Considering food habits as a modifiable risk factor, an early intervention on youth
people could avoid future health and social costs. We aim to determine the level of
compliance with the recommendations of the Mediterranean diet pyramid according to
social determinants in university students and to analyse the association of these
social determinants (and their interaction with gender) with different food group
consumption. We used the records of an electronic cross-sectional survey on university
students (n = 593) from inland Spain. The results show, generally, that university
students do not fully comply with the recommendations and that gender is the social
determinant with the greatest effect on differences in food group consumption. Women
have a lower consumption of dairy products, olives, nuts and seeds, red meat, and
processed meat, sweets, eggs, alcoholic drinks and fast food; and a higher consumption
of fruit, compared with men. Socioeconomic status, geographic area, and whether students
cook for themselves have a limited influence on differences in food group consumption,
which is inconsistent with the literature. Policy makers should consider this gender
gap if they wish to implement a policy based on healthy diet, considering that other
social determinants are also important, and could interact with gender.
Introduction
Economic, cultural, and social resources are known to contribute to the unequal distribution
of health outcomes [1], and people with fewer economic resources have shorter life
expectancies and suffer more illness than the wealthy [2]. Socioeconomic disparities
have been shown to be associated with a greater level of all-cause mortality [3],
and although treating current disease is an urgent priority, we should not disregard
taking action on the underlying social determinants of health [4]. The literature
has evidenced the importance of socioeconomic conditions on health and has demonstrated
that socioeconomic adversity is a modifiable risk factor [5,6].
Diet and nutrition are important factors in the promotion and the maintenance of good
health throughout the entire life course [7]. A healthy diet helps protect against
malnutrition in all its forms as well as a range of noncommunicable diseases, including
diabetes, heart disease, stroke and cancer [8]. However, diet is associated with individual,
life-style, social, economic, and geographical factors, among others [9–14]. In other
words, social and economic conditions can generate a social gradient in diet quality
that contributes to health inequalities [2]. There is evidence showing that adverse
childhood and adulthood socioeconomic status in older men is associated with poor
diet quality [15]. In addition, most studies have shown that women follow a healthier
dietary pattern than men [13,14,16–18], underlining differences in food habits. These
inequalities in health–due to gender or material issues–are avoidable [4]; adequate
policies could help counterbalance social and cultural behaviour.
In terms of a healthy dietary pattern, Mediterranean diet meets requirements from
various perspectives. Mediterranean diet is a healthy dietary pattern that may improve
individual health and also obtain social and environmental benefits, among others
[19,20], but there is a clear shift away from this food pattern [21]. The westernization
of diets -increased intake of meat, fat, processed foods, sugar and salt- is also
driven by socioeconomic factors, among other variables [22], and lower-quality diets
-usually more economical- tend to be selected by groups of lower socioeconomic status
[23].
University students are an important group for the promotion of healthy dietary patterns,
because unhealthy lifestyles -including unhealthy diet- are shaped in youth [24–26],
and bad habits can compromise health across one’s life. There are different determinants
of eating behaviour in university students [27]: individual and environmental (physical,
social and macro) factors, and even the characteristics of the university. The literature
has reported that parental socioeconomic position is associated with children’s dietary
patterns [14,28], showing that higher parental occupation and education level are
associated with higher diet quality [29]. Geographical factors can also interact with
others in a complex manner, shaping dietary patterns [8]. Furthermore, young adults
usually exhibit bad eating behaviours during the transition from adolescence to adulthood,
such as skipping meals (or irregular meal consumption) and frequent snacking, among
others, compromising diet quality [30,31]. For this reason, an early intervention
in youth through food and health policies could help to combat different social gaps
and to reduce future economic burden on health systems.
This work uses a sample of students that was used in an earlier work aiming to study
the factors associated with an unhealthy diet [14]. That study analysed diet quality
through the use of an index, while the current work has adopted a different approach,
using new variables. The aim of this new study is dual. On the one hand, we investigate
the level of compliance with the recommendations of the Mediterranean diet pyramid
[32] based on individual food group consumption among university students according
to social determinants, specifically gender, socioeconomic status, location of the
family home, the degree course, and whether the students cook for themselves. On the
other hand, we analyse how these social determinants and the interaction with gender
may affect the consumption of different food groups, the aim being to illustrate problems
related to the intake of these groups, and to encourage the elaboration of specific
public policies in this regard.
Methods
Design
This study was conducted in the Autonomous Community of Castilla-La Mancha, located
in central Spain. Students from the University of Castilla-La Mancha in the cities
of Albacete, Ciudad Real, Cuenca, Talavera de la Reina and Toledo participated in
the study. We conducted an electronic cross-sectional survey with university students.
The design of the study can be consulted in a previous work [14]. The data were collected
using the Survey Monkey software [33].
Participants and environment
A total of 1077 students participated in the study (n = 1077). The final non-probabilistic
sample comprised 593 participants (n = 593, 249 men and 344 women). Fig 1 shows the
data cleaning process [14]. The information about sample, inclusion and exclusion
criteria of participants may be reviewed in our previous work [14].
10.1371/journal.pone.0227620.g001
Fig 1
Data cleaning process.
Ethics approval and consent to participate
All the students were informed of the aims of the study and participated voluntarily.
The completion of the questionnaire was considered to imply informed consent. The
study worked with anonymised information. This research was conducted according to
the guidelines laid down in the Declaration of Helsinki. The Clinical Research Ethics
Committee of the Health Unit of Cuenca certified that the study doesn’t need ethics
approval according to national guidelines (nr: 2018/P1018).
Variables included
The survey collected information on demographic (age, gender), socioeconomic (location
of family home, parental occupation), and food habit characteristics, among others.
Food habit data were collected using a food frequency questionnaire (FFQ) adapted
from a questionnaire previously validated in Spanish adult population [34,35]. Participants
were asked about their consumption of 141 foods divided into 12 groups: i) dairy products;
ii) eggs, meat and fish; iii) vegetables; iv) legumes; v) cereal; vi) oils and fats;
vii) fruit; viii) sweets and desserts; ix) beverages; x) spices; xi) precooked products;
and xii) fast food (Table A in S1 Supporting Information). Individual foods included
in the FFQ can be also seen in Table A in S1 Supporting Information. We readapted
these food groups to those in the Mediterranean diet pyramid (Table B in S1 Supporting
Information).
