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Gluten-free diets may increase risk of type 2 diabetes

EndocrinologyFocusEating more gluten may lower the risk of developing type 2 diabetes. This is according to a long-term observational study presented at the American Heart Association’s Epidemiology and Prevention/Lifestyle and Cardiometabolic Health 2017 Scientific Sessions. People who eat a gluten-free diet may also be at risk for increased exposure dangerous toxic metals, reports a separate US study.

The report says most participants had gluten intake below 12 grams a day. Within this range, those who ate the most gluten had lower type 2 diabetes risk during 30 years of follow-up. Study participants who ate less gluten also tended to eat less cereal fibre, a protective factor for type 2 diabetes developing.

Gluten is a protein in wheat, rye and barley. It gives bread and other baked goods elasticity during the baking process and a chewy texture in finished products.

The report says a small percentage of the population can’t tolerate gluten due to gluten sensitivity or celiac disease, a chronic autoimmune disorder that impacts both the digestive tract and other parts of the body.

Gluten-free diets have become popular for people without these conditions, though there is lack of evidence that reducing gluten consumption benefits long-term health.

“Gluten-free foods often have less dietary fibre and other micronutrients (such as vitamins and minerals), making them less nutritious, and they also tend to cost more,” said Dr Geng Zong, a research fellow in the department of nutrition at Harvard University’s TH Chan School of Public Health in Boston. “People without celiac disease may reconsider limiting their gluten intake for chronic disease prevention, especially for diabetes.”

Participants in the highest 20% of gluten consumption had a 13% lower risk of developing type 2 diabetes compared to those who ate the lowest daily amount – less than 4 grams.

During the study, which included 4.24m person-years of follow-up from 1984-1990 to 2010-2013, researchers found 15,947 cases of type 2 diabetes. For their study, researchers estimated daily gluten intake for 199,794 participants in three long-term health studies from food-frequency questionnaires every two to four years. The average daily gluten intake was 5.8 grams for the Nurses’ Health Study, 6.8 for the Nurses’ Health Study II and 7.1 for the Health Professionals Follow-up Study.

Abstract
Background: Gluten-free diets have grown in popularity, but evidence is lacking regarding gluten intake and long-term health.
Methods: In Nurses’ Health Study (NHS, n=69,276), NHSII (n=88,610), and the Health Professionals Follow-Up Study (HPFS, n=41,908), we estimated gluten intake using a validated food-frequency questionnaire collected every 2-4 years. Incident T2D was defined as physician diagnosed diabetes and confirmed with supplementary information.
Results: Gluten intake (mean ± standard deviation) was 5.83±2.23, 6.77±2.50, and 7.06±2.76 grams/day in NHS, NHSII, and HPFS, respectively, and strongly correlated with intakes of carbohydrate sources, especially refined grains, starch, and cereal fiber (Spearman correlation coefficients > 0.6). During 4.24 million years of follow-up, 15,947 T2D cases were confirmed. An inverse association between gluten intake and T2D risk was observed in all three cohorts after multivariate adjustment (table), and hazard ratio (HR, 95% confidence intervals [95%CI]) comparing extreme quintiles was 0.80(0.76, 0.84; P<0.001). The associations were slightly attenuated after further adjusting for cereal fiber (HR[95%CI]= 0.87[0.81, 0.93]), but not other carbohydrate components. Among participants without major chronic diseases and aged <65 years, changes in gluten intake were not significantly associated with weight gain in multivariate adjusted model: 4-year weight change (95%CI, lb) was 0.08(-0.06, 0.22; P=0.25) in NHS, -0.05(-0.18, 0.08; P=0.43) in NHSII, and 0.36(-0.24, 0.96; P=0.24) HPFS for each 5 grams increase in gluten intake.
Conclusions: Our findings suggest that gluten intake may not exert significant adverse effects on the incidence of T2D or excess weight gain. Limiting gluten from diet is thus unlikely to facilitate T2D prevention and may lead to reduced consumption of cereal fiber or whole grains that help reduce diabetes risk.

Authors
Geng Zong; Benjamin Lebwohl; Frank Hu, Laura Sampson, Lauren Dougherty, Walter Willett, Andrew Chan, Qi Sun

 

[link url="http://news.heart.org/gluten-may-lower-risk-of-type-2-diabetes/"]Heart Organisation material[/link]
[link url="http://professional.heart.org/idc/groups/ahamah-public/@wcm/@sop/@scon/documents/downloadable/ucm_492225.pdf"]ACC17 Scientific Sessions abstract book (presentation 11)[/link]

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