Dietary intake and occupational status among female youths of Thai Nguyen, Vietnam

Adolescence is a sensitive transition time that affects rights, roles, and responsibilities in food choice, yet limited evidence exists on dietary intakes during this critical period. This study assessed the food consumption pattern and the adequacy of energy, macronutrient, and micronutrient intakes among female youth belonging to three occupational groups in Vietnam. Dietary intakes were measured for 1001 participants aged 16–22 years using INDDEX24's 24‐h recall method. Multivariate regression analyses were conducted to examine differences in diet outcomes among the three occupational groups. Dietary diversity was similar across groups but workers, compared to high school and college students, consumed less baked/grain‐based sweets and fast foods, and more soft drinks, other sweets, and processed meat. Two‐thirds of the sample showed energy intake lower than the estimated energy requirement, while a substantial percentage had insufficient or excessive intake of carbohydrate and fat. The mean probability of adequacy of nutrient intakes was low (0.33) and not different across all three occupational groups except for folate, which favored workers. Our study provides novel evidence supporting the development and implementation of interventions to achieve national targets, with emphasis on female youths who undergo special transitions in education, occupation, and lifestyle.

know too little about nutrition in adolescence, what factors are most determinant in youth's choices, and how programs could effectively address challenges.
One such factor is occupational status.As adolescents move from school to college or engage in paid work, new conditions emerge that may influence their food choice and dietary patterns. 6Several studies indeed reported decreases in consumption of fruits and vegetables, dairy products, and discretionary foods (soft drinks and snacks) as adolescents go from high school to college. 7,8Likewise, increases in consumption of confectionery and sugar-sweetened beverages were observed in their transition out of education. 9Rights, roles, and responsibilities in food choice also transition markedly during adolescence 6 : school-aged adolescents may be more likely to depend on their mother's or caregiver's food choices, whereas college students may have more latitude in deciding what to eat.Those who start working early after high school may have more disposable income-although their decision to start working may relate to their lower economic class; alternately, they may have less time for preparing meals.A study in Myanmar found that a key risk factor for not meeting the minimum dietary diversity among young women was employment. 10In addition, the diet of factory workers who spend a large part of their time in the workplace and eat at least one of their daily meals there may be influenced by workplace environment and policy. 11Notwithstanding all this knowledge, limited evidence exists on the dietary intakes of adolescents as they go through life transitions in LMICs.This study aims to address some gaps in our understanding of those issues, by addressing two specific research questions: (1) What are typical food consumption pattern and the adequacy of energy, macronutrient, and micronutrient intakes among female youths in Thai Nguyen, Vietnam? and (2) How does occupational/educational status affect the quality of those diets?

Study context
This study is part of a broader Action-Research project 12 aimed at helping female youths improve the quality of their diets.The project took place in two secondary cities of LMIC (Medellin in Colombia and Thai Nguyen in Vietnam).In Vietnam, the INDDEX24 platform was used to obtain dietary intake data among female youths.These data, together with information on food market prices, were then processed using Optifood, a nutrition modeling tool, to identify key problem nutrients and to recommend food-based strategies that may affordably overcome those deficiencies.Next, guided by nutrition mentors, a selection of participants engaged in a social innovation challenge to incorporate the Optifood recommendations into their diets and disseminate those solutions among their peer groups.
The study took place against the unique background of Vietnam, a country undergoing a rapid nutritional transition marked by changes in food supplies, food prices, household expenditures, diets, and nutrition outcomes. 13Rising incomes and urbanization have certainly contributed to dietary changes-increasing the accessibility and affordability to a variety of foods-but little specific data exist for Vietnamese youths.The General Nutrition Survey provided diet data for children and adults between 2009 and 2010, 14 but not for adolescents; and the findings from the 2019 to 2020 survey are not yet available.
Findings from the 2019 Global School-based Student Health Survey revealed that unhealthy eating is the second most common lifestyle risk behavior among Vietnamese adolescents, together with physical inactivity and sedentary behavior. 15

Study design, participants, and settings
The study was conducted in 12 communes in Thai Nguyen, a city located in the Northern province of Vietnam.Eight urban and four peri-urban communes were randomly selected from the 21 urban and 11 peri-urban communes of Thai Nguyen City.A census of all households living in these 12 communes yielded a list of 4048 female youths aged 16-22 years.After applying exclusion criteria (being married, being pregnant, having had one or more children, living outside the area, or being unavailable during the study period of November 2021-January 2022), 2721 youths were deemed eligible.From that sampling frame, a total of 1001 youths were randomly selected, proportional to the size for each occupational category (Figure 1).