2.3.1. Food group consumption
The FFQ collected intake frequencies as follows: never or hardly never, one serving
per day, 2 to 3 servings per day, 4 to 5 servings per day, 6 or more servings per
day, 1 to 2 servings per week, 3 to 4 servings per week, 5 or more servings per week,
and 1 to 3 servings per month. We calculated mean daily/weekly servings for each food
group. The food groups and recommended consumption are based on the Mediterranean
diet pyramid [32]. We added an alcoholic beverage group, with the recommended alcohol
intake being based on other studies [36]. Fast food and precooked groups were also
considered in the study. We assumed that recommended consumption of these two groups
was null. There is evidence that shows fast food consumption has associations with
an increased risk of different diseases [37,38]. The composition of the groups can
be consulted in Table B in S1 Supporting Information.
2.3.2. Parental socioeconomic status
Parental occupations were adapted to the major groups in the International Standard
Classification of Occupations (ISCO-08) (one digit) [39], which were then converted
to the International Socio-Economic Index of occupational status (ISEI-08) [40]. The
ISEI-08 is a continuous variable ranged between 10 and 88. This study considered either
the father or mother’s occupation, whichever was the higher [41,42]. Self-employed
parents were included in ISCO group 5 [43], and unemployed/non-working/retired parents
were given the lowest ISEI-08 score (10 points). Mean ISEI scores were calculated
when questionnaire occupations fitted two or more ISCO groups. The ISEI-08 was categorised
into three groups (low, medium and high socioeconomic status), as follows: ISEI<36
(n = 250); 36≤ISEI<62 (n = 238); and ISEI≥62 (n = 105). This categorised variable
is called SES (family’s socioeconomic status) in the study. Table C in S1 Supporting
Information shows the results of this categorisation.
2.3.3. Family home
The questionnaire collected family home as follows: village with < 2,000 inhabitants;
village with 2,001–5,000 inhabitants; small town with 5,001–15,000 inhabitants; small
town with > 15,000 inhabitants; and city. The variable was categorised as follows:
rural (village with < 2,000 inhabitants), suburban (village/small town with 2,001–15,000
inhabitants), and urban (small town with > 15,000 inhabitants and city). This categorisation
was adapted from other study conducted in Spain [44].
2.3.4. Student cooks for him or herself or not
The questionnaire asked whether students cooked for themselves or not. The response
was binomial (yes/no). We named this variable CFHS.
2.3.4. Health or Social Sciences degree
The questionnaire asked students about the degree course they were enrolled on. We
categorised this variable into degrees related to Health Studies or Social Sciences,
calling the variable “Degree”.
Missing data analysis
We performed a multiple imputation procedure to deal with missing data, under the
missing at random assumption (MAR) [45,46]. We excluded from the missing data analysis
participants (n = 153) who: a) did not complete the questionnaire; b) presented invalid
data (i.e.: lack of attention, platform failure). We included participants who completed
the questionnaire, despite their presenting extreme values (i. e. BMI > 35) or missing
values in the data cleaning process. Variables included in the imputation model and
results from pooled regression analyses with imputed values are presented in Table
D in S1 Supporting Information, Table G in S1 Supporting Information, and Figs B-C
in S1 Supporting Information.
Statistical analysis
For the statistical analysis, we conducted a one-way ANOVA (Welch’s ANOVA for unequal
variances) and multiple linear regression. The independent variables were gender,
family’s socioeconomic status, family home, whether the participant cooked for him
or herself during the academic year, and the degree course. The dependent variables
were food groups. We coded independent variables as dummies in the regression, obtaining
the sum of the different comparisons equal to zero [47]. We studied the following
comparisons: a) SES: (1) high and medium SES vs. low SES, (2) high SES vs. medium
SES; b) family home: (1) urban and suburban vs. rural, (2) urban vs. suburban; c)
whether the participant cooked for him or herself during the academic year; d) interaction
effects for: gender and SES (1, 2), gender and family home (1, 2), gender and whether
the participant cooked for him or herself, and gender and the degree course. Following
this regression, we conducted another regression analysis for those dependent variables
which presented significant interactions (p<0.10) among the independent ones, excluding
independent variables with non-significant effects (p>0.10). The correlations between
independent variables were analysed using Spearman’s Correlation Coefficient [48,49]
and they are shown in Fig A in S1 Supporting Information. The dummy coding is shown
in Table E in S1 Supporting Information.
All calculations were made using RStudio [50] and Excel spreadsheet [51].
Results
Table 1 shows the characteristics of the population by student gender. The students’
age, whether they cooked (or not) for themselves, and the degree course were previously
shown in our earlier work [14]. In the present study, we also included the location
of the family home, but using three categories that consider the size of the family
home town. The socioeconomic status of the family is a new variable. The students
mean age was 20.21 years (SD = 3.23) and 42% of respondents were male. Regarding socioeconomic
status, low and medium SES were the broadest groups in both genders, but the low SES
group was larger among women (45.93%). The percentage of students living in an urban
area was 57.17%, followed by suburban (27.32%) and rural (15.51%) areas. In addition,
the percentage of students cooking for themselves was 29.18%. Finally, the percentage
of respondents studying health-related courses was 23.90%, showing significant differences
between genders. Fig A in S1 Supporting Information shows the correlations between
independent variables. The variables have little correlation (|ρ|<0.30).
10.1371/journal.pone.0227620.t001
Table 1
Characteristics of the study sample.
All
Males
Females
P
n (%)
593 (100)
249 (41.99)
344 (58.01)
0.001
Age (mean, SD)
20.21 (3.23)
20.42 (3.21)
20.06 (3.25)
0.176
Family's socioeconomic status (SES) (%)
Low
42.16
36.95
45.93
0.036
Medium
40.13
43.77
37.50
0.146
High
17.71
19.28
16.57
0.457
Family home
Rural
15.51
15.26
15.70
0.976
Suburban
27.32
26.51
26.91
0.776
Urban
57.17
58.23
56.39
0.717
Cooks for him or herself during the academic year (%)
Yes
29.18
28.51
29.65
0.834
No
70.82
71.49
70.35
Degree course (%)
Health Sciences
23.90
14.10
31.10
<0.001
Social Sciences
76.10
85.90
68.90
Note: Gender related-differences between means or percentages calculated using the
t-Student test and χ2.
