Rachel L. Thompson

Development, validation and utilisation of food-frequency questionnaires – a review

OBJECTIVEnThe purpose of this review is to provide guidance on the development, validation and use of food-frequency questionnaires (FFQs) for different study designs. It does not include any recommendations about the most appropriate method for dietary assessment (e.g. food-frequency questionnaire versus weighed record).nnnMETHODSnA comprehensive search of electronic databases was carried out for publications from 1980 to 1999. Findings from the review were then commented upon and added to by a group of international experts.nnnRESULTSnRecommendations have been developed to aid in the design, validation and use of FFQs. Specific details of each of these areas are discussed in the text.nnnCONCLUSIONSnFFQs are being used in a variety of ways and different study designs. There is no gold standard for directly assessing the validity of FFQs. Nevertheless, the outcome of this review should help those wishing to develop or adapt an FFQ to validate it for its intended use.

Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review.

Abstract Objective To review systematically the evidence for an effect of long chain and shorter chain omega 3 fatty acids on total mortality, cardiovascular events, and cancer. Data sources Electronic databases searched to February 2002; authors contacted and bibliographies of randomised controlled trials (RCTs) checked to locate studies. Review methods Review of RCTs of omega 3 intake for 3 6 months in adults (with or without risk factors for cardiovascular disease) with data on a relevant outcome. Cohort studies that estimated omega 3 intake and related this to clinical outcome during at least 6 months were also included. Application of inclusion criteria, data extraction, and quality assessments were performed independently in duplicate. Results Of 15 159 titles and abstracts assessed, 48 RCTs (36 913 participants) and 41 cohort studies were analysed. The trial results were inconsistent. The pooled estimate showed no strong evidence of reduced risk of total mortality (relative risk 0.87, 95% confidence interval 0.73 to 1.03) or combined cardiovascular events (0.95, 0.82 to 1.12) in participants taking additional omega 3 fats. The few studies at low risk of bias were more consistent, but they showed no effect of omega 3 on total mortality (0.98, 0.70 to 1.36) or cardiovascular events (1.09, 0.87 to 1.37). When data from the subgroup of studies of long chain omega 3 fats were analysed separately, total mortality (0.86, 0.70 to 1.04; 138 events) and cardiovascular events (0.93, 0.79 to 1.11) were not clearly reduced. Neither RCTs nor cohort studies suggested increased risk of cancer with a higher intake of omega 3 (trials: 1.07, 0.88 to 1.30; cohort studies: 1.02, 0.87 to 1.19), but clinically important harm could not be excluded. Conclusion Long chain and shorter chain omega 3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer.

Reduced or modified dietary fat for preventing cardiovascular disease

BACKGROUNDnReduction and modification of dietary fats have differing effects on cardiovascular risk factors (such as serum cholesterol), but their effects on important health outcomes are less clear.nnnOBJECTIVESnTo assess the effect of reduction and/or modification of dietary fats on mortality, cardiovascular mortality, cardiovascular morbidity and individual outcomes including myocardial infarction, stroke and cancer diagnoses in randomised clinical trials of at least 6 months duration.nnnSEARCH METHODSnFor this review update, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE, were searched through to June 2010. References of Included studies and reviews were also checked.nnnSELECTION CRITERIAnTrials fulfilled the following criteria: 1) randomised with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) adult humans with or without cardiovascular disease, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available.nnnDATA COLLECTION AND ANALYSISnParticipant numbers experiencing health outcomes in each arm were extracted independently in duplicate and random effects meta-analyses, meta-regression, sub-grouping, sensitivity analyses and funnel plots were performed.nnnMAIN RESULTSnThis updated review suggested that reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14% (RR 0.86, 95% CI 0.77 to 0.96, 24 comparisons, 65,508 participants of whom 7% had a cardiovascular event, I(2) 50%). Subgrouping suggested that this reduction in cardiovascular events was seen in studies of fat modification (not reduction - which related directly to the degree of effect on serum total and LDL cholesterol and triglycerides), of at least two years duration and in studies of men (not of women). There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants). This did not alter with sub-grouping or sensitivity analysis.Few studies compared reduced with modified fat diets, so direct comparison was not possible.nnnAUTHORS CONCLUSIONSnThe findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.

