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6-n-Propylthiouracil: A Genetic Marker for Taste, with Implications for Food Preference and Dietary Habits

1998; Elsevier BV; Volume: 63; Issue: 5 Linguagem: Inglês

10.1086/302124

1537-6605

Beverly J. Tepper,

Advanced Chemical Sensor Technologies

6-n-Propylthiouracil (PROP) and phenythiocarbamide (PTC) are members of a class of compounds known as "thioureas." These compounds carry the chemical group N-C=S, which is responsible for their characteristic bitter taste (for review, see Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar; Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). As is true for many scientific discoveries, the bitterness of PROP and PTC were discovered by accident. In 1931, while Fox was synthesizing PTC in his laboratory, some of the white crystals became airborne. His colleagues perceived a bitter taste, but Fox tasted nothing. This simple observation led to a large number of family studies that investigated genetic variation in the ability to taste PTC and, in later studies, to taste PROP. PTC and PROP are of great interest to taste researchers not only as tools for understanding the genetic transmittance of taste but for gaining insight into the seemingly endless variation in taste preferences and food habits that exists in the population. The purpose of this review is to highlight the evidence supporting a role for genetic variation in taste sensitivity to PROP, in taste perception and food acceptance. Special emphasis will be placed on the potential implications that recent findings have for diet and health. The incidence of taste blindness to PTC/PROP varies around the world, from ∼3% in western Africa to >40% in India (see MIM 171200). Approximately 30% of the adult Caucasian population of North America are taste blind to PTC/PROP (i.e., are nontasters) and 70% are tasters. The term "nontaster" is probably a misnomer, since many so-called nontasters can taste PROP at higher concentrations. The ability to taste PTC/PROP is present in young children and declines slowly with age (Whissell-Buechy Whissell-Buechy, 1990Whissell-Buechy D Effects of age and sex on taste sensitivity to phenylthiocarbamide (PTC) in the Berkeley Guidance sample.Chem Senses. 1990; 15: 39-57Crossref Scopus (39) Google Scholar). The trait is more common in women than in men (Whissell-Buechy and Wills Whissell-Buechy and Wills, 1989Whissell-Buechy D Wills C Male and female correlations for taster (PTC) phenotypes and rate of adolescent development.Ann Hum Biol. 1989; 16: 131-146Crossref PubMed Scopus (24) Google Scholar; Bartoshuk et al.Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar), and there is limited evidence that reproductive hormones may a role in its phenotypic expression. For example, one study found that girls who were PTC/PROP tasters matured ∼3.8 mo earlier than girls who were nontasters (Whissell-Buechy and Wills Whissell-Buechy and Wills, 1989Whissell-Buechy D Wills C Male and female correlations for taster (PTC) phenotypes and rate of adolescent development.Ann Hum Biol. 1989; 16: 131-146Crossref PubMed Scopus (24) Google Scholar). Taste sensitivity to PTC and PROP can be determined by use of threshold methods. The threshold is defined as the lowest concentration of a test solution that can be distinguished from plain water. Tasters have very low thresholds for PROP (i.e., high sensitivity at low concentrations), whereas nontasters have higher thresholds (i.e., poor sensitivity at low concentrations). The distribution of taste thresholds in the population is bimodal. This bimodality is unusual in taste, since most stimuli follow a Gaussian distribution. Evidence from many studies establishes the taste threshold for PROP as being at or near 1.0×10−4 mol/liter for tasters and >2.0×10-4 mol/liter for nontasters (Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). Because PTC has a slight odor, PROP has replaced the use of PTC in most modern taste studies. It was originally thought that the ability to taste PROP was inherited as a dominant Mendelian trait (see MIM 171200), a model that cannot account for the occurrence of taster offspring from nontaster parents, as observed in some studies (Olson et al. Olson et al., 1989Olson JM Boehnke M Neiswanger K Roche AF Siervogel RM Alternative genetic models for the inheritance of the phenylthiocarbamide taste deficiency.Genet Epidemiol. 1989; 6: 423-434Crossref PubMed Scopus (67) Google Scholar). Polygenic models that include a second locus or third allele generally show a better fit with the taste data. The analysis conducted by Reddy and Rao (Reddy and Rao, 1989Reddy BM Rao DC Phenylthiocarbamide taste sensitivity revisited: complete sorting test supports residual family resemblance.Genet Epidemiol. 