Psychology Assignment

Caffeine intake in children in the United States and 10-y trends: 2001–20101–4

Namanjeet Ahluwalia, Kirsten Herrick, Alanna Moshfegh, and Michael Rybak

ABSTRACT Background: Because of the increasing concern of the potential adverse effects of caffeine intake in children, recent estimates of caffeine consumption in a representative sample of children are needed. Objectives: We provide estimates of caffeine intake in children in absolute amounts (mg) and in relation to body weight (mg/kg) to examine the association of caffeine consumption with sociodemo- graphic factors and describe trends in caffeine intake in children in the United States. Design: We analyzed caffeine intake in 3280 children aged 2–19 y who participated in a 24-h dietary recall as part of the NHANES, which is a nationally representative survey of the US population with a cross-sectional design, in 2009–2010. Trends over time be- tween 2001 and 2010 were examined in 2–19-y-old children (n = 18,530). Analyses were conducted for all children and repeated for caffeine consumers. Results: In 2009–2010, 71% of US children consumed caffeine on a given day. Median caffeine intakes for 2–5-, 6–11-, and 12–19-y olds were 1.3, 4.5, and 13.6 mg, respectively, and 4.7, 9.1, and 40.6 mg, respectively, in caffeine consumers. Non-Hispanic black chil- dren had lower caffeine intake than that of non-Hispanic white counterparts. Caffeine intake correlated positively with age; this association was independent of body weight. On a given day, 10% of 12–19-y-olds exceeded the suggested maximum caffeine intake of 2.5 mg/kg by Health Canada. A significant linear trend of decline in caffeine intake (in mg or mg/kg) was noted overall for children aged 2–19 y during 2001–2010. Specifically, caffeine in- take declined by 3.0 and 4.6 mg in 2–5- and 6–11-y-old caffeine consumers, respectively; no change was noted in 12–19-y-olds. Conclusion: A majority of US children including preschoolers con- sumed caffeine. Caffeine intake was highest in 12–19-y-olds and remained stable over the 10-y study period in this age group. Am J Clin Nutr 2014;100:1124–32.

INTRODUCTION

Caffeine is a commonly consumed stimulant present naturally in or added to foods and beverages. Caffeine consumption in children has received considerable interest because of the con- cern of adverse health effects. Caffeine intake of 100–400 mg has been associated with nervousness, jitteriness, and fidgetiness (1, 2). Because of the continued brain development involving myelination and pruning processes, children may be particularly sensitive to caffeine (3, 4). There has been some evidence that has linked caffeine intake in children to sleep dysfunction, el-

evated blood pressure, impairments in mineral absorption and bone health, and increased alcohol use or dependence (1, 5–7). In addition, the routine use of caffeinated sugar-sweetened beverages may contribute to weight gain and dental cavities (8). Caffeine toxicity in children has also been described involving tachycardia, central nervous system agitation, gastrointestinal disturbance, and diuresis (6, 9, 10). Health Canada has put forth maximal daily caffeine intake guidelines for children and ado- lescents (6, 11). Although no such recommendations have been set in the United States, the American Academy of Pediatrics has underscored that “caffeine and other stimulant substances contained in energy drinks have no place in the diet of children” (12).

Caffeine consumption has also been associated with certain health benefits such as increased endurance, attention, and vig- ilance and a reduced reaction time in some studies (9, 13, 14). Perceived positive effects on mood and cognition as well as physical performance may encourage preteens and adolescents to consume caffeinated products (2, 15, 16).

The literature on caffeine consumption in a representative sample of US children has been primarily based on older data, namely the US Department of Agriculture Continuing Survey of Food Intakes by Individuals (CSFII)5 1994–1996 and 1998 (16, 17). In addition, caffeine intake from beverages from the 1999 US Share of Intake Panel (SIP) survey in caffeine consumers has also been published (18). A 2010 US Food and Drug Admin- istration report also presented findings from the analysis of older data from NHANES 2005–2006 (19). Because of the current

1 From the Division of Health and Nutrition Examination Surveys, Na-

tional Center for Health Statistics, CDC, Hyattsville, MD (NA and KH);

the National Center for Environmental Health, CDC, Atlanta, GA (MR);

and the Food Surveys Research Group, Beltsville Human Nutrition Research

Center–Agricultural Research Service, USDA, Beltsville, MD (AM). 2 Findings and conclusions in this report are those of the authors and do

not necessarily represent the official position of the National Center for

Health Statistics, CDC. 3 Thiswork was not supported by any external grant. 4 Address correspondence to N Ahluwalia, Division of Health and Nutri-

tion Examination Surveys, National Center for Health Statistics, CDC, 3311

Toledo Road, Room 4110, Hyattsville, MD 20782. E-mail: naman.ahluwalia@

cdc.gov. 5 Abbreviations used: CSFII, Continuing Survey of Food Intakes by In-

dividuals; MEC, mobile examination center; PIR, poverty income ratio; SIP,

Share of Intake Panel.

