comparison of a self-administered quantitative food amount frequency questionnaire with 4-day...
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Comparison of a self-administered quantitative food amount frequencyquestionnaire with 4-day estimated food records
D.L. Hartwell and C.J.K. Henry
Nutrition and Food Science Group, School of Biological and Molecular Sciences, Oxford BrookesUniversity, Gipsy Lane, Headington, Oxford OX3 OBP, UK
Our objective was to assess the relative validity of a self-administered food amountfrequency questionnaire (FAQ), using 4-day estimated food records (FRs) as areference method, for use in a subsequent clinical study of patients undergoing heartsurgery. Thirty healthy subjects (19 males, 11 females), aged 45–75 years, wererandomly recruited from patient lists generated by two local GP practices in Oxford.Complete data from the FAQ and FR, administered twice 6 months apart, wereavailable for 25 subjects (16 males, 9 females). For absolute nutrient values, intakesof protein, CHO, total fat, PUFA, thiamin, iron, dietary fibre and alcohol were notsignificantly different between the FAQ and FR, and Pearson’s correlationcoefficients ranged from 0.28 for protein to 0.88 for total fat. Estimates from theFAQ were within ± 10% of the estimates produced by the FR for two-thirds ofnutrients. When nutrients were expressed as a percentage of total energy intake, nostatistically significant differences were observed for any nutrient between the twomethods, and correlations ranged from 0.32 for protein to 0.80 for SFA. Inconclusion, the broad dietary patterns obtained by the two methods of assessmentwere comparable. This simple and inexpensive FAQ can be used to usefully estimategroup intakes for a variety of nutrients in the study of patients undergoing heartsurgery.
Introduction
In order to investigate the relationship betweenfood/nutrient intake and disease, a descriptionof dietary intake over time is needed (Larkin etal., 1989). This forms the basis and rationale fordietary assessment methods which can accu-rately reflect habitual intake. Food amountfrequency questionnaires (FAQs) have pre-viously been shown to be a reliable method oflong-term dietary assessment (Bergman et al.,1990; Goldbohm et al., 1994; Fidanza et al.,
1995). According to Bodner et al. (1998), thequestionnaire has become established as theprimary method for assessing dietary intake inepidemiological studies of diet and disease.Since there is no practical, absolute referencemethod for assessing nutrient intake in free-living subjects, there is always going to be acertain amount of discrepancy between meth-ods. The food record (FR) is often employed asa reference method because of its simplicity, the
Correspondence to: D.L. Hartwell.
ISSN 0963-7486 printed/ISSN 1465-3478 online01/020151-09 © 2001 Taylor & Francis LtdDOI: 10.1080/09637480020027000
International Journal of Food Sciences and Nutrition (2001) 52, 151–159
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152 D. L. Hartwell & C. J. K. Henry
fact that it is not dependent on memory andallows direct recording of food items as they areeaten. It is also of minimal inconvenience to thesubject. However, the major limitation of thismethod is that a few days’ measurement cannotfully represent the usual intake of subjects. Thisis because the FR per se is only a snapshot ofthe longer-term diet. People can only be studiedfor a period of time, and consequently FR willalways give an imprecise picture of their long-term dietary intake. However, use of a moreextensive method such as the diet historyinterview, is more time-consuming, labourintensive and reliant to some extent uponmemory. Consequently, the FR was consideredthe most appropriate assessment tool for use inthe validation of the present FAQ. The weighedfood record has been described as one of themost accurate methods of measuring foodintake (Fidanza et al., 1995), and it has beensuggested that weighed FR are more accuratethan estimated FR in measuring daily intake(Bingham, 1991; Edington et al., 1989). How-ever, with untrained subjects weighed FR aremore liable to mistakes. Moreover, it has beenfound that the cooperation and detail required inkeeping weighed FR can influence eating habitsto a significant degree (Stuff et al., 1983;Goldbohm et al., 1994).
This study was designed to test the feasibilityof an FAQ to be used in a subsequent studywhich aimed to collect dietary data on patientsundergoing coronary artery bypass grafting(CABG) surgery. At present in the UK, there issurprisingly very limited information availableon the dietary habits of such patients. The FAQhas the advantages of being low-cost, easy toadminister and can be easily posted to respon-dents. These attributes were an important con-sideration in choosing the FAQ for use in thesubsequent CABG study.
