Abstract
It has been noted that the fragrance of grapefruits has a refreshing and exciting effect, which suggests the activation of sympathetic nerves. In salivary glands, the activation of sympathetic or parasympathetic nerves induces the secretion of proteins (such as the digestive enzyme α-amylase (amylase) and the glycoprotein mucin) or water and ions, respectively. Here, we investigated the effects of the scent from grapefruit oil on body weight and food intake, and its acute effects on salivary fluid and amylase secretion into the oral cavity of rats. When rats were exposed to the scent from grapefruit oil for 5 weeks, their body weight and food intake decreased. When rats were treated with the scent for 20 min, salivary amylase secretion was enhanced without changes in fluid secretion. These findings suggest that the scent from grapefruit oil activates sympathetic nerves, but not parasympathetic nerves, resulting in an anti-obesity effect.
