Raised dietary Zn:Cu ratio increases the risk of atherosclerosis in type 2 diabetes

Abstract

Background: Zinc is an essential micronutrient that has sometimes been found to be deficient in patients with type 2 diabetes mellitus (T2DM). Zinc therapy is accordingly often recommended to these patients. Absorption of zinc is however affected by the macronutrient content of the diet, and is in direct competition with that of other trace elements, especially that of copper, deficiency of which is also harmful. It is hypothesized that micronutrient imbalance increases the risk of atherosclerosis and of later cardiovascular complications in T2DM.

Objective: To evaluate correlation between subclinical atherosclerosis and the dietary zinc to copper ratio (Zn:Cu) and the relationship between Zn:Cu to the dietary pattern of patients with T2DM.

Design: Population-based cross-sectional multicentric study including 216 adults (aged 30-70 years) with T2DM without a diagnosis of atherosclerosis or its complications. All study participants completed 24-h dietary recall captured with the NutriData food composition database and its dietary analysis software. The Goldberg cut-off method was applied for the assessment of dietary misreporting. The ratio of reported energy intake to estimated basal metabolic rate (EIrep: BMRest) indicates the physical activity level (PAL). Subjects whose apparent PAL fell below a defined minimum were classified as under-reporters and were excluded from the analysis. The carotid intima-media thickness (IMT) and occurrence of plaque were evaluated with ultrasound.

Results: A positive correlation between IMT and the Zn:Cu ratio was statistically significant (p = 0.044), and remained so after adjustment for common cardiovascular risk factors (p = 0.025). There was no correlation between Zn:Cu and plaque. The dietary Zn:Cu ratio was significantly higher in patients with low carbohydrate (p < 0.001), high fat (p = 0.004) and high protein (<0.001) intake.

Conclusions: A high dietary Zn:Cu ratio derived from an unbalanced diet in patients with T2DM is significantly related to worse carotid artery IMT. Zinc supplementation will increase the already disturbed balance in the diet and has the potential to aggravate cardiovascular morbidity.

Keywords: Atherosclerosis; Copper; Intima-media thickness; Micronutrient intake; Type 2 diabetes mellitus; Zinc.