Fluid intake of adults in four Chinese cities

Authors


G Ma, National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing 100021, China. E-mail: mags@chinacdc.cn. Phone: +8610-67776285. Fax: +8610-67711815.

Abstract

To investigate the fluid intake and knowledge on water and health in Chinese adults, and to provide a scientific basis for the development of adequate water intake values for people in China. A total of 1,483 adults aged 18–60 years were selected from four provincial capital cities using a multiple-stage random sampling method. The information on the amounts and types of daily fluid intake was collected using a 24-h fluid intake record for 7 consecutive days. Trained interviewers used a questionnaire to assess knowledge on water. The median of daily total fluid intake was 1,488 mL, with a wide range from 86 mL to 7,036 mL. Significant differences were found for fluid intake among the four cities. The medians of daily intakes of plain water, tea, and beverages were 786 mL, 109 mL, and 186 mL, respectively. Approximately 32% of the subjects drank less water than the amount recommended by the Chinese Nutrition Society (1,200 mL/day) and 71.6% of participants lacked knowledge of these recommendations. Moreover, 48.3% of them drank water only when they felt thirsty.

INTRODUCTION

Water is the major component of the human body and accounts for approximately 60–70% of body mass.1,2 Water serves as the essential solvent for cellular biochemical reactions, and life will terminate without it. Nevertheless, overconsumption of water can impair physiological function and health. Therefore, an appropriate water intake that balances losses and thereby assures adequate hydration of body tissues plays a vital role in human health and life.3,4 International organizations and some countries proposed the recommended dietary reference values for water based on the fluid intake studies.3,5,6 For China, however, limited information on fluid intake is available. In order to determine the drinking water intake of the Chinese population and to provide scientific evidence for the development of adequate intake (AI) recommendations for water, a study on fluid intake was carried out among Chinese adults in and near the following four cities: Beijing, Shanghai, Chengdu, and Guangzhou, in 2010.

SUBJECTS AND METHODS

Sampling procedure

A multiple-stage random sampling method was used for subject selection. First, the cities of Beijing, Shanghai, Chengdu, and Guangzhou were selected. Second, one urban and one rural area were randomly selected from each city. Third, two streets/towns were randomly selected from each area. Fourth, two neighborhood committees/villages were randomly selected from each selected street/town. Finally, 12 subjects (6 men and 6 women) were randomly selected from each of four age groups (age ranges: 18–29 years, 30–39 years, 40–49 years, and 50–60 years). Participants were excluded if they hadbeen diagnosed in the past 5 years with liver, kidney, intestinal, heart, or endocrine disease that was not well controlled.

The Ethical Review Committee of the National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention approved the study protocol. Written consent was obtained from all subjects.

Assessment of daily fluid intake

Fluid intake in our study consisted of the following three sources: 1) plain water, including tap water, mineral water, and purified water; 2) tea, including brewed green tea, semi-fermented tea, and fermented tea; and 3) beverages, including tea drinks, carbonated soft drinks, fruit and vegetable drinks, protein drinks (milk, yogurt, milk drinks), functional drinks, solid drinks, and coffee. The total amount of fluid intake was the sum of the amounts of these three sources.

A 24-h fluid record was used to collect the information on fluid intake for 7 consecutive days. Subjects recorded the type, place, and amount of fluid during eight occasions, including before breakfast, during breakfast, after breakfast, during lunch, after lunch, during dinner, after dinner, and during night.

On the first day, investigators introduced a standard container that was used to record the amounts of the water consumed during the following 7 days. The subjects then recorded daily amounts of water by themselves. To ensure record completeness, investigators interviewed each subject by telephone every 2 days.

In the Chinese Dietary Guidelines issued in 2007, the Chinese Nutrition Society recommended that Chinese adults who perform light physical activity at a moderate environmental temperature should drink at least 1,200 mL water a day,2 which was used as a criterion in this study to classify whether the participants' daily water intake was adequate.

Assessment of knowledge of water and health

Participant knowledge of the effects of water on health was assessed using a questionnaire administered by trained interviewers.

