Does Each Menstrual Cycle Elicit a Distinct Effect on Olfactory and Gustatory Perception?

The obesity pandemic has brought forth a scientific interest in food intake and sensory perception interactions. Olfactory perception and gustatory perception are very complex and under the influence of many factors, including the menstrual cycle. This study aims to clarify conflicting findings on the influence of the menstrual cycle on olfactory and gustatory perception. Women were assessed during four consecutive phases of one complete cycle (mid-follicular, ovulatory, mid-luteal, and late luteal phases (N = 21)), in contrast to women measured across the same phases belonging to two menstrual cycles (N = 29). Additional control groups were men (N = 17), postmenopausal women (N = 14), oral contraceptive users (N = 10), and women with an anovulatory cycle (N = 8). Olfactory threshold, odor discrimination, and identification were tested using the “Sniffin Sticks“ test kit. Suprathreshold intensity and hedonic ratings for sweet, salty, sour, and bitter solutions were assessed. One-way ANOVA and ANOVA for repeated measurements was applied in the analysis, along with linear and trigonometric data fitting and linear mixed models. Linear increases in olfactory discrimination, identification, and overall olfactory performance were observed only in women followed across a complete menstrual cycle. Compared to other groups, these women displayed a cyclic pattern characterized by a predilection for sweet solution; reduced distaste for salty and sour solutions; and increased intensity perception of salty, sour, and bitter solutions towards the end of the cycle. These results suggest that a distinct hormonal milieu of a complete menstrual cycle may be affecting both olfactory and gustatory perception.

Estado nutricional y preferencia del sabor dulce en adultos chilenos

El dramático aumento de la prevalencia e incidencia de la obesidad sugiere que factores ambientales y cambios en el estilo de vida contribuyen de forma importante a su tendencia epidémica. En humanos, se han reportado diferencias interindividuales en los umbrales de detección y preferencia del sabor dulce, lo que podría afectar la ingesta habitual de azúcares, y por ende al estado nutricional. Objetivo: El presente estudio busca determinar la relación entre el estado nutricional y la preferencia al sabor dulce en la comunidad de un establecimiento de educación superior. Método: Muestra fue constituida por estudiantes, funcionarios y docentes, entre 18 y 60 años, pertenecientes a la Universidad Mayor, Sede Temuco. Para determinar preferencia al sabor dulce se empleó prueba organoléptica que mide grado de satisfacción frente a solución dulce, junto a ello se realizaron mediciones de peso y talla para determinar el Índice de Masa Corporal. Resultados: Muestra final comprendió de 319 personas, de las cuales un 30,1% fueron hombres y 69,9% mujeres. No se observaron diferencias significativas en la preferencia hacia las soluciones con mayor concentración de sacarosa según el estado nutricional. Sin embargo, el modelo predictivo desarrollado arrojó que hombres prefieren las soluciones con mayor concentración de azúcar independiente de la edad y estado nutricional. Conclusiones: Es necesario desarrollar nuevos estudios que permitan aclarar si la preferencia al sabor dulce favorece el desarrollo de obesidad y sobrepeso, o si es la composición nutricional de los alimentos procesados o ultraprocesados, lo que está teniendo un mayor impacto negativo en el estado nutricional de la población. The dramatic increase in the prevalence and incidence of obesity seems to suggest that environmental factors and lifestyle changes are contributing significantly to the epidemic trend of this pathology. In humans, inter-individual differences in the thresholds of preference of sweet taste have been reported, which could affect habitual sugar intake, and therefore the nutritional status. Objective: The present study seeks to determine the relationship between nutritional status and the preference of sweet taste in the population of a higher education establishment. Method: Sample was constituted by students, officials and teachers between 18 and 60 years, belonging to the Universidad Mayor, Temuco. To determine the perception of the sweet taste, an organoleptic test was used that measures the degree of satisfaction with the sweet solution, along with this, weight and height measurements were made to determine the Body Mass Index. Results: Final sample comprised 319 people, of which 30.1% were men and 69.9% women. No significant differences were observed in the preference for solutions with a higher concentration of sucrose according to nutritional status. However, a predictive model developed showed that men prefer the solutions with the highest concentration of sugar regardless of age and nutritional status. Conclusions: It is necessary to develop new studies to clarify whether the preference for sweet taste favors the development of obesity and overweight, or if it is the nutritional composition of processed or ultraprocessed foods, which is having a greater negative impact on the nutritional status of the population.