1989; 6: 413-421Crossref PubMed Scopus (29) Google Scholar) concluded that variability in the threshold to PTC was controlled by a major locus with incomplete dominance as well as by a multifactorial component. Olson et al. (Olson et al., 1989Olson JM Boehnke M Neiswanger K Roche AF Siervogel RM Alternative genetic models for the inheritance of the phenylthiocarbamide taste deficiency.Genet Epidemiol. 1989; 6: 423-434Crossref PubMed Scopus (67) Google Scholar) proposed a two-locus model in which one locus controlled PROP/PTC sensitivity and the second locus controlled general taste ability. Another model, proposed by Reed et al. (Reed et al., 1995Reed DR Bartoshuk LM Duffy V Marino S Price A Propylthiouracil tasting: determination of underlying threshold distributions using maximum likelihood.Chem Senses. 1995; 20: 529-533Crossref PubMed Scopus (55) Google Scholar), suggested that the large group of PROP tasters might be composed of two subgroups; medium tasters, who show moderate taste sensitivity to PROP, and supertasters, who are highly sensitive. As described below ("PROP Tasters and Nontasters—Different Taste Worlds"), this model is consistent with the results of many taste studies showing that PROP supertasters give higher intensity ratings than do medium tasters, to a wide range of oral stimuli. Some studies have found linkage of PTC to the Kell blood group on chromosome 7, but no other linkages have been identified (MIM 171200). Until the gene(s) for PROP/PTC is identified and cloned, the exact mode of inheritance will remain controversial. Why does the PROP phenotype persist in contemporary human societies? One classic theory postulates that PROP-taste ability provides a selective advantage for avoidance of harmful compounds in the environment that are often bitter tasting (Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). This taste aversion may have special relevance for the avoidance of certain bitter-tasting vegetables. PROP and PTC are chemically related to the isothiocyanates and goitrin, bitter-tasting compounds that are present in cruciferous vegetables such as cabbage, broccoli, Brussel sprouts, turnips, and kale. When eaten in large quantities, these compounds interfere with iodine metabolism, producing thyroid enlargement and goiterlike symptoms. Before the widespread use of iodized salt, endemic goiter was a health problem in isolated areas of the world where iodine was scarce. It has been consistently noted, however, that the incidence of thyroid-deficiency disease is relatively rare among PTC tasters (MIM 171200), and this lower incidence has been attributed to the avoidance of cruciferous vegetables by PTC tasters (Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). Several studies have attempted to demonstrate a relationship between PROP-taste sensitivity and rejection of bitter vegetables, but they have been inconclusive (Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). A major challenge to these studies is that raw vegetables are not a preferred food in our culture (Meiselman Meiselman, 1988Meiselman HL Consumer studies of food habits.in: Piggott JR Sensory analysis of foods. 2d ed. Elsevier Applied Science, London1988: 267-334Google Scholar). Aversions to vegetables may occur for many reasons other than their bitter taste, including their appearance or texture, social or cultural taboos associated with eating them, or their unpleasant gastrointestinal effects for some people. These negative attitudes could overshadow the influence of taster status on the outcome of taste studies. Nevertheless, a colleague and I recently have found, among preschool children, evidence linking taster status with the taste of raw broccoli (B. J. Tepper and L. Steinmann, unpublished data). Taster children disliked raw broccoli, whereas nontaster children liked raw broccoli. These results are striking, given that food rejection is common among young children (Birch et al. Birch et al., 1996Birch LL Fisher JO Grimm-Thomas K The development of children's eating habits.in: Meiselman HL MacFie HJH Food choice, acceptance and consumption. Chapman & Hall, London1996: 161-206Crossref Google Scholar). Our data support previous work by Anliker et al. (Anliker et al., 1991Anliker JS Bartoshuk LM Ferris AM Hooks LD Children's food preferences and genetic sensitivity to the bitter taste of 6-n-propylthiouracil (PROP).Am J Clin Nutr. 1991; 54: 316-320PubMed Google Scholar) that suggested a role for inherited taste characteristics in the development of food preferences in childhood. Other lines of evidence suggest that the avoidance of bitter-tasting