ReceivedDecember 19, 2013. Accepted for publication July 3, 2014.

First published online August 27, 2014; doi: 10.3945/ajcn.113.082172.

1124 Am J Clin Nutr 2014;100:1124–32. Printed in USA. � 2014 American Society for Nutrition

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debate on the safety of caffeine intake by children (1, 12, 18) and deliberations to evaluate maximal intake recommendations, it is important to describe caffeine intake from more recent data available on a nationally representative sample such as the NHANES.

Trends in beverage consumption have changed over time (16, 20), and several caffeinated beverages and energy drinks have been introduced in the past decade, some marketed especially to youth (12, 15, 16). Few reports have described trends in caffeine intake both in milligrams and milligrams per kilogram of body weight by age in the United States (16, 21). Thus, our objective was to provide estimates of the distribution of caffeine intake in absolute amounts and in milligrams per kilogram in a representative sample of American children (2–19 y old) by using the most recent di- etary data available from the NHANES (ie, 2009–2010) in re- lation to demographic characteristics and examine the trends in caffeine consumption between 2001 and 2010 in children.

SUBJECTS AND METHODS

Study design

TheNHANES is a series of large, complex, stratified, multistage probability surveys of the US civilian, noninstitutionalized pop- ulation conducted by the National Center for Health Statistics, CDC (22). Briefly, NHANES is conducted yearly in w5000 individuals, and data are publicly released every 2 y onw10,000 individuals. Participants in the NHANES are administered a se- ries of questionnaires in a detailed in-home interview followed by a scheduled visit at the mobile examination center (MEC). At the MEC visit, participants receive a physical examination as well as a dietary interview, which is commonly referred to as the What We Eat in America component of the NHANES. The NHANES protocol was approved by the National Center for Health Statistics’s Research Ethics Review board. Informed consent was obtained from persons aged $18 y. For participants ,18 y of age, written parental consent was obtained, and child assent was obtained for individuals from 7 to 17 y of age. The most recent available data on caffeine intake from the NHANES (from the 2009–2010 survey) were used for the current analysis to describe caffeine consumption by demographic characteris- tics; data from this single survey cycle were sufficient to provide stable national estimates. We used NHANES data from 2001 to 2010 (2001–2002, 2003–2004, 2005–2006, 2007–2008, and 2009–2010 survey cycles) to conduct the trends analysis; be- cause of changes in the dietary data collection methodology on merging of the CSFII with NHANES in 1999–2000, data from 1999 to 2000 were not included in the trends analysis. The un- weighted total examination response rate for the 5 survey cycles examined for participants 2–19 y of age ranged from 81% to 88% (23).

Dietary interview

The type and quantity of all foods and beverages consumed in a single 24-h period, specifically the 24-h period before the dietary interview (from midnight to midnight) at the MEC, were collected by trained interviewers with the use of a computer- assisted dietary interview system with standardized probes (ie, the USDA’s Automated Multiple-Pass Method). Specifically for

beverages for which caffeine may be removed such as soda, coffee, tea, and energy drinks, probes were used to ascertain if the bev- erage reported was caffeine free. The Automated Multiple-Pass Method is designed to enhance a complete and accurate data collection while reducing the respondent burden (24, 25). For children aged #5 y, interviews were obtained through proxies, generally a parent. Proxies also assisted with dietary interviews of children aged 6–11 y. Dietary intakes were self-reported for participants aged $12 y. Since 2003–2004, a second, telephone- administered 24-h recall has been collected (3–10 d after the first 24-h recall at the MEC), but only one 24-h dietary recall was included in this analysis to maximize the comparability between surveys. Furthermore, one 24-h recall is sufficient to estimate population means because the effects of random errors associ- ated with dietary recall, including the day-to-day variability, are generally assumed to cancel out if days of the week are evenly represented (26).