Pessimistic dairy calves are more vulnerable to pain-induced anhedonia

Pain induces deficits in appreciation of rewards (i.e. anhedonia) and variation in response to pain may be partly explained by individual differences in general expectations (i.e. optimism). Dairy calves are routinely subjected to painful procedures such as hot-iron disbudding. We tested if female Holstein calves (n = 17) display signs of anhedonia (as evidenced by reduced consumption of a sweet solution) after hot-iron disbudding (performed under general and local anesthesia), and whether individual differences in optimism explain the variation in this response. Individual variation in optimism was measured using responses to two judgment bias tests (performed when calves were 25 d old), and anhedonia was measured by comparing consumption of a sweet solution before and after hot-iron disbudding. We found that intake of the sweet solution declined (by mean ± SD: 48.4 ± 44.3%) on the day after disbudding, and that more pessimistic calves were more affected. Sweet solution consumption did not return to baseline for the duration of the study (i.e. 5 days). Calves reduced their intake of a sweet solution after hot-iron disbudding, consistent with pain-induced anhedonia, and more pessimistic calves showed stronger evidence of anhedonia, suggesting that they were more affected by the procedure. However, our results cannot rule out the possibility that calf responses were driven by anorexia.

Role of CRF receptor 1 antagonism in the bed nucleus of the stria terminalis of male rats after intermittent social defeat stress

We recently demonstrated that the experience of brief episodes of social defeat caused impairments in social behaviors. Moreover, we provided evidence that the antagonism of corticotropin-releasing factor binding protein (CRFBP) in the bed nucleus of the stria terminalis (BNST) restored social approach in stressed animals. This study aimed to test the relation between corticotropin-releasing factor receptor type 1 (CRFR1) located in the BNST and the establishment of social stress-disrupted behaviors in rats submitted to social defeat in the resident-intruder paradigm. Animals were tested for sweet solution preference, subjected to the elevated-plus maze (EPM), and to the social interaction three-chamber test. Social behavior was tested after BNST drug infusions. The drug used in this study was a CRF receptor 1 antagonist, CP376395 (CP), administered in two doses: 50 ng/0.20 μL/side, and 500 ng/0.20 μL/side. Saline solution was used as vehicle and administered 0.20 μL/side. Socially stressed animals (n = 11) did not differ compared to control animals (n = 11) in the EPM. Stressed animals displayed impaired social behavior, represented by a decrease in time spent in the interaction zone. The lower dose (CP 50 ng/0.20 μL/side) administered intra-BNST restored social behaviors in stressed animals. On the other hand, the higher dose of the CRFR1 antagonist (CP 500 ng/0.20 μL/side) induced social avoidance in rats without a history of agonistic confrontations. These findings implicate BNST CRFR1 signaling in the modulation of social behaviors in rats given the choice to explore an unfamiliar conspecific.

Ingesting a Bitter Solution: The Sweet Touch to Increasing Short-Term Cycling Performance

Purpose: The authors investigated the potential benefit of ingesting 2 mM of quinine (bitter tastant) on a 3000-m cycling time-trial (TT) performance. Methods: Nine well-trained male cyclists (maximal aerobic power: 386 [38] W) performed a maximal incremental cycling ergometer test, three 3000-m familiarization TTs, and four 3000-m intervention TTs (∼4 min) on consecutive days. The 4 interventions were (1) 25 mL of placebo, (2) a 25-mL sweet solution, and (3) and (4) repeat 25 mL of 2-mM quinine solutions (Bitter1 and Bitter2), 30 s before each trial. Participants self-selected their gears and were only aware of distance covered. Results: Overall mean power output for the full 3000 m was similar for all 4 conditions: placebo, 348 (45) W; sweet, 355 (47) W; Bitter1, 354 (47) W; and Bitter2, 355 (48) W. However, quinine administration in Bitter1 and Bitter2 increased power output during the first kilometer by 15 ± 11 W and 21 ± 10 W (mean ± 90% confidence limits), respectively, over placebo, followed by a decay of 34 ± 32 W during Bitter1 and Bitter2 during the second kilometer. Bitter2 also induced a 11 ± 13-W increase during the first kilometer compared with the sweet condition. Conclusions: Ingesting 2 mM of quinine can improve cycling performance during the first one-third of a 3000-m TT and could be used for sporting events lasting ∼80 s to potentially improve overall performance.