Scotland is in the unenviable position of experiencing the highest age-standardised mortality rates and lowest life expectancy in Western Europe( Reference Whyte and Ajetunmobi 1 ). Although health outcomes have improved in the last 20 years, with premature mortality in those under 75 years of age dropping by over one-third, the gap between the overall age-standardised death rates from all causes for Scotland and the UK as a whole( 2 ) has not reduced. The gap remains at over 100 additional deaths per 100 000 individuals for Scotland, compared with the UK average.
Higher deprivation rates can explain some of these differences, but more than three-quarters of excess deaths cannot be accounted for through this explanation alone( Reference McCartney, Russ and Walsh 3 ). Further support for examining alternative explanations comes from research that compared the largest Scottish city, Glasgow, with two English cities (Liverpool and Manchester) with similar rates of deprivation and life expectancy. The results from that work highlighted that Glasgow experienced 30 % more premature deaths and 15 % more total deaths than these two cities( Reference Walsh, Bendel and Jones 4 ).
These large differences have received considerable critical attention in the literature, with a number of explanations put forward to explain the gap( Reference Walsh, McCartney and McCullough 5 ), such as historically high levels of deprivation, regional economic policies, de-industrialisation and low levels of social capital( Reference Walsh, McCartney and Collins 6 ). The impact of diet and nutrition on health outcomes and life expectancy is of little doubt. Evidence identifies diet and obesity as key factors in CVD, diabetes( 7 ) and some of the most common cancers( 8 ). Nevertheless, dietary differences in relation to Scotland and England, and more specifically Glasgow and similar English cities, have not been investigated adequately. It is estimated that if the Scottish diet were similar to that consumed in England, then potentially 40 % of excess deaths could be avoided( Reference Scarborough, Morgan and Webster 9 ). Comparing three years of food and nutrient data from the Family Food Survey, Scarborough et al.( Reference Scarborough, Morgan and Webster 9 ) found that Scottish households were eating less fruit and vegetables, and more fat, saturated fat and salt, than English households.
Policy context
At a policy level, the need to tackle poor diet and obesity in Scotland has been recognised; however, progress in dietary change is slow( Reference Wrieden, Armstrong and Sherriff 10 ). In addition, large inequalities exist in the nutritional quality of diets( Reference Lang, Dowler and Hunter 11 ), contributing to the risk of chronic diseases and obesity, the rates of which are higher in areas of deprivation( 12 ). The Scottish Dietary Targets( 13 ), reconfigured as Dietary Goals( 14 ), aim to increase fruit, vegetable, whole grains and fish intakes, and reduce saturated fat and added sugar; however, dietary change remains elusive( Reference Wrieden, Armstrong and Sherriff 10 , Reference Lang, Dowler and Hunter 11 ). Given the evidence that deprivation alone does not explain the higher mortality rates observed for Scotland, a key concern for the Scottish Government is to understand what other factors influence the higher prevalence of chronic disease as an important contributor to lower life expectancy and greater burden on local health services. Examining the historical and current dietary differences between Scotland and England in the published literature provides an opportunity to identify key areas for action and further examination.
Aim
The present work was prepared in response to a commissioned call from NHS Health Scotland, a Scottish health board with a national remit to improve health and reduce inequalities. NHS Health Scotland commissioned a rapid review( Reference Wrieden, Chambers and Barton 15 ) to identify and synthesise evidence on current and historical differences in food and nutrient intakes in Scotland and England (including differences between the cities of, and regions surrounding, Glasgow, Liverpool and Manchester). It is this work that the current paper reports.
Methods
Study design
Rapid review is an evidence synthesis methodology that applies a systematic approach to evidence identification and syntheses, but with a more limited scope than a systematic review. Rapid reviews generally seek a response to a policy or a clinically important query in a defined time period, working closely with the stakeholders seeking the answer to the query( Reference Hartling, Guise and Kato 16 ). The need to draw together conclusions from the evidence in a timely manner impacts on the review’s precision( Reference Thomas, Newman and Oliver 17 , Reference Ganann, Ciliska and Thomas 18 ). Rapid reviews range in the methods used and the time period for completion, with some completed within 3 weeks and others taking as long as 6 months( Reference Ganann, Ciliska and Thomas 18 ). The present review was carried out over a 4-month period, and limited its scope by looking at four key databases, including English-language publications only, and by carrying out a restricted search of the grey literature.