foods may have certain health disadvantages for populations consuming Western diets (Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). Epidemiological studies indicate that diets low in fruits and vegetables and high in fat may be associated with increased risk of certain cancers. Since many of the phytochemicals found in fruits and vegetables prevent carcinogenesis in laboratory animals, higher consumption is generally recommended. Despite public-health efforts to increase fruit and vegetable consumption, intake in the population is low. Drewnowski et al. (Drewnowski et al., 1997aDrewnowski A Henderson SA Shore AB Taste responses to naringin, a flavonoid, and the acceptance of grapefruit juice are related to genetic sensitivity to 6-n-propylthiouracil.Am J Clin Nutr. 1997; 66: 391-397PubMed Google Scholar) have hypothesized that the avoidance of bitter-tasting fruits and vegetables by PROP tasters contributes to this unhealthy eating pattern and might pose a barrier to future diet change. Initial studies have demonstrated that solutions containing naringin, the bitter ingredient found in grapefruit juice, were less acceptable to PROP tasters than to PROP nontasters. Taster status was also associated with lower dietary preference for grapefruit juice. More studies are needed to determine the predictive value of PROP-taster status as a marker for cancer risk. Increasing evidence suggests that PROP tasters show greater sensitivity to a wide range of oral stimuli, including bitter tastes not associated with fruits and vegetables, various sweet tastes, oral irritants such as chili pepper, and the textural sensations of fats (see following sections). However, these perceptual differences are of little practical significance unless they can be linked to differences in liking and acceptability. Far fewer studies have investigated the acceptability of these stimuli to tasters and nontasters, and not all studies agree that PROP tasters universally dislike these sensations. One of the difficulties is that the majority of studies utilize laboratory solutions as taste stimuli. Laboratory solutions lack the gustatory qualities of real foods and beverages and are not highly palatable to humans. The use of more-realistic food stimuli in future studies should help to resolve many of the inconsistencies that exist in the current literature. Solutions of caffeine, quinine, and isohumulones (the bittering agents in beer) are more intensely bitter to PROP tasters (Mela Mela, 1990Mela DJ Gustatory perception of isohumulones: influence of sex and thiourea taster status.Chem Senses. 1990; 15: 485-490Crossref Scopus (21) Google Scholar; Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar). Some foods—including sodium benzoate, a common food preservative, and the salt substitute potassium chloride—have bitter aftertastes that are also more noticeable to PROP tasters (Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar). The taste of sucrose is also more intensely sweet to PROP supertasters than to medium tasters and nontasters, and similar results have been reported for some high-intensity sweeteners such as saccharin and neohesperidin dihydrochalone (Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar). Using an unusual approach to assess liking responses, Looy and Weingarten (Looy and Weingarten, 1992Looy H Weingarten HP Facial expressions and genetic sensitivity to 6-n-propylthiouracil predict hedonic response to sweet.Physiol Behav. 1992; 52: 75-82Crossref PubMed Scopus (123) Google Scholar) surreptitiously photographed the facial expressions of subjects while they judged the sweetness intensity of sucrose solutions. PROP tasters more frequently showed classic rejection responses such as frowning and grimacing. In contrast, PROP-taste sensitivity did not predict hedonic responses to sucrose or saccharin in more-recent studies (Drewnowski et al. Drewnowski et al., 1997bDrewnowski A Henderson SA Shore AB Barratt-Fornell A Nontasters, tasters and supertasters of 6-n-propylthiouracil (PROP) and hedonic response to sweet.Physiol Behav. 1997; 62: 649-655Crossref PubMed Scopus (69) Google Scholar). Capsaicin, the compound responsible for the oral burn of chili pepper, is more intensely hot to PROP tasters than to nontasters (Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar; Tepper and Nurse Tepper and Nurse, 1997Tepper BJ Nurse RJ Fat perception is related to PROP taster status.Physiol Behav. 1997; 61: 949-954Crossref PubMed Scopus (216) Google Scholar). Capsaicin has some striking short-term and long-term effects on oral perception. After even a single brief exposure, capsaicin lingers on the palate (Karrer and Bartoshuk Karrer and Bartoshuk, 1991Karrer T Bartoshuk LM Capsaicin desensitization and recovery on the human tongue.Physiol Behav. 