Statistical analyses

The median and the quartile range were used to describe the average amount of daily fluid intake because the amount of fluid intake was found to have a positively skewed distribution. The Kruskal-Wallis rank-sum test was used to compare gender, city, and area differences in the amount of fluid intake. All statistical analyses were performed with SAS 9.1 software (SAS Institute Inc, Cary, NC). A two-tailed P value of <0.05 was regarded as statistically significant.

RESULTS

A total of 1,483 subjects (738 men and 745 women) completed the data collection. The sample sizes are shown in Table 1.

Table 1.  Urban, rural, and total sample sizes of participant groups in and around four cities in China.
ParticipantsTotalBeijingShanghaiChengduGuangzhou
UrbanRuralTotalUrbanRuralTotalUrbanRuralTotalUrbanRuralTotalUrbanRuralTotal
Total7477361,483187171359191189380183190373186185371
Men3733657389383176969419092951879293185
Women3743717459489183959519091951869492186

The median of daily fluid intake was 1,488 mL, with a wide range from 86 mL to 7,036 mL. The daily fluid intake was significantly higher in men than women (1,679 mL versus 1,370 mL; Z = 8.34; P = 0.000). A significant difference in fluid intake was found among the four cities, with the highest in Shanghai (1,793 mL) and the lowest in Chengdu (1,150 mL). No significant difference was found between the urban and rural areas (1,514 mL versus 1,466 mL; Z = −0.81; P = 0.420). However, the differences between the two areas in Shanghai, Chengdu, and Guangzhou were significant; for example, the median daily water intake in the urban area of Shanghai was lower than in the rural area (Table 2).

Table 2.  Daily fluid intake (in mL) of participants in and around four cities in China.
Participant groupBeijingShanghaiChengduGuangzhouTotal X 2 value P value 
MQRMQRMQRMQRMQR
  • Values are given in milliliters, unless otherwise indicated.

  • Significant difference between urban and rural area (P < 0.05).

  • † 

    Significant difference between men and women (P < 0.05).

  • Abbreviations: M, median; QR, quartile range; B, Beijing; S, Shanghai; C, Chengdu, G, Guangzhou.

Total             
 Urban1,5797571,748*8101,339*8971,326*9761,51484634.880.000B = S > C = G
 Rural1,5839561,9001,2439596561,5539441,4661,093158.210.000S > B = G > C
 Total1,5798291,7931,0051,1507721,4679881,488950154.310.000S > B > G > C
Men             
 Urban1,6868311,8048711,3811,0091,5501,0541,63699613.370.004S > C = G
 Rural1,8931,1362,4641,3791,1146981,7391,3211,7291,40383.080.000S > B = G > C
 Total1,7441,0161,9941,1711,2578471,6711,1001,6791,16782.380.000S > B = G > C
Women             
 Urban1,5166061,5866171,3099141,1779091,42579391.520.000B = S = G > C
 Rural1,4007861,5578578706071,3987121,29381724.720.000B = S > C = G
 Total1,4746941,5636761,0437271,3168101,37081280.580.000S > B > G > C

The median of daily intakes of plain water, tea, and beverages of the subjects were 786 mL, 109 mL, and 186 mL, respectively. The amounts of tea intake were significantly higher among men compared with their female counterparts (229 mL versus 57 mL; Z = 7.52; P < 0.01), whereas no significant difference in the intakes of plain water and beverages was found between men and women. Among the four cities, subjects in Guangzhou had the highest intake of plain water (917 mL), followed by Beijing. Subjects in Shanghai had the highest tea and beverage consumption (257 mL and 323 mL, respectively). The intake of plain water, tea, and beverages in Chengdu was the lowest among these four cities. Subjects from urban areas had a lower consumption of plain water than their rural counterparts (693 mL versus 914 mL; Z = 6.88; P = 0.000), but significantly higher consumption of tea (186 mL versus 56 mL; Z = −4.56; P = 0.000) and beverages (286 mL versus 106 mL; Z = −13.00; P = 0.000) (Tables 3–5).

Table 3.  Daily plain water intake (in mL) of participants in and around four cities in China.
Participant groupBeijingShanghaiChengduGuangzhouTotal χ 2 value P value 
MQRMQRMQRMQRMQR
  • Values are given in milliliters, unless otherwise indicated.