Search strategy
An initial scoping search was carried out. This involved identifying key dietary surveys from across the UK via the authors’ expertise and online searches. Google Scholar was also searched using ‘Scotland’, ‘England’, ‘Diet’, ‘Glasgow’, ‘Manchester’ and ‘Liverpool’ as search terms. The keywords of identified studies were then used to create the search terms for the main study searches. Searches were run in four databases from database start dates (Medline, 1946; CINAHL, 1937; Embase, 1947; Web of Science, 1945) until October 2014, using search terms specific to each database (see online supplementary material, Supplemental Tables 1–4). The wide date range was essential for examining historical dietary differences. Search terms were built around the location of the study sample, diet and nutrition outcomes, and study design, specifically population-based observational studies. Medical Subject Heading (MeSH) terms were used for Medline, and Subject Headings for CINAHL and Embase. Inclusion and exclusion criteria were defined to enable publication selection (Table 1).
Table 1 Inclusion and exclusion criteria for the present rapid literature review on dietary differences between Scotland and England
NMES, non-milk extrinsic sugars.
Grey literature searching included searches of key websites and liaison with National Health Service and Local Authority contacts in Glasgow, Liverpool and Manchester. Websites included the sites of UK (e.g. National Diet and Nutrition Survey, Low Income Diet and Nutrition Survey), English (e.g. Health Survey for England) and Scottish (e.g. Scottish Health Survey) national surveys; Glasgow, Manchester and Liverpool City Council websites; and Google (using the search terms ‘Scotland’, ‘England’, ‘Diet’, ‘Glasgow’, ‘Manchester’, ‘Liverpool’).
The reference lists of included grey literature and database papers were also hand-searched. To limit the scope of the work, only those references that could be retrieved within the 4-month study identification period were included.
Two researchers scanned titles and abstracts independently to identify publications requiring full-text review. The project lead acted as a third reviewer when there were disagreements. Inclusion was determined by a single reviewer examining the full text of publications with support from the project lead.
Data extraction
The Cochrane Collaboration( 19 ) data extraction form was adapted to make it more specific to the present review; for example, by removing items referring to experimental and quasi-experimental studies. Variables extracted included geographical area (e.g. country, region), study type (e.g. population-based observational study), survey name (e.g. Scottish Health Survey), study population (e.g. age, gender, socio-economic group), sample size, sampling method (e.g. random, convenience), survey administration (interviewer, mail, telephone, self-report), dietary assessment method (e.g. 24 h recall, weighed diary, FFQ), dietary outcome (e.g. fruit and vegetable intake, energy intake, vitamin intake), units of measurements (e.g. mg/d, portions/d), nutrient database used in the analysis, confounding variables (e.g. age, gender, socio-economic status, income, area deprivation) and dietary analysis software.
Study quality
The Quality Assessment Tool for Observational Cohort and Cross-sectional Studies, developed by the National Institutes of Health/National Heart, Lung, and Blood Institute( 20 ), was used as a checklist for scoring study quality. The checklist assessed how representative the study population was, sample sizes, response rates, reliability and validity of measures, and adjustment for key confounders. An additional criterion was added as to whether the statistical analysis carried out in the study was suitable for answering the review questions. Studies were scored on a continuum of poor–fair–good quality dependent on individual scores for the criteria outlined above. Full information on study quality can be found in the online supplementary material, Supplemental Tables 5 and 6.
Data synthesis
Data were synthesised by dietary outcomes. Comparisons that tested for statistical significance were examined in greatest depth, covering foods consumed, macronutrients and micronutrients. Data that provided information on dietary trends, but did not test for statistical significance, were then examined. Where information was available for an English region only rather than England as a whole, the most relevant region for the study objectives was chosen for comparison. We chose to compare Scottish data with Northern England as this region is demographically the most similar to Scotland. The review was focused on publications with information for both Scotland and England; however, the study team compared national surveys carried out separately in England and Scotland where outcomes had been measured similarly and around the same time period (e.g. difference of 2 years or less).