Caffeine intake for all foods and beverages (including energy drinks) consumed during the 24-h period was calculated by using the USDA Food and Nutrient Database for Dietary Studies (27). The basis of nutrient values for foods and beverages, such as energy drinks, is the USDA National Nutrient Database for Standard Reference. Sources of nutrient data include scientific literature, data provided by food companies and trade associa- tions, and USDA analytical contracts. Caffeine intake was es- timated by summing the caffeine consumed for each food and beverage during the 24-h recall.

Demographic variables

Sex, age, race-Hispanic origin, and poverty income ratio (PIR) were used. Age was categorized as 2–5, 6–11, and 12–19 y

TABLE 1

Percentage of US children aged 2–19 y old who consumed caffeine on

a given day by demographic characteristics: NHANES 2009–20101

Characteristic n (% 6 SE) P

All children 3280 (71.0 6 1.0) — Age ,0.01 2–5 y 861 (58.3 6 2.4) 6–11 y 1154 (74.9 6 1.7) 12–19 y 1265 (74.5 6 2.2)

Sex NS

M 1712 (70.6 6 1.9) F 1568 (71.5 6 1.3)

Poverty income ratio2 NS

#130% 1422 (70.0 6 1.8) 131–349% 1023 (74.2 6 1.9) $350% 555 (69.6 6 2.7)

Race-Hispanic origin3 ,0.001 Non-Hispanic white 1101 (74.9 6 1.8)a

Non-Hispanic black 654 (56.3 6 2.2)b

Mexican American 914 (71.7 6 2.0)a

1NS at P $ 0.05. A test of linear trend was used for ordinal variables

(age and poverty income ratio) and Wald’s F test was used for sex and race-

Hispanic origin; significance was set at P , 0.05. Different superscript letters represent a significant difference between categories compared by

using the t test adjusted with the Bonferroni method for multiple compari-

sons. 2 Index calculated by dividing family income by a federal poverty

threshold specific to family size defined by the US Census Bureau. 3 “Other” race category not shown.

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consistent with NHANES sample-selection methods (28). Self- reported race-Hispanic origin was categorized as non-Hispanic white, non-Hispanic black, Mexican American, and other. Par- ticipants with a race-Hispanic origin categorized as other were included in overall estimates, but findings from this group are not reported (because of the small sample size and unstable variance estimates for a very heterogeneous group). Socioeco- nomic status was defined by using the PIR, which is an index calculated by dividing family income by a federal poverty threshold specific to family size defined by the US Census Bu- reau (29). The PIR was categorized as #130%, 131–349%, and $350%; for reference, a family income that corresponds to a 130% PIR qualifies for the Supplemental Nutrition Assistance Program (formerly the Food Stamp Program) and free school meals (30).

Analytic population

All children and adolescents aged 2–19 y who participated in the examination component of the NHANES were eligible for the dietary interview. In each survey cycle, a small proportion (4–6%) of participants were excluded because their 24-h recalls did not meet the standards of reliability that ensure the com- pleteness of recalls (31). In addition, 5 children who were re- portedly breastfed during the 24-h recall were excluded from the analysis because their caffeine intakes from breast milk could not be ascertained. The final analytic sample, after exclusions, comprised 4288, 3824, 4029, 3159, and 3280 participants aged 2–19 y in 2001–2002, 2003–2004, 2005–2006, 2007–2008, and 2009–2010, respectively.

Data analysis

Statistical analyses were conducted with SAS software (version 9.3; SAS Institute Inc) and SUDAAN software (version 11.0; RTI International). Caffeine intake on a given day was examined in absolute amounts (mg) and in relation to body weight (mg/kg) in all analyses. Caffeine intake displayed a skewed distribution; w30% of the analytic population did not report any caffeine in- take during the 24-h recall period. Thus, logarithmically (base 10) transformed data on caffeine intake were used to test statistical hypotheses because they were identified (by using the Box-Cox procedure in SAS) to be more consistent with a normal distri- bution (32, 33). To accommodate respondents who reported no caffeine consumption on the day of recall, caffeine intakes of zero were set to 0.0001 to allow the log base 10 transformation. Ex- treme values were examined to determine whether they exerted undue influence. Plots of dietary sample weight compared with caffeine intake showed that extreme values were not associated with influential weights. Preliminary analyses indicated that the exclusion of these extreme values did not change the results; thus, no exclusions or corrections were made.

