Reflections on dietary guidance and the status of carbohydrate on both sides of the <scp>A</scp>tlantic

Dietary guidelines that are designed to improve the nation's health have been in place for the past 30 years or more, in one form or another, in both the UK and in the US, yet on both sides of the Atlantic, we are faced with an epidemic of obesity and associated disease that seems out of control, with 26% adults (aged 16 and above) currently obese in England (ICHSC 2011) and 36% obese adults in the US (CDC 2012). Meanwhile, the pros and cons of diets that contain predominantly more protein, more fat, different types of fat, more carbohydrate or different types of carbohydrate, continue to be the subject of both scientific debate and media coverage. As a result, and perhaps not surprisingly, there is a considerable amount of confusion and scepticism among consumers about healthy diets and how to combat overweight and obesity. In this context, a number of significant topics are covered in this issue of Nutrition Bulletin from which some important messages emerge. First among these is the reminder by Slavin (2012, pp. 359–63) that the human body is able to adapt to a diverse range of foods and diets. Indeed, Slavin makes reference to the early dietary intake of humans and points out that we evolved as omnivores, i.e. we are able to fulfil our nutritional needs from a mixed and variable diet. As Slavin observes, traditional diets reflected accessibility of particular foodstuffs, so that for example, the traditional Inuit diet would comprise 80% fat, while that of sub-Saharan Africa comprised 80% carbohydrate. She suggests that there is no blueprint for the perfect diet and providing that individual needs for protein and micronutrients are met, adequate diets may be either high or low in fats and carbohydrates. However, the ongoing debate about the relative merits of low fat vs. low carbohydrate rumbles on, as explored by O'Connor in another article in this issue (2012a, pp. 368–79), and is testimony to the fact that not all nutrition scientists might agree with this viewpoint. Advice to consume a diet that is relatively low in fat (30–35% energy) and high in carbohydrate (50–60% energy) has been the cornerstone of dietary guidance in the US since the mid-1970s when the then controversial McGovern Report (US Senate Select Committee and Human Needs 1977) was published and in the UK since the early 1980s starting with the similarly controversial NACNE (National Advisory Committee on Nutrition Education) report (NACNE 1983) and the COMA (Committee on Medical Aspects of Health) report on cardiovascular disease (DH 1984). In the last decade or so, the increasing popularity of the Atkins diet and its successive variants, such as the South Beach and Dukan diets, and the publication of short-term studies of weight loss using high-protein/low-carbohydrate regimens (see O'Connor 2012b), has led to a growing consumer mistrust of sources of starchy carbohydrate such as bread and potatoes. In the UK, there has been a steady decline in bread consumption since the Second World War. Current advice is to base meals on starchy carbohydrate so that it represents one-third of a meal, as promoted by the eatwell plate model (see Benelam et al. 2012, pp. 344–9; NHS Choices 2012a) and as one of the eight key healthy eating tips (NHS Choices 2012b). Yet according to National Diet and Nutrition Survey (NDNS) data, the decline in the consumption of bread, one of the most important sources of starchy carbohydrate in the UK, has continued, with a further fall of about 12% in the last decade. In this edition of Nutrition Bulletin, O'Connor (2012a, pp. 368–79) examines the reasons behind the declining consumption of one of our UK staple foods and highlights the mismatch between government advice and public attitudes towards bread. The author has undertaken a comprehensive review of the evidence base for consumer perceptions of bread as ‘fattening’, causing ‘wheat allergies’ and contributing to gastrointestinal problems, together with an evaluation of the nutritional implications of avoiding bread. UK consumers are currently failing to meet both the recommended population targets for the proportion of energy derived from starch and the recommended amounts of dietary fibre. Furthermore, some groups of the population are also falling short of micronutrients such as iron, calcium, magnesium and zinc. All these nutrients can be provided by bread, so it is of particular concern that because of an increasingly bad press, much of which is based on either myth or short-term scientific studies, consumers appear to be turning away from this important staple in the misguided belief that it will harm them. This is clearly an example of potentially misleading media messages prevailing in the face of more rational scientific evidence. Confusion about the status of dietary carbohydrates is also addressed elsewhere in this issue in the context of advice to people with diabetes (Stanner 2012, pp. 350–4) and in an article discussing the origins and current status of the Dietary Guidelines for Americans (DGA), Slavin (2012, pp. 359–63) considers the move away from carbohydrate in the US. The 2010 DGAs (USDA 2011a) are the end result of a detailed, systematic, evidence-based set of reviews of the association between health and risk of disease and the full range of dietary components. They maintain the emphasis on sources of starchy carbohydrate, especially those that are wholegrain. The author notes a lack of strong evidence to date to support the benefits of the DGAs on the health of Americans, including little evidence for positive effects on weight maintenance, although in part, this is because long-term studies comparing health outcomes among people who adhere to the guidelines, compared to those who do not adhere to them, have not been carried out. Slavin also considers the other controversial aspect of carbohydrates – the role of ‘added’ or ‘extrinsic’ sugars on health – but suggests that currently, there are only limited data to support either concerns about adverse health outcomes or indeed positive effects of ‘healthy’ carbohydrates such as fruits and vegetables. So the debate goes on and indeed recently escalated with the unpopular approved ban on the sale of large-size ‘sodas’ and other sugary drinks from restaurants and some other outlets in New York City (New York Times 2012). Carbohydrate is again the focus in another article in this issue of Nutrition Bulletin, in which Schenker (2012, pp. 309–23) reviews the role of rice in the UK diet, a staple now purchased by 80% of the UK population. Unlike bread, rice consumption has increased markedly over the past 35 years, albeit from a much lower starting point, alongside increasing