Results
Figure 1 details a flow diagram of the search results. The database searches returned 4231 results. The scoping, Internet and reference list searches identified seventy-two results. After removal of duplicates, titles and abstracts were screened for 4281 results with full-text examination of 197 publications. The team excluded 147 publications due to non-representative samples or no suitable comparison for Scotland and England. From the grey literature, we identified reports from a number of national surveys. These included the Health Survey for England( Reference Sproston and Primatesta 21 – Reference Craig, Mindell and Hirani 24 ), the Scottish Health Survey( Reference Bromley, Chaudhury and Deverill 25 – Reference Bromley, Sproston and Shelton 29 ), the National Diet and Nutrition Survey and predecessors( 30 – Reference Gregory, Collins and Davies 37 ), the National Food Survey/Expenditure and Food Survey/Living Costs and Food Survey( 38 – 54 ), and the Low Income Diet and Nutrition Survey( Reference Nelson, Erens and Bates 55 ). A number of volumes from a single survey report were identified (e.g. Low Income Diet and Nutrition Survey; Scottish Health Survey). Multiple volumes for a survey in the same year were considered a single publication. Included publications provided data on a wide range of dietary outcomes (Tables 2 and 3). Three publications tested differences between Scotland and England as a whole statistically( Reference Scarborough, Morgan and Webster 9 , Reference Nelson, Erens and Bates 55 , Reference Shelton 56 ), as opposed to English regions or England and Wales. A single publication( Reference Shelton 56 ) statistically tested data at the regional level, comparing Greater Glasgow and the North West of England, and Greater Glasgow and Greater Manchester.
Fig. 1 Flowchart showing the studies retrieved for the present rapid literature review on dietary differences between Scotland and England
Table 2 Overview of child studies
BW, body weight; RNI, Recommended Nutrient Intake; NMES, non-milk extrinsic sugars; SIMD, Scottish Index of Multiple Deprivation; NS-SEC, National Statistics Socioeconomic Classification; EAR, Estimated Average Requirement; IMD, Index of Multiple Deprivation.
Dates in parentheses represent the year(s) in which data were collected.
Table 3 Overview of adult studies
NSHD, National Survey of Health and Development; MAFF, Ministry of Agriculture, Fisheries and Food; Defra, Department for Environment, Food and Rural Affairs; NatCen, National Centre for Social Research; UCL, University College London; EAR, Estimated Average Requirement; RNI, Recommended Nutrient Intake; NS-SEC, National Statistics Socioeconomic Classification; IMD, Index of Multiple Deprivation; SIMD, Scottish Index of Multiple Deprivation.
Dates in parentheses represent the year in which data were collected.
Results are presented separately for dietary differences between Scotland and England in children and adults. Tables 2 (children) and 3 (adults) present an overview of the methodology used in each study. Table 3 details studies on adults and includes publications from the National Food Survey/Expenditure and Food Survey/Living Costs and Food Survey( 38 – 54 ) where food purchase data were collected at the household level and analysed to estimate per person intakes of foods and nutrients. Information on child intake is included within the reports from the aforementioned surveys as part of the household sample; however, child-only results were not presented.
Results for those studies that carried out statistical tests of difference on data from Scotland and England are presented in Table 4 (children) and Table 5 (adults or households). Narrative results provide an overview of these studies, as well as referencing other studies that did not test for statistical difference, but support or contradict those studies that did.
Table 4 Significant results from studies with child populations
Table 5 Significant results from studies with adult populations
NSHD, National Survey of Health and Development; NS-SEC, National Statistics Socioeconomic Classification; RDM, recommended daily minimum; RNI, Recommended Nutrient Intake.
Dates in parentheses represent the year in which data were collected.
* Adjusted for behavioural variables: cigarette smoking, food supplements, drinking behaviour, health-related diet.
† The grand mean is the mean of the means for each regional sub-sample.
