Irritable bowel syndrome (IBS) is common, affecting 12% of the population. However, the quality of evidence in support of current medical interventions has been rated as very low, and the majority of those with IBS report their symptoms as being unchanged or worsened over time. Diet is thought to play a significant role in IBS, and there is increasing focus on the therapeutic benefit of diet and supplementation. This study aims to compare dietary composition and serologic markers of nutritional status in those with and without IBS to determine potential targets for therapeutic supplementation.
All 17 national surveys between 1959 and 2019 were screened and only one, the Second National Health and Nutrition Examination Survey (NHANES II) (1976-1980), provided comprehensive data on IBS. We performed a cross-sectional analysis of serology and dietary composition of 12,295 individuals, aged 18 to 74 in NHANES II. Dietary composition was drawn from dietary recall questionnaires, and the diagnosis of IBS was based on self-reporting.
Individuals with IBS had significantly higher copper-zinc ratios (1.70 versus 1.55, P = 0.048) and were more likely to have ratios above 1.8 (odds ratio 1.79, 95% confidence interval 1.02-3.13), suggestive of an underlying zinc deficiency. This deficiency may be due to their avoidance of milk, which was the largest source of dietary zinc in the study population. While they were significantly more likely to report dietary avoidances, they had no other serologic evidence of nutritional deficiencies. Additionally, dietary recall showed that they consumed significantly more daily calories (P = 0.02), were more likely to take vitamin supplements (P = 0.003) and that their macro and micronutrient intake was not significantly different.
The findings suggest that individuals with IBS should be screened for zinc deficiency. Zinc deficiency may perpetuate the underlying pathophysiology of IBS and may contribute to the associated psychiatric conditions through zinc's role in the immune system, “brain-gut” axis, and gastrointestinal barrier integrity. This suggests that zinc supplementation may be a potential therapy both to mitigate underlying pathology as well as improve symptoms. Our findings should be confirmed in future studies, and the association of copper-zinc ratios with symptom severity, and the response of symptoms to supplementation could be investigated.