Summary

Rev Panam Salud Publica/Pan Am J Public Health 24(2), 2008 127

Food consumption in Mexican adolescents

Luis Ortiz-Hernández and Blanca Lilia Gómez-Tello

Objective. To examine the relationship between demographic and socioeconomic factors and food consumption in Mexican adolescents. Methods. A representative sample (n = 7 218) of Mexican adolescents (12–19 years old) was analyzed. Independent variables included age, gender, and main activity of the adoles- cents; gender and age of the head of household; socioeconomic position; size of town (rural, semiurban, or urban); and area of residence. The consumption frequency of 13 food groups was assessed. Through multivariate logistic regression models, the effect of independent variables over consumption frequency was evaluated. Results. Among Mexican adolescents only one-third consumed fruits and vegetables daily, a little less than one-half consumed dairy products daily, one-third drank soft drinks daily, and one-fifth consumed sweets and salty snacks. Males reported higher consumption of legumes. Age increase was associated with higher frequency of milk consumption. Adolescents who worked and those who neither studied nor worked consumed fruits, sweets, and salty snacks less frequently. Eating fruits, vegetables, cereals, dairy products, bread, starchy veg- etables, red meat, white meat, and fast food decreased with regard to socioeconomic position; on the other hand, the lower socioeconomic strata had more frequent consumption of legumes and soft drinks. Conclusions. There are groups of adolescents who are less likely to consume healthy foods (such as fruits, vegetables, and dairy products). Socioeconomic and cultural processes that can explain the differences observed are discussed.

Diet, adolescents, socioeconomic status, gender, Mexico.

ABSTRACT

Obesity in Mexico has been consid- ered a public health problem, as it af- fects a large number of people. In the year 2000, among Mexican adolescents aged 10–17 years, the prevalence of overweight was 24.7% (1). For the year 2006 (2), the prevalence of overweight

and obesity in males 12–19 years of age was 31.2%, while in females it was 32.5%. Similar to some other chronic illnesses, obesity is related to eating habits and consumption of energy and macronutrients. In Mexico, during re- cent decades, there has been an in- crease in morbidity and mortality due to diet-associated diseases, such as obesity, high blood pressure, diabetes mellitus, and coronary cardiopathy (3).

In 2005, 20.4% of Mexicans were be- tween 12 and 19 years of age (4). Char- acterizing eating habits in adolescents

is important because dietary habits ini- tiated at these ages have a higher prob- ability of persisting during adult life (5). Additionally, obese adolescents have a higher risk of morbidity in adulthood due to coronary cardiopa- thy, arteriosclerosis, and gout (6).

With the exception of reproductive health-related topics, other aspects as- sociated with the health and nutri- tional conditions of adolescents have been a matter of less interest. In con- trast, the nutritional status and diet of other age groups, such as preschool

Key words

Investigación original / Original research

Ortiz-Hernández L, Gómez-Tello BL. Food consumption in Mexican adolescents. Rev Panam Salud Pu- blica. 2008;24(2):127–35.

Suggested citation

Health Care Department, Metropolitan Autonomous University–Xochimilco, Mexico City, Mexico. Send correspondence to: Luis Ortiz-Hernández (UAM-X), Calzada del Hueso 1100, Col. Villa Quietud, Coyoacán, 04960 México, D.F., México; phone: (+52) (55) 5483-7573; fax: (+52) (55) 5483-7218; e-mail: [email protected].

and adult populations, have been studied more. This situation probably results from adolescents having low mortality due to infectious and chronic diseases (5).

Nutritional problems frequently ob- served in adolescents from industrial- ized countries comprise the following: low consumption of fruits and vegeta- bles; frequent consumption of foods with high energy density; and defi- ciencies of certain micronutrients such as zinc, calcium, iron, and vitamin A (5, 7). However, few studies have been conducted (8–10) that describe the food consumption of adolescents from middle- and low-income countries.

In industrialized nations, persons of lower socioeconomic position have less healthy diets than individuals with higher socioeconomic position (11); nonetheless, there is evidence (10) that these findings could not be ex- trapolated to middle- or low-income countries. Additionally, there are few studies in adolescents on the role of certain demographic characteristics in food consumption, such as occupa- tional activity or the size of the town where they live. The aim of this re- search was to examine the association of socioeconomic and demographic factors with food consumption in ado- lescents from Mexico.

