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Gluten-free diet’s effect on cardiovascular risk unclear
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A systematic review showed no clear evidence that a gluten-free diet has an overall negative impact on cardiovascular risks in patients with celiac disease.
While the results were inconsistent across studies, and researchers did observe alterations in some cardiovascular risk factors, they concluded the data do not support adopting a gluten-free diet for cardiovascular health in individuals without celiac disease.
“One of the main reasons people alter their diet in general is to modify their long-term cardiovascular risk ... and many people without celiac disease are adopting the gluten-free diet for general health reasons such as these,” Michael D.E. Potter, MBBS (Hons), from the University of New Castle, Australia, told Healio Gastroenterology and Liver Disease. “Our review focuses on the potential of the gluten-free diet to affect modifiable cardiovascular risk factors including weight, blood pressure, cholesterol and blood sugars. We looked for studies which measured these risk factors in individuals before and after the institution of a gluten-free diet.”
Potter and colleagues reviewed 27 studies that evaluated the effect of a gluten-free diet — maintained for a minimum of 6 months — on cardiovascular risk factors such as BMI, waist circumference, blood pressure, fasting glycemia, hemoglobin A1c and serum lipids.
The researchers deemed six cohort studies and two randomized control trials to have a high risk of bias. Both randomized controlled trials had a high risk of bias regarding blinding of participants and one of those also had a high risk of bias regarding concealment, outcome assessment and incomplete data, and was ultimately excluded from data synthesis.
The other 19 studies had a moderate risk of bias as most of the studies restricted participants to a select group of celiac patients.
Regarding reported adherence, the researchers assessed 19 cohort studies and one randomized controlled trial. Methods for measuring adherence varied (serology, self-report, symptomatic response to diet, biopsy, etc.) and one study did not report adherence.
“The literature currently is limited to patients with celiac disease ... and in this group the studies suggest there are small changes in some cardiovascular risk factors associated with the adoption of a gluten-free diet, without an indication of clear benefit or harm to overall cardiovascular risk,” Potter said. “We did see consistently that a gluten-free diet leads to minor weight gain (within a healthy weight range) in celiac patients, but whether this is due to a reversal in the small bowel damage caused by celiac disease, or the diet itself, is unclear.”
Increased BMI within the normal weight range was common among the 12 studies assessed, though three studies reported an increase in the proportion of overweight patients after a gluten-free diet and two reported significantly decreased weight.
Of the three studies that included a report on blood pressure, two showed no significant change and one showed an increase in systolic and diastolic blood pressure.
Two of three studies reported a significant increase in glycemia levels after following a gluten-free diet and one reported no significant difference among patients with type 1 diabetes.
Three of six studies showed a significant increase in total cholesterol; five of six studies showed a significant increase in high density lipoprotein; three of four studies showed no significant changes in low density lipoproteins, while one reported a significant increase; and four of five studies showed no significant change in triglyceride levels, while one reported a significant increase.
“With the evidence we have, there is no basis to recommend a gluten-free diet for cardiovascular health to patients without celiac disease, and there is no strong evidence that the gluten-free diet negatively affects overall cardiovascular risk in patients with celiac disease,” Potter concluded. “We do suggest that patients requiring the diet for medical reasons do it under the supervision of a trained dietitian and medical practitioner to ensure nutritional adequacy and monitoring of cardiovascular risk factors.” – by Talitha Bennett
Disclosure: The authors report no relevant financial disclosures.