Assessment of habitual meal pattern and intake of foods, energy and ...

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European Journal of Clinical Nutrition (2004) 58, 1181–1189

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ORIGINAL COMMUNICATION Assessment of habitual meal pattern and intake of foods, energy and nutrients in Swedish adolescent girls: comparison of diet history with 7-day record ¨ berg1* and L Hulthe´n1 A Sjo 1

Department of Clinical Nutrition, Sahlgrenska Academy at Go¨teborg University, Sweden

Objective: To compare the diet history (DH) method to an estimated 7-day record (7-d) concerning meal pattern and intake of foods, energy and nutrients. Design: After the DH interview, subjects completed the 7-d. Setting: School setting, Go ¨ teborg, Sweden. Subjects: A total of 51 adolescent girls (15–16 y) recruited from 634 girls participating in The Go ¨ teborg Adolescence Study. Results: Two-thirds of the girls had identical or similar main meal pattern, while the number of in-between meals was higher using DH (Po0.001). Breakfast was the meal that agreed best and dinner during weekends. Energy intake (EI) was 8% higher in DH compared to 7-d (P ¼ 0.056). The ratio EI to basal metabolic rate was 1.35 (1.14, 1.65) using DH and 1.26 (1.08, 1.52) using 7-d, indicating under-reporting in both methods. Intake of vegetables, juice, sweets, soft-drinks and jam did not differ between the methods, but for the rest of the intake DH estimates were higher (Po0.05). The calculated nutrient intake was higher by DH, with exception of fat and sucrose. For the main food groups, energy and nutrients, except alcohol, ranking was similar between the methods. Adjusted for EI (10 MJ), intake of fat and sucrose were lower and protein, calcium and fibre were higher by DH (Po0.01). EI did not differ for lunch and dinner, but was higher in breakfast and in-between meals using DH. Intake of foods and nutrients in lunches and meat and fish for lunch and dinner did not differ. Conclusions: The diet history seems to work well as a reference method for dietary assessments in this age group. Sponsorship: The Swedish Medical Research Council (project B94-19X-04721-19A), the Swedish Mill Industry, The Wilhelm and Martina Lundgren Foundation and The Swedish Nutrition Foundation.

European Journal of Clinical Nutrition (2004) 58, 1181–1189. doi:10.1038/sj.ejcn.1601947 Published online 31 March 2004 Keywords: diet survey; interview; food habits; diet record; evaluation studies; adolescent nutrition

Introduction Assessment of food habits is central for studies of the relation between diet and health, and it is important that dietary methods give an adequate measure of dietary intake. Studies of validity are valuable for providing information on the strengths and limitations of a dietary instrument. The daily

¨ berg, Department of Clinical Nutrition, *Correspondence: A Sjo ¨ teborg University, Box 459, Go ¨ teborg SE 405 Sahlgrenska Academy at Go 30, Sweden. E-mail: [email protected] Guarantor: L Hulthe´n. Contributors: Both investigators designed the study, interpreted results and wrote the paper. L Hulthe´n was responsible for the ¨ teborg Adolescence Study and A Sjo ¨ berg was running of The Go responsible for the dietary data and statistical analysis. Received 16 September 2003; revised 4 December 2003; accepted 22 December 2003; published online 31 March 2004

intake of nutrients and foods has been a major focus in studies assessing the relative validity of dietary assessment methods in adolescent populations (Andersen et al, 1995) and in adults (Bingham et al, 1994). However, the meal pattern and intake at a meal level is also important. Assessment of intake in the meal context is, for example, central for estimating the bio-availability of iron (Hallberg & Hulthen, 2000). Breakfast has been suggested to be a useful marker not only of dietary habits but also of other lifestyle ¨ glund et al, factors (Berg-Kelly, 1995; Ruxton & Kirk, 1997; Ho ¨ berg et al, 2003a). In a recently published paper, we 1998; Sjo showed that meal pattern with omission of breakfast or breakfast and lunch was related to a clustering of less healthy lifestyle factors and food choice that might lead to a poorer ¨ berg et al, 2003a). The concept of nutrient intake (Sjo glycaemic index is also based on the intake at the meal level (Jenkins et al, 1987).

