TASTE PSYCHOPHYSICS

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The long term goal of this research is to relate variation in taste ability to variation in food preferences, and food consumption. Individuals are born as nontasters, medium tasters, and supertasters based on their ability to taste a bitter substance called PROP (6-n- propylthiouracil). Nontasters have the fewest taste buds and supertasters, the most. Women are more likely than men to be supertasters. Supertasters experience the most intense tastes from a variety of sweet and bitter substances present in foods. For prepubertal girls and post menopausal women, liking for sweets is related to their abilities to taste PROP; those who taste PROP to be the most bitter (and thus have the most tastebuds) like sweets the most. However, for women in their child bearing years, this reverses: women who taste PROP to be the most bitter, dislike sweets the most. In a sample of elderly women, greater ability to taste PROP associated with nutritional indexes that indicate lower risk for cardiovascular disease (e.g., lower body mass index). These examples show that PROP offers an important key to taste-nutrition links. One reason that the powerful connection between the sense of taste and nutrition has been hard to document in the past is the presence of taste pathology. The sense of taste can be altered by common medical problems (ear infections, mild head injuries). Four experiments are proposed that make use of new understanding of these pathologies. First, a diverse population will be assessed psychophysically for the ability to taste PROP. The number and location of their fungiform papillae and taste buds will be determined with videomicroscopy, and any taste pathologies will be identified. Second, 15 women will be followed through two menstrual cycles with psychophysical and anatomical studies of their taste systems to determine whether or not there are variations in taste ability and number of taste buds that can be related to variation in sex hormones. Third, approximately 100 families will be recruited to participate in a classic family study on the mode of inheritance of PROP tasting. The genetic model under test is that tasting is incompletely dominant; nontasters carry two recessive alleles (tt), medium tasters carry one dominant allele (Tt), and supertasters carry two dominant alleles (TT). Anomalies in earlier family studies (e.g., a taster child born to nontaster parents) are expected to be associated with taste pathology (e.g., a nontaster parent may be a genetic taster but test as a nontaster because of taste damage). Fourth, food preference and consumption questionnaires will be given to all subjects in experiments 1-3. This will permit links between taste genetics and food behavior to be demonstrated in subjects where the effects of taste pathology can be assessed. In addition, a subset of the subjects will be tested psychophysically for their perceptions of simple taste solutions. This will permit a test of the hypothesis that food dislikes in supertaster women of child bearing age are produced by the increases in the perceived intensities of bitter and sweet tastes. An oral irritant will also be tested. Since taste buds are innervated by the trigeminal nerve which carries irritation sensations, perceived irritation may prove to be a useful marker of changes in the number of taste buds.