Critical Review on Zeolite Clinoptilolite Safety and Medical Applications in vivo

Abstract

Unique and outstanding physical and chemical properties of zeolite materials make them extremely useful in a variety of applications including agronomy, ecology, manufacturing, and industrial processes. Recently, a more specific application of one naturally occurring zeolite material, clinoptilolite, has been widely studied in veterinary and human medicine. Due to a number of positive effects on health, including detoxification properties, the usage of clinoptilolite-based products in vivo has increased enormously. However, concerns have been raised in the public about the safety of clinoptilolite materials for in vivo applications. Here, we review the scientific literature on the health effects and safety in medical applications of different clinoptilolite-based materials and propose some comprehensive, scientifically-based hypotheses on possible biological mechanisms underlying the observed effects on the health and body homeostasis. We focus on the safety of the clinoptilolite material and the positive medical effects related to detoxification, immune response, and the general health status.

Keywords: antioxidant properties; clinoptilolite; immunostimulation; toxicology; zeolite.

FIGURE 1

The generally accepted and studied clinoptilolite effects on the human body in vivo. Observed clinically relevant effects on organs and systems for different clinoptilolite materials in vivo are due to major clinoptilolite properties: detoxification, antioxidant effect, release of trace elements, and positive influence on the microbiota status in the intestine as described in Table 1. These effects were documented in animals and humans for clinoptilolite material used as supplementation to regular diet in a powdered form.

FIGURE 2

A simplified schematic of the clinoptilolite structure: linked SiO₄ tetrahedra and pores with metal cations available for ion-exchange with environmental cations (e.g., caesium, Cs⁺) that are consequently trapped into the clinoptilolite pores. As naturally occurring clinoptilolite comes with pre-loaded cations (e.g., calcium, Ca²⁺), ion-exchange may occur depending on the ion-exchange capacity and cation affinity of the material, as well as on physical properties of the surrounding environment. In the herein presented simplified example, Cs⁺ enters in the zeolite pores instead of Ca²⁺ (adapted from http://www.chemtube3d.com/solidstate/SS-Z-Clinoptilolite.htm Creative Commons Attribution-Non-commercial-Share Alike 2.0 UK: England and Wales License). A detailed explanation of the clinoptilolite structure is given in the Database of Zeolite Structures (http://europe.iza-structure.org/IZA-SC/ftc_table.php).

FIGURE 3

Proposed model of clinoptilolite positive immunomodulatory effect in the intestinal epithelium (denoted with red arrows) through interaction of clinoptilolite tuff particles with microfold cells (M-cells). Clinoptilolite tuff released particles are denoted by ‘C.’ M-cells are hypothesized to transport luminal clinoptilolite tuff released particles across the epithelial barrier and present them to immunological cells (e.g., dendritic cells) in the lamina propria and the Peyer’s patches. The latter are rich in T cells, macrophages, and clinoptilolite- activated IgA secreting B and plasma cells. The single layer of the intestinal epithelium is protected by mucus containing mucin glycoproteins where immunoglobulin A (IgA) and antimicrobial peptides prevent interaction of microbiota with the cell surface. Question marks (?) and blue arrows denote still unknown interactions of clinoptilolite with microbiota and microbiota with the lumen and epithelia.