MATERIALS AND METHODS

The 2005 National Youth Survey (NYS05) database was analyzed (12). The sample design was probabilistic, stratified, and multistage. For sam- pling, Mexico was divided into five geographic regions (described later). In each region, census tracts were se- lected in proportion to the number of inhabitants. Sampling stages included census tracts, blocks, households, and subjects. In households, one subject aged 12–29 years was selected; if there were two or more eligible respon- dents in the household, the subject whose birth date was nearer in time was chosen to interview. After data were edited, the sample (n) included 7 218 cases that represented the entire adolescent 12- to 19-year-old popula-

tion of Mexico. Using the sampling weights, these data correspond to an estimated total population (N) size of 16 384 551 adolescents. The nonre- sponse rate was 15%, and the error margin was 1.8%. Information was gathered by means of a questionnaire applied at face-to-face interviews. Par- ticipant adolescents gave verbal con- sent, and they were isolated from their families to ensure confidentiality and thus improve the quality of the data.

The following demographic char- acteristics were analyzed: age of the adolescents (12–14, 15–17, and 18–19 years), main activity of the adolescents (only studying, only working, study- ing and working, and neither studying nor working), and gender and age of the head of household (≤ 29, 30–39, 40–49, 50–59, and ≥ 59 years).

Socioeconomic position was evalu- ated through two indicators: edu- cation of the head of household (as defined by the interviewee) and household assets. Four categories were used with respect to education: very low (primary school or less), low (secondary school or secretarial ca- reer), middle (high school, technical career, or teacher training), and high (bachelor’s degree or more). Assets found less frequently in Mexican households were selected to estimate an index based on household posses- sions (4): washing machine, refrigera- tor, telephone, car or van, computer, and heater or gas boiler. The number of assets in each household were added, and four strata were formed: very low (two or fewer assets); low (three or four assets); medium (five as- sets), and high (six assets).

Town size was divided into three categories: rural (≤ 2 499 inhabitants), semiurban (2 500–19 999 inhabitants), and urban (≥ 20 000 inhabitants). The 32 Mexican states were divided into five regions or area of residence: Northwest, Northeast, Central-West, Central, and South.

The frequency of intake of 13 food groups was assessed: fruits, vegetables, cereals (wheat and oats), starchy veg- etables (potatoes and sweet potatoes), legumes (beans, broad beans, and lentils), dairy products, red meat (beef

and pork), white meat (chicken and fish), soft drinks, sweets, salty snacks, fast food (hot dogs, sandwiches, and tortas), and bread. Response options were the following: never, every now and then, at sometime during the week, and daily. All the response options were dichotomized. For fruits, vegeta- bles, cereals, dairy products, bread, soft drinks, sweets, and salty snacks, the fol- lowing groups were formed: (1) daily consumption, and (2) consumption at sometime during the week, every now and then, and never. For starchy veg- etables, legumes, red meat, white meat, and fast food, the groups were (1) daily consumption and at sometime during the week, and (2) consumption every now and then and never.

For statistical analysis, sample weights considering sample post- stratification were used, because they allowed the sample’s gender and age distribution to better approximate that registered by the 2000 General Popula- tion and Housing Census. Analysis was done with SAS software, which al- lows taking into account NYS05’s com- plex design. Absolute and relative fre- quencies of variables were obtained. Later, multivariate logistic regression models were estimated, in which the dependent variables were food con- sumption and the independent vari- ables comprised age, gender, and main activity of the adolescents; socioeco- nomic position, age, and gender of the head of household; size of town; and area of residence. As a first step, all in- dependent variables in each model were included and were progressively dismissed if their association with food consumption was not statistically sig- nificant (P > 0.050). From logistic re- gression models, odds ratios (ORs) were estimated with their correspond- ing 95% confidence intervals (95% CI).

RESULTS

In Table 1, descriptive characteristics of the population are shown. There was nearly the same proportion of fe- males and males; most adolescents were between 12 and 14 years old, and adolescents who only studied predom-

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Original research Ortiz-Hernández and Gómez-Tello • Food consumption in Mexican adolescents

inated. With both education and assets, the low and very low socioeconomic statuses predominated. For head of household, 17.6% were females and 39.4% were 40–49 years of age.

Frequency of food consumption of adolescents is presented in Table 2. Foods such as dairy products, bread, legumes, fruit, vegetables, and soft drinks were consumed most fre- quently, while foods consumed least frequently were fast food, red meat, and starchy vegetables.