Methods
Questionnaire designThe questionnaire was a 162-item food amountfrequency questionnaire, designed to be self-administered. The food items listed were con-sidered to be representative of the range offoods commonly consumed by the subjectpopulation. Respondents were required to reporttheir habitual diet by indicating how often theyusually consume each of the food items listed as
the number of times per day, week, month oryear. A ‘year’ category was provided because itpermits the capture of some foods which maymake an important contribution to averageintake even though infrequently eaten. It is alsouseful because it permits the reporting ofirregular consumption of some foods, such asseasonal items (Block et al., 1986). Respon-dents were given an opportunity at the end ofeach small section to indicate any ‘other’ fooditem regularly eaten that was not on the list. Inan attempt to quantify intake, subjects wereasked to record usual portion sizes. These wereestimated in either common household meas-ures (e.g. tablespoons of mashed potato, cups oftea, scoops of ice-cream, etc.), or in whole units(e.g. number of apples, slices of bread). Wherethis was not possible (e.g. rice, shepherd’s pie,etc.), subjects were asked to indicate whethertheir usual portion size was ‘small, medium orlarge’. Food photographs of 65 food items wereprovided to help the subjects in their portionsize estimation.
SubjectsA total of 30 healthy subjects, consisting of 19males and 11 females, were randomly recruitedfrom patient lists generated by two local GPpractices in Oxford. The criteria limiting partic-ipation included: (1) age not below 45 years –this is because onset of coronary heart disease(CHD) more commonly affects people in laterlife, and it was intended that subjects for thisvalidation be representative of the population tobe used in the subsequent CABG study; (2) nomajor medical condition – in case the medicalcondition influenced usual dietary habits. Thesewere taken into account by the staff at the GPpractices when generating the patient lists. Thecharacteristics of the 25 subjects (16 males, 9females) completing the study did not differsignificantly from those at initial recruitmentand are presented in Table 1.
Study protocolEthical approval was granted by Central OxfordResearch Ethics Committee (COREC) andrecruitment of subjects was on a voluntarybasis. Subjects were visited in their home wheredetailed instructions for completion of the FAQwere given. Subjects were left to complete theFAQ independently to avoid any bias in respon-ses (e.g. under-reporting of foods such as cakes
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Comparison of food amount frequency questionnaires and food records 153
and biscuits because they feel this is a ‘bad’diet). After checking FAQ responses and clar-ifying any uncertainties, the estimated foodrecords were administered. This order waschosen because food recording tends to makepeople more aware of their eating habits, andcan subsequently influence responses to theFAQ.
Subjects were asked to keep a record of theirfood intake on 4 separate days, incorporating 3week days and 1 weekend day. Amounts of eachfood item were indicated in common householdmeasures, as in the FAQ. Subjects were reques-ted to select days when they were consumingtheir normal diet as far as possible. A third visitwas made to collect the FR, and again this timewas used to clarify any discrepancies. The sameprocedure was repeated for the FAQ and FRafter 6 months to take seasonal variation intoaccount. The results presented are an average ofthe two administrations.
Nutrient analysisAll nutrient estimates from both the FAQ andFR were calculated using the DIET5 forWindows dietary analysis computer program(Univation Ltd, Aberdeen). To derive individualnutrient intake, the frequency of consumption ofeach food item was multiplied by the portionweight to obtain the total weight of foodconsumed. These values were then expressed asconsumption (g)/day for each food item, e.g.once a week was weighted as 1�7. The weights ofhousehold measures and small/medium/largeportions of foods were derived through use ofthe DIET5 program and from published values(Crawley, 1993).
Results for 14 nutrients were determined,namely: energy, protein, carbohydrate (CHO),total fat, saturated fatty acids (SFA), mono-
unsaturated fatty acids (MUFA), polyunsatu-rated fatty acids (PUFA), cholesterol, thiamin,vitamin C, calcium (Ca), iron (Fe), dietary fibre(DF) and alcohol. The nutrients were selectedon the basis of their association with CHD, aswell as being a representation of the range ofnutrients in a usual diet in terms of macro- andmicro-nutrients.
