Abstract
Previous studies of autonomic nervous system responses before and after eating when controlling patient conditions and room temperature have provided inconsistent results. We hypothesized that several physiological parameters reflecting autonomic activity are affected by outdoor temperature before and after a meal. We measured the following physiological variables before and after a fixed meal in 53 healthy Japanese women: skin temperature, systolic and diastolic blood pressure, salivary amylase, blood glucose, heart rate, and heart rate variability. We assessed satiety before and after lunch using a visual analog scale (100 mm). We recorded outdoor temperature, atmospheric pressure, and relative humidity. Skin temperature rose significantly 1 h after eating (greater in cold weather) (P = 0.008). Cold weather markedly influenced changes in diastolic blood pressure before (P = 0.017) and after lunch (P = 0.013). Fasting salivary amylase activity increased significantly in cold weather but fell significantly after lunch (significantly greater in cold weather) (P = 0.007). Salivary amylase was significantly associated with cold weather, low atmospheric pressure, and low relative humidity 30 min after lunch (P < 0.05). Cold weather significantly influenced heart rate variability (P = 0.001). The decreased low frequency (LF)/high frequency (HF) ratio, increased Δ LF/HF ratio, and increased Δ salivary amylase activity imply that cold outdoor temperature is associated with dominant parasympathetic activity after lunch. Our results clarify the relationship between environmental factors, food intake, and autonomic system and physiological variables, which helps our understanding of homeostasis and metabolism.Electronic supplementary materialThe online version of this article (doi:10.1007/s00484-014-0800-1) contains supplementary material, which is available to authorized users.
Highlights
Behavior and the environment influence human physiology, with the autonomic nervous system and endocrine axes playing a central role in maintaining homeostasis
Lower atmospheric pressure was significantly associated with increased skin temperature, but otherwise neither atmospheric pressure nor relative humidity appeared to have any influence on the physiological parameters recorded (Table 3)
We found that colder outdoor temperatures were associated with increased diastolic blood pressure, increased salivary amylase activity, and increased blood glucose concentration in fasting healthy volunteers
Summary
Behavior and the environment influence human physiology, with the autonomic nervous system and endocrine axes playing a central role in maintaining homeostasis. There has been significant interest in the role played by the autonomic nervous and endocrine systems in the relationships between outdoor temperature and skin temperature, blood pressure, blood glucose concentration, salivary amylase activity, and heart rate variability. As a result of endocrine responses to the autonomic nervous system, several physiological mechanisms are affected that relate to maintaining homeostasis (Koska et al 2002; Kanikowska et al 2013). Eating strongly influences many of these physiological parameters, possibly through similar mechanisms (Harthoorn and Dransfield 2008). The findings of these studies have been inconsistent, and the interplay between outdoor temperature and eating has not been examined
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