Multivariate logistic regression- model results are presented in Tables 3 to 5, with consumption of food groups as the dependent variable. Fruit con- sumption was higher in adolescents living in households headed by older persons but was lower in those who both studied and worked; who neither studied nor worked; who belonged to the low and very low education status; and who lived in Northeastern, North- western, and Southern Mexico. Vege- table consumption was lower in ado- lescents who neither studied nor worked, who had low socioeconomic position (according to education or household assets), and who lived in the Northwest and South. Frequency of cereal consumption was lower in adolescents who worked, in those who neither studied nor worked, in those with low socioeconomic status (de- fined by the two socioeconomic posi- tion indicators), and in those who lived in Northwestern Mexico. Dairy products were less frequently con- sumed by adolescents who worked; those who neither studied nor worked; those with low socioeconomic posi- tion; those who lived in Northeastern, Northwestern, and Southern Mexico; and those who lived in households headed by males.

Bread consumption was less fre- quent in adolescents with low socio-

economic position and in those who lived in Northeastern, Northwestern, Central-Western, and Southern re- gions. There was a higher frequency of starchy vegetable consumption in in- dividuals residing in semiurban locali- ties; on the other hand, there was less consumption of this food by individu- als who worked, who had low socio- economic status (defined by house- hold assets), and who resided in households in which the head was older. Adolescents with low socioeco- nomic position (defined by education and household assets) and those who resided in rural areas consumed less red meat. White meat consumption was lower in subjects living in rural areas, in those who neither studied nor worked, and in those with very low socioeconomic status (defined by household assets).

Soft drinks were less frequently con- sumed by those residing in house- holds headed by a male and in rural areas; in contrast, soft drink intake was higher in those with low socioeco- nomic status. Adolescents with low so- cioeconomic position consumed less fast food, whereas those living in Northeastern and Central-Western Mexico consumed more of these foods. Consumption of sweets was lower in adolescents who worked and studied, in those who neither studied nor

Rev Panam Salud Publica/Pan Am J Public Health 24(2), 2008 129

Ortiz-Hernández and Gómez-Tello • Food consumption in Mexican adolescents Original research

TABLE 1. Sample descriptive characteris- tics of Mexican adolescents, 2005

No. %

Sex Male 3 471 49.2 Female 3 747 50.8

Age (years) 12–14 2 793 38.3 15–17 2 653 35.5 18–19 1 772 26.2

Main activity Study 5 511 73.2 Work 543 9.8 Study and work 250 4.8 Neither study nor work 914 12.2

SEP,a education Very low 3 002 45.4 Low 1 907 24.3 Medium 1 533 20.0 High 702 10.3

SEP, assets Very low 2 079 33.2 Low 2 636 31.9 Medium 1 309 16.6 High 1 194 18.3

Sex of family’s head Male 6 066 82.4 Female 1 152 17.6

Age of family’s head (years) 29 or less 297 5.8 30–39 2 279 29.4 40–49 2 825 39.4 50–59 1 108 15.7 ≥ 60 691 9.7

Size of town Rural 547 0.5 Semiurban 1 669 12.5 Urban 5 002 87.0

Region Central 1 178 31.0 Northeast 1 614 12.8 Northwest 384 7.4 Central-West 2 679 24.4 South 1 363 24.4

a SEP = socioeconomic position.

TABLE 2. Food consumption frequency of Mexican adolescents, 2005

Na ENTb SW c EDd

No. (%) (%) (%) (%)

Fruits 7 203 1.1 19.3 40.5 39.1 Vegetables 7 208 2.8 17.5 43.3 36.4 Cereals 7 200 7.8 25.8 39.6 26.8 Starchy vegetables 7 200 3.6 32.1 45.9 18.4 Dairy products 7 203 1.9 15.4 33.8 48.9 Legumes 7 204 0.8 19.8 38.4 41.0 Red meat 7 207 1.4 29.8 56.3 12.5 White meat 7 205 0.8 29.9 54.0 15.3 Soft drinks 7 205 4.1 28.3 34.5 33.1 Sweets 7 203 6.0 32.8 34.7 26.5 Salty snacks 7 205 7.1 35.6 33.5 23.8 Fast food 7 193 12.3 43.7 32.7 11.3 Bread 6 974 1.1 19.9 35.8 43.2

a N = never. b ENT = every now and then. c SW = sometime during the week. d ED = every day.

worked, in those who lived in house- holds headed by a male, and in ado- lescents living in rural areas. Salty snacks were less frequently consumed by adolescents who worked, who nei- ther studied nor worked, who lived in households headed by a male, and who lived in rural areas.