  • Significant difference between urban and rural areas (P < 0.05).

  • Abbreviations: M, median; QR, quartile range; B, Beijing; S, Shanghai; C, Chengdu, G, Guangzhou.

Total             
 Urban709647500571664585836700693*64344.740.000G > B = C > S
 Rural1,0698189439716786141,00783891483242.720.000B = S = G > C
 Total81478969384267157991777178674353.310.000G > B > S = C
Men             
 Urban69365947151963064586198967170028.90.000G > B = C > S
 Rural1,2001,1936791,1078006409711,14387193616.370.001B = G > S = C
 Total7759465618077146439001,09375785737.650.000B = G > S = C
Women             
 Urban72662954359367955081448671058660.080.000B = S = G > C
 Rural1,0367001,1148715435181,04361494373616.130.001B = S = G > C
 Total81465784380761153293460080065041.010.000B = S = G > C
Table 4.  Daily tea intake (in mL) of participants in and around four cities in China.
Participant groupBeijingShanghaiChengduGuangzhouTotal χ 2 value P value 
MQRMQRMQRMQRMQR
  • Values are given in milliliters, unless otherwise indicated.

  • Significant difference between urban and rural area (P < 0.05).

  • † 

    Significant difference between men and women (P < 0.05).

  • Abbreviations: M, median; QR, quartile range; B, Beijing; S, Shanghai; C, Chengdu, G, Guangzhou.

Total             
 Urban22966430088618668668429186*65718.80.000B = S = C > G
 Rural294041141,17101711075005649124.750.000S = G > B = C
 Total114571257957714368645710959317.330.001S > B = C = G
Men             
 Urban3006714571,06836478912956428676412.260.007S = C > G
 Rural1005719862,15703662799861861,01448.090.000S > G > B = C
 Total1466575961,4898660718668622986437.070.000S > B = C = G
Women             
 Urban225629200686157507463431435576.930.074 
 Rural112570116014357161016412.10.007G > B = S
 Total10751404934225754264573506.50.090 
Table 5.  Daily beverage intake (in mL) of participants in and around four cities in China.
Participant groupBeijingShanghaiChengduGuangzhouTotal χ 2 value P value 
MQRMQRMQRMQRMQR
  • Values are given in milliliters, unless otherwise indicated.

  • Significant difference between urban and rural areas (P < 0.05).

  • Abbreviations: M, median; QR, quartile range; B, Beijing; S, Shanghai; C, Chengdu, G, Guangzhou.

Total             
 Urban363371500441221235118214286*371209.520.000S > B > C > G
 Rural1462711433434314312125710626239.560.000B = S = G > C
 Total264369323514107262121236186348137.080.000B = S > C = G
Men             
 Urban4004435143452142479428230044398.920.000B = S > C > G
 Rural12934311128736891142648623620.450.000B = S = G > C
 Total2905003195438625011026416136570.690.000B = S > C = G
Women             
 Urban32131749347723618714319327132918.20.000B = S > C > G
 Rural16923614335763179146282129264112.630.000B > G > S > C
 Total24930333243614325714322919331564.680.000B = S > C = G

Approximately 32.4% of the subjects drank < 1,200 mL of water per day, with a higher rate among women (χ2 = 24.80; P < 0.01). No significant difference in the proportion was found between rural and urban areas (χ2 = 3.07; P = 0.080). However, the proportion in the rural area of Chengdu was higher than its counterparts (χ2 = 28.32; P < 0.01), and the proportion in the rural area of Guangzhou was lower than its counterparts (χ2 = 9.9124; P < 0.01) (Table 6).

Table 6.  Proportion of participants with a daily fluid intake below 1,200 mL.
Participant groupNo. (%) of participants χ 2 value P value
BeijingShanghaiChengduGuangzhouTotal
  • Significant difference between men and women (P < 0.05).

  • † 

    Significant difference between urban and rural area (P < 0.05).