Statistical proceduresStatistical analyses were carried out using Excel’97. All data were found to be normallydistributed, and thus parametric tests were usedaccordingly. The data represent the means of thetwo administrations of the FAQ and FR com-pleted 6 months apart. Means, standard devia-tions (SD) and Pearson correlation coefficients(r) were calculated for absolute nutrients esti-mated by both the FAQ and 4-day estimated FR.These values were also calculated for macro-nutrients expressed as a percentage of totalenergy intake. Student’s paired t-tests werecarried out on each individual nutrient to test fordifferences between the means. The strengthand statistical significance of the correlationcoefficients were also tested using the hypoth-esis test (Rees, 1994). Many dietary validationstudies have reported results in this manner(Colditz et al., 1987; Edington et al., 1989;Margetts et al., 1989; Engle et al., 1990; Mares-Perlman et al., 1993; Goldbohm et al., 1994).
However, it has been suggested that the useof correlation coefficients may be an inap-propriate method of analysis, as they measurethe strength of a relation between two variables,rather than the agreement between them (Bland& Altman, 1986; Delcourt et al., 1994). For thisreason, absolute differences and percentagedifferences between the FAQ and FR were alsocalculated, and Student’s paired t-tests were
Table 1. Characteristics of subjects completing the study
All (n = 25)* ± SE Male (n = 16)* ± SE Female (n = 9)* ± SE
Age (yrs) 58.1 1.7 58.5 2.4 57.4 2.5Height (m) 1.73 0.02 1.77 0.02 1.64 0.03Weight (kg) 75.8 3.3 81.7 3.1 65.5 6.1BMI (kg/m2 )† 25.2 0.7 25.9 0.6 24.0 1.7
* Values are means.† Body mass index = weight/height2 .
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154 D. L. Hartwell & C. J. K. Henry
carried out on each individual nutrient to test forany statistically significant differences betweenmethods. Many other dietary validation studieshave reported results in this way (Young et al.,1952; Cade, 1988; Pietinen et al., 1988; Larkinet al., 1989; Thompson & Margetts, 1993;Karim and Margetts, 1995). Results were ana-lysed on the whole group, and also for malesand females separately to investigate any gen-der differences in FAQ and FR response.
Results
Comparison of absolute nutrientsIt may be seen in Table 2 that the FAQconsistently resulted in slightly higher meanestimates for energy and nutrient intake com-pared with the FR, with the exception ofthiamin. Absolute estimates of protein, carbohy-drate, total fat, PUFA, thiamin, iron, dietaryfibre and alcohol were not significantly differ-ent between the FAQ and FR. The differencebetween the methods was greatest for alcohol;the FAQ estimate was 21.9% greater than theFR estimate for the mean sample. For all othernutrients, the estimates from the FAQ werewithin ±20% of the estimates produced by themean of the 4-day FR. For protein, CHO, totalfat, MUFA, PUFA, cholesterol, thiamin, iron
and dietary fibre, estimates were within ±10%.The least difference between the FAQ and FRnutrient estimates was observed for thiamin,with a value of –2.5%.
Pearson correlation coefficients, measuringthe degree to which the two methods are related,ranged from 0.28 for protein to 0.88 for total fat,with a mean of 0.63 (Table 3). The nutrients of
Table 2. Comparison of absolute nutrient estimates for the FAQ and FR
Daily nutrient intake FAQa ± S.D. FRb ± S.D. Differencec ± S.D. Differenced %
Energy kJ 9114 ± 1967 8008 ± 1743* 1106 ± 1939 10.1(kcal) (2180 ± 471) (1916 ± 417) (265 ± 464)
Protein (g) 87 ± 17 80 ± 19 8 ± 22 6.0CHO (g) 255 ± 50 233 ± 61 22 ± 55 7.6Total fat (g) 87 ± 28 82 ± 23 5 ± 13 3.2SFA (g) 34 ± 12 29 ± 9* 5 ± 8 11.4MUFA (g) 27 ± 7 24 ± 6* 3 ± 5 9.3PUFA (g) 15 ± 6 14 ± 5 1 ± 4 4.5Cholesterol (mg) 312 ± 100 270 ± 108* 42 ± 92 9.2Thiamin (mg) 2 ± 0.3 2 ± 0.5 0 ± 0.4 –2.5Vitamin C (mg) 102 ± 38 81 ± 40* 21 ± 26 19.1Calcium (mg) 1062 ± 245 916 ± 247* 145 ± 212 12.5Iron (mg) 13 ± 4 12 ± 3 1 ± 3 6.6Dietary fibre (g) 21 ± 5 19 ± 5 2 ± 5 5.6Alcohol (g) 12 ± 13 11 ± 13 1 ± 9 21.9
a Mean of the two administrations of the FAQ.b Mean of the two administrations of the 4-day FR.c Mean of (FAQ – FR).d Mean of (FAQ – FR)/FAQ*100).*Mean values were significantly different from FAQ (P < 0.05).
