Variation in the bitter-taste receptor gene TAS2R38, and adiposity in a genetically isolated population in Southern Italy

OBJECTIVE

Variation in the bitter-taste receptor gene, TAS2R38 confers the ability to taste 6-n-propylthiouracil (PROP). The objective of this study was to relate TAS2R38 haplotypes and PROP-tasting phenotypes to adiposity in a genetically isolated population. We hypothesized that the nontaster phenotype would be associated with higher BMI and waist circumference (WC) in females, and that dietary restraint would mediate this relationship.

METHODS AND PROCEDURES

Participants were 540 healthy inhabitants of the genetically isolated village of Carlantino in southern Italy who were 15-89 years of age at the time of the study. Haplotype analyses were performed and PROP tasting was assessed using a filter paper method. Height, weight, and WC were measured and restrained eating was assessed using a brief questionnaire.

RESULTS

Nontaster females had higher BMI and WC than females who were phenotypic tasters, and this relationship was specific to females with low dietary restraint. Regression analysis showed that BMI declined by 1.7 units across taster groups in females when the model included the PROP by restraint interaction. PROP phenotype was not significantly associated with WC in the regression models. Polymorphisms in TAS2R38 were not associated with BMI or WC in females. Neither TAS2R38 haplotype nor PROP phenotype was strongly related to BMI or WC in males.

DISCUSSION

These data support previous findings of a relation between the nontaster phenotype and higher BMI in females that is modified by dietary restraint. Assessment of PROP phenotypes might provide unique information about adiposity that is not captured by haplotype analysis alone.

PROP taster status and self-perceived food adventurousness influence food preferences

OBJECTIVE

To determine the influence of 6-n-propylthiouracil (PROP) taster status and food adventurousness on liking of bitter, hot, and pungent foods.

DESIGN

Self-reported survey of food likes/dislikes for 70 foods. Subjects were classified as tasters or nontasters of PROP using a standard screening procedure. By their response to a query regarding their perceived frequency of trying unfamiliar foods, subjects were characterized as being more or less adventurous.

SUBJECTS

A convenience sample of 232 healthy adults, 18 to 55 years of age, was recruited from the local community. Statistical analyses Individual foods were grouped using Principal Component Analysis. Analysis of variance was used to assess differences in liking of food groups as a function of PROP status and food adventurousness.

RESULTS

PROP tasters who were more food adventurous liked chili peppers and hot sauce, other pungent condiments, strong alcohol, and bitter fruits and vegetables more than tasters who were less food adventurous (P< or =.05-.001). Nontasters liked most foods, and food adventurousness had little influence on food liking for these individuals.

CONCLUSIONS

Food adventurous PROP tasters liked a wide variety of strong-tasting foods, whereas tasters who were less food adventurous showed the classic dislike of bitter, hot, and pungent foods. Previous studies might have overestimated the influence of PROP taster status on rejection of strong-tasting foods by not distinguishing individuals by food adventurousness.

Influence of genetic taste sensitivity to 6-n-propylthiouracil (PROP), dietary restraint and disinhibition on body mass index in middle-aged women

A previous study from our laboratory reported a small, inverse association between taste sensitivity to 6-n-propylthiouracil (PROP) and body mass index (BMI) among lean, young-adult males. Weaknesses in study design precluded making this same observation in females. To overcome these shortcomings, the present study investigated this relationship in older, heavier women characterized by dietary restraint and disinhibition. We tested the hypothesis that lower taste sensitivity to PROP would be associated with higher BMI but that high dietary restraint would mask this association. Thus, no relationship between taster status and BMI was expected in those with high dietary restraint. Eighty-six, middle-aged women (39.0+/-1.0 years) with a mean BMI of 27.4+/-0.8 participated. They were classified as PROP nontasters (n=23), medium tasters (n=32) or supertasters (n=31). Initial analyses revealed that disinhibition had a strong positive influence on BMI that was unrelated to PROP status (P< or =.001). After adjusting for disinhibition, a strong interaction between PROP status and restraint on BMI was noted. Among women with low dietary restraint, nontasters (P< or =.01) and medium tasters (P< or =.05) were heavier than supertasters by 6 and 4 adjusted BMI units, respectively. No differences in BMI were found across taster groups in women with high dietary restraint. These data confirm that the inverse association between PROP status and BMI reported earlier in men is also present in women and that this relationship becomes apparent when variables relevant to eating behavior in women are taken into consideration. These findings are discussed in the context of emerging theories relating genetic differences in taste to fat acceptance, fat intake and body weight.