Children and young people
Seven studies identified statistically significant differences in the diets of children living in Scotland and England. The main findings from these data were that dietary intake in Scotland appeared to be lower in nutritional quality than that in England or Northern England. Dietary differences were present as early as 1950, although not always negatively for Scotland. Prynne et al.( Reference Prynne, Paul and Mishra 57 ) found that 4-year-old children living in Scotland had lower intakes of vegetables and fruit; however, they also found positive differences, with higher intakes of porridge and soup, and lower intakes of cakes, biscuits, fried foods and bacon. Energy intakes were lower in children living in Scotland in 1950, which perhaps explains why macro- and micronutrient intakes were also lower( Reference Prynne, Paul and Mishra 57 , Reference Prynne, Thane and Prentice 58 ). Lower micronutrient intake was identified in Scotland for a number of vitamins and minerals in three additional studies( 30 , Reference Crawley 59 , Reference Watt, Dykes and Sheiham 60 ). In contrast, in the 2007 Low Income Diet and Nutrition Study( Reference Nelson, Erens and Bates 55 ), boys living in low-income households in Scotland were less likely than those living in England to have intakes of Ca, K and Zn below the Low Nutrient Reference Intakes. No other studies provided data on significant differences in macronutrient intakes; however, intakes of fibre were lower for 16- and 17-year-olds living in Scotland in 1986( Reference Crawley 59 ). Differences in food consumption were identified and included children in Scotland being less likely to consume vegetables( 30 , Reference Prynne, Paul and Mishra 57 , Reference Crawley 59 , Reference Watt, Dykes and Sheiham 60 ), fruit( Reference Nelson, Erens and Bates 55 , Reference Prynne, Paul and Mishra 57 ), spreading fat( Reference Prynne, Paul and Mishra 57 ), skimmed milk( Reference Crawley 59 ), breakfast cereals( Reference Gregory and Lowe 36 , Reference Crawley 59 ) and cakes( 30 , Reference Prynne, Paul and Mishra 57 ). Children in Scotland were more likely to consume chips( Reference Crawley 59 ) and soup( 30 , Reference Prynne, Paul and Mishra 57 ). Consistent findings were identified only for soup, cake, vegetable and fruit consumption.
Similar results were reflected in studies that did not test for statistical differences in relation to lower fruit and vegetable intakes( Reference Craig and Hirani 22 – Reference Craig, Mindell and Hirani 24 , Reference Bromley, Dowling and Gray 26 – Reference Corbett, Dobbie and Doig 28 ). In the Health Behaviour in School-aged Children surveys a higher percentage of children in Scotland reported eating fruit daily in 2001/2( Reference Currie, Roberts and Morgan 61 ), but this pattern was demonstrated only for 11-year-olds, not 13- and 15-year-olds in 2005/6( Reference Currie, Gabhainn and Godeau 62 ) and 2009/10( Reference Currie, Zanotti and Morgan 63 ). In line with the patterns identified in other studies, a lower percentage of children in Scotland reported eating vegetables daily in 2005/6( Reference Currie, Gabhainn and Godeau 62 ) and 2009/10( Reference Currie, Zanotti and Morgan 63 ), and a higher percentage of children living in Scotland reported drinking sweetened beverages daily in 2001/2( Reference Currie, Roberts and Morgan 61 ) and 2005/6( Reference Currie, Gabhainn and Godeau 62 ). By 2009/10, a higher proportion of English children reported drinking them daily( Reference Currie, Zanotti and Morgan 63 ). The EURO-URHIS 2 study found little difference in regular fruit and vegetable consumption between teenagers living in Glasgow and Greater Manchester; however, consumption was higher in Merseyside( 64 – 66 ).
In the only study to examine overall diet quality as a single variable, Watt et al.( Reference Watt, Dykes and Sheiham 60 ) analysed the percentage of pre-school children meeting five dietary parameters (recommended nutrient intakes for Fe, Zn, vitamins A and C, and percentage of energy from non-milk extrinsic sugars of less than 10 %). Their analysis showed that children living in Scotland were less likely to meet one or more of the recommended dietary parameters.