Dietary fat intake and prevention of cardiovascular disease: systematic review

Abstract Objective: To assess the effect of reduction or modification of dietary fat intake on total and cardiovascular mortality and cardiovascular morbidity. Design: Systematic review. Data sources: Cochrane Library, Medline, Embase, CAB abstracts, SIGLE, CVRCT registry, and biographies were searched; trials known to experts were included. Included studies: Randomised controlled trials stating intention to reduce or modify fat or cholesterol intake in healthy adult participants over at least six months. Inclusion decisions, validity, and data extraction were duplicated. Meta-analysis (random effects methodology), meta-regression, and funnel plots were performed. Results: 27 studies (30 902 person years of observation) were included. Alteration of dietary fat intake had small effects on total mortality (rate ratio 0.98; 95% confidence interval 0.86 to 1.12). Cardiovascular mortality was reduced by 9% (0.91; 0.77 to 1.07) and cardiovascular events by 16% (0.84; 0.72 to 0.99), which was attenuated (0.86; 0.72 to 1.03) in a sensitivity analysis that excluded a trial using oily fish. Trials with at least two years follow up provided stronger evidence of protection from cardiovascular events (0.76; 0.65 to 0.90). Conclusions: There is a small but potentially important reduction in cardiovascular risk with reduction or modification of dietary fat intake, seen particularly in trials of longer duration. What is already known on this topic The epidemiological relation between dietary fat intake and cardiovascular disease is central in strategies aimed at risk reduction in populations and individuals Systematic review of randomised controlled trials supports manipulation of dietary fat to control serum lipid concentrations, though evidence of effect on one risk factor does not rule out an opposite or reinforced effect on another unstudied risk factor Randomised controlled trials of dietary fat reduction or modification have shown varying results on cardiovascular morbidity and mortality What this study adds Systematic review of trials of modified fat intake shows that reduction or modification of dietary fat intake results in reductions in cardiovascular events, but only in trials of at least two years duration There is little effect on total mortality Despite decades of effort and many thousands of people randomised, there is still only limited and inconclusive evidence of the effects of modification of total, saturated, monounsaturated, or polyunsaturated fats on cardiovascular morbidity and mortality

Prevalence of risk of undernutrition is associated with poor health status in older people in the UK

Objective: To establish the prevalence of the risk of undernutrition, using criteria similar to those used by the Malnutrition Advisory Group (MAG), in people aged 65u2005y and over, and to identify relationships between risk of undernutrition and health and demographic characteristics.Design: A cross-sectional nationally representative sample of free-living and institutionalized older people in the UK (65u2005y of age and over). Secondary analysis of the National Diet and Nutrition Survey based on 1368 people aged 65u2005y and over.Results: About 14% (21% in those living in institutions) were at medium or high risk of undernutrition based on a composite measure of low body mass index and recent reported weight loss. Having a long-standing illness was associated with a statistically significantly increased risk of undernutrition (odds ratio: men 2.34, 95% CI 1.20–4.58; women 2.98; 1.58–5.62). The risk of undernutrition increased: in women reporting bad or very bad health status; in men living in northern England and Scotland; for those aged 85u2005y and older; for those hospitalized in the last year, and those living in an institution. Lower consumption of energy, meat products or fruit and vegetables and lower blood measures of zinc, vitamins A, D, E and C were associated with statistically significantly increased risk of undernutrition.Conclusion: A substantial proportion of the older population of the UK is at risk of undernutrition. High-risk subjects are more likely to have poorer health status. It is unlikely that the individuals at high risk are being detected currently, and therefore effective care is not being provided, either in the community or in institutions.Sponsorship: This analysis was partly funded by a grant from the Department of Health. We are grateful for helpful comments from Professor MJ Wiseman and the anonymous reviewers.

The Health Education Authority's health and lifestyle survey 1993: who are the low fruit and vegetable consumers?

STUDY OBJECTIVE: Firstly, to determine the demographic and behavioural characteristics of low fruit and vegetable consumers. Secondly, to investigate whether knowledge and attitudes are barriers to consumption of fruit and vegetables. DESIGN: Cross sectional survey: an interviewer administrated questionnaire was used to assess the demographic, knowledge, attitude, and behavioural characteristics of the respondents. SETTING: England. PARTICIPANTS: Random sample of 5553 men and women aged between 16 and 74 years. Response rate 70%. MAIN RESULTS: The main demographic characteristics of the respondents identified as low consumers of fruit and vegetables (less than daily consumption of either fruit or vegetables) were age, sex, and smoking status. The adjusted odds ratios were 2.59 for those aged 16-24 years compared with those aged 45-74 years, 2.17 for men compared with women, and 1.77 for current smokers compared with never smokers. The most important knowledge and attitude statements after adjusting for the demographic variables were disagreeing with the statement healthy foods are enjoyable (odds ratio 1.90) and agreeing with the statement I dont really care what I eat (odds ratio 1.76). The impact of knowledge seemed less important than attitudes about a healthy diet in characterising a low fruit and vegetable consumer. CONCLUSIONS: These findings are relevant to future strategies for improving intake of fruit and vegetables, but demonstrate the complexity of interventions required, and the dangers inherent in assuming simplistic relations between psychosocial factors and behaviour.

Policy and action for cancer prevention

Kirsty Beck, Science and Policy Project Manager, and Dr Rachel Thompson, Science Programme Manager (Nutrition), at the World Kirsty Beck, Science and Policy Project Manager, and Dr Rachel Thompson, Science Programme Manager (Nutrition), at the World Cancer Research Fund International, highlight the importance of addressing health inequalities in the fight against cancer

Dietary advice given by a dietitian versus other health professional or self‐help resources to reduce blood cholesterol