1991; 49: 757-764Crossref PubMed Scopus (148) Google Scholar), making it a difficult substance for use in taste studies. Multiple brief exposures cause "sensitization," or enhancement of the perceived burn (Green Green, 1990Green BG Effects of thermal, mechanical and chemical stimulation on the perception of oral irritation.in: Green BG Mason JR Kare MR Chemical senses: irritation. Vol 2. Marcel Dekker, New York1990: 171-192Google Scholar). Sensitization may be responsible for the steady increase in hotness that typically occurs with successive bites of spicy foods. Repeated exposure to capsaicin (over the course of days) decreases the overall burn intensity (Stevenson and Prescott Stevenson and Prescott, 1994Stevenson RJ Prescott J The effects of prior experience with capsaicin on ratings of its burn.Chem Senses. 1994; 19: 651-656Crossref PubMed Scopus (51) Google Scholar). This phenomenon might explain why frequent consumers of chili are less sensitive to its perceived burn (Stevenson and Yeomans Stevenson and Yeomans, 1993Stevenson RJ Yeomans MR Differences in ratings of intensity and pleasantness for the capsaicin burn between chili likers and non-likers: implications for liking development.Chem Senses. 1993; 18: 471-482Crossref Scopus (31) Google Scholar). The acquisition of a taste preference for chili is not well understood. Chili pepper is generally aversive to those tasting it for the first time, but liking develops with repeated exposure (Rozin and Schiller Rozin and Schiller, 1980Rozin P Schiller D The nature and acquisition of a preference for chili pepper by humans.Motiv Emotion. 1980; 4: 77-101Crossref Scopus (204) Google Scholar). Chili enjoys widespread use as a basic flavor principle in the cuisine of many diverse cultures (Rozin Rozin, 1978Rozin P The use of characteristic flavorings in human culinary practice.in: Apt CM Flavor: its chemical, behavioral and commercial aspects. Westview Press, Boulder1978: 101-127Google Scholar). If liking of chili was closely linked with PROP-taster status, then areas of the world where chili is widely consumed would have a high frequency of nontasters in the population. Also, most chili lovers would be expected to be nontasters. Evidence in support of these hypotheses is currently lacking, although laboratory studies addressing these questions have yet to be done. Resolving the complex interactions among genetic taste factors, dietary experience, and liking of chili pepper will pose intriguing challenges for taste researchers in the future. Studies have also examined the perception of other pungent spices that are structurally related to capsaicin, such as piperine, from black pepper, and zingerone, isolated from ginger (Silver and Finger Silver and Finger, 1991Silver WL Finger TE The trigeminal system.in: Getchel TV Doty RL Bartoshuk LM Snow Jr, JB Smell and taste in health and disease. Raven Press, New York1991: 97-108Google Scholar). In taste studies, these compounds offer several advantages to capsaicin, because they elicit weaker burn intensities with a shorter duration (Prescott and Stevenson Prescott and Stevenson, 1996Prescott J Stevenson RJ Psychophysical responses to single and multiple presentations of the oral irritant zingerone: relationship to frequency of chili consumption.Physiol Behav. 1996; 60: 617-624Crossref PubMed Google Scholar). Prescott and Stevenson (Prescott and Stevenson, 1996Prescott J Stevenson RJ Psychophysical responses to single and multiple presentations of the oral irritant zingerone: relationship to frequency of chili consumption.Physiol Behav. 1996; 60: 617-624Crossref PubMed Google Scholar) recently observed that the frequent use of chili decreased the psychophysical response to zingerone, suggesting that the two compounds act through a common mechanism. This observation is especially intriguing in light of data, in rodents, showing that capsaicin, zingerone, and piperine bind to different subtypes of a common receptor (Liu and Simon Liu and Simon, 1996Liu L Simon SA Similarities and differences in the currents activated by capsaicin, piperine and zingerone in rat trigeminal ganglion cells.J Neurophysiol. 1996; 76: 1858-1869PubMed Google Scholar). It would be of interest to determine whether PROP-taster status plays a role in the perception or acceptance of these pungent spices. Recent studies from our laboratory have focused on the relationship between PROP-taste sensitivity and perception and liking for fat (Tepper and Nurse Tepper and Nurse, 1997Tepper BJ Nurse RJ Fat perception is related to PROP taster status.Physiol Behav. 