Food Components and Supplements

The major part of food consists of chemical compounds that can be used for energy production, biological synthesis, or maintenance of metabolic processes by the host. These components are defined as nutrients, and can be categorized into macronutrients (proteins, carbohydrates, triglycerides, and alcohol), minerals, and micronutrients. The latter category comprises 13 vitamins and a hand full of trace elements. Many micronutrients are used as food supplements and are ingested at doses exceeding the amounts that can be consumed along with food by a factor of 10–100. Both macro- and micronutrients can interact with enzyme systems related to xenobiotic metabolism either by regulation of their expression or direct interference with their enzymatic activity.
During food consumption, we consume a wide range of xenobiotics along with the consumable food, either as an original part of the food (e.g., secondary plant metabolites such as flavonoids), or as contaminants that enter the food chain at different stages or during the food production process. For these components, a wide spectrum of biological effects was observed that ranges from health-threatening impacts (e.g., polycyclic aromatic amines acting as carcinogens) to health-protective effects (e.g., flavonoids ameliorating detrimental effects of mitochondrial oxidative stress). In particular, secondary plant metabolites along with vitamins, specific types of macronutrients and live bacteria (probiotics) as well as substances promoting the growth of these bacteria (prebiotics) are added to food to achieve health effects exceeding its pure nutritional function. Several of these effects are mediated by enzyme systems involved in xenobiotic and drug metabolism, and in some cases this might lead to undesired interactions with medication. The supplements and contaminants can compete directly with drug oxidation, induce or suppress the expression of xenobiotic-metabolizing enzymes, change the bioavailability of drugs, and, in the case of live bacteria, bring in their own xenobiotic metabolism, including cytochrome P450 (CYP) activity. In numerous cases, nutrients, food contaminants, and secondary plant metabolites can themselves
become substrates for xenobiotic-metabolizing enzymes, resulting in health-promoting or health-threatening products.
This chapter focuses on how important components of our daily nutrition and supplements can interfere with xenobiotic metabolism, and how knowledge of this interaction might be exploited in avoiding unwanted nutrition–drug interactions,
but also to promote bioavailability of poorly absorbed drugs. Moreover, important mechanisms of direct interactions between compounds found in food (nutrients, secondary plant metabolites, and contaminants) and the host’s xenobiotic metabolism are pointed out. As some of the health-promoting effects of secondary plant metabolites and vitamins are caused by antagonizing adverse mechanisms of natural or artificial contaminants of food, this chapter starts with the role of the host’s xenometabolism in the detrimental effects of these contaminants.