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1182 Validation of energy intake (EI) with total energy expenditure (TEE) measured with doubly labelled water (DLW) is considered a reliable instrument for dietary assessment methods. But the fact that a dietary method is valid concerning energy intake does not imply the validity for intake of foods and nutrients and gives no information about validity at a meal level. For comparison of the daily intake of foods and nutrients, of meal pattern and intake of foods and nutrients in meals another dietary method is the only instrument available. Prospective dietary methods, for example, food records, have been used to assess the relative validity of retrospective dietary methods as the diet history (DH) (Mensink et al, 2001) or the food frequency questionnaire (FFQ) (Andersen et al, 1995). To our knowledge, the relative validity of meal pattern and dietary intake in meals has not been presented earlier. The current study was performed to evaluate the DH method used in two cross-sectional studies to examine the effects of the removal of general iron fortification of white wheat flour on iron status in Sweden in 1995 ¨ berg et al, 2003a). It was considered important both (Sjo to study the food habits and specific factors important for the iron situation. The EI of the DH method has been validated with energy expenditure measured using ¨ berg et al, DLW in a group of adolescent boys and girls (Sjo ¨ berg et al, 2003b) showed 2003b). That validation study (Sjo that the current DH method was able to capture EI for the group of boys and girls and to rank the subjects’ EI compared to TEE. The EI was close to TEE measured with DLW and for 57% (20 of 35) of the subjects EI was considered to be valid. In the current study, we compared the DH method, ¨ teborg Adolescence Study, with an designed for The Go estimated 7-day (7-d) record. Our aim was to assess how the DH measured food habits of a selected group of teenage girls compared to the estimated 7-d record. Meal pattern, intake of foods and nutrients in the meals and as a daily intake were compared, concerning both group intake and individual intake.

Subjects and methods Study design and subjects The DH evaluated in this study was designed to study the food habits in adolescents (15–16 y) in two cross-sectional ¨ teborg in the years 1994 and 2000. The first studies in Go study included 1245 and the second 1025 adolescents. All ¨ teborg were invited to students in grade 9 in 13 schools in Go participate. To achieve a representative sample of adolescents ¨ teborg, a great effort was made in selection of schools of Go using the socio-economic area index (high-, medium- and ¨ berg et al, 2003a). In low-status areas) (Elme´n et al, 1995; Sjo the current study, we invited a subgroup of the 634 girls ¨ teborg Adolescence Study 1994, to participating in The Go register the food intake. Girls were selected because motivaEuropean Journal of Clinical Nutrition

tion to register dietary intake and high participation rate was expected in this group. The girls were invited in sequence after completion of the DH. A total of 54 girls were invited, 51 returned complete 7-d while one girl had registered for 5 days only and two girls never returned their 7-d. Girls from ¨ teborg eight of the 13 schools participating in The Go Adolescence Study were included. The distribution of participants from high-, medium- and low-status areas in the current study agreed with the distribution in The ¨ teborg Adolescence Study 1994. The study consisted of Go four parts: a detailed dietary questionnaire, medical survey, individual dietary interview with a dietician and the estimated 7-d record, and all data were collected in the schools. The subjects and their parents gave written informed consent and the study was approved by the Ethics Committee of the Medical Faculty at the University of ¨ teborg. Go

Diet history Our aim was to cover the whole diet with meal pattern as well as quality and quantity of the usual intake. Food habits ¨ teborg Adolescence Study have been described in The Go ¨ berg et al, 2003a). The questionnaire was introduced (Sjo and completed in the classroom under the supervision of two dieticians. It was divided into sections to capture the intake during different time periods of the school-day: intake in the morning before school, during lunch break and dinner in the afternoon/evening. For evaluation of main meals, the quality of the intake was characterised. Intake before school was defined as breakfast if it contained a cereal component and at least one milk product or one fruit/juice or a meat/fish/egg product. Lunch could be a prepared meal or other consumption in the school restaurant, at home or in a cafeteria. Dinner was a prepared warm or cold meal or a bread meal in the afternoon after school or in the evening. Intake that was consumed in other time periods than in main meals were defined as in-between meals. In-between meals intake was constituted of bread meals, leftovers from dinner as well as sweet baked goods, soft-drinks, sweets and snacks. Subjects were asked to specify the intake with fixed questions of frequency and amounts of foods in household measures. There were openended questions to capture foods not specified in the questionnaire and for intake from in-between meals and during weekends. For the interview (about 30 min), the trained dietician followed a protocol to check the questionnaire completeness and to obtain additional information about food habits. This additional information included food choice, serving sizes and frequencies of dishes for dinner. The usual type of bread (white bread, brown bread and whole-meal bread), thickness of bread and spread were estimated. Sweets, potato crisps, nuts and popcorn, packages of common trademarks and varying portion sizes were shown to get the portion size of the habitual intake.