Study quality
Overall study quality ranged from ‘poor’ to ‘good–fair’. The main limitations of the studies were that sample sizes were often small in Scotland( Reference Lang, Dowler and Hunter 11 , Reference Sproston and Primatesta 21 , 45 – 47 , 52 , 53 , 67 , 68 ), limiting the ability to find statistically significant differences, and results often did not adjust for confounders( Reference Sproston and Primatesta 21 – Reference Craig, Mindell and Hirani 24 , Reference Bromley, Dowling and Gray 26 – 30 , Reference Gregory and Lowe 36 , Reference Gregory, Collins and Davies 37 , Reference Nelson, Erens and Bates 55 , Reference Currie, Roberts and Morgan 61 – 66 ) or descriptive results were presented only( Reference Sproston and Primatesta 21 – Reference Craig, Mindell and Hirani 24 , Reference Bromley, Dowling and Gray 26 – 30 , Reference Gregory and Lowe 36 , Reference Gregory, Collins and Davies 37 , Reference Prynne, Thane and Prentice 58 , Reference Watt, Dykes and Sheiham 60 – Reference Currie, Zanotti and Morgan 63 ). The validity of dietary measures was less problematic. Only two surveys (with results reported across six reports)( Reference Currie, Roberts and Morgan 61 – 66 ) used a food frequency measure with no information on whether these measures had been validated. The remaining studies used either weighed 4d or 7d diaries( 30 , Reference Gregory and Lowe 36 , Reference Gregory, Collins and Davies 37 , Reference Prynne, Thane and Prentice 58 – Reference Watt, Dykes and Sheiham 60 ) or interviewer-assisted 24 h recalls( Reference Sproston and Primatesta 21 – Reference Craig, Mindell and Hirani 24 , Reference Bromley, Dowling and Gray 26 – Reference Bromley, Sproston and Shelton 29 , Reference Nelson, Erens and Bates 55 , Reference Prynne, Paul and Mishra 57 , Reference Prynne, Thane and Prentice 58 ).
Adults
Six studies presented statistically significant findings of differences between the diets of adults living in Scotland and adults living in England. Differences in energy intake appeared to vary by gender. For example, Gregory et al.( Reference Gregory, Foster and Tyler 35 ) reported that energy intake for men in Scotland was 210 kcal/d (879 kJ/d) lower compared with men in the North of England, but no differences were reported for women. Braddon et al.( Reference Braddon, Wadsworth and Davies 69 ) found a similar result, with men living in Scotland consuming 0·4 MJ/d less than men living in Northern England. However, women living in Scotland in the same survey had higher energy intakes (0·3 MJ/d) than women in England.
There were no notable significant differences in macronutrient intakes, other than fibre. Fibre intake (NSP) was 1·2 g/d lower in women living in low-income households in Scotland compared with similar women in England( Reference Nelson, Erens and Bates 55 ) and 17 % fewer women in Scotland achieved the recommended daily minimum compared with women in England. More mixed results for fibre were found by Braddon et al.( Reference Braddon, Wadsworth and Davies 69 ), with men in Scotland reporting lower fibre intakes than those in Northern England, but women in Scotland reporting higher intakes than women in Northern England.
Few studies reported statistically significant differences in micronutrient intakes. Na intake was higher in Scotland than in English regions for men( Reference Gregory, Foster and Tyler 35 ) in 1987 (dietary intake), with this difference still present in 2001( Reference Ji, Kandala and Cappuccio 70 ) (dietary intake and urinary Na). The four dietary sodium surveys( 68 , 71 – Reference Sadler, Nicholson and Steer 73 ) (adults 19–64 years) undertaken in Scotland and England between 2006 and 2011 found that salt intake (measured from urinary Na levels) was 0·5 g/d higher in men in Scotland in 2006 compared with men in England. Salt intakes were higher for both men (0·7 g/d) and women (0·9 g/d) living in Scotland in 2009 compared with those in England in 2011. Although these differences were not tested for significance, they indicate that earlier differences have remained.
For other micronutrients, consistent trends were identified, such as lower intakes in Scotland for vitamins A, C, D and E; however, these differences have narrowed( 38 – 54 ) over time. In contrast, Haleem et al. found that antioxidant intake in Scotland was higher than that in Northern England, particularly among men( Reference Haleem, Barton and Borges 74 ).
