Are people who have a better smell sense, more affected from satiation?

Abstract Introduction: The olfactory system is affected by the nutritional balance and chemical state of the body, serving as an internal sensor. All bodily functions are affected by energy loss, including olfaction; hunger can alter odour perception. Objective: In this study, we investigated the effect of fasting on olfactory perception in humans, and also assessed perceptual changes during satiation. Methods: The "Sniffin' Sticks" olfactory test was applied after 16 h of fasting, and again at least 1 h after Ramadan supper during periods of satiation. All participants were informed about the study procedure and provided informed consent. The study protocol was approved by the local Ethics Committee of Gaziosmanpaşa Taksim Education and Research Hospital (09/07/2014 no: 60). The study was conducted in accordance with the basic principles of the Declaration of Helsinki. Results: This prospective study included 48 subjects (20 males, 28 females) with a mean age of 33.6 ± 9.7 (range 20-72) years; their mean height was 169.1 ± 7.6 (range 150.0-185.0) cm, mean weight was 71.2 ± 17.6 (range 50.0-85.0) kg, and average BMI was 24.8 ± 5.3 (range 19.5-55.9). Scores were higher on all items pertaining to olfactory identification, thresholds and discrimination during fasting vs. satiation (p < 0.05). Identification (I) results: Identification scores were significantly higher during the fasting (median = 14.0) vs. satiation period (median = 13.0). Threshold (T) results: Threshold scores were significantly higher during the fasting (median = 7.3) vs. satiation period (median = 6.2). Discrimination (D) results: Discrimination scores were significantly higher during the fasting (median = 14.0) vs. satiation period (median = 13.0). The total TDI scores were 35.2 (fasting) vs. 32.6 (satiation). When we compared fasting threshold value of >9 and ≤9, the gap between the fasting and satiety thresholds was significantly greater in >9 (p < 0.05). Conclusion: Olfactory function improved during fasting and declined during satiation. The olfactory system is more sensitive, and more reactive to odours, under starvation conditions, and is characterised by reduced activity during satiation. This situation was more pronounced in patients with a better sense of smell. Olfaction-related neurotransmitters should be the target of further study.

摘要 引言：嗅觉系统作为人体内部感知传感器，可受机体营养平衡与化学状态的调控。机体各项生理功能均会受到能量流失的影响，嗅觉亦不例外；饥饿状态可改变个体的气味感知能力。
研究目的：本研究旨在探究禁食对人类嗅觉感知的影响，并评估饱食状态下的感知变化。
研究方法：分别在禁食16小时后，以及斋月晚餐后至少1小时的饱食状态下，采用嗅棒测试（Sniffin' Sticks）对受试者进行嗅觉检测。所有受试者均知晓研究流程并签署了知情同意书。本研究方案经加齐奥斯曼帕夏·塔克西姆教育与研究医院当地伦理委员会批准（2014年7月9日，编号：60），且研究实施符合《赫尔辛基宣言》的基本原则。
研究结果：本前瞻性研究共纳入48名受试者（男性20名，女性28名），平均年龄为33.6±9.7岁（年龄范围20~72岁）；平均身高169.1±7.6cm（身高范围150.0~185.0cm），平均体重71.2±17.6kg（体重范围50.0~85.0kg），平均身体质量指数（Body Mass Index, BMI）为24.8±5.3（范围19.5~55.9）。与饱食状态相比，禁食状态下受试者的嗅觉识别、嗅觉阈值与嗅觉辨别相关各项评分均更高（p<0.05）。
嗅觉识别（Identification, I）结果：禁食状态下的识别评分（中位数=14.0）显著高于饱食状态（中位数=13.0）。
嗅觉阈值（Threshold, T）结果：禁食状态下的阈值评分（中位数=7.3）显著高于饱食状态（中位数=6.2）。
嗅觉辨别（Discrimination, D）结果：禁食状态下的辨别评分（中位数=14.0）显著高于饱食状态（中位数=13.0）。
总TDI评分分别为35.2（禁食状态）与32.6（饱食状态）。当将禁食阈值分为>9与≤9两组进行比较时，>9组的禁食与饱食阈值差值更为显著（p<0.05）。
研究结论：禁食状态下嗅觉功能得以提升，而饱食状态下嗅觉功能则出现下降。饥饿状态下，嗅觉系统对气味的敏感性与反应性均更强；饱食状态下则表现为嗅觉活动减弱。这一现象在嗅觉功能更佳的受试者中更为显著。与嗅觉相关的神经递质可作为后续研究的目标方向。