Consumption of legumes (n = 7 204, N = 16 374 443) was higher in males

(OR = 1.66, 95% CI = 1.09–2.51, χ2 = 5.62, P = 0.018) and in individ- uals with low socioeconomic status as defined by education (χ2 = 15.30, P = 0.002; middle socioeconomic sta- tus: OR = 2.91, 95% CI = 1.58–5.34; low status: OR = 2.40, 95% CI = 1.41–4.10; very low status: OR = 2.28, 95% CI = 1.27–4.10) (results not shown in tables).

DISCUSSION

Considering dietary recommenda- tions (13), the following findings are worrisome: among Mexican adoles- cents only one-third consumed fruits and vegetables daily, a little less than one-half consumed dairy products daily, one-third drank soft drinks daily, and one-fifth of Mexican adoles-

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TABLE 3. Regression models having as dependent variables Mexican adolescents’ consumption of fruits, vegetables, cereals, and dairy products, 2005

Fruitsa Vegetablesa Cerealsa Dairy productsa

OR 95% CI OR 95% CI OR 95% CI OR 95% CI

n b 7 120 7 134 7 127 7 129 N b 16 189 000 16 216 049 16 207 862 16 206 347

Age (years) χ2 = 8.69, P = 0.013 12–14 NAc NA NA 1.00 15–17 1.26 0.89–1.78 18–19 1.81 1.22–2.67

Main activity χ2 = 14.92, P = 0.002 χ2 = 9.01, P = 0.029 χ2 = 17.22, P = 0.001 χ2 = 9.81, P = 0.020 Study 1.00 1.00 1.00 1.00 Work 1.16 0.62–2.19 0.73 0.44–1.22 0.45 0.24–0.85 0.58 0.35–0.95 Study and work 0.50 0.26–0.95 0.94 0.51–1.74 1.18 0.61–2.29 0.56 0.30–1.05 Neither study nor work 0.51 0.34–0.77 0.55 0.36–0.82 0.47 0.30–0.72 0.60 0.37–0.97

SEP,d education χ2 = 35.92, P = 0.000 χ2 = 8.98, P = 0.030 χ2 = 7.81, P = 0.050 χ2 = 10.13, P = 0.018 Very low 0.21 0.12–0.36 0.58 0.32–1.08 0.57 0.32–0.99 0.41 0.22–0.74 Low 0.27 0.16–0.46 0.43 0.23–0.78 0.54 0.30–0.95 0.39 0.21–0.71 Medium 0.41 0.23–0.72 0.47 0.26–0.87 0.83 0.48–1.42 0.50 0.28–0.92 High 1.00 1.00 1.00 1.00

SEP, assets χ2 = 22.63, P = 0.000 χ2 = 33.66, P = 0.000 χ2 = 14.75, P = 0.002 Very low NA 0.32 0.19–0.54 0.26 0.16–0.42 0.38 0.23–0.64 Low 0.64 0.41–1.01 0.43 0.29–0.65 0.66 0.43–1.01 Medium 0.79 0.48–1.29 0.65 0.40–1.04 0.72 0.44–1.16 High 1.00 1.00 1.00

Sex of family’s head χ2 = 3.75, P = 0.053 Male NA NA NA 0.68 0.46–1.01 Female 1.00

Age of family’s head χ2 = 9.72, P = 0.045 29 or less 1.00 NA NA NA 30–39 1.64 0.70–3.84 40–49 2.13 0.91–4.97 50–59 2.36 1.01–5.61 60 or more 3.46 1.32–9.10

Region χ2 = 32.26, P = 0.000 χ2 = 16.71, P = 0.002 χ2 = 23.28, P = 0.000 χ2 = 21.55, P = 0.000 Central 1.00 1.00 1.00 1.00 Northeast 0.54 0.34–0.85 0.70 0.44–1.10 0.76 0.49–1.20 0.50 0.33–0.76 Northwest 0.32 0.18–0.56 0.37 0.22–0.62 0.43 0.25–0.73 0.47 0.27–0.80 Central-West 1.12 0.78–1.61 0.85 0.59–1.22 1.32 0.97–1.81 0.84 0.62–1.13 South 0.53 0.32–0.88 0.58 0.35–0.97 0.67 0.41–1.10 0.45 0.28–0.72

a The “every day” consumption frequency was modeled. b The sample sizes are different because of differences in amount of complete (or missing) data for different combinations of variables. c NA = not available because variables were not statistically significant in regression models. d SEP = socioeconomic position.

cents consumed sweets and salty snacks. Low consumption of fruits and vegetables has also been observed in adolescents in Belgium (14), Costa Rica (8), Spain (15–17), England (18, 19), and Scotland (20).