Tables 2–6 show mean differences in food group consumption for each social determinant.
Table 7 shows and summarises whether students meet recommendations based on the Mediterranean
diet pyramid [32]. Finally, Tables 8 and 9 shows results from the multiple regression
with complete-case analysis. The results of the multiple linear regression with imputed
data can be found in S1 Supporting Information. Figs D-O show the interaction effects
between gender and the other social determinants across food groups and Table F in
S1 Supporting Information summarises the information on these figures.
10.1371/journal.pone.0227620.t002
Table 2
Mean differences in food group consumption by gender (n = 593).
Gender
Food group
All
Men(n = 249)
Women(n = 344)
Daily
Servings
a
Mean (SD)
Mean (SD)
Mean (SD)
P
Dairy products
2
2.93 (2.02)
3.26 (2.14)
2.70 (1.90)
<0.001
Olives, nuts, seeds
1–2
0.34 (0.48)
0.39 (0.50)
0.31 (0.45)
0.045
Herbs, spices, garlic, onions
-
0.57 (0.74)
0.62 (0.87)
0.53 (0.63)
0.153
Fruits
3–6
2.89 (2.34)
2.66 (1.75)
3.06 (2.68)
0.029┼
Vegetables
≥ 6
2.23 (2.40)
2.08 (2.61)
2.33 (2.23)
0.205
Olive oil
3
1.17 (0.90)
1.10 (0.90)
1.23 (0.90)
0.074
Bread, pasta, rice, other cereals
3–6
2.28 (1.44)
2.36 (1.46)
2.22 (1.43)
0.236
Weekly
Potatoes
≤ 3
1.32 (1.49)
1.35 (1.44)
1.30 (1.52)
0.685
Red meat and processed meat
< 2
12.90 (9.10)
14.09 (9.04)
12.05 (9.05)
0.007
Sweets
≤ 2
6.39 (6.32)
7.07 (6.90)
5.89 (5.83)
0.026
White meat
2
3.46 (3.35)
3.68 (3.42)
3.31 (3.30)
0.185
Fish, seafood
≥ 2
5.61 (4.35)
5.19 (4.38)
5.70 (4.34)
0.570
Eggs
2–4
2.79 (3.24)
3.61 (4.28)
2.20 (2.02)
<0.001┼
Legumes
≥ 2
3.50 (2.75)
3.75 (2.73)
3.32 (2.75)
0.056
Other food groups of interest
Alcoholic drinks (daily)
1–2 AU/d
0.70 (1.40)
0.98 (1.74)
0.50 (1.05)
<0.001┼
Fast food (weekly)
0
4.48 (2.98)
4.99 (3.20)
4.12 (2.76)
<0.001┼
Precooked food (weekly)
0
7.20 (6.11)
7.12 (4.87)
7.26 (6.87)
0.796
Abbreviations: AU: Alcohol Units
a. Recommendations based on the Mediterranean diet pyramid and other studies [32,36]
Level of significance of the observed differences between means as assessed by one-way
ANOVA or Welch's ANOVA (┼).
10.1371/journal.pone.0227620.t003
Table 3
Mean differences in food group consumption by family’s socioeconomic status (n = 593).
Socioeconomic status
Food group
Servings
a
H
M
L
(n = 105)
(n = 238)
(n = 250)
Daily
Mean (SD)
Mean (SD)
Mean (SD)
P
Dairy products
2
2.77 (1.51)
2.98 (2.07)
2.95 (2.16)
0.663
Olives, nuts, seeds
1–2
0.35 (0.45)
0.34 (0.47)
0.34 (0.50)
0.968
Herbs, spices, garlic, onions
-
0.50 (0.66)
0.57 (0.74)
0.60 (0.76)
0.531
Fruits
3–6
2.65 (2.07)
2.92 (2.46)
2.97 (2.33)
0.473
Vegetables
≥ 6
2.52 (3.02)
2.23 (2.53)
2.10 (1.93)
0.330
Olive oil
3
1.27 (1.04)
1.13 (0.86)
1.18 (0.88)
0.421
Bread, pasta, rice, other cereals
3–6
2.29 (1.58)
2.29 (1.45)
2.27 (1.37)
0.985
Weekly
Potatoes
≤ 3
1.30 (1.27)
1.40 (1.43)
1.26 (1.62)
0.564
Red meat and processed meat
< 2
12.73 (10.01)
13.93 (9.10)
12.01 (8.62)
0.064
Sweets
≤ 2
6.34 (7.08)
6.37 (6.23)
6.42 (6.09)
0.994
White meat
2
3.09 (2.60)
3.67 (3.54)
3.42 (3.44)
0.325
Fish, seafood
≥ 2
5.74 (4.65)
5.81 (4.21)
5.37 (4.36)
0.508
Eggs
2–4
3.04 (4.30)
2.71 (2.91)
2.76 (3.03)
0.677
Legumes
≥ 2
3.35 (2.01)
3.68 (2.94)
3.39 (2.82)
0.422
Other food groups of interest
Alcoholic drinks (daily)
1–2 AU/d
0.74 (1.48)
0.62 (0.99)
0.78 (1.68)
0.437
Fast food (weekly)
0
0.67 (0.46)
0.67 (0.45)
0.60 (0.39)
0.163
Precooked food (weekly)
0
1.09 (1.00)
1.06 (0.74)
0.98 (0.93)
0.420
Abbreviations: AU: Alcohol Units; H: high; M: medium; L: low; SES: socioeconomic status.
a. Recommendations based on the Mediterranean diet pyramid and other studies (32,36).
Level of significance of the observed differences between means as assessed by one-way
ANOVA.
10.1371/journal.pone.0227620.t004
Table 4
Mean differences in food group consumption by location of the family home (n = 593).
