Is Bitterness Only a Taste? The Expanding Area of Health Benefits of Brassica Vegetables and Potential for Bitter Taste Receptors to Support Health Benefits

Bitter taste sensitivity, cruciferous vegetable intake, obesity, and diabetes in American adults: a cross-sectional study of NHANES 2013-2014

Objective: To examine the associations between bitter taste sensitivity, cruciferous vegetable consumption, and likelihood of obesity and diabetes among American adults. Research design and method: Cross-section observation of 2129 adults aged 40-80 years of the National Health and Nutrition Examination Survey (NHANES) 2013-2014. Bitter taste sensitivity was estimated by the generalized labeled magnitude scale (gLMS) rating for bitterness (non-tasters: the lowest 25%, the others were tasters). Consumption of cruciferous vegetables was recorded by the 2 day 24 hours dietary records. Obesity was defined as body mass index (BMI) ≥30 kg m-2. Diabetes was defined as self-reported physician-diagnosed diabetes, or who reported taking diabetes medication or individuals with a fasting plasma glucose (FPG) ≥ 126 mg dL-1 or Hemoglobin A1c ≥ 6.5%. Results: The proportion of participants who ate cruciferous vegetables over the two days was 29.5% among bitter tasters, significantly lower than that (35.7%) among non-tasters (P = 0.04) after adjustment of age, gender, race/ethnicity, dietary energy intake, physical activity, education, smoking and income levels. Among participants who ate cruciferous vegetables, bitter tasters on average consumed 15.5 g (±7.0) grams less cruciferous vegetables per day compared to non-tasters. The multi-variates adjusted odds ratio of obesity was 1.29 (95% confident interval (CI): 0.76-2.17), 1.40 (95% CI: 0.90-2.18) and 1.68 (95% CI: 1.05-2.67) among bitter tasters who ate cruciferous vegetables, among non-tasters who did not ate cruciferous vegetables, and among bitter tasters who did not eat cruciferous vegetables, respectively, as compared with non-tasters who ate cruciferous vegetables. The prevalence of diabetes was 17.3% and 13.0% among bitter tasters and non-tasters, respectively, with a multi-adjusted odds ratio of 1.32 (95% CI: 1.02-1.69, P = 0.033) for diabetes comparing bitter tasters with non-tasters, which was attenuated to 1.26 (95% CI: 0.95-1.67, P = 0.108) by further adjustment of cruciferous vegetables consumption and obesity, with a mediation effect of 17.8% (95% CI: 2.9%-60.9%; P = 0.069). Conclusion: Bitter taste sensitivity was associated with less consumption of cruciferous vegetables and a high likelihood of obesity, which may mediate its association with diabetes.

Bitter taste receptors along the gastrointestinal tract: comparison between humans and rodents

For decades bitter taste receptors (TAS2R) were thought to be located only in the mouth and to serve as sensors for nutrients and harmful substances. However, in recent years Tas2r have also been reported in extraoral tissues such as the skin, the lungs, and the intestine, where their function is still uncertain. To better understand the physiological role of these receptors, in this paper we focused on the intestine, an organ in which their activation may be similar to the receptors found in the mouth. We compare the relative presence of these receptors along the gastrointestinal tract in three main species of biomedical research (mice, rats and humans) using sequence homology. Current data from studies of rodents are scarce and while more data are available in humans, they are still deficient. Our results indicate, unexpectedly, that the reported expression profiles do not always coincide between species even if the receptors are orthologs. This may be due not only to evolutionary divergence of the species but also to their adaptation to different dietary patterns. Further studies are needed in order to develop an integrated vision of these receptors and their physiological functionality along the gastrointestinal tract.