1997; 61: 949-954Crossref PubMed Scopus (216) Google Scholar, Tepper and Nurse, 1998Tepper BJ Nurse RJ PROP taster status is related to the perception and preference for fat.Ann NY Acad Sci. 1998; 855: 802-804Crossref PubMed Scopus (140) Google Scholar). Normal-weight young adults were classified as nontasters, medium tasters, or supertasters of PROP and evaluated fat content and liking of high-fat (40% fat) and low-fat (10% fat) salad dressings. As shown in figure 1A, the nontasters could not distinguish the two dressings in terms of fat content, whereas the medium tasters and supertasters gave higher fat-content ratings to the 40%-fat dressing. The liking responses were more difficult to interpret than the fat-content ratings. As shown in figure 1B, the nontasters liked the high-fat dressing more than the low-fat dressing, whereas the medium tasters and supertasters liked both samples equally well. Since nontasters found no difference in fat content between the two samples, it is unclear what attributes drove their preference for the high-fat dressing. On the other hand, perhaps medium tasters and supertasters perceived the high-fat dressing to be too oily or fatty, which contributed to their lack of preference for this sample. This response might be analogous to the dislike of intensely sweet stimuli by PROP tasters in the sucrose studies mentioned previously (Looy and Weingarten Looy and Weingarten, 1992Looy H Weingarten HP Facial expressions and genetic sensitivity to 6-n-propylthiouracil predict hedonic response to sweet.Physiol Behav. 1992; 52: 75-82Crossref PubMed Scopus (123) Google Scholar). Many more high-fat foods will have to be tested before the nutritional relevance of these findings can be determined. Anatomical studies have provided clues as to why PROP tasters may be more sensitive to such a broad range of oral stimuli. The taste papillae are the structures that hold and orient the taste buds on the tongue. PROP tasters have both a higher density of taste papillae on the apex of the tongue and more-functional taste buds (Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar; Tepper and Nurse Tepper and Nurse, 1997Tepper BJ Nurse RJ Fat perception is related to PROP taster status.Physiol Behav. 1997; 61: 949-954Crossref PubMed Scopus (216) Google Scholar). This might explain the greater sensitivity of PROP tasters to basic tastes such as bitter and sweet. In rodents, the taste buds are surrounded by trigeminal fibers (Bartoshuk et al. Bartoshuk et al., 1994Bartoshuk LM Duffy VB Miller IJ PTC/PROP tasting: anatomy, psychophysics, and sex effects.Physiol Behav. 1994; 56: 1165-1171Crossref PubMed Scopus (574) Google Scholar). The trigeminal (5th cranial) nerve carries information about oral irritation, including chemical heat and cooling, and pungency (Green Green, 1990Green BG Effects of thermal, mechanical and chemical stimulation on the perception of oral irritation.in: Green BG Mason JR Kare MR Chemical senses: irritation. Vol 2. Marcel Dekker, New York1990: 171-192Google Scholar). If a similar configuration exists in humans, this might explain why PROP tasters have increased sensitivity to capsaicin and, possibly, other pungent spices. The trigeminal nerve is also involved in other sensory functions, including the perception of fat. The perception of fat in food is primarily a function of its texture, with flavor playing a more minor role (Mela and Marshall Mela and Marshall, 1991Mela DJ Marshall RJ Sensory properties and perceptions of fats.in: Mela DJ Dietary fats: determinants of preference, selection and consumption. Elsevier Applied Science, New York1991: 43-57Google Scholar). Although not well studied, texture perception is mediated by mechanoreceptors located on the surface of the tongue and palate and between the teeth (Cardello Cardello, 1996Cardello AV The role of human senses in food acceptance.in: Meiselman HL MacFie HJH Food choice, acceptance and consumption. Chapman & Hall, London1996: 1-82Crossref Google Scholar). Texture sensations are due to mouth-feel characteristics such as the presence of moistness or particles and to mechanical characteristics that are associated with resistance to applied forces in the mouth. Sauces and gravies that lack particles are perceived as smooth and creamy in the mouth. In contrast, the force of chewing a food such as peanut brittle defines its primary texture characteristic—hardness. The presence of more trigeminal fibers on the surface of the tongue might give PROP tasters an advantage in perceiving fat in viscous fluids such as salad dressings and in creamy foods such as mayonnaise and margarine. Interestingly, sweet-fat mixtures, such as sweetened dairy products, fail to show the expected responses in PROP tasters (Drewnowski et al. Drewnowski et al., 1998Drewnowski A Henderson SA Barratt-Fornell A Genetic sensitivity to 6-n-propylthiouracil and sensory responses to sugar and fat mixtures.Physiol Behav. 