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1183 7-d record The 54 invited girls were given thorough verbal and written information on how to complete a 7-d food record within a 3-week period after the interview. The food record form used comprised six pages. The front page contained instructions for correct completion of the record. The dietician carefully instructed each participant how to register everything eaten or taken as beverage during seven consecutive days. The participants were instructed to always bring a record form and to register and specify any intake of food, beverage, sweets or snacks. It was stressed that it was very important to retain the usual food habits during the registration period and to write everything in the notebook. The portion sizes were primarily in household units or by weight. When the amount was given in household units, the same standard portion sizes used in the DH were also used. For slices of bread and spread, household units or more exact descriptions from subjects were primarily used, if unavailable, the individual standard portions that the dietician and the student had determined during the DH interview were used. When returned, all food records were checked and coded by the same dietician who performed the DH interview.

75 percentiles (P25, P75) were used. The Mann–Whitney U-test was used to compare the intake of girls in this ¨ teborg Adolescence evaluation study to the girls in The Go Study. The differences in intake of energy, foods, nutrients and energy-adjusted intake of nutrients (in 10 MJ) between dietary methods were analysed using the Wilcoxon matched-pairs test. Spearman rank correlation coefficients were used to compare the ranking. The tests were considered significant at Po0.05. Differences between EI by dietary methods were plotted against the mean EI, as proposed by Bland and Altman (1986), to study the individual agreement, and the Pearson correlation coefficient was used for correlation between the mean and the difference. Inter- and intraindividual variations of daily intake of energy and nutrients in the 7-d and the ratio of these were calculated (Beaton et al, 1979). Based on the inter- and intra-individual variations of nutrient intakes, the reliability of 7-d was calculated as the number of days required to assess individual intakes (Beaton et al, 1979) and to rank persons with precision rZ0.9 (Nelson et al, 1989). Statistical calculations were performed using the SPSS for Windows (version 10.0) software programme.

Results Nutrient calculations In Sweden, a free prepared meal is served for lunch at school to all students. For the DH, the school lunch menus were used to assess frequencies of types of dishes served for lunch. For dinners, the frequency of different types of dishes was asked for during the interview. Calculations for foods, energy and nutrients for both methods used the same database (Swedish National food Administration, 1994). Supplemental vitamin and mineral preparations were not included.

Anthropometry Body weight in light underwear was measured to the nearest 0.1 kg using the same scale in all schools, and height was measured to the nearest 0.5 cm. We calculated the body mass index (BMI) from weights and heights (kg/m2) and the basal metabolic rate (BMR) from subjects’ age, gender, height and weight (Schofield, 1985). To control if the EI was meeting the energy requirements, a ratio was made between EI and the calculated BMR (EI/BMR) (Goldberg et al, 1991). The ratio EI/ BMR for the group was compared with the expected physical activity level for moderate active populations, 1.55 (FAO/ WHO/UNU, 1985). The cutoff limit of the ratio EI/BMR below 1.20 was used to define the potential under-reporting (Bingham, 1994).

Statistics and calculations The Wilks Shapiro test of normality showed that the total daily intake of energy and some nutrients was normally distributed, but some nutrients, the food groups and the intakes in different meals were skewed, so medians, 25 and

Daily intake Body weight was 59.0 (51.4, 65.8) kg, body height was 166 (162, 170) cm and BMI was 20.6 (19.2, 22.7) kg/m2. There were no significant differences in anthropometric measures between girls in this study group and the rest of the girls in ¨ teborg Adolescence Study. EI using the DH was 8.1 The Go (6.9, 10.2) MJ and in the 7-d was 7.5 (6.1, 9.4) MJ, the 8% difference was nonsignificant (P ¼ 0.056). The DH was able to rank the subjects’ EI compared to the 7-d (Spearman rank correlation coefficient, r ¼ 0.63, Po0.001). The Bland and Altman plot with each individual’s difference between EI from 7-d and EI from DH plotted against the mean of the methods illustrates a mean difference of 0.96 MJ (Figure 1). The 95% limits of agreement between EI by the two methods were 4.67–2.75 MJ. For two subjects, there were large discrepancies in EI. The plot did not indicate any trend in differences with increased EI. The percentage of agreement within quartiles of EI between DH and 7-d was 43% (n ¼ 22) in the same quartile, 41% (n ¼ 21) in the adjacent quartile and 2% (n ¼ 1) in the opposite quartile. EI/BMR was 1.35 (1.14, 1.65) for DH and 1.26 (1.08, 1.52) for 7-d. Underreporting was found for 14 girls by the DH, 17 girls by the 7-d and for nine girls by both dietary methods. Calculated as the daily intake of bread, meat and fish, milk, potatoes and roots, fruit and berries and ice cream, intakes were, respectively, 10, 25, 27, 59, 74 and 250% higher by DH than by 7-d (Table 1). Intake of sweets was similar and intake of sweet baked goods was 16% lower by DH. Doubled intake of brown bread, wholemeal bread and crisp bread was indicated in the DH, while white bread was lower than in 7-d. DH was able to rank the intake of all food groups compared to 7-d. With the exception of fat and sucrose, the European Journal of Clinical Nutrition

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1184 calculated nutrient intake was higher by DH, the difference was 7% for iron to 35% for calcium and vitamin C. DH was able to rank the daily nutrient intake, with the exception of alcohol (Table 2). In 10 MJ, fat and sucrose were lower and protein, fibre and calcium were higher by DH than by 7-d.