Total93 (25.9)63 (16.6)199 (53.4)125 (33.7)480 (32.4)125.440.000
Gender       
 Men38 (21.6)20 (10.5)88 (47.1)48 (26.0)194 (26.3)0.0000.000
 Women55 (30.1)43 (22.6)*111 (59.7)*77 (41.4)*286 (38.4)*0.0000.000
Region       
 Urban48 (25.7)29 (15.2)72 (39.3)77 (41.4)226 (30.3)40.540.000
 Rural45 (26.2)34 (18.0)127 (66.8)48 (26.0)254 (34.5)122.010.000

The proportion of subjects who were unaware of the recommended daily water intake proposed by the Chinese Nutrition Society was 28.4%, with higher values in women (32.4% versus 24.4%; χ2 = 11.55; P < 0.01) and the highest value in Chengdu (41.8%). The proportion of subjects unaware of the deleterious effects of dehydration was 14.4%, and was higher in Chengdu (18.5%) and Guangzhou (18.3%) and higher in rural subjects than their urban counterparts (18.6% versus 10.2%; χ2 = 21.47; P < 0.01). Moreover, nearly half (48.3%) of all subjects drank water when they felt thirsty. The proportion in Chengdu was the highest (59%). Approximately 20% of subjects did not know that plain water is the best source for water.4 In contrast, 17.9% of them considered beverages other than water as the best source.

DISCUSSION

On the basis of fluid intake survey data, Europe and the United States have developed adequate intake (AI) values for total water intake and fluid intake.5 A 24-h fluid intake recall for 1 day, combined with dietary recall methods, was used in the United States to estimate the daily drinking water intake and water from food,6 whereas a 7-day dietary record was used in France and in the United Kingdom.7,8 The method of assessing fluid intake in the dietary survey requires the subjects to record or recall a large amount of data, which will reduce compliance and may underestimate the fluid intake.5 The method used in the Drinking Water Consumption Survey9 in the United States collects information on how often, when, and how much water is consumed at specific time periods during the day. This approach was specifically designed to assess fluid intake by reducing burdens on the subjects, improving accuracy, and reducing omissions. However, this method can only obtain information about daily fluid intake, not the types of drinking water. The protocol in our study was designed for adults to specifically have the advantages as the Drinking Water Consumption Survey approach. Moreover, information on the types of drinking water was also obtained.

Britain, France, and Mexico have recommended a daily fluid intake of 1,500–2,000 mL, based on the national data of actual drinking water intake among individuals.4,5 The United States and Canada proposed AIs for fluid of 3,700 mL for men and 2,700 mL for women aged ≥19 years based on the results from the Third National Health and Nutrition Examination Survey.6 The World Health Organization proposed a daily water intake recommendation of 1,500 mL, taking into account the differences in national groups.5 The Chinese Nutrition Society proposed a daily intake of 1,200 mL of water in the 2007 Chinese Dietary Guideline, based on the relationship between energy metabolism and water requirements.2 In the current study, the median daily fluid intake of subjects from the four cities studied was 1,488 mL. Both the recommended water intake and the actual daily fluid intake in China are lower than in other countries. This difference may be due to the different eating behaviors and dietary patterns. Plant foods are the main foods in China, and steaming, stewing, and stir-frying are the most commonly used cooking methods, which can retain most of the water in the food. Moreover, some foods contain water that is added during cooking. Therefore, a larger proportion of the total water intake comes from solid food, which may reduce the amount of fluid consumed. In addition, there are ethnic differences in body size and resting metabolic rate that will result in different water requirements.

CONCLUSION

The average intake of fluid in Chinese adults, as measured in and around four cities, is higher than the present recommended dietary intake of water for the Chinese population. However, approximately one-third of the participants in the present study did not meet the recommended level of intake. The current study provides useful information for developing an AI for water for the Chinese population.

Acknowledgments

The authors acknowledge support from the Xicheng District Center for Disease Control and Prevention, Beijing; Huairou District Center for Disease Control and Prevention, Beijing; Shanghai Municipal Center for Disease Control and Prevention; Chengdu Center for Disease Control and Prevention; and the Center for Disease Control and Prevention of Guangdong Province. The authors also acknowledge support from all of the team members and the participants. This study was funded by the Danone Waters Research and Development Center in China.

Declaration of interest.  There authors have no relevant interests to declare.

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