Dietary sample weights were used to account for a differential probability of selection and adjust for nonresponse, noncoverage, and sample design. These publically available sample weights also include a poststratification step to balance recalls across days of the week (31).

Weighted, untransformed estimates of the 50th (median), 75th, 90th, and 95th percentiles and percentages (6SEs) were com- puted for children and adolescents (aged 2–19 y) by demo- graphic characteristics. Statistical hypotheses regarding the

TABLE 2

Caffeine intake on a given day by demographic characteristics for US children 2–19 y old: NHANES 2009–20101

Characteristics

Caffeine

Pn Median2 75th percentile 90th percentile 95th percentile

mg/d

All children 3280 4.6 30.8 94.6 147.6 —

Age ,0.0001 2–5 y 861 1.3 5.9 13.4 23.8

6–11 y 1154 4.5 19.2 49.7 72.3

12–19 y 1265 13.6 70.9 147.9 260.5

Sex NS

M 1712 4.7 30.0 102.1 169.5

F 1568 4.5 31.3 85.1 132.5

Poverty income ratio3 NS

#130% 1422 4.5 30.2 77.4 131.7

131–349% 1023 5.5 36.4 106.5 141.9

$350% 555 3.6 26.5 88.9 153.0

Race-Hispanic origin4 ,0.0001 Non-Hispanic white 1101 6.4a 43.2 112.0 177.9

Non-Hispanic black 654 1.3b 9.7 55.2 93.1

Mexican American 914 4.2a 22.7 70.3 112.8

1Medians and percentiles were calculated from untransformed weighted data; 5th and 25th percentiles are not

presented and were essentially equal to zero because of a high proportion of children who did not consume any caffeine.

A test of linear trend was used for ordinal variables age and poverty income ratio. Wald’s F test was used for sex and race-

Hispanic origin. Significance was set at P , 0.05. Different superscript letters represent a significant difference between categories compared by using the t test adjusted with the Bonferroni method for multiple comparisons.

2All statistical tests were performed on log-transformed means. 3 Index calculated by dividing family income by a federal poverty threshold specific to family size defined by the US

Census Bureau. 4 “Other” race category not shown.

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proportion of children who consumed caffeine in relation to sociodemographic variables were tested on weighted, untrans- formed percentages. Hypotheses concerning caffeine intake (mg and mg/kg) in relation to sociodemographic variables were tested by using weighted means of the log-transformed variable. SEs were estimated by using Taylor’s series linearization. Statistical hypotheses were tested by using Wald’s F tests with a = 0.05. If the hypothesis that the mean or percentage of all subgroups being equal was rejected, pairwise t tests were performed. An adjustment for multiple comparisons was made by using the Bonferroni method (34). Linear trends in log-transformed caffeine intake by age and PIR were determined by using orthogonal contrast matrices (35). We also tested for linear trends in log-transformed caffeine intake across the survey periods between 2001 and 2010 by using orthogonal contrast matrices (35); tests were conducted for all children and within age groups over time. Analyses were carried out for all children in the analytic population and re- peated for children who consumed caffeine (consumers only). For the purpose of the current analyses, caffeine consumers were defined as children who reported the consumption of caffeine on the 24-h dietary recall.

RESULTS

A majority (71%) of 2–19-y-olds consumed caffeine on a given day (Table 1). A linear trend was noted in the proportion of 2–19-y-olds who consumed caffeine with age but not PIR. No differences were seen between males and females in terms of the proportion of children who consumed caffeine. However, dif-

ferences were noted in caffeine consumption by race-Hispanic origin as follows: non-Hispanic black children (56%) were less likely to consume caffeine than were non-Hispanic white (75%) or Mexican American (72%) children (Table 1); however, no differences between non-Hispanic white or Mexican American children were noted.

The distribution of caffeine intake (mg) on a given day by selected demographic characteristics (Table 2) showed that the median caffeine intake by US children 2–19 y of age was 4.6 mg. An increasing linear trend in caffeine intake was noted by age. No significant associations were shown between the PIR and caffeine intake. Non-Hispanic black children consumed significantly less caffeine than did non-Hispanic white or Mexican American children (Table 2). No differences in caffeine intake between non-Hispanic white and Mexican American children were noted.