Dietary assessment
Dietary intake was assessed among adolescents in various days of the week youth using INDDEX24's multiple-pass quantitative 24-h recall. 16,17To estimate the distribution of usual intake and to account for within-person variation, a subset of participants (10%) was selected to have a second 24-h recalls in a nonconsecutive day.
Food intakes were converted to nutrient intakes using the Vietnamese food composition table 2007, 18 adjusted for nutrient retention of cooked foods. 19,20Foods for which nutrient information was missing were updated based on the food composition database from the Vietnam General Nutrition Survey 2019-2020, the Thai food composition table, 21 and the Asian food composition table. 22Dietary intake data were then used to generate analytical nutrition variables, including the Minimum Dietary Diversity for Women (MDD-W), Global Dietary Recommendations, the estimated energy requirement (EER), and the probability of adequacy (PA) and mean probability of adequacy (MPA) of macronutrient and micronutrient intakes, all of which were applied to the sampled individuals.
All reported foods were recategorized into the MDD-W's 10 food groups where the quantity of consumption for each food group was at least 15 g, as per the MDD-W guide. 23The Food Group Diversity Score was calculated by summing the number of food groups consumed, where MDD was defined as consuming ≥5 food groups.In addition to dietary diversity, we also reported unhealthy food group consumption which included six food groups (soft drinks, baked/grain-based sweets, other sweets, processed meat, deep-fried food, fast food and instant noodles, and packed ultra-processed salty snacks) based on the Global Dietary Recommendation. 24 I G U R E 1 Participant flow.
The EER was calculated using the WHO age-adjusted formula. 25w energy intake was considered when total energy intake was less than 85% of the EER.The percent energy from macronutrient intakes was compared to the acceptable macronutrient distribution ranges (AMDR) recommended by the U.S. Institute of Medicine (IOM) for assessing insufficient or excessive intake. 26,27The AMDR for protein and fat are 10%-30% and 25%-35%, respectively, for people aged 16-18 years.Cutoffs for these macronutrients are 10%-35% and 20%-35%, respectively, for people aged 19-22 years.For carbohydrates, the optimal range is 45%-65%.
For micronutrient, usual intakes were estimated using the intraperson or intra-day variance method. 28The estimated average requirements (EAR) and standard deviations for age and sex were based on WHO/FAO recommendations, 29 the IZiNCG recommendations for zinc, 30 and the IOM recommendations for calcium, 31 assuming low levels of bioavailability for iron (5%) and zinc (15%).The PA for 11 micronutrients (vitamin A, vitamin C, thiamin, riboflavin, niacin, vitamin B6, vitamin B12, folate, calcium, zinc, and iron) was based on the difference between the reported intake and the EAR.The MPA of micronutrient intake was calculated as the mean of the probability of adequacy for the 11 micronutrients. 28,32

Other data collection
Individual and household characteristics were collected through faceto-face interviews by trained enumerators.Individual-level data (in addition to dietary intake) included information on adolescent's age, ethnicity, education, occupation, and diet restrictions.Household-level data included information on housing quality (e.g., house style), ownership of garden and pond, and household assets (11 different types of durable goods), then processed using principal components analysis to create the household socioeconomic status (SES) index 33,34 and classified into sample-specific quintiles.

Data quality control
To ensure the quality of data collection, six field supervisors were trained to identify operational research needs arising from unexpected data collection situations and providing timely support to enumerators.Two Vietnamese dietary experts carried out weekly data checks of all interviews, verifying their completeness, appropriate food coding, the plausibility of portion size estimations, and the conversion method codes used for all foods reported during the recall.