Family home
Food group
Servings
a
U
SU
R
(n = 339)
(n = 162)
(n = 92)
Daily
Mean (SD)
Mean (SD)
Mean (SD)
P
Dairy products
2
3.01 (2.12)
2.89 (1.88)
2.72 (1.88)
0.458
Olives, nuts, seeds
1–2
0.36 (0.49)
0.28 (0.44)
0.40 (0.48)
0.127
Herbs, spices, garlic, onions
-
0.62 (0.83)
0.54 (0.62)
0.45 (0.55)
0.155
Fruits
3–6
2.92 (2.45)
2.79 (2.15)
3.01 (2.26)
0.746
Vegetables
≥ 6
2.40 (2.62)
2.05 (2.33)
1.90 (1.39)
0.110
Olive oil
3
1.20 (0.95)
1.09 (0.82)
1.25 (0.85)
0.332
Bread, pasta, rice, other cereals
3–6
2.35 (1.48)
2.08 (1.31)
2.37 (1.51)
0.106
Weekly
Potatoes
≤ 3
1.35 (1.60)
1.21 (1.31)
1.43 (1.36)
0.455
Red meat and processed meat
< 2
12.49 (8.38)
13.31 (10.74)
13.73 (8.46)
0.414
Sweets
≤ 2
6.68 (6.73)
5.51 (5.01)
6.82 (6.73)
0.116
White meat
2
3.17 (3.15)
3.65 (3.08)
4.21 (4.28)
0.022*
Fish, seafood
≥ 2
5.63 (4.43)
5.52 (4.49)
5.68 (3.82)
0.946
Eggs
2–4
2.64 (2.91)
2.88 (3.96)
3.18 (2.99)
0.343
Legumes
≥ 2
3.57 (2.98)
3.21 (2.13)
3.77 (2.83)
0.229
Other food groups of interest
Alcoholic drinks (daily)
1–2 AU/d
0.69 (1.60)
0.72 (1.13)
0.72 (1.02)
0.970
Fast food (weekly)
0
0.64 (0.42)
0.62 (0.38)
0.67 (0.5)
0.627
Precooked food (weekly)
0
1.03 (0.75)
1.00 (0.82)
1.07 (1.28)
0.828
Abbreviations: AU: Alcohol Units; U: Urban; SU: Suburban; R: Rural.
a. Recommendations based on the Mediterranean diet pyramid and other studies (32,36).
Level of significance of the observed differences between means as assessed by one-way
ANOVA.
* Significant differences in consumption between urban and rural area (the post-hoc
analysis was performed with Tukey Honest Significant Differences).
10.1371/journal.pone.0227620.t005
Table 5
Mean differences in food group consumption depending on whether students cook for
themselves or not (n = 593).
CFHS
Food group
Servings
a
Yes
No
Daily
Mean (SD)
Mean (SD)
P
Dairy
2
2.86 (1.91)
2.97 (2.06)
0.527
Olives, nuts, seeds
1–2
0.29 (0.36)
0.37 (0.51)
0.059
Herbs, spices, garlic, onions
-
0.56 (0.81)
0.57 (0.71)
0.850
Fruits
3–6
3.05 (2.52)
2.83 (2.26)
0.312
Vegetables
≥ 6
2.33 (2.96)
2.18 (2.12)
0.500
Olive oil
3
1.21 (0.92)
1.16 (0.9)
0.601
Bread, pasta, rice, other cereals
3–6
2.07 (1.34)
2.37 (1.47)
0.020
Weekly
Potatoes
≤ 3
1.43 (1.85)
1.28 (1.31)
0.280
Red meat and processed meat
< 2
12.55 (9.54)
13.06 (8.91)
0.541
Sweets
≤ 2
5.58 (4.81)
6.72 (6.82)
0.045
White meat
2
3.79 (3.52)
3.33 (3.27)
0.131
Fish, seafood
≥ 2
5.24 (3.92)
5.76 (4.51)
0.181
Eggs
2–4
3.32 (4.38)
2.57 (2.61)
0.037┼
Legumes
≥ 2
3.25 (2.92)
3.60 (2.67)
0.151
Other food groups of interest
Alcoholic drinks (daily)
1–2 AU/d
0.77 (1.24)
0.68 (1.46)
0.484
Fast food (weekly)
0
0.63 (0.44)
0.64 (0.42)
0.769
Precooked food (weekly)
0
1.03 (1.11)
1.03 (0.76)
0.941
Abbreviations: AU: Alcohol Units; CFHS: cooks for him or herself
a. Recommendations based on the Mediterranean diet pyramid and other studies [32,36]
Level of significance of the observed differences between means as assessed by one-way
ANOVA or Welch's ANOVA (┼)
10.1371/journal.pone.0227620.t006
Table 6
Mean differences in food group consumption by degree course (n = 593).
Degree
Food group
Servings
a
Health Sciences
Social Sciences
Daily
Mean (SD)
Mean (SD)
P
Dairy
2
2.85 (1.90)
2.96 (2.06)
0.589
Olives, nuts, seeds
1–2
0.36 (0.46)
0.34 (0.48)
0.691
Herbs, spices, garlic, onions
-
0.56 (0.68)
0.57 (0.76)
0.878
Fruits
3–6
3.02 (2.05)
2.85 (2.43)
0.458
Vegetables
≥ 6
2.56 (2.11)
2.12 (2.47)
0.059
Olive oil
3
1.48 (1.07)
1.08 (0.82)
<0.001┼
Bread, pasta, rice, other cereals
3–6
2.57 (1.50)
2.19 (1.41)
0.005
Weekly
Potatoes
≤ 3
1.39 (1.33)
1.30 (1.53)
0.536
Red meat and processed meat
< 2
12.07 (8.80)
13.17 (9.18)
0.210
Sweets
≤ 2
5.85 (6.74)
6.55 (6.18)
0.251
White meat
2
3.00 (2.07)
3.61 (3.65)
0.061
Fish, seafood
≥ 2
5.59 (3.85)
5.62 (4.50)
0.952
Eggs
2–4
2.58 (2.93)
2.85 (3.33)
0.388
Legumes
≥ 2
3.57 (2.82)
3.48 (2.73)
0.739
Other food groups of interest
Alcoholic drinks (daily)
1–2 AU/d
0.29 (0.54)
0.83 (1.56)
<0.001┼
Fast food (weekly)
0
0.60 (0.40)
0.65 (0.43)
0.229
Precooked food (weekly)
0
0.93 (0.75)
1.06 (0.91)
0.107
Abbreviations: AU: Alcohol Units; CFHS: cooks for him or herself
a. Recommendations based on the Mediterranean diet pyramid and other studies [32,36]
Level of significance of the observed differences between means as assessed by one-way
ANOVA or Welch's ANOVA (┼)
10.1371/journal.pone.0227620.t007
Table 7
Compliance with the recommendations of the Mediterranean diet pyramid (n = 593).