When these analyses were restricted to children who con- sumed caffeine (ie, consumers only) (Table 3), the median caffeine intake on a given day was 12.4 mg. The significant linear trend for caffeine intake and age remained, with the oldest age group (12–19-y-olds) having the highest caffeine intake (40.6 mg). Non-Hispanic black children consumed significantly less caffeine (8.0 mg) than did non-Hispanic white children (14.4 mg) (Table 3). No other racial-ethnic group differences were noted.

When caffeine intake (mg) was expressed in relation to body weight (kg), the median caffeine consumption for US children 2–19 y of age was 0.15 mg/kg (Table 4). Associations of caffeine intake (mg/kg) with age and race-Hispanic origin were similar

TABLE 3

Caffeine intake in consumers of caffeine on a given day by demographic characteristics for US children 2–19 y old:

NHANES 2009–20101

Characteristics

Caffeine

Pn Median2 75th percentile 90th percentile 95th percentile

mg

All children 2230 12.4 52.2 116.6 184.0 —

Age ,0.0001 2–5 y 485 4.7 10.3 20.9 36.1

6–11 y 826 9.1 31.4 58.5 85.3

12–19 y 919 40.6 96.6 186.3 284.4

Sex NS

M 1154 12.1 56.2 124.0 223.6

F 1076 12.6 49.0 105.3 148.0

Poverty income ratio3 NS

#130% 952 14.3 51.6 98.9 155.3

131–349% 717 11.6 55.4 119.4 184.2

$350% 382 9.5 48.7 113.3 204.4

Race-Hispanic origin4 ,0.01 Non-Hispanic white 819 14.4a 60.1 137.3 220.2

Non-Hispanic black 367 8.0b 41.3 89.4 109.6

Mexican American 633 11.6a,b 42.5 91.5 131.5

1Medians and percentiles were calculated from untransformed weighted data. A test of linear trend was used for

ordinal variables age and poverty income ratio. Wald’s F test was used for sex and race-Hispanic origin. Significance was

set at P , 0.05. Different superscript letters represent a significant difference between categories compared by using the t test adjusted with the Bonferroni method for multiple comparisons.

2All statistical tests were performed on log transformed means. 3 Index calculated by dividing family income by a federal poverty threshold specific to family size defined by the US

Census Bureau. 4 “Other” race category not shown.

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as noted for caffeine intake in absolute amounts (mg). Non- Hispanic black children had significantly lower caffeine intake (0.04 mg/kg) than did other race-ethnicities examined (Table 4).

When analyses of caffeine intake (mg/kg) were restricted to children who consumed caffeine, (ie, consumers only) (Table 5), the median caffeine intake was 0.40 mg/kg on a given day. A linear trend in caffeine intake (mg/kg) with age was again observed. As for the results concerning the absolute amount (mg) of caffeine ingested in consumers only, the finding that non-Hispanic black children consumed significantly lower caffeine (0.24 mg/kg) than did non-Hispanic white children (0.47 mg/kg) remained unaltered (Table 5). No other race-ethnic differences were noted.

Caffeine intake did not differ by sex or poverty level whether expressed as total intake (mg) or in relation to body weight (mg/kg) for all children 2–19 y of age or in caffeine consumers 2–19 y of age (Tables 2–5).

We estimated 90th and 95th percentiles of caffeine intake by various sociodemographic factors to provide national estimates that may be useful for policy makers in future evaluations of the upper end of the distribution. As expected, the 90th percentile of caffeine intake (mg) was lower in all children than caffeine consumers (Tables 2 and 3, respectively). Health Canada has put forth maximal caffeine intake (mg) guidelines for children that vary by age; specifically, 45, 62.5, and 85 mg caffeine/d have been suggested as maximum caffeine intakes for 4–6-, 7–9-, and 10–12-y-olds, respectively (11). Our analyses show that most (90–95%) children ,12 y old had caffeine intakes below these guidelines (Tables 2 and 3). For older children, caffeine con-

sumption guidance has been based on milligrams per kilogram of body weight; Health Canada has suggested that daily caffeine intake for children .12 y of age should be ,2.5 mg/kg (6, 11). Our findings indicated that 90% of children 12–19 y of age and $75% and,90% of 12–19-y-old caffeine consumers on a given day met these guidelines and had caffeine intakes ,2.5 mg $ kg21 $ d21 (Tables 4 and 5, respectively).