Meals Number of main meals agreed at group level (Table 3), but there was a higher frequency of in-between meals by DH

Figure 1 Difference between EI from the 7-d record and the DH plotted against the mean of the two methods (n ¼ 51).

(Po0.001). In 24 subjects (47%), the main meal pattern was identical between the methods. In 12 girls (24%), only one eating occasion during 1 week differed between the methods. This means that 71% had identical or similar main meal pattern. Breakfast agreed best between methods, 44 girls (86%) had identical frequency. Forty-five girls (88%) had breakfast regularly before school according to DH and 44 girls (86%) had breakfast all weekdays in 7-d. Thirty-five girls (69%) had identical lunch pattern by both methods and 21 (41%) had identical frequency of prepared lunches. Thirtynine girls (76%) had lunch regularly during schooldays according to DH and 38 girls (75%) had lunch all schooldays in 7-d. Thirty-four girls (67%) had identical number of dinners. Twenty-two girls (43%) had the same intake of prepared dinners. During weekends, all girls reported identical number of breakfasts. Twenty-seven subjects (53%) reported identical frequency of lunches. Dinner habits during weekend days seemed to be stable, 47 subjects (92%) had identical intake by both methods and there was always a prepared dinner. EI consumed at breakfast and in-between meals differed significantly between methods, while there was no difference in EI consumed at lunch and dinner (Table 4). Intake of foods consumed with breakfast was higher by DH, but for foods usually consumed with breakfast DH was able to rank intake compared to 7-d (Table 5). Nutrient intake at breakfast differed to the same extent as EI, with the exception of vitamin C that was 75% higher by DH (Table 4). For lunches, only intake of fish differed significantly between methods (Table 5). The DH was able to rank the intake for meat and

Table 1 Daily intake of foods in the 7-d record and the DH (n ¼ 51) 7-day record Intake of foods (g)

Median (P25, P75)

Diet history a

Median (P25, P75)a Spearman rank correlation coefficientb Wilcoxon matched pairs test P-value

Vegetables and vegetarian dishes Potatoes and roots Fruit and berries Juice

62 54 82 61

(32, 116) (33, 74) (50, 151) (0, 175)

58 86 143 125

(37, 94) (56, 114) (60, 210) (25, 175)

0.46*** 0.32* 0.61*** 0.59***

0.14 o0.001 o0.001 0.20

Milk and milk products Cheese Meat and fish Meat Fish Bread White bread Brown bread Wholemeal bread Crisp bread Sweets Potato crisps, nuts and popcorn Soft drinks Ice cream Jam and sugar Buns, pastry and biscuits

489 12 92 71 20 111 46 21 5 5 25 0 139 6 12 19

(286, 571) (7, 33) (67, 123) (48, 103) (0, 33) (77, 131) (32, 72) (0, 50) (0, 34) (2, 9) (8, 49) (0, 7) (57, 205) (0, 16) (4, 17) (6, 34)

621 24 115 84 23 122 19 43 10 10 25 4 107 21 10 16

(474, 951) (12, 38) (86, 140) (61, 111) (13, 35) (88, 161) (0, 58) (5, 93) (0, 50) (7, 15) (9, 43) (0, 14) (29, 190) (9, 39) (0, 18) (5, 25)

0.66*** 0.47*** 0.52*** 0.56*** 0.31* 0.40** 0.52*** 0.37** 0.63*** 0.34* 0.71*** 0.32* 0.37** 0.30* 0.59*** 0.30*

o0.001 0.022 o0.001 0.012 0.039 0.0051 o0.001 o0.001 0.0067 o0.001 0.88 0.0053 0.27 o0.001 0.32 0.031

a

P25, P75 ¼ 25th and 75th percentiles. Spearman rank correlation coefficients, P-values: ***Po0.001, **Po0.01 and *Po0.05.

