- Maija E Miettinen, Suvi M Virtanen, BMJ.com 1
Until recently, incidence of type 1 diabetes has been increasing in the western world, pointing towards environmental triggers in the disease process. Despite decades of intensive research, we still cannot identify the factors responsible for the increase, and therefore have no means to prevent new cases. At the moment, special interest lies in the maternal and childhood dietary factors. Large scale prospective studies with carefully collected data are needed to define and confirm associations so that effective interventions can finally be planned and implemented.
- Objective: To examine the association between prenatal gluten exposure and offspring risk of type 1 diabetes in humans.
- Design: National prospective cohort study.
- Setting National health information registries in Denmark.
- Participants: Pregnant Danish women enrolled into the Danish National Birth Cohort, between January 1996 and October 2002
- Main outcome measures: Maternal gluten intake, based on maternal consumption of gluten containing foods, was reported in a 360 item food frequency questionnaire at week 25 of pregnancy. Information on type 1 diabetes occurrence in the participants’ children, from 1 January 1996 to 31 May 2016, were obtained through registry linkage to the Danish Registry of Childhood and Adolescent Diabetes.
- Conclusions High gluten intake by mothers during pregnancy could increase the risk of their children developing type 1 diabetes. However, confirmation of these findings are warranted, preferably in an intervention setting.
Three points are worth considering when evaluating the results of Antvorskov and colleagues’ study.
Firstly, is high intake of gluten associated with an unhealthy diet or other dietary characteristics that could possibly predispose individuals to type 1 diabetes?
- Gluten containing grains are ingested through breads, pastas, pastries, and breakfast cereals, possibly indicating the intake of refined grains and a diet of poor nutritional quality. High gluten intake might also indicate a high energy diet, although in the linked study, statistical adjustment for total energy intake made no difference to the results. Characterisation of the dietary patterns associated with a high gluten intake could provide useful information for future studies.
Secondly, gluten comes from certain grains, so could there be something else in these grains responsible for the association?
- For example, cereal products that are baked at high temperatures contain advanced glycation end products that have been suggested as a risk factor for type 1 diabetes. Grains also contain several other components generally considered harmful to health but that have not yet been studied in relation to type 1 diabetes, such as mycotoxins, heavy metals, and remnants of pesticides and fertilisers.
Thirdly, mothers with high gluten intake might provide a high gluten diet to their children, and importantly, gluten proteins (gliadin) are passed from the mother to the infant through breast milk.
- So infants could be exposed to gluten immediately after birth through lactation. Therefore, Antvorskov and colleagues’ study cannot determine whether the possible adverse effects of gluten that might eventually trigger type 1 diabetes come through prenatal exposure, childhood exposure, or both.
- This is the first study to suggest a clear dose-dependent association between maternal gluten intake and risk of type 1 diabetes.
If confirmed, the findings could help resolve inconsistencies in the existing literature. Nevertheless, human studies investigating the physiological effects of high gluten intake in relation to the developing immune system are needed to identify whether the proposed association really is driven by gluten, or by something else in the grains or the diet.
- Given that a causal association between maternal gluten intake and type 1 diabetes in children has not yet been established, it is too early to change dietary recommendations on gluten intake in pregnancy.
However, doctors, researchers, and the public should be aware of the possibility that consuming large amounts of gluten might be harmful, and that further studies are needed to confirm or rule out these findings, and to explore possible underlying mechanisms.
SOURCE ARTICLE: BMJ 2018; 362 doi: https://doi.org/10.1136/bmj.k3867 (Published 19 September 2018) Cite this as: BMJ 2018;362:k3867