ethnic diversity and as we have embraced a much wider range of different cuisines within our own food culture, which at least, in part, may explain the decline in bread consumption. In the meantime, the image of popular staple protein foods such as eggs also waxes and wanes according to the popularity of ‘low-carb’ diets and health issues promulgated by both scientists and the media. In this issue of Nutrition Bulletin, Benelam et al. (2012, pp. 344–9) report on a new compositional survey of UK chicken eggs, recently published by the Department of Health and carried out by a consortium including the Institute of Food Research and the British Nutrition Foundation, which shows some important changes in total fat, fatty acid and cholesterol and in vitamin D and selenium content, since the previous analyses were carried out (Holland et al. 1989; FSA 2002), and includes new data on vitamin K and choline. Interestingly, these changes, which appear to reflect a combination of alterations in hen feeding practices, average egg size and, in the case of some micronutrients, changes in analytical methodology, are in line with changes in the nutritional composition of eggs that have been reported in the US (USDA 2011b). In the US, the DGAs are translated into practical guidance in the form of MyPlate, which has superseded the food pyramid as the preferred educational model (USDA 2011c). MyPlate depicts a schematic plate divided into four different coloured sections representing approximately 30% grains (i.e. starchy carbohydrates), 30% vegetables, 20% protein and 20% fruits; it is accompanied by a smaller circle representing dairy foods in the form of a cup of milk or yogurt. Although this simpler model is acknowledged to be an improvement on its complex multilayered predecessor, it has been criticised for omitting details such as the type of grain, sources of proteins and failing to show what type of fats are used (see Harvard School of Public Health 2012). The UK practical guidance is also in the form of a plate model. The eatwell plate (NHS Choices 2012a), formerly the Balance of Good Health, was originally developed almost 20 years ago and is arguably a stronger model, depicting real food on a plate in contrast to the schematic US plate model. Nevertheless, despite having a strong model and the associated eight tips on living well (see Ballam 2012), it seems that only a very small minority of the UK population currently meet all aspects of recommended UK dietary advice. Harland et al. 2012, pp. 324–43) has undertaken an important analysis of data generated by the NDNS rolling programme, exploring the extent to which UK consumers meet the five targets implicit in the eatwell plate: fat, saturated fat, 5 A DAY fruit and vegetables, fibre (non-starch polysaccharide) and protein intake. The article identifies useful information on the characteristics of designated ‘achievers’ and ‘non-achievers’, showing that a mere 4% of UK consumers meet all five dietary targets; if the oily fish target from the eight guidelines is also included, only 1% of the population currently consume a diet that is in line with recommended UK dietary guidance. These findings complement the observations of O'Connor (2012a, pp. 368–79) that UK consumers are unclear about why starchy carbohydrates make an important contribution to a healthy diet and about the proportion of the eatwell plate that they should provide. The sustainability of the global food supply is a key matter of concern for everyone and a major public health challenge to all involved in feeding expanding populations [see Nutrition Bulletin 2012, and also in this issue, a conference report on Food Security 2012 (Weichselbaum 2012, pp. 389–94)]. In this context, Harland and colleagues (2012) also explored whether those consumers who achieved the eatwell targets were eating in a more sustainable fashion. It appears that this is not the case, although the authors believe that there is scope to use the model to promote a more sustainable diet by including more plant proteins and starchy foods. However, as acknowledged by the authors and as is borne out by O'Connor's analysis, it is clear that before moving forward in this regard, there is a need for greater investment in helping consumers understand and put into practice the nutrition advice that is implicit in the eatwell plate and eight guidelines for healthy eating. Other approaches to shape the UK diet are described in this issue by Dr Susan Jebb (2012, pp. 355–8), who is the chair of the Department of Health's Public Health Responsibility Deal Food Network. The Responsibility Deal provides a mechanism by which all sectors of society work in partnership to improve the nation's health and the Food Network works through a series of pledges that various food industry sectors are encouraged to sign up to and that it is hoped will help to ‘nudge’ consumers to adopt healthier diets. There are similarities in this approach on both sides of the Atlantic, as our Washington-based Regional Editor, Kristen Ciuba, reported in a recent issue of Nutrition Bulletin. In the US, mandatory calorie labelling on menus of ‘quick service chain’ restaurants was first introduced in New York City in 2008 and subsequently has been introduced in some other states. The results of initial studies indicate little evidence of beneficial effects on consumer behaviour (Ciuba 2012). However, before writing off this approach because of lack of evidence of success, we should look to the longer term, as there will certainly be no quick fix for the entrenched poor eating styles that are evident on both sides of the Atlantic. As Ciuba has emphasised, monitoring of both consumer behaviour and restaurant practices in the longer term is essential, not least because it is possible that when such measures are in place, over time, restaurants may reduce the energy density of their meals by ingredient manipulation and that public understanding of the energy density of both foods and meals may improve – such a process is bound to take time. The UK food industry is not faced with mandatory action but has the option of voluntary commitments, but the Food Network has gone further than the US authorities with a Calorie Reduction Pledge that through multiple initiatives (depending on the sector), which include product reformulation, portion control and schemes that incentivise customers to make lower calorie choices, aims to create a ‘calorie consciousness’ that it is hoped will help reverse the relentless tide of obesity. Only time will tell whether such approaches will bear fruit or whether recourse to more stringent mandatory measures, as parts of the US are experimenting with, will eventually be necessary.

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