Although differences by gender have been reported for consumption of fruits, vegetables, dairy products, and red meat (21), in Mexican adolescents

the only difference was found with re- spect to legumes: males exhibited a higher consumption. In Costa Rican adolescents, the same trend was ob- served (8), while in adolescents from Scotland there were no differences (22). NYS05 analysis showed that increased age was associated with more frequent consumption of dairy products. Food- associated meanings could explain

these patterns: increased age and the adoption of certain social roles (i.e., marriage) coincide with increased con- sumption of foods that are symboli- cally related to adulthood (i.e., dairy products) (23).

In Mexico, adolescents who studied and worked and those who neither studied nor worked consumed fruits, sweets, and salty snacks less fre-

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Ortiz-Hernández and Gómez-Tello • Food consumption in Mexican adolescents Original research

TABLE 4. Regression models having as dependent variables Mexican adolescents’ consumption of bread, starchy vegetables, red meat, and white meat, 2005

Breada Starchy vegetablesb Red meatb White meatb

OR 95% CI OR 95% CI OR 95% CI OR 95% CI

n c 6 974 7 182 7 133 7 205 N c 15 406 961 16 337 921 16 207 060 16 371 606

Main activity χ2 = 13.47, P = 0.004 χ2 = 12.92, P = 0.005 Study NAd 1.00 NA 1.00 Work 0.37 0.21–0.66 0.60 0.32–1.12 Study and work 0.71 0.37–1.38 0.70 0.34–1.46 Neither study nor work 0.66 0.40–1.09 0.46 0.29–0.74

SEP,e education χ2 = 15.59, P = 0.001 Very low NA NA 0.34 0.20–0.59 NA Low 0.39 0.22–0.69 Medium 0.45 0.24–0.84 High 1.00

SEP, assets χ2 = 10.73, P = 0.013 χ2 = 13.42, P = 0.004 χ2 = 8.88, P = 0.031 χ2 = 11.41, P = 0.010 Very low 0.53 0.33–0.85 0.57 0.35–0.93 0.47 0.26–0.86 0.40 0.23–0.70 Low 0.96 0.64–1.45 1.06 0.66–1.73 0.87 0.52–1.44 0.69 0.42–1.13 Medium 0.68 0.42–1.10 1.25 0.72–2.16 0.77 0.43–1.39 0.59 0.34–1.04 High 1.00 1.00 1.00 1.00

Sex of family’s head χ2 = 3.65, P = 0.056 Male 0.71 0.50–1.01 NA NA NA Female 1.00

Age of family’s head χ2 = 10.24, P = 0.034 29 or less NA 1.00 NA NA 30–39 0.36 0.15–0.88 40–49 0.42 0.17–1.03 50–59 0.58 0.24–1.44 60 or more 0.32 0.12–0.81

Size of town χ2 = 7.61, P = 0.022 χ2 = 10.26, P = 0.006 χ2 = 7.88, P = 0.020 Rural NA 1.11 0.65–1.91 0.45 0.27–0.76 0.47 0.27–0.81 Semiurban 1.78 1.18–2.68 1.01 0.65–1.56 0.98 0.63–1.52 Urban 1.00 1.00 1.00

Region χ2 = 42.70, P = 0.000 Central 1.00 NA NA NA Northeast 0.41 0.26–0.64 Northwest 0.22 0.13–0.36 Central-West 0.55 0.39–0.77 South 0.55 0.35–0.87

a The “every day” consumption frequency was modeled. b The “sometime during the week” and “every day” consumption frequency were modeled. c The sample sizes are different because of differences in amount of complete (or missing) data for different combinations of variables. d NA = not available because variables were not statistically significant in regression models. e SEP = socioeconomic position.

quently; those who neither studied nor worked consumed vegetables, cereals, dairy products, and white meat less frequently. Adolescents who worked ate cereal, dairy products, and starchy vegetables less frequently. Similar pat- terns were observed in Irish adoles- cents (22). These results could indicate that entering the labor market is re- lated to the adoption of unhealthy eat- ing habits, which could result from these adolescents having their own in- come, which allows them to consume meals prepared outside the home,

which tend to have fewer nutrients and higher energy density (24, 25).

