Taste responses to naringin, a flavonoid, and the acceptance of grapefruit juice are related to genetic sensitivity to 6-n-propylthiouracil

Abstract

Increased consumption of vegetables and fruit has long been the focus of dietary strategies for disease prevention. Some vegetables and fruit have bitter tastes, which can be aversive to consumers, particularly children. The present study tested the hypothesis that acceptance of grapefruit juice is influenced, in part, by sensitivity to the bitter taste of 6-n-propylthiouracil (Prop), a heritable trait. A sample of 123 women, mean age 28 y, was divided into nontasters (n = 39), tasters (n = 49), and supertasters (n = 35) of Prop by using procedures validated previously based on Prop detection thresholds and on intensity scaling of five suprathreshold solutions of Prop and sodium chloride. The subjects tasted and rated five solutions of the bioflavonoid naringin in 4% sucrose. Naringin, the principal bitter ingredient of grapefruit juice, has been implicated in the regulation of cytochrome P-450 enzymes. Increased taste acuity for both Prop and naringin was associated with greater dislike for each bitter compound. Prop supertasters disliked bitter naringin solutions significantly more than did either tasters or nontasters. Prop sensitivity was also associated with reduced acceptability of grapefruit juice. Acceptability of orange juice, which does not contain naringin, was unrelated to Prop taster status. Is the acceptability of other bitter vegetables and fruit also limited by inherited taste factors? If so, then genetic taste markers might limit dietary exposure to valuable dietary constituents and pose a barrier to current strategies for dietary change.

Variation in the Ability to Taste Bitter Thiourea Compounds: Implications for Food Acceptance, Dietary Intake, and Obesity Risk in Children

“…Observations in adults that PROP tasters perceive greater oral intensity from a wide range of compounds, including bitter (39,64), sweet (65,142), and fat (46,65,110,131), provoked the possibility that the PROP phenotype might serve as a marker of dietary intake with important nutritional implications. Interest in the potential association between taste sensitivity to bitter thiourea compounds like PROP and dietary patterns grew from data from surveys conducted in adult populations by Fischer and colleagues (53) and Glanville & Kaplan (57).…”

“…Plant foods are the most common source of bitter-tasting compounds in the diet, and the majority of plants are capable of synthesizing bitter compounds for protection against predators (25,51). Tasters have been hypothesized to have lower acceptance and intake of bitter-tasting fruits and vegetables (e.g., grapefruit juice, cruciferous vegetables) on the basis of early studies demonstrating a positive association between PROP taste sensitivity and perceived bitterness in compounds, such as caffeine (90), quinine (64), and naringin (the bitter compound in grapefruit) (39). These findings could have important health implications because many of the bitter-tasting compounds in foods (e.g., flavonoids, phenols, glucosinolates) are anticarcinogenic.…”

Taste and food preferences as predictors of dietary practices in young women

“…7 for review) distinguished only between PROP tasters and nontasters, new research has identified non-tasters, regular tasters and supertasters of PROP. Those distinctions were based on PROP detection thresholds and the magnitude of bitterness ratings for more concentrated PROP solutions 18,21,22 . Supertasters, most of whom are said to be women, on average had more fungiform papillae and a higher density of taste buds per papilla than did either regular tasters or non-tasters of PROP 23 .…”

“…PTC or PROP sensitivity was linked to a greater number of dislikes for green and cruciferous vegetables (cabbage, Brussels sprouts, spinach and kale), rhubarb, sauerkraut, beer, coffee, brown bread and various sharp cheeses 20,25,26 . More recent studies have linked PROP taste responsiveness to reduced acceptance of naringin solutions, soy products and Japanese green tea 22,27 . The latter studies are particularly relevant to the cancer prevention literature, given that many of the antioxidant phytochemicals are said to be found in green and cruciferous vegetables, soy products, citrus fruit and tea 28,29 .…”

Sweetness and bitterness taste of meals per se does not mediate gastric emptying in humans

“…Those bitter tastants that can safely be administered to the human gastrointestinal tract in adequate quantities (e.g., quinine and naringin) have also been reported to be rated less bitter by those who cannot taste PTC compared with those who can (6,7). This raises the possibility that genotypic differences in responsiveness to bitter tastants might also exist in the gastrointestinal tract.…”