Table 3. Pearson correlation coefficients for FAQ and FR
NutrientPearson correlation
coefficient (r)
Energy 0.46*Protein 0.28CHO 0.52†Total fat 0.88‡SFA 0.78‡MUFA 0.70‡PUFA 0.81‡Cholesterol 0.61†Thiamin 0.57†Vitamin C 0.79‡Calcium 0.63‡Iron 0.64‡Dietary fibre 0.34Alcohol 0.78‡
Correlations between the FAQ and FR were statisticallysignificant at *P < 0.05; †P < 0.01; ‡P < 0.001.
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Comparison of food amount frequency questionnaires and food records 155
most interest in the subsequent CABG study,namely energy, total fat, SFA, MUFA, PUFAand cholesterol, showed fairly high correlationcoefficients, ranging from 0.46 for energy to0.88 for total fat. Correlations were statisticallysignificant for all nutrients except protein anddietary fibre.
Comparison of nutrients as a percentage oftotal energyTable 4 shows a comparison of the percentageenergy contribution of nutrients between thetwo dietary methods. An important feature ofthis analysis was that when the macronutrientswere expressed as a percentage of the totalenergy intake, no statistically significant differ-ences were observed between estimatesobtained from the FAQ and FR. The percentagedifference between the two dietary methods was£ 5% for all the macro-nutrients. Pearson corre-lation coefficients ranged from 0.32 for proteinto 0.80 for SFA, with a mean correlation of0.59. Correlations were statistically significantfor energy, total fat, and the three individualclasses of fatty acids.
Gender differencesTable 5 shows the difference in correlationsbetween the two methods for males and femalesfor each of the 14 nutrients. Correlations forfemales were higher for all nutrients except SFAand dietary fibre. Correlation coefficients infemales reached statistical significance (P <
0.05) for 11 nutrients, compared to 9 nutrientsfor males. Correlations for females ranged from0.49 for dietary fibre to 0.96 for alcohol;compared to a slightly negative correlation of–0.14 for protein to 0.84 for total fat for males.For the six nutrients of most interest in theCABG study (i.e. energy, total fat, SFA, MUFA,PUFA and cholesterol), agreement between thetwo dietary methods was high for both genders.
Table 4. Nutrient estimates as a percentage of total energy for the FAQ and FR
Nutrient intake% energy contribution FAQa ± SD FRb ± SD Differencec %
Correlationcoefficient (r)
Energy kJ 9114 ± 1967 8009 ± 1743* 10.1 0.46d
(kcal) (2180 ± 471) (1916 ± 417)
Protein (%) 16.5 ± 0.5 17.1 ± 0.6 –5.0 0.32
CHO (%) 48.1 ± 1.2 50.3 ± 2.5 –5.0 0.35
Total fat (%) 34.7 ± 1.1 35.1 ± 1.1 –1.7 0.72‡SFA (%) 13.7 ± 0.6 13.4 ± 0.5 0.8 0.80‡MUFA (%) 11.1 ± 0.3 11.3 ± 0.3 –2.5 0.70‡PUFA (%) 6.0 ± 0.4 5.8 ± 0.3 0.2 0.76‡
a Mean of the two administrations of the FAQ.b Mean of the two administrations of the 4-day FR.c Mean of ((FAQ – FR)/FAQ*100).*Mean value was significantly different from FAQ (P < 0.05). Correlations between the FAQ and FR were statistically
significant at dP < 0.05; ‡P < 0.001.
Table 5. Pearson correlation coefficients for males andfemales for FAQ and FR
NutrientMale correlations
(n = 19)Female correlations
(n = 11)
Energy 0.52* 0.70*Protein –0.14 0.60*CHO 0.34 0.78†Total fat 0.84‡ 0.92‡SFA 0.76‡ 0.70*MUFA 0.58† 0.64*PUFA 0.75‡ 0.93‡Cholesterol 0.54* 0.51Thiamin 0.18 0.82†Vitamin C 0.82‡ 0.79†Calcium 0.52* 0.53Iron 0.26 0.90‡Dietary fibre 0.28 0.49Alcohol 0.71‡ 0.96‡Mean 0.50 0.73
Correlations between the FAQ and FR were statisticallysignificant at *P < 0.05; †P < 0.01; ‡P <0.001.
