Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study
Lebwohl B, Cao Y, Zong G et al. British Medical Journal May 2017 ; 357 :j1892
Diets that limit gluten intake have gained popularity over recent years. In a follow-up analysis of America’s National Health and Nutrition Examination Survey (NHANES), adoption of a gluten-free diet by people without coeliac disease rose from 0.52% prevalence in 2009-10, to 1.69% prevalence in 2013-14. Concerns exist that a gluten-free or gluten-restricted diet may be nutritionally suboptimal. This prospective cohort study sought to examine the association between long term intake of gluten and the development of incident coronary heart disease (CHD).
Diets that limit gluten intake have gained popularity over recent years. In a follow-up analysis of America’s National Health and Nutrition Examination Survey (NHANES), adoption of a gluten-free diet by people without coeliac disease rose from 0.52% prevalence in 2009-10, to 1.69% prevalence in 2013-14. Concerns exist that a gluten-free or gluten-restricted diet may be nutritionally suboptimal. This prospective cohort study sought to examine the association between long term intake of gluten and the development of incident coronary heart disease (CHD).
Participant data was drawn from the Nurses Health Study (NHS) and Health Professionals Follow-up Study (HPFS). Following exclusions, records from a total of 64714 women and 45303 men without a history of CHD and who had completed a 131 item semi-quantitative, validated food frequency questionnaire in 1986 (updated every 4 years through to 2010) were available for analysis. Exclusion criteria included implausible daily energy intake, missing gluten data, a diagnosis of cancer or coeliac disease. Participants were not asked specifically about consumption of gluten-free substitute foods or whether they specifically adhered to a gluten free diet. Quantity of gluten consumed was calculated on the basis of the estimated protein content of wheat, rye, barley based on ingredient lists from food product labels. Gluten intake correlated inversely with alcohol intake, smoking, total fat intake and unprocessed red meat intake. Gluten intake correlated positively with whole grain and refined grain intake. During 26 years of follow-up, 2431 women and 4098 men developed CHD. Compared with participants in the lowest fifth of gluten intake, who had a CHD incidence rate of 352 per 100,000 person years, those in the highest fifth had a rate of 277 events per 100,000 person years, leading to an adjusted rate difference of 75 fewer cases of CHD per 100,000 person years. However, after adjustment of known risk factors, participants in the highest fifth of estimated gluten intake had a multivariable hazard ratio for CHD of 0.95 (95% CI 0.88-1.02; P=0.29), representing a non-significant relationship between gluten intake and CHD risk. After additional adjustment for intake of whole grains (leaving the remaining variance of gluten corresponding to refined grain intake), the multivariate hazard ratio was 1.00 (95% CI 0.92-1.09; P=0.77). In contrast, after adjustment for intake of refined grains (leaving variance of gluten intake correlating with whole grain intake), higher estimated gluten consumption was associated with a significantly lower risk of CHD (multivariate hazard ratio 0.85, 0.77-0.93; P=0.002). This finding is consistent with the fact that whole grain intake has been found to be inversely associated with coronary heart disease risk and cardiovascular mortality across numerous other studies.
In these two large, prospective cohorts, the consumption of foods containing gluten was not significantly associated with the risk of CHD. The avoidance of dietary gluten may result in a low intake of wholegrains, which are associated with health benefits.
This study highlights the importance of access to high quality dietetic support when implementing a restricted diet in order to maintain nutritional adequacy. The inclusion of suitable gluten-free whole grain foods and adherence to general healthy eating principles will assist in offsetting the undesirable effects of reducing gluten-containing whole grains when implementing a gluten-free diet.
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In these two large, prospective cohorts, the consumption of foods containing gluten was not significantly associated with the risk of CHD. The avoidance of dietary gluten may result in a low intake of wholegrains, which are associated with health benefits.
This study highlights the importance of access to high quality dietetic support when implementing a restricted diet in order to maintain nutritional adequacy. The inclusion of suitable gluten-free whole grain foods and adherence to general healthy eating principles will assist in offsetting the undesirable effects of reducing gluten-containing whole grains when implementing a gluten-free diet.
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