BACKGROUNDnThe average level of blood cholesterol is an important determinant of the risk of coronary heart disease. Blood cholesterol can be reduced by dietary means. Although dietitians are trained to provide dietary advice, for practical reasons it is also given by other health professionals and occasionally through the use of self-help resources.nnnOBJECTIVESnTo assess the effects of dietary advice given by a dietitian compared with another health professional, or the use of self-help resources, in reducing blood cholesterol in adults.nnnSEARCH STRATEGYnWe searched The Cochrane Library (to Issue 2 1999), MEDLINE (1966 to January 1999), EMBASE (1980 to December 1998), Cinahl (1982 to December 1998), Human Nutrition (1991 to 1998), Science Citation Index, Social Sciences Citation Index, hand searched conference proceedings on nutrition and heart disease, and contacted experts in the field.nnnSELECTION CRITERIAnRandomised trials of dietary advice given by a dietitian compared with another health professional or self-help resources. The main outcome was difference in blood cholesterol between dietitian groups compared with other intervention groups.nnnDATA COLLECTION AND ANALYSISnTwo reviewers independently extracted data and assessed study quality.nnnMAIN RESULTSnEleven studies with 12 comparisons were included, involving 704 people receiving advice from dietitians, 486 from other health professionals and 551 people using self-help leaflets. Four studies compared dietitian with doctor, seven with self-help resources, and one compared dietitian with nurse. Participants receiving advice from dietitians experienced a greater reduction in blood cholesterol than those receiving advice only from doctors (-0.25 mmol/L (95% CI -0.37, -0.12 mmol/L)). There was no statistically significant difference in change in blood cholesterol between dietitians and self-help resources (-0.10 mmol/L (95% CI -0.22, 0.03 mmol/L)). No statistically significant differences were detected for secondary outcome measures between any of the comparisons with the exception of dietitian versus nurse for HDLc, where the dietitian groups showed a greater reduction (-0.06 mmol/L (95% CI -0.11, -0.01)). No significant heterogeneity between the studies was detected.nnnREVIEWERS CONCLUSIONSnDietitians were better than doctors at lowering blood cholesterol in the short to medium term, but there was no evidence that they were better than self-help resources. The results should be interpreted with caution as the studies were not of good quality and the analysis was based on a limited number of trials. More evidence is required to assess whether change can be maintained in the longer term. There was no evidence that dietitians provided better outcomes than nurses.

The validity of dietary assessment in general practice.

OBJECTIVE: To validate a range of dietary assessment instruments in general practice. METHODS: Using a randomised block design, brief assessment instruments and more complex conventional dietary assessment tools were compared with an accepted relative standard--a seven day weighed dietary record. The standard was checked using biomarkers, and by performing test-retest reliability in additional subjects (n = 29). OUTCOMES: Agreement with weighed record. Percentage agreement with weighed record, rank correlation from scatter plot, rank correlation from Bland-Altman plot. Reliability of the weighed record. SETTING: Practice nurse treatment room in a single suburban general practice. SUBJECTS: Patients with risk factors for cardiovascular disease (n = 61) or age/sex stratified general population group (n = 50). RESULTS: Brief self completion dietary assessment tools based on food groups caten during a week show reasonable agreement with the relative standard. For % energy from fat and saturated fat, non-starch polysaccharide, grams of fruit and vegetables and starchy foods consumed the range of agreement with the standard was: median % difference -6% to 12%, rank correlation 0.5 to 0.6. This agreement is of a similar order to the reliability of the weighed record, as good as or better than test standard agreement for more time consuming instruments, and compares favourably with research instruments validated in other settings. Under-reporting of energy intake was common (40%) and more likely if subjects were obese (body mass idex (BMI) > or = 30 60% under-reported; BMI < 30 29%, p < 0.001). CONCLUSION: Under-reporting of absolute energy intake is common, particularly among obese patients. Simple self assessment tools based on food groups, designed for practice nurse dietary assessment, show acceptable agreement with a standard, and suggest such tools are sufficiently accurate for clinical work, research, and possibly population dietary monitoring.

The association between diet and chronic obstructive pulmonary disease in subjects selected from general practice

It is unclear why some smokers develop chronic obstructive pulmonary disease (COPD) whilst the majority do not. Antioxidants found in food may protect against lung tissue injury, but previous epidemiological studies are inconsistent and do not focus on those most at risk of COPD, namely smokers. This case-controlled study measured the difference in dietary intake between smokers and exsmokers with and without COPD. Cases were patients >45u2005yrs of age with >10 pack-yrs of smoking, a forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) of ≤70% and a FEV1 of ≤80% of predicted. Controls were patients >45u2005yrs of age with >10 pack-yrs of smoking, a FEV1/FVC of >70% and a FEV1 >80% pred. Data were collected using validated questionnaires. Logistic regression analysis for an unmatched case-controlled study was performed. After controlling for other independent predictors of COPD, those with vegetable intake of ≥1 portion·day−1 (93u2005g) were less likely to have COPD, as were those consuming ≥1.5 portions·day−1 of fruit. This was not due to an overall reduction in food/calorie intake caused by the disease because: 1) adjusting for body mass index did not alter the estimates; 2) the effect was specific to fruit and vegetables, i.e. not other food groups; and 3) the estimates from incident cases were similar. In conclusion, fruit and vegetable consumption is inversely associated with chronic obstructive pulmonary disease and may explain why some smokers do not develop chronic obstructive pulmonary disease.