Scientists have long assumed that bitter taste evolved as a defense mechanism to detect potentially harmful toxins in plants. The Current Biology paper provides the first direct evidence in support of this hypothesis by establishing that variants of the bitter taste receptor TAS2R38 can detect glucosinolates, a class of compounds with potentially harmful physiological actions, in natural foods.
"The findings show that our taste receptors are capable of detecting toxins in the natural setting of the fruit and vegetable plant matrix," said senior author Paul Breslin, a Monell sensory scientist.
Glucosinolates act as anti-thyroid compounds. The thyroid converts iodine into thyroid hormones, which are essential for protein synthesis and regulation of the body's metabolism. Glucosinolates inhibit iodine uptake by the thyroid, increasing risk for goiter and altering levels of thyroid hormones. The ability to detect and avoid naturally-occurring glucosinolates would confer a selective advantage to the over 1 billion people who presently have low iodine status and are at risk for thyroid insufficiency.
In the study, 35 healthy adults were genotyped for the hTAS2R38 bitter taste receptor gene; the three genotypes were PAV/PAV (sensitive to the bitter-tasting chemical PTC,) AVI/AVI (insensitive), and PAV/AVI (intermediate).
Subjects then rated bitterness of various vegetables; some contained glucosinolates while others did not. Examples of the 17 glucosinolate-containing vegetables include watercress, broccoli, bok choy, kale, kohlrabi, and turnip; the 11 non-glucosinolate foods included radicchio, endive, eggplant and spinach. Subject
Source:Monell Chemical Senses Center