Emily Kirk's talk was drawn from the results of a systematic review of evidence of the GF diet’s nutritional adequacy which Kirk undertook at Coeliac UK last year, working alongside gastroenterologists and other dietitians, and which focused particularly on iron, calcium, folate and other B vitamins – the usual key nutrients of concern to both newly diagnosed and established coeliacs.
After giving the delegates background information concerning coeliac disease – including prevalence, susceptibility, symptoms, diagnosis, and complications – she emphasised the importance to coeliacs of access to the three categories of starchy foods that feature in their diets, namely:
* natural GF foods – such as rice, potatoes, corn;
* processed GF foods – such as any manufactured food ‘by chance’ GF;
* substitute GF foods – such as rendered breads and specially manufactured flours.
While some of these foods may be available on prescription, and others now more widely sourceable via supermarkets and specialist online suppliers, Kirk pointed out that while legislation exists to ensure gluten-containing wheat flour is fortified with iron, calcium and B vitamins, no such law existed covering GF flours, or the foods made from them. With an increasing number of specialist ‘free from’ manufacturers now in business, a consequence of the lack of legislation is that the nutritional composition of the producers’ flours and foods is likely to vary greatly, depending on whether or not they choose to fortify their products, and by how much. With a wide variation in volume consumption of these foods among GF patients, the issue of nutritional adequacy is clearly relevant.
There have been reports of deficiencies of the core nutrients in GF diets compared to standard diets, but there had not yet been a systematic review of the evidence.
The team’s aim, therefore, was to inform the Food Standards Agency (who funded the research) of the status of the evidence, perform a structured literature review, and make recommendations on potential strategies or policies.
The search strategy took in three phases:
1. An electronic searching of bibliographic databases to identify published studies.
2. A hand searching of reference lists for published papers.
3. An attempt to identify as much unpublished research as possible, by contacting GF manufacturers, independent authors and worldwide organisations.
This process identified 20 relevant papers.
From these, excluded were case reports, papers with ambiguous methodologies, animal studies, studies performed on patients with histologically unproven coeliac disease, patients diagnosed within the last six months, or patients with other diseases.
This left eleven papers, ten of which were case-control, one of which was cohort, and these were independently assessed by two reviewers. Seven were deemed of medium risk of bias, and four of high risk. None was considered low risk.
Most papers found coeliac patients on a GF diet have the same nutritional intake as the general population. Where differences were found, there were no statistical analyses presented, so the reviewers felt unable to comment.
The unpublished studies found higher energy intake in women – but not men – and this extra energy was accounted for by simple sugars. Kirk later agreed it was possible that women may be more likely to ‘treat’ themselves more readily or overcompensate for the restrictions of a GF diet with more GF sweet foods. She acknowledged that the energy content of GF and non-GF ‘treat’ foods had not yet been systematically compared, and that it was possible that rendered GF ‘treats’ may be more calorific.
In conclusion, the available evidence was deemed to be limited and generally of poor quality. There was found to be no firm evidence that those with coeliac disease following a GF diet have an inadequate intake of key nutrients, though this may reflect the lack of data rather than the absence of a nutritional difference between conventional and GF diets.
Kirk closed by stating that there is no high-level evidence to support the statement “Those with coeliac disease have optimal nutrition status” and that individuals should continue to receive ongoing dietetic support to optimise their nutrition intake.
More robust research, including studies with larger sampler sizes, is necessary to investigate this subject further, she said. This is particularly important as those with coeliac disease often have increased nutritional requirements, for instance of calcium.
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