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Female ranges were 0.51 for cholesterol to 0.93for PUFA; whilst male ranges were 0.52 forenergy to 0.84 for total fat.
Discussion
The validity of a 162-item self-administeredFAQ to measure usual diet was evaluated in ahealthy population in Oxford. Nutrient esti-mates obtained by the FAQ method werecompared with those obtained from the use of4-day estimated FR.
Comparison of nutrientsIn the validation study, absolute intakes esti-mated by the FAQ gave larger mean values forall nutrients except thiamin, compared with FR(Table 2). This problem of over-estimation ofintakes as derived from questionnaires is con-sistent with the literature. Stuff et al. (1983)measured the dietary intakes of lactatingwomen using an FAQ and diet records of 1 day,3 days and 7 days. Estimated mean daily intakesof energy and nutrients for 40 subjects werefound to be consistently higher when measuredby the FAQ compared to diet records of anylength. Similar trends have been reported inmany other validation studies (Sorenson et al.,1985; Larkin et al., 1989; Engle et al., 1990;Fidanza et al., 1995; Karim & Margetts, 1995;Robinson et al., 1996, 1999). However, not allstudies report higher mean intakes for the FAQcompared with another dietary assessmentmethod. Block et al. (1990) developed ashortened dietary questionnaire and validated itagainst three 4-day FR in a group of middle-aged women. The absolute values of thenutrient estimates by the FAQ were found to belower than estimates from the FR for energy andmost nutrients. Other studies have reportedsimilar findings (Yarnell et al., 1983; Kemppai-nen et al., 1993).
Whether a questionnaire over-estimates orunder-estimates intake compared with anotherdietary method can be explained to some extentby the number and appropriateness of the list offoods presented in the FAQ. For example,under-reporting can be caused by an incompletelist of foods available to the subject, and also ifthe foods listed are not representative of thetype of foods usually consumed in the studypopulation. In contrast, over-reporting can becaused by long lists of the same sort of food
items. However, Block and Hartman (1989)reported that the former usually counteracts thelatter. It is important, therefore, to take thesepoints into consideration when designing theFAQ. A number of factors may explain thehigher mean nutrient intakes obtained with theFAQ in the present study, not least the fact thatthe food records per se are only a snapshot ofthe usual diet. Complete agreement wouldtherefore not be expected due to the comparisonof average usual consumption with a diet of 4days (Yarnell et al., 1983). In addition, foodseaten frequently (e.g. once per week or more)are often remembered better than foods eatenless often, possibly resulting in an over-estima-tion of foods eaten in the FAQ (Bergman et al.,1990).
When the macro-nutrients were expressed asa percentage of the total energy intake, nostatistically significant differences wereobserved between estimates obtained from theFAQ and mean of 4-day FR (Table 4). Thissuggests that intakes estimated from the FAQare comparable to those estimated from the FR,when total energy intake is taken into account.In studies by Pietinen et al. (1988), Bergman etal. (1990) and Goldbohm et al. (1994), thepercentage contribution of the macro-nutrientsranged from 14–18% for protein, 41–49% forcarbohydrate and 33–40% for total fat. Thecontribution of these nutrients in the presentstudy is comparable, being 16.5 and 17.1% forprotein, 48.1 and 50.3% for carbohydrate, and34.7 and 35.1% for total fat for the FAQ and FRrespectively.
Comparison of correlation coefficientsCorrelation coefficients for nutrient intakebetween the two methods in the validation studywere positive for all nutrients, ranging from0.28 for protein to 0.88 for total fat, with a meanof 0.63 (Table 3). Energy and all nutrients,except protein and dietary fibre, were found tobe statistically significant (P < 0.05). These twonutrients exhibited fairly low correlation coeffi-cients (0.28 and 0.34 respectively). All othernutrients were between 0.5 and 0.9. There havebeen widely varying degrees of correlationsbetween nutrient values obtained by FAQ andFR reported in the literature, both high values(Balogh et al., 1968; Goldbohm et al., 1994)and low values (Sorenson et al., 1985; Margettset al., 1989; Engle et al., 1990; Robinson et al.,
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Comparison of food amount frequency questionnaires and food records 157
1996; Bell et al., 1999). The range of correla-tion coefficients observed in the present valida-tion study is comparable to many other valida-tion studies (Yarnell et al., 1983; Willett et al.,1985; Gelissen & Roberts, 1992; Rimm et al.,1992; Fidanza et al., 1995).