The most consistent differences for food consumption were for fruit and vegetable intake. Shelton( Reference Shelton 56 ) found that consumption of five or more portions of fruit and vegetables daily was lower in Scotland for men and women than in England. No significant differences were identified; however, the odds of eating five or more portions daily for men or women was greater in Cheshire and Merseyside compared with Greater Glasgow. In Greater Manchester men were less likely to eat five portions of fruit and vegetables each day compared with Greater Glasgow. Consistent findings were reported, although not compared statistically, in the 2008 Scottish Health Survey and the Health Survey for England( Reference Bromley and Shelton 75 ). Respondents from England ate an average of half a portion more of fruit and vegetables daily than those in Scotland, and a lower percentage of respondents in Scotland reported eating five or more portions of fruit and vegetables daily (men: difference=5·1 %, 95 % CI 2·8, 7·4 %; women: difference=5·2 %, 95 % CI 3·1, 7·3 %). Similar findings were identified in a range of the included studies( Reference Sproston and Primatesta 21 – Reference Corbett, Dobbie and Doig 28 , Reference Gregory, Foster and Tyler 35 , 38 – Reference Nelson, Erens and Bates 55 , Reference Whichelow, Erzinclioglu and Cox 76 ). Other differences noted were higher intakes of processed potatoes and meat, and soft drinks in Scotland( Reference Sproston and Primatesta 21 – Reference Corbett, Dobbie and Doig 28 , Reference Gregory, Foster and Tyler 35 , 38 – Reference Nelson, Erens and Bates 55 , Reference Whichelow, Erzinclioglu and Cox 76 ). In England intakes of carcass meat( 38 – 54 , Reference Currie, Zanotti and Morgan 63 ) and fresh potatoes( 52 – 54 , Reference Currie, Zanotti and Morgan 63 ) were higher. Reported confectionery intake has been higher in Scotland compared with England in more recent years( 38 , 49 , Reference Nelson, Erens and Bates 55 ).
Study quality
Studies with adult populations had similar issues with study quality as those reported for children: low sample sizes in Scotland( Reference Henderson, Gregory and Irving 31 , Reference Henderson, Gregory and Swan 32 , Reference Henderson, Irving and Gregory 33 , Reference Gregory, Foster and Tyler 35 , Reference Nelson, Erens and Bates 55 , 68 – Reference Ji, Kandala and Cappuccio 70 , Reference Haleem, Barton and Borges 74 ), lack of adjustment for confounders( Reference Craig and Hirani 22 – Reference Craig, Mindell and Hirani 24 , Reference Bromley, Dowling and Gray 26 – Reference Corbett, Dobbie and Doig 28 , Reference Henderson, Gregory and Irving 31 – Reference Henderson, Irving and Gregory 33 , 38 – Reference Nelson, Erens and Bates 55 , 68 , Reference Braddon, Wadsworth and Davies 69 , 71 – Reference Haleem, Barton and Borges 74 , Reference Whichelow, Erzinclioglu and Cox 76 ) and limited statistical analysis( Reference Walsh, McCartney and Collins 6 , 7 , 13 – Reference Thomas, Newman and Oliver 17 , Reference Craig and Hirani 22 – Reference Craig, Mindell and Hirani 24 , Reference Corbett, Given and Gray 27 – 30 , Reference Henderson, Gregory and Swan 32 , Reference Hoare, Henderson and Bates 34 – 44 , 54 , Reference Prynne, Paul and Mishra 57 – Reference Crawley 59 , 68 , Reference Sadler, Nicholson and Steer 73 , Reference Whichelow, Erzinclioglu and Cox 76 , Reference Shelton and Knott 77 ). The largest sample sizes were in reports from the Scottish Health Survey( Reference Bromley, Dowling and Gray 26 – Reference Corbett, Dobbie and Doig 28 ), the Health Survey for England( Reference Craig and Hirani 22 – Reference Craig, Mindell and Hirani 24 ), and the National Food Survey/Expenditure and Food Survey/Living Costs and Food Survey( 38 – 54 ), which had no statistical testing of differences between the two countries and, in the case of the latter, were reliant on household rather than individual-level data. Response rates were also relatively low for a number of studies( 68 , Reference Ji, Kandala and Cappuccio 70 , 72 – Reference Haleem, Barton and Borges 74 ) and although the data were weighted to account for this on key demographic variables, it increases the likelihood of bias in the results.