Food group
Gender
SES
Family home
CFHS
Degree Course
Daily
Servings
a
M
W
H
Med.
L
U
SU
R
Yes
No
HE
SO
Dairy
2
Olives, nuts, seeds
1–2
Herbs, spices, garlic, onions
NA
Fruits
3–6
Vegetables
≥ 6
Olive oil
3
Bread, pasta, rice, other cereals
3–6
Weekly
Potatoes
≤ 3
Red meat and processed meat
< 2
Sweets
≤ 2
White meat
2
Fish, seafood
≥ 2
Eggs
2–4
Legumes
≥ 2
Other food groups of interest
Alcoholic drinks (daily)
1–2 AU/d
Fast food (weekly)
0
Precooked food (weekly)
0
Abbreviations: AU: Alcohol Units; CFHS: Cooks for him or herself; H: High; HE: Health
Studies; L: Low; M: Men; Med.:
Medium, R: Rural, SES: socioeconomic status; SO: Social Sciences SU: Semiurban; U:
Urban; W: Women
a. Recommendations based on the Mediterranean diet pyramid and other studies [32,36]
10.1371/journal.pone.0227620.t008
Table 8
Multiple regression analysis of food groups based on the Mediterranean diet pyramid,
social determinants and interactions.
Food group
Gender
Socioeconomic position
Family home
CFHS
Degree
Interactions
Daily
SES (1)
SES (2)
Family home (1)
Family home (2)
Gender x SES (1)
Gender x SES (2)
Gender x Family home (1)
Gender x Family home (2)
Gender x CFHS
Gender x Degree
Dairy
0.043
-0.054
-0.047
0.051
0.035
-0.020
-0.013
-0.048
-0.072
0.065
0.037
-0.010
-0.037
Olives, nuts, seeds
0.127
┼
-0.018
0.005
-0.070
0.060
-0.068
0.058
-0.016
0.009
0.036
0.044
0.049
0.079
Herbs, spices, garlic, onions
0.064
-0.060
-0.033
0.067
0.059
0.013
0.002
0.043
0.017
-0.025
0.056
-0.003
-0.003
Fruits
-0.046
-0.030
-0.040
-0.011
0.026
0.039
0.036
-0.012
<0.001
0.029
-0.050
-0.024
0.070
Vegetables
-0.100
0.057
0.045
0.060
0.067
0.066
0.025
0.042
0.013
0.005
0.031
0.024
-0.104
┼
Olive oil
0.001
0.008
0.058
-0.045
0.032
0.024
0.197***
-0.043
0.041
-0.006
-0.017
-0.03
0.062
Bread, pasta, rice, other cereals
0.140*
0.007
<0.001
-0.053
0.033
-0.087*
0.130**
0.118*
0.041
0.010
-0.077
┼
0.015
0.017
Weekly
Potatoes
-0.009
0.028
-0.026
-0.031
0.045
0.039
0.042
-0.009
-0.032
0.001
0.018
-0.115*
0.064
Red meat and processed meat
0.120
┼
0.083
┼
-0.050
-0.039
-0.045
-0.020
0.004
0.053
0.016
0.052
0.081
┼
0.033
0.072
Sweets
0.066
-0.039
-0.006
-0.048
0.082
┼
-0.081
┼
-0.032
-0.032
0.023
0.051
0.048
0.009
0.022
White meat
0.093
0.028
-0.061
-0.079
┼
-0.049
0.054
-0.032
0.017
-0.040
0.016
0.015
0.090
┼
0.056
Fish, seafood
-0.066
0.034
-0.014
-0.025
0.004
-0.059
-0.008
-0.043
-0.061
0.001
0.027
-0.022
0.011
Eggs
0.272***
0.032
0.052
-0.022
-0.036
0.106*
0.023
0.021
0.067
0.050
-0.078
┼
0.025
0.029
Legumes
0.139*
0.031
-0.047
-0.067
0.035
-0.039
0.027
0.091*
-0.036
-0.035
-0.013
0.121*
-0.025
Other food groups of interest
Alcoholic drinks
0.056
-0.067
0.032
0.006
0.029
0.010
-0.162***
-0.096*
-0.028
0.007
0.041
-0.036
-0.061
Fast food
0.182**
0.079
┼
0.003
-0.059
0.008
-0.010
-0.021
0.049
-0.005
-0.099*
-0.016
-0.022
0.007
Precooked food
-0.054
0.06
0.011
-0.022
0.017
0.010
-0.064
-0.040
-0.098*
0.035
-0.013
0.005
0.034
Data reported as standardised beta coefficients (β’). Abbreviations: CFHS: Cooks for
him or herself; SES: socioeconomic status.
┼P<0.10;
*P<0.05;
**P<0.01;
***P<0.001
10.1371/journal.pone.0227620.t009
Table 9
Multiple regression analysis: Fitted models for significant interactions.
Food group
Gender
Socioeconomic position
Family home
CFHS
Degree
Interactions
Daily
SES (1)
SES (2)
Family home (1)
Family home (2)
Gender x SES (1)
Gender x SES (2)
Gender x Family home (1)
Gender x Family home (2)
Gender x CFHS
Gender x Degree
Dairy
-
-
-
-
-
-
-
-
-
-
-
-
-
Olives, nuts, seeds
-
-
-
-
-
-
-
-
-
-
-
-
-
Herbs, spices, garlic, onions
-
-
-
-
-
-
-
-
-
-
-
-
-
Fruits
-
-
-
-
-
-
-
-
-
-
-
-
-
Vegetables
-0.102
┼
-
-
-
-
-
0.033
-
-
-
-
-
-0.103
┼
Olive oil
-
-
-
-
-
-
-
-
-
-
-
-
-
Bread, pasta, rice, other cereals
0.113*
0.001
-
-
0.029
-0.080
┼
0.122**
0.108*
-
-
-0.077
┼
-
-
Weekly
Potatoes
-0.036
-
-
-
-
0.040
-
-
-
-
-
-0.128**
-
Red meat and processed meat
0.073
┼
0.080
┼
-
-
-0.043
-
-
-
-
-
0.098*
-
-
Sweets
-
-
-
-
-
-
-
-
-
-
-
-
-
White meat
0.089*
-
-
-0.085*
-
0.056
-
-
-
-
-
0.080
┼
-
Fish, seafood
-
-
-
-
-
-
-
-
-
-
-
-
-
Eggs
0.239***
-
-
-
-0.032
0.100*
-
-
-
-
-0.074
-
-
Legumes
0.145*
0.046
-
-
-
-0.027
-
0.098*
-
-
-
0.134**
-
Other food groups of interest
Alcoholic drinks
0.137**
-0.066
-
-
-
-
-0.135**
-0.076
┼
-
-
-
-
-
Fast food
0.177***
0.070
┼
-
-0.055
-
-
-
-
-
-0.090*
-
-
-
Precooked food
-0.036
-
-0.006
-
-
-
-
-
-0.087*
-
-
-
-
Data reported as standardised beta coefficients (β’). Abbreviations: CFHS: Cooks for
him or herself; SES: socioeconomic status.