In Mexico, increased age of the head of household was positively related to adolescent fruit consumption as well as to lower consumption of starchy vegetables. It is possible that as heads of household advance in age, they de- velop more child-rearing skills and are more concerned about healthy behav- iors; thus, they tend to provide more food in the home that is perceived to be healthy. With regard to the latter, among Australian adults (26), those

aged between 35 and 49 years con- sumed more fruits, vegetables, and fish but fewer cereals, dairy products, meat, snacks, and sweets than the 18- to 34-year age group.

Considering that women more com- monly adopt health-associated behav- iors (16, 18, 27, 28), we expected that adolescents from households headed by females would have higher con- sumption of foods such as fruits, veg- etables, and milk and lower consump- tion of foods with high energy density. The lower consumption of dairy prod-

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Table 5. Regression models having as dependent variables Mexican adolescents’ consumption of soft drinks, fast food, sweets, and salty snacks, 2005

Soft drinksa Fast foodb Sweetsa Salty snacksa

OR 95% CI OR 95% CI OR 95% CI OR 95% CI

n c 7 205 7 119 7 203 7 205 N c 16 378 624 16 189 514 16 373 658 16 377 539

Main activity χ2 = 16.12, P = 0.001 χ2 = 12.23, P = 0.007 Study NAd NA 1.00 1.00 Work 0.54 0.28–1.02 0.50 0.26–1.00 Study and work 0.44 0.22–0.85 0.40 0.19–0.84 Neither study nor work 0.50 0.32–0.78 0.61 0.39–0.96

SEP,e education χ2 = 13.03, P = 0.005 Very low NA 0.65 0.36–1.16 NA NA Low 0.67 0.38–1.21 Medium 1.43 0.77–2.65 High 1.00

SEP, assets χ2 = 7.86, P = 0.050 χ2 = 20.40, P = 0.000 Very low 0.85 0.54–1.33 0.34 0.21–0.54 NA NA Low 1.43 0.98–2.09 0.59 0.39–0.88 Medium 1.20 0.76–1.91 0.56 0.37–0.90 High 1.00 1.00

Sex of family’s head χ2 = 10.21, P = 0.001 χ2 = 5.29, P = 0.022 χ2 = 4.21, P = 0.040 Male 0.53 0.36–0.78 NA 0.59 0.38–0.93 0.62 0.39–0.98 Female 1.00 1.00 1.00

Size of town χ2 = 21.47, p = 0.000 χ2 = 16.27, P = 0.000 χ2 = 14.40, P = 0.001 Rural 0.31 0.18–0.52 NA 0.35 0.21–0.58 0.31 0.17–0.57 Semiurban 0.62 0.42–0.91 0.88 0.58–1.35 1.00 0.65–1.51 Urban 1.00 1.00 1.00

Region χ2 = 12.54, P = 0.014 Central NA 1.00 NA NA Northeast 2.01 1.32–3.06 Northwest 1.27 0.80–2.03 Central-West 1.44 1.07–1.92 South 1.17 0.75–1.84

a The “every day” consumption frequency was modeled. b The “sometime during the week” and “every day” consumption frequencies were modeled. c The sample sizes are different because of differences in amount of complete (or missing) data for different combinations of variables. d NA, not available because variables were not statistically significant in regression models. e SEP = socioeconomic position.

ucts observed in Mexican adolescents living in households headed by males supports this idea; nonetheless, these adolescents also consumed bread, soft drinks, sweets, and salty snacks less frequently. A possible reason for this finding is that, in households headed by males, it is more likely that a woman (i.e., the wife) plans, pur- chases, and prepares family meals. On the other hand, when a female is the head of household, she is usually a sin- gle mother holding a salaried job, which limits her time for planning, buying, and preparing meals. Thus, fe- male heads of household tend to pur- chase convenient and industrially processed food items.

In Mexican adolescents, consump- tion of fruits, vegetables, cereals, dairy products, starchy vegetables, bread, red meat, white meat, and fast food di- minished with decreasing socioeco- nomic position; conversely, individuals in a low social position consumed legumes and soft drinks more fre- quently. In industrialized countries, adolescents with low social status had lower consumption of fruits (29, 30), vegetables (15, 31–34), cheese (34, 35), and milk (30, 34). It has been observed that Australian adults with low socio- economic position consumed more legumes (26). In adolescents in North- ern, Southern, and Western European countries (15, 29), soft-drink consump- tion was negatively related to socio- economic position; the opposite was observed in Central and Eastern Euro- pean countries (29). There is no consis- tent pattern for the remaining foods. In Spanish adolescents, consumption of salty snacks was negatively related to socioeconomic position (15), whereas in Swedish adolescents it was not re- lated to fast food consumption (34); however, in Swedish female adoles- cents—but not in males—a socioeco- nomic index of residence areas was negatively related to meat, fish, and egg intake (34). In Finnish children and adolescents, there were no socioeco- nomic differences in consumption of meat and meat products (30). In adoles- cents from two Chinese provinces, con- sumption of fruits, juices, milk, yogurt, and soft drinks was lower in the low