b

European Journal of Clinical Nutrition

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1185 Table 2 Intake of nutrients in the 7-d record and the DH (n ¼ 51) 7-day record Nutrients Protein, g Fat, g Carbohydrate, g Sucrose, g Fibre, g Vitamin C, mg Calcium, mg Iron, mg Zinc, mg Alcohol, g

Median

Diet history a

(P25, P75)

Median

68 (54, 77) 82 63 (52, 79) 65 244 (199, 286) 277 50 (38, 69) 44 15 (11, 17) 18 63 (48, 97) 85 944 (700, 1211) 1276 14 (12, 16) 15 9 (8, 11) 11 0.0 (0.0, 0.2) 0.4

(P25, P75)a

Spearman rank correlation coefficientb Wilcoxon matched pairs test P-value

(64, 94) (50, 81) (218, 332) (36, 65) (15, 22) (53, 123) (980, 1626) (12, 19) (8, 13) (0.0, 1.2)

0.67 0.63 0.65 0.66 0.71 0.66 0.64 0.61 0.57 0.25

Energy adjusted intake (10 MJ) Protein, g 90 (78, 98) 96 (88, 105) Fat, g 84 (78, 89) 78 (71, 86) Carbohydrate, g 323 (308, 333) 323 (304, 336) Sucrose, g 66 (53, 84) 57 (42, 70) Fibre, g 18 (16, 22) 21 (18, 26) Vitamin C, mg 92 (67, 122) 106 (69, 152) Calcium, mg 1326 (955, 1453) 1490 (1225, 1736) Iron, mg 19 (17, 21) 18 (16, 19) Zinc, mg 13 (11, 13) 13 (12, 14) Alcohol, g 0.0 (0.0, 0.3) 0.5 (0.0, 1.3)

o0.001 0.33 0.0011 0.25 o0.001 0.0013 o0.001 0.026 o0.001 o0.001 o0.001 0.0072 0.55 o0.001 o0.001 0.077 o0.001 0.19 0.061 o0.001

a

P25, P75 ¼ 25th and 75th percentiles. Spearman rank correlation coefficients, all Po0.001 except alcohol P ¼ 0.079.

b

Table 3 Number of meals per day determined by the 7-d record and in the DH (n ¼ 51) Meals

7-day record

Diet history

Main meals

2.66 (0.36)

2.72 (0.34)

Breakfast Lunch Dinner

0.94 (0.18) 0.78 (0.17) 0.94 (0.13)

0.96 (0.16) 0.82 (0.18) 0.95 (0.15)

In-between meals

1.89 (0.66)

2.36 (0.73)

Sum of meals

4.54 (0.83)

5.08 (0.83)

(mean, s.d.).

fish and for milk. Intake of sucrose was lower in the DH compared to the 7-d; the other nutrients did not differ. For dinner, intake of milk was doubled and intake of fruit was significantly higher by DH (Table 5). Intake of meat and fish did not differ and ranking of meat intake was high. Intakes of calcium and vitamin C were higher in DH than in 7-d, while intake of vitamin C was lower. Ranking of calcium was high also for dinner. In in-between meals, intake of bread, milk, cheese and fruit were significantly higher in DH compared to 7-d (Table 5). Difference of food intake at the meal level varied from 57% (bread at dinner) to þ 275% (fruit at dinner), for nutrients difference varied from 40% (sucrose at dinner) to þ 75% (vitamin C at breakfast).

Did the 7-d capture food habits? Calculations of intra- to inter-individual variation (ratio ranging from 1.0 to 1.39) of energy and nutrients indicated that 7-d was able to capture habitual intake at the 720% level for the group, for this only 1–2 days were required. But for calcium, vitamin C and sucrose at the 710% level, 7 days was not enough. The 7-d was able to rank persons for daily intake of energy and calculated nutrients. However, for sucrose, iron and vitamin C, 8–9 days would be required according to these calculations. The 7-d was less able to capture habitual intake for individuals, approximately 8 days were required to capture individual intake of energy and protein. For energy, protein, carbohydrate and zinc, 7-d was enough to capture the habitual intake at the 720% level for the majority of participants. Concerning vitamin C, 7-d did not capture habitual intake for any of the subjects.