We also examined trends in caffeine intake from 2001 to 2010. The caffeine intake in 2–19-y-old children decreased overall in the 10-y study period for all children (Figure 1A; n = 18,530 and P , 0.05) and caffeine consumers only (Figure 1B; n = 12,776 and P , 0.001). No major trends were noted for specific age groups in all children (caffeine consumers and non- consumers) (Figure 1A). However, when trends analyses were restricted to caffeine consumers only, 2–5- and 6–11-y-olds showed a significant decrease in caffeine intakes from 2001– 2002 to 2009–2010 (Figure 1B; P-trend , 0.001 for both age groups); the magnitude of these changes, however, was small, by 3.0 and 4.6 mg in children 2–5 and 6–11 y of age, respectively. Identical findings were noted with caffeine intake expressed as milligrams per kilogram of body weight (data not shown) for all children (consumers and nonconsumers of caffeine) as well as for children who consumed caffeine.

DISCUSSION

Caffeine intake in children has received much attention be- cause of potential adverse health effects (1, 2, 10, 36). Most

TABLE 4

Caffeine intake in relation to body weight on a given day by demographic characteristics for US children 2–19 y old:

NHANES 2009–20101

Caffeine

Characteristic n Median2 75th percentile 90th percentile 95th percentile P

mg/kg

All children 3280 0.15 0.75 1.78 2.70 —

Age ,0.01 2–5 y 861 0.11 0.36 0.86 1.43

6–11 y 1154 0.15 0.62 1.68 2.49

12–19 y 1265 0.22 1.13 2.45 3.27

Sex NS

M 1712 0.15 0.72 1.83 2.98

F 1568 0.15 0.80 1.69 2.58

Poverty income ratio3 NS

#130% 1422 0.15 0.77 1.71 2.76

131–349% 1023 0.17 0.86 1.87 2.70

$350% 555 0.13 0.63 1.47 2.44

Race-Hispanic origin4 ,0.001 Non-Hispanic white 1101 0.19a 0.90 2.09 3.02

Non-Hispanic black 654 0.04b 0.28 1.07 1.55

Mexican American 914 0.14a 0.65 1.47 2.21

1Medians and percentiles were calculated from untransformed weighted data. Fifth and 25th percentiles are not

presented and were essentially equal to zero because of a high proportion of children who did not consume any caffeine.

A test of linear trend was used for ordinal variables age and poverty income ratio. Wald’s F test was used for sex and race-

Hispanic origin. Significance was set at P , 0.05. Different superscript letters represent a significant difference between categories compared by using the t test adjusted with the Bonferroni method for multiple comparisons.

2All statistical tests were performed on log transformed means. 3 Index calculated by dividing family income by a federal poverty threshold specific to family size defined by the US

Census Bureau. 4 “Other” race category not shown.

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healthy persons tolerate caffeine well; however, there is a large variation in individuals in their responses to caffeine (37, 38). Estimates of caffeine consumption in a nationally representative sample of young children that were based on recent data may be informative for updating recommendations. To our knowledge, this is the first report of caffeine intake in US children aged 2–19 y, which was examined both in absolute amount (mg) and milli- grams per kilogram of body weight, and its associations with sociodemographic factors from the most-recent available na- tional data from NHANES 2009–2010. In addition, trends in caffeine consumption (both in mg and mg/kg) over a decade (2001–2010) are reported for the first time to our knowledge.

In the current study, 71% of US children aged 2–19 y con- sumed caffeine on a given day. Our finding that 58% of 2–5-y- olds and 75% of 6–11-y-olds consumed caffeine on a given day was lower than estimates reported by Frary et al (16) on the basis of older national data from the CSFII in these age groups. In that study, 76% of 2–5-y-olds and 86% of 6–11-y-olds con- sumed caffeine. For older children, Frary et al (16) reported that 91 and 88% of 12–17-y-old boys and girls, respectively, con- sumed caffeine on a given day. Because of differences in ages reported, no direct comparison could be made for older children.

We showed that over one-half of US children aged 2–5 y and 3 in 4 children aged $6 y consumed caffeine on a given day. This finding is important because food habits are formed early and continue into later years and in light of the American Academy of Pediatrics recommendation that “caffeine and other stimulant substances contained in energy drinks have no place in the diet of children” (12).