Discussion
The current rapid review study was a response to NHS Health Scotland’s request for an overview of the evidence on whether aspects of diet and nutrition differ, or have differed historically, between Scottish and English populations. Examining the current and historical differences in food and nutrient intakes in Scotland and England, we identified for Scotland lower intakes of fruit and vegetables, fibre and vitamins, and higher intakes of salt. Differences in fruit and vegetable intake appear to have persisted over time, as have differences in micronutrient intakes. There were few other consistent differences in food consumption over time that could be identified from the included studies.
What is clear is that dietary differences between Scotland and England are apparent from the early years, as demonstrated in the literature reporting on surveys of pre-school children from 1950 and 1992( Reference Prynne, Thane and Prentice 58 ), and appear to continue throughout adolescence( 30 ) and into adulthood( Reference Scarborough, Morgan and Webster 9 , Reference Shelton 56 ). In line with evidence that suggests that eating habits are established in childhood( Reference Kelder, Perry and Klepp 78 , Reference Mikkila, Rasanen and Raitakari 79 ), our results indicate that in Scotland nutritional disparities with England begin in the early years and persist. The impact of nutritional deficiencies, such as lower fruit and vegetable consumption, was highlighted by Oyebode et al.( Reference Oyebode, Gordon-Dseagu and Walker 80 ) in an analysis of Health Survey for England data. Higher fruit and vegetable consumption was associated with lower likelihood of all-cause, cancer and cardiovascular mortality. The lowest mortality risk from any cause was identified for those eating seven or more portions of fruit and vegetables daily, with consumption of vegetables, salad and fresh or dried fruit associated with decreased mortality. Similar results were found in an Australian study, which again highlighted the protective effect of seven or more daily portions of fruit and vegetables on all-cause mortality( Reference Nguyen, Bauman and Gale 81 ). A systematic review and meta-analysis of 142 prospective studies concluded that the greatest protective effect for all-cause mortality and CVD resulted from consumption of ten portions of fruit and vegetables per day( Reference Aune, Giovannucci and Boffetta 82 ).
There was little evidence to determine whether there were differences in dietary intake in the cities of and/or regions surrounding Glasgow, Liverpool and Manchester. These cities have been used as exemplars in demonstrating the inequalities in mortality outcomes that exist between Scotland and England( Reference Walsh, McCartney and McCullough 5 ).
Only three studies tested differences for Scotland and England statistically at a national level( Reference Scarborough, Morgan and Webster 9 , Reference Nelson, Erens and Bates 55 , Reference Shelton 56 ). The majority of studies reported data from Northern England. As Northern England has a more similar demographic profile to Scotland than southern English regions, it is likely to minimise the dietary differences that exist at a national level. The same is true of studies reporting data from England and Wales jointly. Caution is urged also as the dietary data (except for the sodium surveys which measured Na excretion in urine) are self-reported or reported by parents and carers of children, and prone to reporting bias. It is recognised, for example, that obese adults tend to under-report energy intake( Reference Braam, Ocké and Bueno-de-Mesquita 83 , Reference Heitmann and Lissner 84 ). Reported energy intake tended to be lower in Scotland, but it is unclear whether this reflects lower intakes or a greater tendency to under-report within Scotland. For example, Scotland has not reported lower levels of overweight and obesity, which would be the expected outcome of lower energy intakes( Reference Bromley and Shelton 75 ). At a population level there are not yet objective measures of dietary intake that can be utilised( Reference Subar, Freedman and Tooze 85 , Reference Dhurandhar, Schoeller and Brown 86 ); however, we would not expect dietary assessment data collected in Scotland to be less accurate than those collected in England. Weighed intake (considered the gold standard) was used in many of the studies, with only a small number using non-validated food frequency measures. Nevertheless, under- and misreporting are still likely to occur even with gold standard measures( Reference Gibson 87 ). Additional limitations identified were relatively limited statistical analysis and a failure to adjust for key confounders.
