Justine Bold. Senior Lecturer, University of Worcester
The nutritional quality of gluten free diets (GFD) has been debated recently across mainstream media, with concerns expressed that gluten free (GF) foods are often high in salt, sugar and fats with some research linking a GFD to health problems such as metabolic syndrome (1). There are also reports of nutritional deficiencies of protein, fibre and micronutrients (2) in patients with coeliac disease (CD), though on-going absorption problems can in part explain some of these deficiencies. Whilst a GFD is not recommended for the general population without CD or symptoms related to gluten ingestion, it is still the safest treatment for those with CD (3), particularly if GF whole foods and grains are consumed to support both micronutrient and fibre intake.
Media reports about the nutritional quality of GF foods raise important issues but to date have rarely considered how food safety issues such as contamination with gluten may impact on those with gluten-related, in particular CD where symptoms may be persistent.
Regulation around allergen labelling in food was introduced in the European Union (EU) in 2005 (3). This legislation specified that allergens such as gluten, wheat, rye, barley and oat had to be detailed in the main list of ingredients. EU legislation from 2009 specified GF food had to have ≤20 ppm (or parts per million = ppm) of gluten per mg/kg (3). This is because the amount of gluten capable of initiating the immune response has been estimated to be >20 mg/kg of gluten (3). Contamination below this level of 20 ppm is generally considered safe and under 10 mg a day of gluten is not thought to cause abnormal histology (4) in most coeliac patients.
A recent study published in the journal Nutrients reports on safety aspects of GF foods and specifically details findings on the contamination risk with gluten (5). Over 3000 GF products were analysed across an eighteen-year period from 1998 to 2016. The analysis undertaken in Spain is one of the largest research projects on GF foods and has some important findings for health professionals working with those with CD (5).
The data presented shows that in general grain based foods for people with CD have become better with less contamination through the period of the study (5). However, there were increases in the number of samples of white flour with gluten contamination at 100 mg/kg in the period of 2013–2016 (5). GF white flour is used extensively in home cooking and baking so this is very concerning especially as contamination at this level can be problematic for patients with CD as it is over the 20mg/kg threshold specified in the EU GF foods legislation.
The study also showed that more than three quarters of oat samples tested were contaminated with gluten (5), hence health professionals working with patients with CD should consider highlighting the importance of buying certified GF oats and oats-based products. The study also reported on many foods that are naturally GF such as the wholegrains buckwheat and quinoa (5). This is particularly interesting for those giving dietary advice to patients with CD. It should however be noted that contamination was reported in samples of both buckwheat and lentils (5). Obviously, any nutritional counselling on a GFD should emphasize the importance of the consumption of a healthy balanced diet with intake of moderate amounts of sugars, saturated fats and inclusion of healthy fats.
The study also reports that cheaper GF foods have higher levels of gluten contamination (5), suggesting more control around manufacture has cost implications. Health professionals should be aware that this may be more of an issue for lower income patients, who may opt for cheaper GF options and in doing so may have more risk of gluten exposure (3). This is particularly an issue as GF food prescriptions in the UK are now under threat and many patients with CD are having to source and buy GF foods themselves. The ongoing regulation and control of certified GF foods alongside on-going assessment of contamination levels is of paramount importance to ensure the safety of coeliac patients.
1 Tortora R, Capone P, De Stefano G, Imperatore N, Gerbino N, Donetto S, Monaco V, Capooraso N, Rispo A. Metabolic syndrome in patients with coeliac diseaseon a gluten-free diet. Aliment. Pharmacol. Ther. 2015; 41:352–359.
2 Saturni L, Ferretti G, Bacchetti T. The gluten-free diet: Safety and nutritional quality. Nutrients 2010; 2:16–34.
3 Rostami K, Bold J, Parr A, Johnson MW Gluten-Free Diet Indications, Safety, Quality, Labels, and Challenges. Nutrients. 2017 Aug 8;9(8).
4 Catassi C, Fabiani E, Lacona G et al. A prospective, double blind, placebo-controlled trial to establish a safe gluten threshold for patients with coeliac disease. Am J Clin Nutr 2007; 85:160–166.
5 Akobeng AK, Thomas AG. Systematic review: tolerable amount of gluten for people with coeliac disease. Aliment Pharmacol Ther 2008; 27:1044–1052.
6 Bustamante MA, Fernandez-Gil MP, Churruca I, Miranda J, Lasa A, Navarro V, Simon E. Evolution of gluten content in cereal-based gluten-free products: An overview from 1998 to 2016. Nutrients. 2017;9:21.