We noted a positive linear trend between age and caffeine consumption (expressed as mg or mg/kg) as has been reported in other studies (16, 18, 19, 39). This association may be driven by biological changes such as disrupted sleep rhythm in puberty (40) as well as psychosocial factors including a greater autonomy in beverage purchase and consumption, peer pressure, and desire for enhanced academic or physical performance (1, 15, 41, 42). Limited comparative estimates of caffeine intake are available from large representative studies (16, 18, 19, 43). Besides dif- ferences in study designs, methodologies, time periods, and the use of different age and sex groups, an additional complexity arises because most studies have reported mean intakes (despite a skewed distribution for caffeine). For comparison purposes, we computed mean caffeine intakes (6SEs) for 2–5-, 6–11-, and 12–19-y-olds. These intakes were 5.8 6 0.45, 17.2 6 1.1, and 58.3 6 6.4 mg, respectively, in all children and 10.0 6 1.0, 23.0 6 1.4, and 78.3 6 7.4 mg, respectively, in caffeine con- sumers. These estimates are similar to those reported for the NHANES 2005–06 (19) but lower than those reported for caffeine consumers in the SIP survey (1-5-y olds: 13.5 mg/d) (18) and the CSFII in middle to late 1990s (2–5-y-olds: 16 mg) (16).

Caffeine is generally regarded as a safe substance; however, the US Food and Drug Administration has suggested the use of the .90th percentile to indicate a “heavy consumption” of caffeine (18, 19). Our results showed that, in adolescents ages 12–19 y, caffeine intake at the 90th percentile was 2.45 mg/kg. This intake is identical to the maximal consumption limit sug- gested for children by Health Canada (6, 11) that was based on reported behavioral effects (44). On the basis of the NHANES

TABLE 5

Caffeine intake in relation to body weight on a given day in caffeine consumers by demographic characteristics for US

children 2–19 y old: NHANES 2009–20101

Characteristic n

Caffeine

PMedian2 75th percentile 90th percentile 95th percentile

mg/kg

All children 2230 0.40 1.13 2.27 3.18 —

Age ,0.01 2–5 y 485 0.29 0.62 1.34 1.34

6–11 y 826 0.30 0.90 1.80 2.77

12–19 y 919 0.64 1.47 2.66 3.65

Sex NS

M 1154 0.39 1.18 2.49 3.26

F 1076 0.40 1.09 2.11 2.77

Poverty income ratio3 NS

#130% 952 0.44 1.10 2.19 3.47

131–349% 717 0.43 1.24 2.46 3.04

$350% 382 0.31 0.86 1.79 3.10

Race-Hispanic origin4 ,0.01 Non-Hispanic white 819 0.47a 1.32 2.58 3.28

Non-Hispanic black 367 0.24b 0.74 1.46 1.86

Mexican American 633 0.35a,b 0.93 1.81 2.56

1Medians and percentiles were calculated from untransformed weighted data. A test of linear trend was used for

ordinal variables age and poverty income ratio. Wald’s F test was used for sex and race-Hispanic origin. Significance was

set at P , 0.05. Different superscript letters represent a significant difference between categories compared by using the t test adjusted with the Bonferroni method for multiple comparisons.

2All statistical tests were performed on log transformed means. 3 Index calculated by dividing family income by a federal poverty threshold specific to family size defined by the US

Census Bureau. 4 “Other” race category not shown.

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2009–2010, we showed that 10% of children 12–19 y of age consumed .2.5 mg caffeine/kg on a given day and ,25% of 12–19-y-old caffeine consumers had intakes greater than this guideline.

Children may metabolize caffeine differently than adults do (18) and show a large variation in body weight across childhood, and recommendations to limit caffeine intake have been based on body weight for children by Health Canada (6, 11). Few reports have examined caffeine intake in children expressed as milli- grams per kilogram, and they presented findings in caffeine consumers only (16, 18, 21, 43). Thus, there has been no comparative literature on caffeine consumption in all children (caffeine consumers and nonconsumers) as has been provided in this study.

Our estimates of caffeine intake (mg/kg) in caffeine consumers were generally lower than those previously reported (16, 18, 21). Frary et al (16), on the basis of older CSFII data, reported 0.4, 0.4, 0.5, and 0.6 mg/kg for 2–5-, 6–11-, and12–17-y-old boys and 12– 17-y-old girls, respectively, compared with our estimates of 0.3 mg/kg for 2–5- and 6–11-y-olds. Barone and Roberts (21) re-

viewed studies up to the early 1990s and showed that caffeine intake (mg/kg) declined between 1975 and 1989. Our finding of a significant linear decreasing trend from 2001 to 2010 sug- gested that this trend has likely continued since that report (21) and could explain our lower estimates.

