PTC taste threshold distributions and age in Mennonite populations.

A number of tlutlic* rrjwrt an impairment of the genetically inherited ability to taste ITC a.% a function of age. but ignore the cumulative effect of smoking on taste deterioration. Thi* «tudy examine* the effect of aging on taste sensitivity in nonsmoking: Mennonite population*. The results obtained preclude a cause and effect relationship between age and ITC taste sensitivity. These results are congruent with the claims \thich ascribe the observed deterioration in PTC taste sensitivity to the cumulative effects of smoking, rather than to the effects of aging per sr. A number of papers have been published on the effect of aging on diverse aspects of sensor)' function, including sensitivity to tactile stimuli (Axelrod and Cohen, 1961), vibration (Goffet al. 1965), thermal stimuli (Kragand Kountz, 1950), pain (Procacci et al. 1970), and auditor)* stimuli (Glorig and Nixon, 1962). The taste (e.g., Byrd and Gertman, 1959; Cooper et al. 1959; Hughes, 1969) and smell modalities (e.g., Kimbrell and Furghott, 1963; Rovee et al. 1975) also attracted attention in view of the obvious role that they play in the orientation and the reaction of an organism to its physical environment (Engen, 1977). The taste modality is generally investigated with reference to the primary taste qualities of sweet, sour, salt)', and bitter. Several investigators (e.g., Harris and Kalmus, 1949; Basu and Ghash, 1968; Akcasu and Ozalp, 1977) specifically focused on the genetically inherited ability to detect the bitterness of the chemical substance phenylthiocarbamide or phenylthiourea (PTC). Individual differences in detecting ITC were first noted by Fox (1931; 1932). It was subsequently suggested that ITC tasting is inherited as a simple Mendelian autosomal trait (Blakeslee and Salmon, 1931; Snyder, 1932), or at least it represents a trait on the borderline of a good Mendelian character (Bodmer and Cavalli-Sforza, 1976). PTC "tasters" are either homozygous for the dominant allele (T) or heterozygous (Tt) while "nontasters" are homozygous for the recessive allele (t). Recent claims (Rychkov and Borodina, 1969; Ibraimov and Mirrakhaimov, 1979) argue 'Anthropology. Ohio University. Athens. Ohio 45701 2Laboratory of Biological Anthropology, University of Kansas, Lawrcncc, Kansas 66045 Human Biology, September; 1982. Vol. 5-f So. 3. pp. 635-6-16. ° Wayne Stale University Press. 1982 636 T. A. Koertvelyessy, M. II. Crawford and J. Hutchinson for the existence of two co-dominant alleles (Ti and T2), both dominant to the non-taster allele (t), with T2 being responsible for hypersensitivity to PTC. The linkage relationships of the PTC locus with other loci have been of considerable interest (e.g., Gedde-Dahl and Monn, 1967; 1968; Chautard-Freire-Maia, 1974; Cjrandall and Spence, 1974). While Conneally et al. (1976) showed its linkage to the Kell locus, its assignment to a given chromosome is yet to be made. Most population studies of PTC tasting show a bimodal distribution of taste threshold frequencies, but reports also exist of polymodal distributions in some populations (e.g., Lugg, 1966a; 1966b). A review of the relationships between PTC tasting and disease may be found in Mourant et al. (1978). Its association with thyroid disorders is particularly interesting. While PTC is not a naturally occurring substance, the thiocarbamide group (S = C-N-H), responsible for the bitter taste of the compound is also found in a number of antithyroid food sources (e.g., cabbage, Brussels sprouts). It has been, therefore, hypothesized that PTC tasting functions as an oral mechanism for the detection and avoidance of bitter tasting natural goitrogens (Kitchin et al. 1959; Green, 1974). According to this argument, non-tasters and less sensitive tasters may be at a selective disadvantage during the first and second decades of life due to thyroid stress resulting from the ingestion of greater amounts of naturally occurring goitrogens, especially if this is coupled with already low iodine intake. It is noteworthy that Azevedo et al. (1965) found that adenomatous goiter occurs in a significantly higher frequency in non-tasters than in tasters, especially in males. At the same time, the homozygous taster genotype may be at a selective disadvantage during the third and fourth decades of life due to hyperthyroidism. A number of studies reported an impairment of PTC taste sensitivity with increasing age (e.g., Harris and Kalmus, 1949; Kalmus and Trotter, 1962; Mohr, 1951; Akcasu and Ozalp, 1977). However, these studies ignored the cumulative effect of smoking on the reported deterioration of the ability to taste PTC (Fischer et al. 1963; Kaplan et al. 1964; Eriksson et al. 1970). The purpose of this paper is to report the distribution of PTC taste threshold frequencies in non-smoking