fluid intake, water intake from food, and metabolic water accounted for There was a statistical difference in the percentage of metabolic water and TEE between females and males The amount of water loss through urine excretion, skin evaporation, respiration, and feces excretion accounted for In this study, the energy expenditure, sources, and loss of water among young adults were determined.
In China, the data of direct determination of total energy expenditure by doubly labeled water method are limited. Some studies have also pointed out that although the results of the doubly labeled water method were more accurate, the results were also affected by region, physical activity, food intake, physical health status, and so on.
The increase in physical activity among people also significantly increases their TEE. The research conducted by Luo Wei et al. In , it was proposed by the United States that water requirement was 1—1. Thus, water requirement of participants in this study can be calculated. The results of this study showed that the proportion of metabolic water accounting for the total water sources was the smallest, which was only about one-tenth of the total water sources.
This study found that the total water intake of young adults was mL, of which the median daily fluid intake was mL, and the median water intake from food was mL. Compared with the results of studies carried out in similar populations in the same region, the average daily fluid intake was mL, and the average water intake from food was mL among young male adults in Hebei Province in a study conducted in [ 9 ].
The results of another study in found that the daily fluid intake was mL and the water intake from food was mL [ 32 ]. Calculated separately by sex, the median water intake from food among young male adults in this study mL was close to the results of the study in , and the water intake from food among young male and female adults mL was close to the results of the study in [ 32 ].
The amount of water intake among different population groups varied widely. The fluid intake among participants in the study was lower than those of the two studies in and [ 9 , 32 ].
Fluid intake and water intake from food were the two main water sources for young adults, and they accounted for a high proportion of the total water sources.
This conclusion was inconsistent with the data of European and American countries. This discrepancy may be due to the different dietary structure and habits of the population between China and European and American countries. The dietary structure of Chinese residents is mainly plant foods with rich water content, and the most common cooking methods are steaming, stewing, and frying.
These cooking methods not only retain most of the original water in the food but also add water during cooking. The dietary structure of European and American countries is mainly animal food with relatively low water content, and the food cooking method is mainly baking, which loses most of the water in food [ 1 , 33 , 34 ].
The data on water intake from different sources would be useful to develop a recommendation on adequate water intake for the Chinese population. This study found that the median daily urine excretion of young adults was mL.
The survey among male adult college students in Hebei Province in showed that the daily urine excretion was mL [ 9 ]. Another study conducted among young adults in Hebei in showed that the daily urine excretion was mL [ 32 ]. The results of this study were similar to those of the above two studies.
In this study, urine excretion accounts for Urine excretion was the main method of water loss. The participants did not carry out moderate- to high-intensity physical activities during the study, and they mainly carried out mild physical activities every day.
Therefore, the formula used in this study was mainly to calculate the amount of non-dominant sweating, which was mainly affected by body surface area and ambient temperature and humidity.
The results of this study showed that the water loss through skin evaporation and respiration accounted for In the study, the average number of feces was 0. The results of water loss through feces excretion were 64 mL, and the proportion of water loss through feces excretion in the total water loss of the human body was the smallest.
It was also generally recognized in some other studies that the water loss through the digestive tract by the human body is — mL every day [ 10 , 12 , 35 ].
The determination of water loss would be useful to estimate water requirements and develop a recommendation on adequate water intake. This study has some strengths and weaknesses. Referring to the participants, these young adults were recruited from a university, so their sources of food and places of physical activity were similar.
They were basically in an environment with relatively unified quality criteria. The age range of the participants was concentrated, which can analyze the energy expenditure, water sources, and water loss more precisely.
The method used to determine the energy expenditure, sources, and loss of water was considered the gold standard. Additionally, this was the first study to analyze the amount and the proportion of water sources and losses in the human body in China. In consideration of weakness, a larger sample can provide more representative data.
Only young adults, excluding people at other physiological stages, such as elderly and pregnant women, were studied. Energy value and expenditure, water sources and losses, and their proportions are affected by many factors, including age, gender, physiological stage, physical activity level, and so on.
More research is needed to be conducted. In this study, plasma osmolality was also determined to reflect the hydration state of the participants.
Studies with participants in optimal hydration status may provide more information and useful reference data for developing recommendations of adequate water intake.
The results of this study provide reference data for the development of reference intake on energy and water intake. It is necessary to conduct more high-quality studies to determine the energy expenditure, sources, and loss of water among young adults and populations in other physiological stages or other occupations.
The corresponding author will provide the data in a de-identified form used in the manuscript, code book, and analytic code available to editors upon request either before or after publication.
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A formula to estimate the approximate surface area if height and weight be known. And another study , published in the International Journal of Sports Medicine , found that dehydration increases your body's production of cortisol, the stress hormone.
These are just a few examples of what else water can do:. Scientists still don't know the exact mechanism, but given water's important role in the majority of your bodily functions, it makes sense that it would be instrumental in skin health, too. In a study published in the journal Clinical, Cosmetic and Investigational Dermatology , researchers found that increasing water intake would affect the skin the same way as a topical moisturizer and could positively impact normal skin physiology, including elasticity the loss of which is related to sagging and wrinkles.
This makes it tougher for blood to flow where it needs to flow, increasing the stress placed on the heart. In addition, when your body's cells don't have enough water, the brain secretes a chemical that constricts the blood vessels, which can lead to hypertension or high blood pressure, which in turn can increase the risk of stroke and heart disease.
Staying hydrated keeps your blood vessels from constricting so blood can flow normally. You've probably heard the common "eight 8-ounce glasses per day" rule, but the reality is, the amount of water needed varies greatly depending on age, gender, health, physical activity, tendency to sweat, and more.
The majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide, according to the National Academies of Sciences, Engineering, and Medicine, or NASEM. The average American adult drinks nearly five cups of water a day, according to the Centers for Disease Control and Prevention.
The general recommendation from the NASEM is approximately 91 ounces about 11 cups of water each day for women and approximately ounces about 15 and a half cups for men.
One way to determine whether you're drinking enough water is to peek in the pot after you pee. Aim for light yellow. The science does show that drinking water may facilitate weight loss and encourage other positive health outcomes. But drinking more water should be only one small part of your wellness journey.
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Michael Boschmann, Jochen Metaoblism, Uta Hille, Jens Tank, Frauke Adams, Arya M. Sharma, Susanne Nad, Friedrich C. Drinking Metabolis, of water is commonly espoused Healthy heart support weight Healthy heart support regimens and is regarded as healthy; however, few systematic studies address this notion. In 14 healthy, normal-weight subjects seven men and seven womenwe assessed the effect of drinking ml of water on energy expenditure and substrate oxidation rates by using whole-room indirect calorimetry. The effect of water drinking on adipose tissue metabolism was assessed with the microdialysis technique.Video
Metabolism \u0026 Nutrition, Part 1: Crash Course Anatomy \u0026 Physiology #36 Welcome hyxration the new-look MARS. See something that needs attention? Healthy heart support our "Send Hydeation link at page bottom. etd Mason Electronic Theses and Dissertations. College of Health and Human Services. The Effects of Drinking Water on Resting Energy Expenditure.
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