Statistical analysis
Descriptive analysis was used to report the characteristics of the study population.Bivariate analyses were conducted to test for associations between occupation and food intake outcomes.These outcomes were analyzed as binary variables (the proportion of participants consuming each food group, percentage of macronutrient intakes in insufficiency, optimal range, or excessive categories) and continuous variables (quantity of food groups consumption and nutrient intakes).Nutrient intakes were tested for normality using Shapiro-Wilk tests.As the distribution of most micronutrient intakes was skewed, median intakes (interquartile ranges, IQRs) were reported.Significant levels were obtained from models adjusted for the clustering effect at the commune

RESULTS
The mean age of respondents was 18.6 years old (ranging from 16 to 22 years); with 62% of them being less than 19 years (Table 1).
Workers were more likely to live in households with lower SES compared to students (e.g., more than 40% of workers lived in the lowest quintile of SES, whereas 20% of high school students and only 10% of college students lived in this SES group).About a third of participants were underweight (body mass index (BMI) < 18.5 kg/m 2 ) and 5.6% of them were overweight/obese (BMI > 25 kg/m 2 ).Few respondents (7%) mentioned restricting their diets, and those who did mostly limited their rice or grain consumption for weight concern.The pandemic, which at the time of the survey had made only moderate inroads in Vietnam, does not appear to have markedly affected food consumption in this population.
Food group consumption was similar among the three occupations except for nuts and seeds which were consumed more frequently by workers (Table 2).While almost all participants (95%-98%) consumed grain, meat, poultry, and fish daily, only a third consumed eggs and dairy.About 20% of participants consumed legumes, and less than 10% of them ate nuts.Nearly two-thirds consumed fruits and vegetables, but only about 13% ate vitamin A-rich fruits and vegetables.On average, adolescents consumed ∼5 food groups each day with nearly 60% consuming five food groups or more per day.Regarding amounts consumed, an average of 315 g of total grains, white roots, tubers, and plantains were consumed with no difference by occupation.The consumption of protein plants was low (25.2 g pulses and 2.7 g nuts and seeds), although workers and college students consumed more nuts and seeds than high school students (3.4 vs. 1.6 g).The quantity of meat, poultry, and fish was about 156 g, but the intakes of dairy, fruits, and vegetables were low, especially vitamin A-rich fruits and vegetables (16 g) (Table 2).
When examining the consumption of unhealthy foods, the consumption of fast food and instant noodles was highest (27%), followed by processed meat (22%) and baked/grain-based sweets (20%) (Figure 2).
Compared to high school and college students, workers consumed a significantly lower proportion of fast food and instant noodles, and baked/grain-based sweets, while they consumed a higher proportion of soft drinks, other sweets, and processed meat.
Energy intake was low compared to WHO's EER (Table 3).On average, daily energy intake was 1524 kcal and 65% of participants' energy intake was less than 85% of EER.The percentage of energy intake <85% EER was significantly higher in workers (72%) than in high school or college students (63%).Most energy intake overall came from carbohydrate (56%), followed by fat (27%) and protein (17%).Mean carbohydrate intake was lower than Vietnam's recommendation 35 for TA B L E 2 Food groups consumption, by occupation of adolescents.adolescents and adults (208 g compared to 240-300 g per day), but nearly 25% of girls consumed excessive carbohydrate.Almost all participants had an optimal range of protein consumption, whereas only 41% of them consumed fat in the optimal range.Workers were more likely to have an optimal range of fat intake (52%) compared to high school students (33%) or college students (44%).A fifth of participants had excessive fat intake with no differences between the occupational groups.
Median intake of selected micronutrients was lower than the EAR for most nutrients except vitamin C, thiamin, and vitamin B6 (Table 4).
The probabilities of adequate intakes were low: only 3 out of 11 listed micronutrients had a PA higher than 0.5, with calcium (0.01) and iron (0.03) being particularly low.The MPA of nutrient intakes was 0.33 and there was no significant difference among the three groups on this except for folate, which favored working youths (Table 4).

