Interactions between Infections, Nutrients and Xenobiotics

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During recent years there have been several incidents where symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g. TCDD). Furthermore, outbreaks of infections in food producing animals have attracted major attention with regards to the safety for consumers (e.g., BSE and influenza in chicken). As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and possibly other diseases as well. Also, during ongoing infection, xenobiotic uptake and distribution is often changed resulting in increased toxic insult to the host. The interactions between infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology, as well as in food-born diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects between microorganisms, nutrients, and xenobiotics will have to be considered. Such effects may otherwise gradually change the disease panorama in society. The author of this report is senior food toxicologist at the National Food Administration, Uppsala, Sweden. He is PhD and Adjunct Professor in Experimental Infectious Diseases at the Faculty of Medicine, Uppsala University, Sweden, and a great part of his scientific production has been devoted to the theme covered in this report.



Effects of Xenobiotics on Host Resistance

Important negative effects of potentially harmful xenobiotics present in the environment and in food have been shown to be directed against our immune system, which in the long term, could affect our susceptibility to infections and autoimmune diseases (Burchiel, 1999; Van Loveren et al., 1998; Zelikoff et al., 1994). A chemical substance could disturb the normal homeostasis of the immune system, resulting in enhanced pathogen invasion and growth and tissue damage, or in immune-mediated toxicity on the immune system itself, or on other organ systems. The immune system seems particularly sensitive to modulation by certain classes of environmental chemicals, including polycyclic aromatic hydrocarbons (PAHs), halogenated aromatic hydrocarbons (such as TCDD), and nonessential trace elements (such as Pb, Cd, Hg and Ni) that are all common pollutants in the food and the environment. A number of potentially toxic metals have even been ranked in terms of their immunosuppressive qualities, i.e., Hg>Cu>Mn>Co>Cd>Cr (Lawrence, 1981). However, it is important to distinguish between small and biologically unimportant changes in immune parameters presumed to be without health consequences and those changes that may jeopardise our host defence. In many studies an alteration in immune function has been observed in the absence of a demonstrable change in host resistance (Kimber and Dearman, 2002).


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