We also examined sociodemographic patterns in caffeine consumption related to race-Hispanic origin and income. Our finding that non-Hispanic black children consumed significantly less caffeine than that of non-Hispanic white children was consistent with findings from the Bogalusa study (39) and CSFII (17). However, to our knowledge, this is the first report to show higher caffeine intake byMexican American compared with non- Hispanic black 2–19-y-olds. In the current study, we did not find any difference in caffeine intake in relation to socioeconomic status that was contrary to findings from a small study that in- volved 24–32-mo-old children (45). Other authors have reported lower caffeine intakes by female than male children (46); this difference was more pronounced particularly at older ages (16, 19). However, we did not find a significant association with sex, which was consistent with findings from the SIP survey (18).

FIGURE 1. Trends over time in caffeine intake on a given day (mg) in US children aged 2–19 y: 2001–2010. Trends are shown for all children aged 2–19 y (A) (n = 18,530) and caffeine consumers aged 2–19 y (B) (n = 12,776). P-linear trend , 0.05 by using the t statistic for all children 2–19 y of age (A); NS for specific age groups (A). P-linear trend , 0.001 by using the t statistic for caffeine consumers 2–19 y of age, and P-linear trend , 0.001 for both 2–5- and 6– 11-y-old groups (B). Error bars represent 6 1 SE; bars capped by diamonds, circles, dashes, and triangles represent variations for all (solid line), 2–5-y-old (dashed and dotted line), 6–11-y-old (dotted line), and 12–19-y-old (dashed line) children, respectively.

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Overall, findings for the association of caffeine intake with sociodemographic factors were consistent whether caffeine in-

take was expressed as an absolute amount or in milligrams per

kilogram. Moreover, results were similar when analyses were

conducted with all children or consumers only. The only ex-

ception was that differences in caffeine intake by race-Hispanic

origin were less prominent in consumers only. Specifically,

caffeine intake of non-Hispanic black and Mexican American

children was no longer different in consumers. Last, our results from the trend analysis showed a significant,

albeit small, decline over the 10-y study period (2001–2010) in

caffeine intake in all children and caffeine consumers only re-

gardless of how caffeine intake was expressed (ie, mg or mg/kg).

The decrease in caffeine intake (mg) observed over this period

was significant only in younger caffeine consumers (ages ,12 y), which suggested that caffeine intake by adolescents (aged

12–19 y) who consumed the highest amounts of caffeine in all

age groups examined remained stable over the 10-y study pe-

riod. In view of an increasing choice of products that contain

caffeine such as energy drinks targeted to youth, another pos-

sibility is that children may be replacing some of their caffeine

intakes from sodas by other caffeinated products such as energy

drinks. This hypothesis fits well with the findings from the

NHANES that showed a decrease in soda along with a signifi-

cant increase in energy or sport-drink consumption in 2–19-y-

olds (20). The NHANES design allows the estimation of caffeine con-

sumption on a representative sample and examination of the

association of caffeine consumption with sociodemographic

factors including race-Hispanic origin. The continuous nature of

the NHANES since 1999 offers the possibility of evaluating

trends over time from different survey cycles that used the same

data-collection methodology and are linked to nutrient data banks

that are updated periodically to capture new products introduced

during the survey years. The current analyses were based on

a single 24-h recall that was sufficient to estimate population-

level estimates because random errors associated with a dietary

recall, including the day-to-day variability, can be generally

assumed to cancel out if days of the week are evenly represented

(26). The database used in this study did not include caffeine

intake from herbals, supplements including energy shots, or

medications. In conclusion, this study provides updated national estimates

of caffeine intakes in children that may be useful in the context of

the mounting evidence of adverse health effects associated with

high caffeine intake while balancing benefits of caffeine. Future

research should identify the contribution of specific foods and

beverages to caffeine intake as well as the chief sources of

caffeine in children and adolescents.

We are grateful to Margaret Carroll for her expert guidance with the sta-

tistical analysis.

The authors’ responsibilities were as follows—NA: was responsible for

the concept development, supervision of the statistical analysis, and writing

of the manuscript; KH: conducted the statistical analysis and assisted with

preparing the tables and figure; NA and KH: were responsible for the final

content of the manuscript; and all authors: provided input on the writing of

the manuscript and reviewed and provided critical feedback on the manu-

script. None of the authors had a conflict of interest.

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