┼P<0.10;
*P<0.05;
**P<0.01;
***P<0.001
Gender
Table 2 shows mean differences in the number of servings of food groups between men
and women. Following the recommendations based on the Mediterranean diet pyramid [32],
men failed to comply with the recommendations on olives, nuts and seeds; fruits; vegetables;
olive oil; bread, pasta, rice, and other cereals; red meat and processed meat; sweets;
and alcoholic beverages (Table 7). Women showed the same habits but complied with
recommendations on fruit intake. Men consumed more dairy products, olives, nuts and
seeds, red meat and processed food, sweets, eggs, alcohol and fast food compared to
women, while women consumed more fruit (Table 2). The multiple regression analysis
(Table 8) shows a positive association (p<0.05) between being male and consumption
of bread, pasta, rice, other cereals, eggs, legumes, and fast food. In addition, the
fitted model for interaction effects (Table 9) also suggests a positive association
between being male and alcohol consumption.
Parental socioeconomic status
Table 3 shows mean differences in the number of servings of food groups between high,
medium and low socioeconomic status (SES). Students comply with the recommendations
on dairy products, potatoes, white meat, fish and seafood, eggs and legumes, despite
socioeconomic position (Table 3). There is no difference in mean food group consumption
across different categories. Students with high or medium SES exhibit a positive association
between the consumption of red meat and fast food compared with students with low
SES at 0.10 level of significance (Table 8). Interaction effects (Tables 8–9 and F)
suggest that men in this social group present higher consumption of servings of bread,
pasta rice, other cereals and legumes, and a lower consumption of alcoholic drinks.
This means that men with low SES have a higher mean consumption of alcoholic beverages.
This is also shown in Table 9 at 0.10 level of significance. Comparing men with high
SES and medium SES, men in the former group show a lower consumption of precooked
food. Being female with high/medium SES is negatively associated with the consumption
of bread, pasta, rice, other cereals and legumes, but female students with high SES
(in contrast to medium SES) show a higher consumption of precooked food.
Location of family home
Table 4 shows mean differences in the number of servings of food groups between students
with family homes in urban, suburban or rural areas. On the one hand, there are no
differences in compliance with the recommendations depending on the location of the
family home, except for fruit consumption in rural area (vs. urban area) (Table 7).
There are mean differences in white meat consumption between urban and rural areas.
Multiple linear regression results show there are no significant associations between
food group consumption and the location of family home at 5% level of significance.
At 0.10 level of significance, being from a family living in a rural area is positively
associated with the consumption of white meat (compared with urban/rural area), while
being from a family living in an urban area shows a positive association with sweet
consumption (compared with suburban area).
Interaction effects (Table F) suggest that men from a family living in an urban or
suburban area have a lower consumption of fast food; and, at 0.10 level of significance,
those from a family living in an urban area (vs. a suburban area) have a higher consumption
of bread, pasta, rice, other cereals and red meat and processed meat, and a lower
consumption of eggs, but this effect was lost when we fitted the model (Table 9).
On the other hand, being female from a family living in an urban or suburban area
shows a positive association with the consumption of fast food; and women from a family
living in an urban area vs. a suburban area also show a positive association with
the consumption of bread, pasta, rice, other cereals, eggs (effect lost in the fitted
model), and a negative association with the consumption of red meat.
Student cooks for him or herself or not
We analysed whether students cooked for themselves or not yielded differences in the
mean number of servings across food groups (Table 5). Students who cook for themselves
meet recommendations on fruit consumption, but there are no other differences in meeting
recommendations. Participants who cook for themselves have lower consumption of bread,
pasta, rice, other cereals and sweets, and higher level of consumption of eggs.
The results of the regression analysis indicate that students who do not cook for
themselves show a positive association with the consumption of bread, pasta, rice,
and other cereals (at 0.05 level of significance). At 0.10 level of significance,
this group shows a positive association with the consumption of sweets. In addition,
the results show that students who cook for themselves are positively associated with
consumption of eggs. Interaction effects (Table F) show that men who cook for themselves
show a positive association with the consumption of potatoes and a higher consumption
of white meat and legumes, while women who cook for themselves have a higher consumption
of potatoes and a lower consumption of legumes.
Degree course
Table 6 shows food group consumption by degree course: Health Studies or Social Sciences.
Students enrolled on a health-related degree course meet recommendations on fruit
consumption, but show the same behaviour as students enrolled in Social Sciences in
the rest of food groups. There are significant mean differences in consumption of
olive oil, bread, pasta, rice, other cereals, and alcoholic drinks between Health
and Social Sciences students, showing that Health Sciences students have a higher
consumption of olive oil and cereals, and a lower alcohol consumption. The results
of the regression show that students studying health-related courses are positively
associated with the consumption of olive oil, bread, pasta, rice and other cereals,
and negatively with the consumption of alcohol. Interaction effects suggest that women
studying health-related courses have a higher consumption of vegetables, while consumption
among their male peers is lower, comparing both analyses with social sciences students.
Results of multiple imputation
We performed two additional regressions with imputed data (m = 5 and m = 30 subsets).