socioeconomic group, although rice in- take was higher; in addition, males with high socioeconomic position had higher consumption of shrimp, pork, hamburgers, and chocolate (10). In Costa Rican adolescents, the parents’ educational level was positively related to fruit and vegetable intake (9).

Socioeconomic differences regarding food consumption observed among Mexican adolescents could be partially attributed to food prices in the coun- try: the least expensive products com- prise sugar, oils, and cereals, followed by meat and canned fish, dairy prod- ucts, vegetables, and fruits; the most expensive product is fresh seafood (36). Although in Mexico the prices of beef and chicken, industrialized food (which includes snacks), and food prepared outside the home have de- creased over the past years, these products remain more expensive than others such as sugar and legumes. Moreover, during the past decade the price of basic cereals, such as corn, has increased (36).

With NYS05 data, it was observed that the two indicators for socioeco- nomic position were independently associated with consumption of cer- tain foods. In multivariate models, the head of household’s education and the indicator based on household assets were positively associated with con- sumption of vegetables, cereals, dairy products, red meat, and fast food. This result supports the notion that each so- cioeconomic position indicator mea- sures a different dimension of social stratification (37); therefore, they can be independently related to health be- haviors. Education is the cultural di- mension indicator of socioeconomic stratification, while the household as- sets indicator reflects the wealth of the household. The head of household’s education was negatively related to consumption of legumes; additionally, soft drink consumption was higher in the low and medium strata, as defined by the household-assets indicator, but it was lower in the high and very low socioeconomic strata. This pattern can- not be explained by food prices, be- cause legumes are inexpensive and therefore are accessible to individuals

in the higher strata, while soft drinks in Mexico remain more expensive than other food types (36). Bourdieu (27) stated that starchy foods (such as cere- als and legumes) and those with high energy density are preferred by per- sons with low socioeconomic position because these foods have been sym- bolically associated with qualities such as physical strength.

Compared with Mexican adoles- cents residing in urban localities, those living in rural areas consumed red meat, white meat, soft drinks, sweets, and salty snacks less frequently; ado- lescents from semiurban localities con- sumed starchy vegetables more fre- quently but fewer soft drinks. These differences can be attributed to the fact that urbanization leads to a greater availability of food, especially indus- trially processed food products. In Chinese male adolescents, those resid- ing in urban areas exhibited a higher intake of fruits, juice, milk, and yogurt; in Chinese female adolescents, differ- ences were also observed in fruit and milk consumption, but the opposite pattern was observed for rice con- sumption in both genders and for veg- etables in males (10). In Costa Rican adolescents, those living in urban areas had a higher intake of vegetables but a lower intake of fruits (8). In high- income countries, no clear patterns have been observed with respect to food consumption when comparing urban and rural localities (15, 34).

Compared with adolescents in Cen- tral Mexico, those residing in North- eastern and Central-Western Mexico consumed fast food more frequently. These regions are characterized as having greater economic development and more livestock; additionally, be- cause of their geographic proximity to the United States, it may be implied that these are the first regions where fast food restaurants appeared. On the other hand, adolescents in Central Mexico tended to consume more fruits, vegetables, dairy products, cere- als, and bread. Mexico City is included in this region, where one-fifth of the Mexican population lives and where the country’s most important food dis- tribution centers are located.

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Ortiz-Hernández and Gómez-Tello • Food consumption in Mexican adolescents Original research

In Mexico, one-third of adolescents are overweight or obese (2); the regions with the highest rates are the North (29.4% in males and 31.1% in females) and Mexico City (28.5% and 31.6%, re- spectively); in contrast, the South (20.0% and 24.9%, respectively) has the lowest prevalence of overweight and obesity. Our findings show that the fre- quency and distribution of consump- tion of food with high energy density are similar to the rates of overweight and obesity; the proportion of adoles- cents who daily ingested soft drinks, sweets, and salty snacks are 33.1%, 26.5%, and 23.8%, respectively. Coinci- dentally, the North region is where more adolescents eat fast food. This sit- uation must translate in the design and execution of nutrition education pro- grams focused on reducing the intake of food with high energy density, espe- cially in the North and Mexico City.