DISCUSSION
Dietary diversity was largely similar among the three occupational groups, averaging five food groups overall with nearly 60% of the sample achieving the MDD-W.Some differences were noted in unhealthy food consumptions by occupation, workers consuming less baked/grain-based sweets, and fast food than high school and college students, but they consumed more soft drinks, other sweets, and processed meat.Two-thirds of the sample showed energy intake lower than the EER with workers faring significantly worse in that regard.
Almost all participants had an optimal range of protein consumption, but a substantial percentage had an insufficient or excessive intake of carbohydrate and fat with workers showing higher intake of fat.The median intake of micronutrients was lower than the EAR for most measured nutrients, and the MPA of nutrient intake was at a low 0.33, with no significant difference among the occupational groups except for folate, which favored workers.
Nearly all adolescents in our study consumed starchy staple foods and the quantity of consumption achieved the Vietnamese Food Pyramid recommendation, 35 yet less than 10% consumed whole grains, revealing a large gap between refined and whole grains consumption.
The importance of consuming a balance of whole grains, enriched and fortified grain products in improving shortfall nutrients and diet quality, raises the need to close the gap, particularly in Vietnam where grain enrichment and fortification are unpopular.The consumption of animal protein in the forms of meat, poultry, and fish was similar to the national survey, 14 but the most common forms of animal protein in Vietnam were pork and beef which are recommended to consume in limited amount by the global dietary recommendation. 24These foods TA B L E 4 Dietary intakes of selected micronutrients.d Zinc was for refined diets as defined by the International Zinc Consultative Group. 30parently provide essential nutrients so the amount of consumption should be carefully considered in interpreting the findings and making recommendations.
7][38][39][40] Compared to the Vietnam General Nutrition Survey 2019-2020, the average quantity of consumption was higher for fruits (177 vs. 141 g) but lower for vegetables (130 vs. 230 g). 14Despite this apparent improvement, the consumption of fruits and vegetables was still very low compared to the dietary guideline recommendations. 35r study, in line with studies conducted in adolescents in LMICs, reported serious shortfalls in energy and the intake of calcium, iron, vitamin A, and vitamin C. The average energy intake in our study was much lower than the EER (1524 vs. 2110 kcal for girls aged 15-19 years). 41Diet composition by macronutrients as represented by the caloric supply derived from carbohydrates, fat, and protein was aligned with the recommended dietary allowance, 41 and showed a better balance than a 2013 study conducted in women of productive age (56%, 27%, and 17% vs. 66%, 19%, and 15%). 42The difference in the diet composition between the two studies may reflect the nutrition transition trend of reduced carbohydrate and increased fat and protein intakes in Vietnam.Also, and similar to an earlier study of women of reproductive age in Vietnam, 43 our study showed inadequate intakes of most selected micronutrients among female youths.
The mean dietary diversity score was about 5 out of 10 food groups, which can be used as a proxy indicator for a relatively high micronutrient adequacy; 44 yet, the MPA for the 11 key micronutrients was only 0.33.This finding demonstrates the importance of tracking quantities in predicting nutrients adequacy: while the sample had a moderate dietary diversity, the low quantity intake of most food groups lead to a low probability of adequacy in almost all tracked micronutrients.Evidence-based educational programs should, therefore, focus not only on diet diversity but also on the appropriate quantity of each group to consume.
Significant differences were seen in the consumption of unhealthy food groups between workers and students.In line with the trend observed in a previous study, workers were less likely to consume fruits but more likely to consume soft drinks. 9This pattern might be explained by poor knowledge on sugary beverages, time constraints, incomes, and food accessibility in the workplace.Calory-dense soft drinks might help workers to compensate for lost energy after exhausting work.Moreover, workers might have a limited time to prepare and eat fresh fruits, unless factory meals provide them.On the other hand, students (most of whom live with their parents) were less likely to consume processed meat, reflecting the protective effect of parental control of the diet. 45Meals provided and cooked by parents/guardians typically contained less processed meat than dishes prepared and cooked by street food vendors.
The findings above come with some limitations.First, the diet level.Data were analyzed with STATA software version 16.
assessment was conducted during the COVID-19 period which might have influenced the typical diet pattern.Students who virtually attended classes in unusual timeframes might have lost the meals they normally obtain at school.The pandemic also possibly influenced food markets, reducing the availability of all foods (including street foods) and/or increasing their prices.Second, the database does not allow to distinguish between the different kinds of carbohydrates and fats consumed.Stratifying the consumption of high-and low-quality carbohydrates and fats would provide more guidance on how to improve diet quality.Despite those challenges, this study provides unique insights on the dietary intake of female youths undergoing occupational transitions, a topic that has been largely unexplored in Vietnam and elsewhere.It also lends credibility (though not definite proof) to the hypothesis that occupational status may affect diets in meaningful ways.While unhealthy diets are considered an important health risk among youths,15,46 no assessment had yet been conducted for this age group.Tellingly, the 2021-2030 Viet Nam National Strategy on Nutrition set targets to improve the nutritional diets for mothers, children, and adolescents, but most of the specific objectives focus on children and pregnant women, leaving adolescents behind.This research provides essential evidence supporting the development and implementation of interventions to achieve national targets, including female youths who undergo special transitions in education, occupation, and living lifestyles.
Energy and macronutrient consumption.