Table G in S1 Supporting Information shows a summary of the results of these regressions
compared with complete-case regression at 0.10 level of significance. The comparison
partially confirms the results from our complete-case analysis. Regarding gender,
the association with the consumption of olives, nuts, and seeds, bread, pasta, rice
and others, eggs, and fast food is confirmed by the three analyses. The association
with red meat and legume consumption is confirmed by two analyses. The association
with the consumption of fast food is confirmed in the case of families with high or
medium socioeconomic status in all analyses, and red meat consumption is confirmed
in two of them. The three analyses confirmed white meat consumption (urban/suburban
vs. rural areas) and sweet consumption (urban vs. suburban areas). The consumption
of bread, pasta, rice, and others, and eggs is confirmed by the three analyses in
the cooking habits variable, and sweet consumption in two of them. The three analyses
also confirmed the consumption of bread, pasta, rice and other cereals, and alcoholic
drinks among health and social science students. As regards interactions, they are
wholly confirmed for only two regressions: i) gender and socioeconomic position (high/medium
vs. low socioeconomic position) interact with the consumption of bread, pasta, rice,
and others; ii) gender and degree course interact with the consumption of olive oil.
Discussion
This study had two main objectives, which we addressed by means of two analyses. First,
we studied the level of compliance with the recommendations of the Mediterranean diet
pyramid, stratifying a university sample by five social determinants: gender, socioeconomic
status, location of family home, whether the student cooks for him or herself, and
the degree course. In this analysis, we included the study of mean differences in
food group consumption. Second, we studied differences in food group consumption according
to these social determinants and the interaction with gender of socioeconomic status,
location of family home, whether the students cook for themselves, and the degree
course. To develop this analysis, we performed multiple regression analysis using
both complete-case data and imputed data. Our participants had similar ages to those
in other studies in university population [31,52–54].
The results from the first analysis indicate, generally, that university students
do not fully comply with the recommendations. These results coincide with other studies
in the case of fruits and vegetables consumption [55], but not in fish consumption.
In addition, in our study female students and participants (both gender) with the
family home located in a rural area moderately comply with the recommendations on
fruits. Most students, regardless of social determinants, do not comply with the recommendations
on daily consumption of olives, nuts and seeds, fruits, vegetables, olive oil, bread,
pasta, rice and other cereals, which is consistent with another study [52]. The weekly
recommended consumption of red meat and processed meat and sweets is not satisfied,
coinciding with the findings of another study using different dietary guidelines [52].
Low compliance with the recommendations of the Mediterranean diet pyramid has been
assessed in other studies [56,57], showing that adherence to the Mediterranean dietary
pattern is declining among adults and shifting towards a less healthy Western dietary
pattern. The loss of the Mediterranean dietary pattern has significant implications
in individual health and healthcare systems. It has been widely reported that greater
adherence to Mediterranean diet may improve health status [20], and thus promoting
the Mediterranean diet is a key point for public health policy not only due to individual
health outcomes, but also for its social, economic and environmental benefits [19].
The results of the second analysis indicate that gender is the social determinant
with the largest effect on mean differences in food group consumption. Many works
have shown that gender is associated with food habits [13,14,16–18,52,54,58], and,
as we indicated in the Introduction section, women usually exhibit better food habits
than their male counterparts [13,14,16–18]. In the case of male students, our study
shows they have a higher intake of dairy products, olives, nuts and seeds, red meat
and processed meat, sweets, eggs, alcoholic drinks and fast food. Despite women not
complying with most of the Mediterranean diet recommendations, they appear to have
healthier dietary patterns than men, according to the literature. The multiple regression
analysis confirms these results for the groups of olives, nuts, seeds (at 0.10 level
of significance), bread, pasta, rice and others, red meat, eggs, legumes, and fast
food, but not for the alcoholic drinks and sweets. This suggests that other variables
could influence the consumption of sweets, and alcoholic drinks. In our analysis,
we found interactions with socioeconomic position for the alcoholic drink food group.
However, the fitted models for interactions showed a positive association between
being male and alcohol consumption, with the interaction effect being maintained with
socioeconomic position. This last analysis also shows a positive association between
being female and vegetable consumption and a positive interaction with studying health-related
courses. These results in men coincide with other studies in university and adult
population for the case of red meat [52,59,60]. Other studies also indicate that men
have a higher consumption of alcoholic drinks [53,60,61], eggs [52,61], and sweets
[52]. In addition, in the case of female students, fruit consumption is higher than
among their male counterparts [52,54,59,61].
Our results indicate that socioeconomic status, geographic area, whether the students
cook for themselves, and the degree course have a limited influence on differences
in food group consumption. Socioeconomic status shows no differences in any of the
food groups, which is inconsistent with the previous literature in adult population
[9,62–64]. However, the interaction with gender in the regression analyses show differences
in bread, pasta, rice and other cereals, legumes, alcoholic drinks, and precooked
food. Geographical differences, measured by location of the family home -urban, suburban,
or rural- have been found for white meat consumption, where students whose families
live in rural areas show a higher consumption comparing with urban areas. The limited
influence of geographic area has been reported in another study [61]. Moreover, the
interaction effect of geographic area with gender shows there are differences in consumption
of bread, pasta, rice and others, red meat, eggs and fast food. However, when the
fitted models were studied, the interaction of family home with egg consumption was
lost. Students who cook for themselves have a lower consumption of bread, pasta, rice
and other cereals, sweets, and a higher consumption of eggs. In addition, the interaction
of gender with this variable shows differences in consumption of potatoes, white meat
and legumes. Studying Health or Social Sciences degree courses shows differences in
the consumption of olive oil, bread, pasta, rice, and others, and alcoholic drinks,
which are confirmed by the regression analysis. Students of Social Sciences show higher
consumption of alcoholic drinks, supported by an article with similar results [65].
The lack of notable differences between the two student profiles (Health and Social
Sciences) was unexpected, because a previous work found that studying a non-health
related course was associated with an unhealthy diet [14]. This could be explained
because that particular work used an index and not the overall consumption of food
groups. However, and coinciding with our results, a study on a sample of Health Science
students showed that studying health-related courses did not guarantee better choices
in food habits [66].
Despite our results being partly inconsistent with other results in the previous literature
on social determinants [9,67], they do coincide in the low adherence to Mediterranean
diet and we have previously discussed the importance of this dietary pattern. In a
previous work [14], 47.90% of students exhibited an unhealthy dietary pattern, which
was equivalent to low adherence to Mediterranean diet, and the results of this new
work and the earlier one coincide in the importance of developing healthy food habits
among university students.