1998; 63: 771-777Crossref PubMed Scopus (80) Google Scholar). This observation could be due to the phenomenon of masking, wherein adding sweetness to fat tends to mask the perception of the fat (Drewnowski and Schwartz Drewnowski and Schwartz, 1990Drewnowski A Schwartz M Invisible fats: sensory assessment of sugar/fat mixtures.Appetite. 1990; 14: 203-217Crossref PubMed Scopus (92) Google Scholar). Since masking reflects integration of signals at higher brain centers (Cardello Cardello, 1996Cardello AV The role of human senses in food acceptance.in: Meiselman HL MacFie HJH Food choice, acceptance and consumption. Chapman & Hall, London1996: 1-82Crossref Google Scholar), it is probably unrelated to PROP-taster status. It is not known whether PROP tasters are more sensitive to other textural sensations, such as the crunchiness of snack chips and crackers, which could also influence food choice and dietary intake. Laboratory studies provide a reliable means of characterizing taster-nontaster differences in perception and liking for specific foods. However, laboratory taste tests have limitations in that only a few representative foods can be tested at one time. For this reason, food-preference surveys may be more revealing of the complex food habits and experiences of tasters and nontasters. Food-preference surveys consistently show that PROP tasters have more overall food dislikes than do nontasters and that they dislike strong-tasting foods such as anchovies, sauerkraut, dark beer and ales, black coffee, and strong cheeses (Drewnowski and Rock Drewnowski and Rock, 1995Drewnowski A Rock CL The influence of genetic taste markers on food acceptance.Am J Clin Nutr. 1995; 62: 506-511PubMed Google Scholar). A final consideration is whether the diets of PROP tasters are fundamentally different from those of nontasters. For example, do PROP tasters consume bland or monotonous diets, as the results of food-preference surveys seem to suggest? Are the diets of PROP tasters lower in cancer-fighting fruits and vegetables or lower in fat, diet patterns associated with varying degrees of chronic-disease risk? These questions can only be answered by use of food-consumption data, typically derived from food-intake questionnaires or food diaries. Diet studies are difficult to accomplish because they are labor intensive and usually involve large numbers of subjects. Although comprehensive analyses of the dietary patterns of tasters and nontasters have yet to appear in the literature, they are undoubtedly the focus of current investigations in several laboratories. Another interest in my laboratory is in understanding the relationship between taster status and body weight. We hypothesized that, if PROP tasters followed the restrictive diets typically ascribed to them, they should have lower body weights. Among male subjects who participated in the fat-perception study mentioned previously, we observed that PROP supertasters had slightly but not significantly lower body weights than did medium tasters or nontasters (Tepper and Nurse Tepper and Nurse, 1998Tepper BJ Nurse RJ PROP taster status is related to the perception and preference for fat.Ann NY Acad Sci. 1998; 855: 802-804Crossref PubMed Scopus (140) Google Scholar). A second study, involving middle-aged men, also revealed that those who were classified as PTC tasters had slightly lower body weights than did nontasters (B. J. Tepper and N. Ullrich, unpublished data). These provocative findings require further confirmation, but they provide indirect evidence that the dietary patterns of PROP tasters may have important implications for weight status. This relationship was not observed in women. Studies are presently underway to determine whether this difference represents a true sexual dimorphism or simply reflects the greater influence of dieting on body weight in women. Finally, research over the past several decades has yielded many new and exciting findings about the relationship between inherited taste characteristics, taste preferences, and food selection. Current studies raise more questions than they answer about the potential role for genetic taste factors in human health and disease, and the exact nature of this relationship remains to be elucidated. A better understanding of the genetic basis of taste, including identification of the relevant genes and DNA markers, will accelerate progress in the field. This work was supported by a Charles and Johanna Busch Biomedical Research Grant from Rutgers University.