Discussion The DH evaluated in this study was designed to measure food habits in a representative sample of 15–16 y boys and ¨ teborg Adolescence Study was girls in Sweden. The Go dimensioned to detect changes in iron status in girls. In the current study, for DH, the school lunch menus were used to assess the frequencies of types of dishes served for lunch. This is not the usual protocol for the DH method, although a similar technique has been reported earlier using DH in children and adolescents (Livingstone et al, 1992). The European Journal of Clinical Nutrition

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1186 Table 4 Intake of energy and some nutrients from meals in the 7-d record and the DH (n ¼ 51) 7-day record

Diet history

Median

(P25, P75)

Median

(P25, P75)a

Breakfast Energy, MJ Calcium, mg Iron, mg Vitamin C, mg Sucrose, g

1.5 241 2.9 12 7

(1.0, 1.9) (124, 341) (1.9, 4.6) (1, 34) (4, 12)

1.8 293 3.6 21 8

(1.2, 2.2) (199, 386) (2.1, 5.0) (1, 50) (2, 15)

0.75*** 0.63*** 0.76*** 0.62*** 0.41**

Lunch Energy, MJ Calcium, mg Iron, mg Vitamin C, mg Sucrose, g

1.7 226 3.1 7 4

(1.3, 1.9) (137, 312) (2.5, 3.6) (3, 11) (2, 8)

1.4 257 2.4 9 2

(1.2, 1.8) (108, 331) (2.0, 3.3) (5, 14) (1, 3)

0.29* 0.60*** 0.16n.s. 0.19n.s. 0.07n.s.

0.32 0.57 0.15 0.16 o0.001

Dinner Energy, MJ Calcium, mg Iron, mg Vitamin C, mg Sucrose, g

2.3 232 4.2 15 10

(1.7, 2.8) (173, 327) (3.4, 5.3) (8, 25) (5, 12)

2.5 366 4.3 21 6

(2.1, (255, (3.5, (15, (3,

2.8) 516) 5.2) 40) 9)

0.40** 0.70*** 0.32* 0.49*** 0.25n.s.

0.21 o0.001 0.57 o0.001 o0.001

In-between meals Energy, MJ Calcium, mg Iron, mg Vitamin C, mg Sucrose, g

2.1 232 3.2 26 27

(1.7, (175, (2.3, (14, (17,

2.5 379 3.7 25 27

(2.0, (259, (2.5, (11, (17,

4.0) 475) 6.2) 46) 42)

0.59*** 0.34** 0.41** 0.53*** 0.70***

o0.001 o0.001 0.0064 0.14 0.16

Energy and nutrients in meals

a

2.9) 322) 4.4) 38) 42)

Spearman rank correlation coefficientb

Wilcoxon matched pairs test P-value o0.001 0.013 0.0042 0.025 0.93

a

P25, P75 ¼ 25th and 75th percentiles. Spearman rank correlation coefficients, P-values: ***Po0.001, **Po0.01 and *Po0.05.

b

results in the current study were obtained in adolescent girls ¨ berg et al, 2003b) supports the and the validation study (Sjo usefulness of the current dietary method also in adolescent boys. The diet history seems to work well as a reference method for dietary assessment in this age group. The food record has often been used as reference method for retrospective dietary assessment methods since it does not rely on the subjects’ memory and ability to estimate the consumption (Andersen et al, 1995; Mensink et al, 2001). In DH the participants’ ability to remember and estimate the frequency and amount of the dietary intake is central. Food records, on the other hand, are more demanding on the participants to report during a longer time and there is also a risk that the usual dietary intake is affected (Nelson & Bingham, 1998). A changed eating behaviour with under-eating during the recording period has been observed (Goris & Westerterp, 1999). Validation studies including DLW measurements during the last decade have demonstrated that dietary methods are often biased towards underestimation of intake in adolescents (Livingstone & Robson, 2000) as well as adults (Livingstone & Black, 2003). Several studies have shown that the recording method was biased towards under-reporting of intake (Livingstone et al, 1992; Bratteby et al, 1998), European Journal of Clinical Nutrition

especially in subjects with high BMI (Bandini et al, 1990; Price et al, 1997; Høidrup et al, 2002). Lower EI/BMR have been shown for registration methods than for DH in studies on children and adolescents (Livingstone & Robson, 2000). The ratio EI/BMR 1.35 for DH and 1.26 for 7-d in the current study were both low, both DH and 7-d underestimated energy intake in this group of girls. However, EI by 7-d was lower than by DH, indicating a somewhat higher degree of under-reporting by the 7-d. Seven-day record was used in two contemporary Swedish dietary surveys including adolescents. EI/BMR calculated from these studies varied from 1.34 to 1.38 in the boys and from 1.19 to ¨ m et al, 1993; Samuelson et al, 1996) 1.28 in the girls (Bergstro i.e. clear under-reporting of EI in all groups. In our larger study, using DH, from which the girls in the current study were recruited, the ratio EI/BMR was 1.48 in the girls and ¨ berg et al, 2003a). This indicates some 1.73 in the boys (Sjo degree of under-reporting in the girls also using DH compared to 1.55 for moderate active populations (FAO/ WHO/UNU, 1985). In the validation study with DLW ¨ berg et al, 2003b), reporting accuracy in the DH was (Sjo related to gender and over-reporting was more frequent among the boys while under-reporting was more frequent among the girls.