The previous work [14] aimed to analyse the association of individual and social characteristics
of the sample with quality of diet, categorising an index of adherence to the Mediterranean
diet as healthy/unhealthy diet [36,68]. The previous work [14] aimed to analyse the
association between the individual and social characteristics of the sample and quality
of diet, categorising an index of adherence to the Mediterranean diet as healthy/unhealthy
diet [36,68]. We decided to adopt a different approach in this work because the previous
study presented a knowledge gap that we wish to fill. Despite an index usually being
a good indicator and showing a general picture of the food habits in the study sample
through a global score, it does not clearly show in what food groups decision makers
should improve public policies. The previous work studied individual characteristics
of the sample (such body mass index), but in this work we focus on social determinants,
disregarding the former. For this reason, we followed a different approach in order
to show which food groups pose (or not) a problem in the pursuit of a healthier dietary
pattern, which could improve long-term health. This new approach may facilitate the
elaboration of public policies in some particular groups of students for a specific
food group.
Following our results, policy makers should make an effort to promote the Mediterranean
diet among university population due to its many benefits [19,20], as students do
not fully comply with the recommendations on different food groups. In addition, they
should to address the gender gap in the consumption of unhealthy foods, such as sweets,
alcoholic drinks and fast food (men showed a higher consumption of these groups),
and in healthy foods, such as vegetables or fruits, where men showed a lower consumption,
but legumes consumption is higher among men with a better socioeconomic position and
who also cook for themselves. Regarding other social determinants, knowledge of healthy
food habits should be improved among Social Science students considering the interaction
with gender. Despite our results not showing a substantial association with socioeconomic
position, it should be considered since previous literature has shown the influence
of socioeconomic status on food habits. In addition, and concerning family home, policy
efforts may not be necessary.
This study is not without limitations and the results should be interpreted with caution.
First, self-reported food consumption by FFQ can give rise to measurement error [69].
Second, given the characteristics of food frequency questionnaires a memory and social
desirability bias might have influenced the results. Third, we could not assess the
recommended servings of herbs, spices, garlic and onions because of a lack of information
in dietary guideline. A further limitation regards the sample. The final sample represented
4% of the population (593/15,278). Using multiple imputation techniques, we were working
with 924 students, who represented 6% of the population. In addition, we did not distinguish
between students by year of study (i.e.: first, second- or third-year students).
However, the study has certain strengths. To address FFQ measurement error, we used
the criterion of recommended intake in kilocalories, which has no substantial differences
from other methods [70,71]. In addition, we dealt with the missing data by using a
multiple imputation technique. The multiple regression with the imputed data confirms
partially the results from the multiple regression with complete-case analysis and
produced comparable standard errors.
The absence of substantive differences by socioeconomic status, geographic area, whether
the students cook for themselves, and the degree course could have various explanations.
The study population was young and, as noted in a particular study [22], there is
a global “nutrition transition” around, which is associated with different diseases
and is related to the westernization of diets, and our sample could be affected by
these changes. In addition, studies examining socioeconomic disparities usually focus
on adult or adolescent populations, and their behaviour may differ from that of a
university population. Moreover, university students are a group with special characteristics:
small age range, first life stage with more permissive parental control, changes in
physical environment, generational socio-cultural norms and values, among others [27].
However, the weak or non-existent in three of four social determinants in our university
sample is still important. If policy makers wish to implement a policy based on healthy
diet (e.g. Mediterranean diet) in a university population, they must focus their attention
on the gender gap (here, the case of women is partially more favourable). Evidently,
policy makers should also not forget the social gradient in diet quality. Public policies
and health strategies could shape the material conditions of society, helping to improve
populations’ long-term health.
Conclusion
This study shows that university students do not fully comply with recommendations
on the Mediterranean diet pyramid. In addition, gender is the social determinant with
the largest effect on food group consumption. Women have a lower consumption of dairy
products, olives, nuts and seeds, red meat, and processed meat, sweets, eggs, alcoholic
drinks and fast food, and a higher consumption of fruit, compared with men. Despite
our study showing that socioeconomic status, geographic area, and if students cook
for themselves have a limited influence on differences in food group consumption,
a large body of literature has reported a social gradient in food habits. For this
reason, and following our results, in order to avoid future health costs, policy makers
should consider the gender gap when implementing policies based on a healthy diet,
without forgetting the importance of the other social determinants.
Supporting information
S1 Supporting information
Supporting information.
Click here for additional data file.
This file includes:
Multiple regression outputs of complete-case analysis, and multiple imputation analyses
(m = 5 and m = 30 subsets).
Table A. Foods and food groups collected in questionnaire.
Table B. Food groups in the Mediterranean diet pyramid and foods from the FFQ
Table C. Occupations collected in the questionnaire: ISCO, ISEI-08 and SES
Table D. Variables sorted by percentage of missing
Table E. Independent variables: dummy coding
Table F. Summary of interactions between gender and the other social determinants
across food groups
Table G. Results from complete-case and imputed data regressions
Fig A. Correlation across independent variables
Fig B. Density plots of food groups after imputation of values: complete-case analysis
and multiple imputation (m = 5)
Fig C. Density plots of food groups after imputation of values: complete-case analysis
and multiple imputation (m = 30)
Fig D. Interaction effect between SES (1) and gender in the food group “Bread, pasta,
rice, and other cereals” (n = 593)
Fig E. Interaction effect between SES (1) and gender in the food group “Legumes” (n
= 593)
Fig F. Interaction effect between SES (1) and gender in the food group “Alcoholic
drinks” (n = 593)
Fig G. Interaction effect between SES (2) and gender in the food group “Precooked”
(n = 593)
Fig H. Interaction effect between family home (1) and gender in the food group “Fast
food” (n = 593)
Fig I. Interaction effect between family home (2) and gender in the food group “Bread,
pasta, rice, and other cereals” (n = 593)
Fig J. Interaction effect between family home (2) and gender in the food group “Red
meat and processed meat” (n = 593)
Fig K. Interaction effect between family home (2) and gender in the food group “Eggs”
(n = 593)
Fig L. Interaction effect between CFHS and gender in the food group “Potatoes” (n
= 593)
Fig M. Interaction effect between CFHS and gender in the food group “White meat” (n
= 593)
Fig N. Interaction effect between CFHS and gender on Legumes food group (n = 593)
(DOCX)