Nutritional status in irritable bowel syndrome: A North American population-based study

Irritable bowel syndrome (IBS) affects 12% of the population, and the evidence supporting current medical interventions is poor. There is increasing focus on the therapeutic benefit of diet and supplementation. We aim to compare dietary composition and hematologic and biochemical markers 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 1, the Second National Health and Nutrition Examination Survey (NHANES II) (1976-1980), provided comprehensive data on IBS. We performed a cross-sectional analysis of hematologic and biochemical markers and dietary composition of 12 295 individuals, aged 18-74, in NHANES II.

Individuals with IBS had significantly higher copper-zinc ratios (1.70 vs 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), indicative of underlying copper-zinc imbalance. While more likely to report dietary avoidances, they had no other evidence of nutritional deficiencies. In addition, dietary recall showed that those with IBS consumed more 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 copper-zinc imbalance. Given zinc's role in the immune system, the "brain-gut" axis, and the gastrointestinal barrier, the identified copper-zinc imbalance may play a role in perpetuating the underlying pathophysiology of IBS. Further studies are needed to investigate this hypothesis and the potential role of therapeutic zinc supplementation.