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1187 Table 5 Intake of foods from meals with the 7-d record and the DH (n ¼ 51) 7-day record

Diet history Median

(P25, P75)a

Spearman rank correlation coefficientb

Wilcoxon matched pairs test P-value

(13, 75) (0, 9) (26, 62) (0, 132) (0, 21)

66 9 60 50 0

(24, 88) (0, 15) (39, 70) (0, 138) (0, 0)

0.60*** 0.63*** 0.74*** 0.72*** 0.26n.s.

0.0068 0.016 o0.001 0.011 0.0020

18 0 26 53 0 14 0 4

(11, 29) (0, 9) (14, 38) (25, 85) (0, 4) (7, 27) (0, 0) (0, 18)

19 9 30 63 0 13 0 0

(13, 28) (5, 12) (18, 39) (13, 88) (0, 2) (9, 20) (0, 0) (0, 15)

0.40** 0.32* 0.50*** 0.61*** 0.34* 0.22n.s. — 0.40**

0.98 o0.001 0.13 0.98 0.067 0.30 0.038 0.19

Dinner Meat (g) Fish (g) Meat & fish (g) Milk (g) Cheese (g) Bread (g) Juice (g) Fruit (g)

45 14 64 44 0 14 0 8

(33, 66) (0, 24) (46, 88) (14, 88) (0, 4) (6, 21) (0, 0) (0, 21)

53 12 70 88 0 6 0 30

(38, 68) (6, 21) (53, 91) (50, 150) (0, 2) (2, 19) (0, 14) (0, 45)

0.51*** 0.22n.s. 0.43** 0.66*** 0.16n.s. 0.21n.s. 0.14* 0.43**

0.41 0.46 0.29 o0.001 0.67 0.045 0.74 o0.001

In-between meals Milk (g) Cheese (g) Bread (g) Juice (g) Fruit (g)

34 4 26 0 53

(20, 48) (0, 10) (14, 39) (0, 40) (30, 91)

53 9 35 0 83

(13, 100) (0, 16) (21, 63) (0, 50) (45, 150)

0.34* 0.40** 0.44** 0.28n.s. 0.58***

0.0019 0.0076 o0.001 0.73 0.0011

Food intake in meals

Median

(P25, P75)

Breakfast Milk (g) Cheese (g) Bread (g) Juice (g) Fruit (g)

44 3 48 25 0

Lunch Meat (g) Fish (g) Meat & fish (g) Milk (g) Cheese (g) Bread (g) Juice (g) Fruit (g)

a

a

P25, P75 ¼ 25th and 75th percentiles. Spearman rank correlation coefficients, P-values: ***Po0.001, **Po0.01 and *Po0.05.

b

Daily intake of foods and nutrients With regard to the ability to rank intakes, our DH method worked well compared to the 7-d. The correlation coefficients were high compared to other studies where food records have been used for assessment of the relative validity in adolescents (Andersen et al, 1995) as well as to studies in adults ( Jain et al, 1996; Heath et al, 2000; Mensink et al, 2001). However, the food record is not a Gold Standard of dietary assessments and should not be considered as a reference method in the current study. We have simply made a comparison since the 7-d has often been used to assess food habits and because it was used in two other contemporary Swedish studies on adolescents. The higher intake of ice cream in DH is probably due to seasonal variation since the 7-d were completed during autumn and winter when ice cream consumption is low and DH was aimed to capture habitual intake. Sweet baked goods differed in the opposite direction and may have been consumed instead of ice-cream in the 7-d. Other interesting differences in diet quality were reported, for example, higher intake of wholemeal bread,

fruit and root crops, all this resulting in a higher fibre intake in the DH. Since the EI was higher in DH, intake that was not different as reported, fat and sucrose, became lower when adjusted for EI (10 MJ). This calculation could indicate a diet with lower intake of fat and sucrose and higher intake of fibre by DH than by 7-d. Relatively few studies have been published on adolescents, but, in adult women, fat was lower and fibre was higher in DH compared to food record (Mensink et al, 2001). The lower fat intake in 10 MJ in the current study had similarities, with differences shown for girls identified as under-reporters in the validation study for ¨ berg et al, 2003b). In 10 MJ, the underthis DH method (Sjo reporting girls had significantly lower intake of fat and sucrose but higher intake of vitamin C compared to adequate reporting girls. One study reported a relation between social desirability and intake of vegetables and fruit, but negative correlation with snack-food in adult women (Worsley et al, 1984). The selected group of girls in the current study resembled the under-reporting girls in our validation study ¨ berg et al, 2003b). Though sources of error as social (Sjo European Journal of Clinical Nutrition

Comparison of diet history with 7-day record A Sjo¨berg and L Hulthe´n

1188 desirability and compliance may be subject-specific and not independent between two dietary methods (Livingstone & Black, 2003), the DH may be more sensitive to these factors. To capture also young girls’ food habits is important, but the dietary assessment methods traditionally used need to be improved. This is an important task for future work in this field.

