Constituents and Origins of Physiological Malodor

Abstract

This study investigated unpleasant components of physiological malodor to clarify their origins from a microbiological perspective. 1. Expired air from healthy adults with physiological malodor was found to contain more than 15 volatile components, including low-molecular weight fatty acids, nitrogen compounds, and sulfur compounds (VSC). The concentration of methyl mercaptan (CH₃SH) in the expired air of subjects with physiological malodor was always above the CH₃SH recognition threshold, and was highly correlated with the degree of maloder present. 2. The origin of CH₃SH in physiological malodor was examined. The proportion of CH₃SH in VSC was higher in mouth air and in the salivary headspace than in expired air. The production of CH₃SH in the oral cavity was found to increase following mouth rinsing with a L-methionine solution. The most effective method of reducing the CH₃SH concentration in the physiological malodor was to remove the tongue coating. 3. The CH₃SH production capacity of 71 oral strains of various genera and species was tested. The genera Porphyromonas, Fusobacterium, Spirochetes, which are presumed to originate with periodontal disease, demonstrated high CH₃SH production capacity. In addition, Veillonella, a genus consisting of major microorganisms found in the tongue coating, demonstrated similar abilities. From these results, it was cleared that CH₃SH is one of the primary components of physiological malodor and produced mainly from tongue coating which harbors sizable Veillonella populations.