Correlation coefficients for nutrients whenexpressed as a percentage of the total energyintake ranged from 0.32 for protein to 0.80 forSFA (Table 4), with a mean of 0.59. Allnutrients, except protein and CHO, reachedstatistical significance (P < 0.05). Similarresults were reported by Gelissen and Roberts(1992) and Goldbohm et al. (1994) withcorrelation coefficients ranging from 0.60 to0.70, and 0.50 to 0.60, respectively whenmacro-nutrients were expressed as a percentageof energy intake. Lower correlation coefficientsrelating FAQ with FR may be due in part to thegreater day-to-day variability in intake reflectedin the FR data (Mares-Perlman et al., 1993).This is particularly true for nutrients whosedaily intake can vary considerably, like vitaminA, iron and dietary fibre; this can be seen in thelower reported correlation of dietary fibre in thepresent study, being 0.34. Thus, the result of thiswithin-person variability is poorer agreementbetween methods. On the other hand, if therecord period is prolonged, the subjects can gettired and bored and become generally lesscooperative, so the accuracy of the records doesnot necessarily improve. The three most com-mon sources of error which ultimately result inlowered agreement between methods include:considerable difference between food consump-tion for a short period, and sustained foodhabits; large day-to-day variability within sub-jects; and errors in recording techniques bysubjects (McHenry et al., 1945).
Comparison of males and femalesWhen absolute nutrient intake from the FAQand FR were assessed, correlations for femaleswere found to be higher for all nutrients, exceptSFA and dietary fibre, with a mean of 0.73. Agroup mean of 0.50 was observed for malecorrelations. A study by O’Donnell et al. (1991)also found that females tended to achieve highercorrelations compared to males, although thisdifference was not consistent. It was suggestedthat the difference may be attributed toincreased compliance and better reliability ofresponses given by females. The sex difference
may also be explained by the fact that womentend to spend more time than men in thepurchasing and cooking of meals, thus makingthem more aware of food portion sizes andfrequency of consumption.
Correlations for SFA were higher in malescompared to females, and this may suggest thatmales can more reliably estimate their SFAintake. This point is worth noting when weconsider that subjects in the CABG study are allmales. Furthermore, for energy and the fats,agreement between the FAQ and FR, and alsowithin the FAQ, was acceptable for both malesand females.
The purpose of presenting the results of thispresent study in a number of different ways wasto enable comparison with related literature.Although it is useful to compare results fromrecent dietary validation studies with the exist-ing literature, this comparison is made difficultdue to each FAQ having its own characteristicsregarding the number and type of food items,the way in which intake is quantified, thenumber of frequency categories, the way inwhich it is administered, the ability of subjectsto complete the FAQ, and so on (Fidanza et al.,1995). Whether dietary constituents areweighed, recorded or elicited by questioning,errors will inevitably creep in. The errors canarise from two main sources: the subjects understudy, and also from analysis of results. Owingto the need to secure cooperative subjects, it isusually impossible to get anything like arandom sample of the population (Woolf, 1954).Furthermore, it is inevitable that there will be adisturbance (even of the smallest magnitude) inthe normal dietary intake of subjects, due to theeffect of observation. Secondly, whether doneby chemical analysis or calculated from tables,the translation of foodstuffs into nutrients willbe subject to variation, depending on the brandof food product, the time of year, and so on. Itis sufficient to say that such errors are generallyunavoidable, and one can only strive to limitthem as far as possible.
Conclusions
Food amount frequency questionnaires offermany advantages as a means of dietary assess-ment among groups of people. They are apractical, inexpensive method which offer mini-mal intrusion to subjects in measuring habitual
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diets. Horwath (1990), in reviewing the foodfrequency method, suggests that FAQs areappropriate for studies where the aim is toassess mean group intake, or when the focus ison describing patterns of food intake. This is thecase in the subsequent CABG study, wherehabitual diet is assessed before, and following,coronary artery bypass grafting surgery.
In reviewing the results of the present study,it may be concluded that this simple and
inexpensive self-administered FAQ can usefullymeasure group intakes for a variety of nutrients,specifically energy, fat, SFA and PUFA. Conse-quently, the FAQ can be used with confidencein the CABG clinical study to assess thenutrient intake in a group of CHD patients pre-and post-CABG.
Acknowledgement s—We are grateful to Oxford NutritionLtd for their financial support for this study.
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