One limitation of this research comprises the dietary assessment in- strument. This is due to the following: (1) The investigated food groups in the questionnaire were general; thus, a more detailed analysis concerning spe- cific foods was not possible. (2) It would be helpful to evaluate sepa- rately certain food items included in the same groups (i.e., fish and chicken), because their consumption might not

be related. (3) The consumption of some important foods in the Mexican diet was not assessed, such as eggs, tortillas, and Mexican dishes. (4) Cer- tain consumption-frequency options are ambiguous (i.e., “every now and then,” and “sometime during the week”) and do not permit evaluating the number of servings consumed. Al- though the questionnaire did not allow us to know food consumption in grams, it did allow us to identify dif- ferences in consumption levels. In ad- dition, a strength of the investigation lies in that a probabilistic sample was interviewed, which makes it possible to obtain a general view of dietary habits in Mexican adolescents.

The analysis allowed us to identify groups of adolescents with problem- atic food consumption: the young- est adolescents consumed milk less frequently; those who studied and worked and those who neither studied nor worked consumed fruits less fre- quently, and the group living in house- holds headed by younger persons con- sumed less fruit. In addition, those residing in households headed by fe- males consumed more bread, soft drinks, sweets, and salty snacks; ado- lescents with low socioeconomic posi- tion consumed fruits, vegetables, and dairy products less frequently but

drank soft drinks more frequently; groups considered in a high socioeco- nomic position consumed more fast food but consumed legumes less fre- quently; subjects living in urban areas consumed more soft drinks, sweets, and salty snacks, and those residing in Northeastern and Central-Western Mexico consumed more fast food. Some of the observed results in the Mexican sample are similar to those re- ported by others, which confers higher validity to the conclusions obtained here. This knowledge can be used to design nutritional education pro- grams. Nevertheless, it should be considered that certain differences in consumption can be the result of so- cioeconomic or cultural processes, which are difficult to modify. Finally, some of the proposed explanations for understanding the observed differ- ences in food consumption require ver- ification through qualitative research.

Acknowledgments. We are grateful to the Mexican Institute of Youth for allowing access to the Youth National Survey (YNS) 2005 database. This work could not have been conducted without technical information on the YNS graciously provided by Lic. Sofia Serrano-F. (Instituto Mexicano de la Juventud).

134 Rev Panam Salud Publica/Pan Am J Public Health 24(2), 2008

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REFERENCES

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Objetivo. Examinar la relación entre algunos factores demográficos y socioeconó- micos y el consumo de alimentos en adolescentes mexicanos. Métodos. Se analizó una muestra representativa (n = 7 218) de adolescentes mexica- nos (de 12–19 años). Como variables independientes se emplearon la edad, el sexo y la actividad principal de los adolescentes; el sexo y la edad del jefe del hogar; la posi- ción socioeconómica; el tamaño de la población de residencia (rural, semiurbana o ur- bana) y la zona del país. Se determinó la frecuencia del consumo de 13 grupos de ali- mentos y se evaluó el efecto de las variables independientes sobre la frecuencia de consumo mediante modelos de regresión logística multifactorial. Resultados. Solo una tercera parte de los adolescentes mexicanos consumía frutas y vegetales diariamente, poco menos de la mitad consumía diariamente productos lác- teos, un tercio bebía refrescos todos los días y una quinta parte consumía dulces y go- losinas saladas. Los varones presentaron un mayor consumo de legumbres. Una mayor edad se asoció con una mayor frecuencia de consumo de leche. Los adolescen- tes que trabajaban y los que no trabajaban ni estudiaban consumían frutas, dulces y golosinas saladas con menor frecuencia. El consumo de frutas, vegetales, cereales, productos lácteos, pan, vegetales ricos en almidón, carne roja, carne blanca y comidas instantáneas disminuyó según la posición socioeconómica; además, los grupos de más baja posición socioeconómica consumían legumbres y refrescos con mayor fre- cuencia. Conclusiones. Hay grupos de adolescentes menos propensos a consumir alimentos saludables (como frutas, vegetales y productos lácteos). Se discuten las condiciones socioeconómicas y culturales que pueden explicar las diferencias observadas.

Dieta, adolescente, nivel socioeconómico, México.

RESUMEN

Consumo de alimentos en adolescentes mexicanos

Palabras clave

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Manuscript received on 16 October 2007. Revised version accepted for publication on 19 May 2008.