Meals Intake from meals is a complex situation, and at a meal level there were larger differences between the methods. The meal pattern agreed well for the main meals, the foods consumed in the meals differed more. For breakfast and in-between meals, intake of foods was generally higher by DH than by 7-d. Breakfast showed higher intake of energy, iron, calcium and vitamin C, which might result in different estimations of bioavailability of iron by DH compared to 7-d. In dinners, intake of calcium and vitamin C was higher by DH than by 7-d and this might affect the estimation of bio-availability of iron. It is important to note that there was no difference in intake of foods and nutrients in lunches. Further, intake of meat, and meat and fish, did not differ for lunch and dinner and correlation was high. But for fish, which was consumed more seldom, intake differed. In-between meals contributed a substantial part of the dietary intake and this consumption showed the largest difference between methods in the current study. Number of meals in DH was 25% higher and EI was 19% higher in DH. It could be the lack of memory of the usual consumption in in-between meals or a choice to not eat during the recording period, what has earlier been described as under-eating (Goris & Westerterp, 1999). Iron followed EI but calcium was considerably higher using DH compared to 7-d, and this may have implications for the estimation of bio-availability of iron. We calculated if the 7-d captured intake on group level, ranking level or individual level to find out on which level comparison between the two dietary methods was meaningful. The 7-d was sufficient for satisfactory ranking of the subjects in our population, and in two other Scandinavian methodological studies on adolescents it was also found that 7-d was sufficient for ranking of subjects (Andersen et al, 1995; Hedgren et al, 1995). In one of these studies, it was also shown that the 7-d did not capture individual intakes (Hedgren et al, 1995), similar to the results in the current study. In the comparison at the individual level of EI, the Bland Altman plot showed differences between methods for individuals, however, the ratios EI/BMR demonstrated that both methods underestimated habitual EI. One study on adults indicated that variation within individuals of intake of foods may be larger than intake of nutrients, and larger for foods as legumes, roots crops, fish and specific meats, that are consumed occasionally, than for foods consumed daily as milk and milk products (Hartman et al, 1990). If variation in intake is the reason, comparison becomes less reliable between DH and 7-d for detailed intake as specific foods European Journal of Clinical Nutrition

and intake in meals. Since meal pattern is an important marker of food choice and lifestyle, and the intake on meal level is important from several point of views, we judge it to be important also to compare the intake at that level. However, ranking of intakes may be the most proper level for the current comparison. To assess food habits in adolescents is a challenge in multiple ways. Adolescents have increased needs for energy and nutrients, but they may vary in ability and motivation to report their dietary intake. Participation rates in dietary assessments partly vary between the dietary methods used. In the two Swedish studies using the 7-day record, 66–76% of ¨ m et al, 1993; invited adolescents participated (Bergstro Samuelson et al, 1996). In one study, higher participation ¨ m et al, rate was found among girls than among boys (Bergstro 1993).We have performed DH interviews in two representa¨ berg et al, 2003a) of tive samples (Hulthe´n et al, 2003; Sjo ¨ teborg 15–16 y boys and girls in compulsory schools in Go with high participation rates (80–90%). It was fundamental to that study that all data were collected in school face to face with the subject. The individual interview was central for compliance because the dietician could individualise the interviews. The alternative to instead ask the students to register intake would have resembled homework and probably resulted in lower participation rates. In conclusion, comparison of the DH method to the 7-d record showed that two-thirds of the girls had identical or similar main meal pattern. For the main food groups, energy and nutrients ranking was similar between the methods. For intake of specific foods and intake of nutrients in the meals, the ranking differed more. However, ranking was similar for intake at breakfast and intake of milk in all meals. Intake of foods and nutrients in lunches and intake of meat and fish for lunch and dinner did not differ. In the current study, the diet history seems to work well as a reference method for dietary assessments in this age group.

Acknowledgements We thank the dieticians Ewa Silander and Gabriele Eiben for performing the dietary assessments.

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