Coping with Plant Volatiles in Spicy Food (“Burping Exercise”)

Abstract

Humans, like many other land vertebrates, take up a large variety of plant secondary metabolites (PSMs) and other xenobiotics in their diet. Xenobiotics constitute a wide category of compounds, including synthetic ones, in the environment that are potentially harmful when ingested, especially in large amounts. Mammals and birds have evolved many mechanisms to render harmless these PSMs and other toxins (Iason 2005). These detoxication mechanisms include elimination of the compounds themselves, metabolizing them into less toxic and/or better excretable compounds, or developing tolerance, as for instance, garter snakes have in response to the very potent tetrodotoxin of newts (Brodie et al. 2002). These countermeasures start in the mouth where plant volatiles escape during mastication. Normal body temperature suffices to volatilize monoterpenoids (Welch et al. 1989). Therefore, in mammals, such plant constituents in the diet can be reduced by mastication and eructation, among other processes such as absorption and excretion (Welch et al. 1989).

Once in the stomach, PSMs still can be belched up, in addition to swallowed air or other gases such as carbon dioxide. Most of us have experienced this normal physiological reaction after eating foods such as cucumbers, hot peppers, or garlic, or drinking coffee or herbal teas. If obserbed through the gut, metabolic deactivation takes place in the liver by the hepatic microsomal cytochrome P450. There, the PSMs are activated by oxidation, reduction, or other processes and then conjugated with glucuronic acid or other compounds to make them excretable in urine or bile.