Study limitations
The main limitation of the current rapid review was that a more extensive search of additional databases and grey literature was not possible due to commissioners’ time constraints. Within the scope of the rapid review, the team took the decision to limit reports to those that were easily accessible within the limited review period of 4 months. We therefore did not include historical reports from the National Food Survey which began in 1940. Our first included report from this survey is from 1997, meaning that over 50 years of evidence on food expenditure was not included. These reports provided descriptive data only, with no adjustment for confounding factors. We therefore believe that these reports would not have altered the main findings of the review, which focused more on studies that tested for statistical differences between Scotland and England.
The review did identify a number of large-scale studies, such as the National Diet and Nutrition Survey, the Health Survey for England and the Scottish Health Survey, which provide data from representative samples in these regions. In recognition of the need to increase Scottish samples in national surveys, the National Diet and Nutrition Survey rolling programme included a Scottish boost sample for 2008/9 to 2011/12. The report from these data was excluded from the review as it only compared results from respondents living in Scotland with respondents from the full UK sample rather than England specifically. Differences identified included lower energy intakes in women aged 19–64 years living in Scotland and, in line with the review findings, lower intakes of fibre and vegetables across age groups and gender among respondents living in Scotland( Reference Bates, Lennox and Prentice 88 ). Given the cost required, and the interest in academic and policy groups of undertaking robust dietary surveys, it is likely that the review identified all relevant studies. One exception to this is food purchase market analysis data such as those collected by Kantar Worldpanel UK. Scottish data have only recently been published and were outside the time frame of the original review; however, there is no equivalent report available on English data( 67 ).
An additional limitation was that only a single reviewer decided on study inclusion after reading the full text and a single reviewer extracted data. There is a possibility that bias may have been introduced into the information selected due to this compromise( Reference Schünemann and Moja 89 ). We believe that the risk was minimised through a clear protocol agreed by all authors before the review took place. In addition, the project lead provided an additional opinion on any areas of uncertainty.
Conclusions
There were limited comparisons of dietary intake between Scotland and England in the published literature and only two studies that allowed for comparisons at more local levels. In general, there were lower intakes of fruit and vegetables, vitamins and fibre in Scotland compared with England. Increasing fruit, vegetable and fibre intakes are key targets within the Scottish Dietary Goals, and the review results suggest that both adults and children need to be encouraged through policy action and implementation to improve in these areas. Review results were limited by small sample sizes for Scotland and limited adjustment for confounding factors. It is recognised that dietary quality is poorer in populations experiencing higher levels of deprivation( Reference Barton, Wrieden and Sherriff 90 , Reference Maguire and Monsivais 91 ). In addition, dietary differences exist with regard to age and gender( Reference Henderson, Gregory and Irving 31 , Reference Henderson, Gregory and Swan 32 , Reference Henderson, Irving and Gregory 33 , Reference Gregory and Lowe 36 , Reference Gregory, Collins and Davies 37 ). It is essential, therefore, that comparisons between Scotland and England are examined using large representative samples, with data that have been collected robustly and allow for confounders to be taken into account. Such work is necessary to provide insight into the potential causes of excess mortality in Scotland compared with England and to contribute to policy recommendations to address these inequalities.
Acknowledgements
Acknowledgements: The authors would like to acknowledge Candida Fenton for advice on the review search strategy and Gerry McCartney (NHS Health Scotland) and David Walsh (Glasgow Centre for Population Health) for their support during the project. Financial support: This work was supported by NHS Health Scotland (grant number 2014/15 RE007). NHS Health Scotland had no role in the design, analysis or writing of this article. S.C. was supported by a Medical Research Council Strategic Award (grant number MC_PC_13027) and MRC Grants (grant numbers MC_UU_12017/12 and MC_UU_12017/14), and by the Chief Scientist Office of the Scottish Government Health Directorates (grant numbers SPHSU12 and SPHSU14). Conflict of interest: None. Authorship: All authors contributed to the design of the research and managed the project (as members of the steering group). S.C., V.A. and W.L.W. conducted the research; S.C. synthesised the data; all authors contributed to writing the article and had primary responsibility for the final content. All authors read and approved the final manuscript. Ethics of human subject participation: As the study synthesised existing literature, ethical approval was not required.
Supplementary material
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