Research on the nutritional adequacy of the gluten-free diet

Introduction

Coeliac diseaseA condition where a person is unable to eat gluten as it makes their body attack itself. is a life-long autoimmuneA reaction to a trigger which causes the body to attack itself. disease affecting around 1% of the UK population. To date, the only effective treatment for coeliac disease is strict adherence to a gluten-freeWhen a food has less than 20 parts per million (ppm) of gluten so it is safe for people with coeliac disease to eat. diet, which involves eliminating the cereals wheat, rye, barley (and in some cases oats) from the diet. GlutenA protein that is found in the cereals wheat, barley and rye. -free staple products including bread and pasta are available, made from a variety of ingredients such as rice, maize, potato and soya flours. The nutrient composition of wheat flour used to make gluten-containing bread is covered by national regulations; and is fortified with calcium and iron, and the B vitamins thiamin and nicotinic acid. For gluten-free substitute products, this is not the case. Information on the nutritional adequacy of the gluten-free diet is not well established. The nutritional status of people with coeliac disease may be affected by a complex range of factors and will be affected by adherence to the gluten-free diet, affecting absorption of nutrients and also depend on individual choice and accessibility of food.

The aim of this research project was to carry out a systematic review to assess the evidence base on the nutritional adequacy of the gluten-free diet.

Methods

This systematic literature review involved a comprehensive search of databases, in order to identify all relevant studies, followed by hand searching of reference lists and contact with researchers who may have been involved in research that hadn’t yet been published. All first authors of identified papers, key professional bodies, groups and individuals were contacted. A quality assessment of each paper was carried out by two independent reviewers to assess the level of the evidence available.

Results         

Eleven papers were included in the systematic review; ten case-control studies and one cohort. The studies involved small numbers of people and there were inconsistencies in the protocols. All papers were found to have moderate or high risk of bias. Most papers concluded that individuals with coeliac disease following a gluten-free diet had the same nutritional status as the general population. Where the results were found to differ between these groups, there was often no values recorded to demonstrate statistical significance making it difficult to comment on these results.  

Discussion

There is a need to try and define more clearly the composition of the gluten-free diet and to consider the significance to health of any differences as compared to the diet of the general population. The most significant difference is that wheat based staples are replaced by gluten-free substitute products. The impact on nutritional status is not clear. At the moment, there is not enough evidence to support fortification of gluten-free staple substitute products, although there is an argument for fortification of gluten-free flours used in the production of gluten-free substitute staple products so that nutritional composition is comparable to gluten-containing staple products. More robust research is required, ensuring adequate sample sizes, to investigate further the nutritional adequacy of the gluten-free diet in people medically diagnosed with coeliac disease.

Conclusion 

There is no evidence to suggest that nutritional deficiency is a significant problem in individuals diagnosed with coeliac disease who are established on a gluten-free diet. However, these conclusions may reflect the paucity of data, rather than a genuine absence of nutritional deficiencies in people following a gluten-free diet.

More information is available on the Food Standards Agency website