Mennonite populations from Kansas and Nebraska, with special attention to the possible effect of aging on PTC taste sensitivity. MATERIALS AND METHODS Subjects. During fieldwork in 1979 and 1980 among Mennonite communities of Kansas and Nebraska by members of a multidisciplinary PTC Taste Threshold and Age 637 research team investigating aspects of the aging process, 1157 individuals were tested for PTC taste thresholds. Of this total, 552 were males and 605 were females, with 526 individuals (244 males and 282 females) being members of the Goessel, Kansas, community, 87 (39 males and 48 females) belonging to the Meridian Mennonite congregation, and the remaining 544 individuals (269 males and 275 females) being from the Henderson, Nebraska community. With a few exceptions, all subjects were adults within the 18 to 92 age range. Historical background. Mennonites are a denomination of the broad Anabaptist movement. The origins of this movement may be traced to the turbulance of the sixteenth century and to geographical areas of present day Holland, Switzerland, Poland, and Germany. The historical details of the movement are discussed elsewhere (e.g., Dyck, 1967; Bender and Smith, 1964; Klassen, 1953; and Hostetler, 1959). Let it suffice to say that Mennonite history is complex, and involves the movement of ideas as well as that of people. The persecution experienced by Mennonites in Europe, eventually resulted in the immigration of many Mennonite families to the Unites States and Canada. Dyck (1967, p. 145) identifies eight major waves of Mennonite immigrants to the American continent. In the first wave, approximately 100 Mennonites entered the United States between 1683 and 1705 from the Lower Rhine region, while in waves 2 to 5 about 8,000 Swiss Mennonites came between 1707 and 1895. These immigrants first settled in the eastern part of the United States, and then gradually spread westward. The Meridian sample in this study is based on the congregation of Meridian Church of God in Christ Mennonite Church, located near Hesston, Kansas, and organized in 1873. Since the membership of this church is largely Pennsylvania Dutch (Mennonite Encyclopedia, 1973), it seems to represent the descendents of those immigrating with waves 1-5. The Mennonites settling in the Molotschna Colony of the Ukraine between the late 1780's and the mid 1830's were split by a schism into two factions, one of which became the Mennonite Brethern and the other the General Conference of Mennonite Church. Of these, some 18,000 individuals, largely of Dutch origin, left for the United States and Canada between 1873 and 1884 when it appeared that the Russians might renege on an earlier agreement concerning the permanent exemption of Mennonites from military service. The Goessel and the Henderson samples represent the descendents of these wave 6 immigrants. Approximately 2,000 Mennonites reside in the Goessel, Kansas, area (Mennonite Encyclopedia, 1973). This region has been inhabited since 1874 by Mennonites, and is currently served by six churches. The Goes/*. A. Kotrttrly^My. St. II. Cruivfvrd and J. llutchimon sel sample was obtained from the three General Conference churches, namely, Alexandenvohl Mennonite Church, Tabor Mennonite Church, and Goessel Mennonite Church. The Alexandenvohl church was organized in 187-1 by 265 Mennonites immigrating en mass from Alexandenvohl village in Russia. Tabor and Goessel Mennonite Churches are both offshoots of the Alexandenvohl congregation. Tabor was organized in 1908 and Goessel in 1920, both in response to overcrowding in the Alexandenvohl congregation. Henderson, Nebraska was first settled in 1874 by 207 Mennonite immigrants from the Molotschna settlement in the Ukraine (Mennonite Encyclopedia, 1973). There are now about 3,000 Mennonites in the Henderson area. The sample was obtained from the four churches now serving this community, namely, Henderson Mennonite Brethren Church, Evangelical Mennonite Brethren Church, Bethesda Mennonite Church, and Calvary Bible Church. Bethesda, a member of the General Conference, was organized in 1874, and Henderson in 1876. The Evangelical Mennonite Brethren Church began in 1882 and the Calvary* Church in the 1950*s as the result of schisms. Procedures. All subjects were tested under Held conditions with a modified version of the Harrison and Kalmus (1949) technique. First, serially numbered solutions of ITC were prepared according to 1.3 X 2<a-t» grams/liter, where n is the solution serial number. Subjects were administered the PTC solutions as squirts from polyethylene wash hotdes, interspersed with distilled water and the liberal use of tap water as mouth-rinse in order to avoid the build-up of the chemical stimulus. An individual's taste threshold was then scored as the serial number of the weakest PTC solution correctly distinguished from water.