Invited Commentary How healthy is a gluten-free diet?

A diet that excludes the gliadin and glutenin protein fractions in wheat, rye and barley is the only treatment available for individuals with coeliac disease. There is, however, a growing enthusiasm for a gluten-free diet (GFD) or wheat avoidance in those without formally-diagnosed coeliac disease for its perceived benefit on health, weight loss, treating disease and/or minimising future risk of disease. In Australia, for example, a recent large and detailed survey of over 1000 adults indicated that almost 11 % had chosen to avoid wheat, nearly half of those being gluten-free (GF), despite a prevalence of those diagnosed with coeliac disease being much <1 %. About four out of five of those did it to help relieve symptoms such as bloating or abdominal pain. This contrasts with marketing information from USA, which suggests that most of the 30 % of the population who were considering being GF did so for ‘good health’. In a UK survey, 42 % of a cohort of patients with irritable bowel syndrome (IBS) believed they had gluten sensitivity, 15 % had tried a GFD and 12 % were still following it. With such a high proportion of the population following a restrictive diet, it is imperative that the nutritional adequacy of the diet in general and of the available GF processed foods specifically is well understood. There has been an unwritten assumption that GF alternatives are healthier than their gluten-containing counterparts. This premise may lead to overconsumption of processed/ packaged GF products including staple items (such as bread, cereals and pasta) and/or so-called energy-rich and nutrient-poor ‘discretionary’ items (such as cereal bars, biscuits and potato crisps), a scenario that appears to have been exploited by some marketers and food manufacturers. Likewise, it is often stated that GF processed and packaged foods are less healthy than their gluten-containing counterparts due to relatively higher content of fat, sugar and salt. Contemporary data on this issue are scarce, underlining the importance of the supermarket evaluation of GF foods published by Wu et al.. This Australian study was a comprehensive comparison of the nutritional quality of GF v. matched non-GF products. An impressive total of 3213 food products were assessed across ten food categories, and included staple and discretionary products. The primary outcome of the analysis was the difference in health star rating – a new front-of-pack labelling system being introduced in Australia. It rates products between 0·5 and 5 stars in increasing 0·5 star increments, with a higher star rating indicating better nutritional quality. This rating system is based on an algorithm incorporating energy, SFA, total sugar, protein, fibre and Na contents of the product. Overall, for GF staple items (pasta, bread and ready-to-eat breakfast cereals), there was no difference in mean rating for each group compared with the corresponding gluten-containing category, except for GF pasta, which scored 0·5 stars lower. On secondary analysis, the protein content of each of the three staple groups was lower in GF v. gluten-containing groups. Given the small protein contribution of grains to the overall diet, this can be considered as a negligible finding. No other differences were found between staple food groups for total energy, Na, SFA and total sugars. There were some differences in fibre content between staple groups, but dietary fibre content was not available for all products. Of importance, GF products were not consistently lower in fibre content. GF discretionary items were largely not different in star rating from their corresponding glutencontaining products, but, in fact, were rated more highly for three discretionary food groups, ice cream, maize and potato crisps and sugar-based confectioneries, largely driven by a lower mean content of SFA or total sugar. In summary, this analysis indicated that Australian GF products are not significantly different in their nutritional quality compared with their gluten-containing counterparts. This dispels the widely stated idea that GF processed foods are in general higher in fat, salt and sugar – a finding that could be interpreted as a positive outcome for many individuals with coeliac disease who regularly rely on these products. Perhaps the more important corollary of this, however, was that no nutritional advantage was demonstrated for GF foods. In other words, the notion that GF labelling might infer a health benefit is not warranted. There were certain limitations of this analysis, some of which the authors acknowledge. First, these data are based on nutrition information from the food label, rather than on the gold standard composition analysis of the food, which also prevented systematic assessment of certain important micronutrients that are often fortified in gluten-containing staple items (such as folate and Fe), and are important contributors to dietary intake (particularly fibre), but were not available on the label. Second, the primary outcome of this study was a comparison using the healthy star rating, which is not generalisable worldwide, although it is based on sound criteria. Third, only Australian-sourced products were included. Fourth, this analysis grouped foods into core food groups and analysed the nutrient content for each core group. Like-for-like analysis between foods – for example, GF v. gluten-containing white British Journal of Nutrition (2015), 114, 1539–1541 © The Authors 2015