Sharif et al. reported that daily consumption of oral royal jelly (1000 mg) for eight weeks was effective in alleviating menopausal symptoms [5].
There were no reports on the effectiveness for dry mouth sensation with normal saliva function. This is the first report on the effects of the royal jelly on dry mouth sensation with normal saliva function by double-blind, randomized, placebo controlled clinical trial.
Bergdahl et al. suggested that although there are many unknown factors, depression, stress, and anxiety have complex interactions with subjective dry mouth sensation with normal salivary function [2].
In our results, HADS scale and GHQ12 scale improved over time with royal jelly supplements. It is considered that royal jelly supplements are effective for depression and anxiety associated with the subjective dry mouth sensation. Both scales significantly improved 12 weeks after the administration of royal jelly tablets, in comparisons with placebo administration. This result suggests that oral administration of royal jelly tablets at 12 weeks may be effective for treating dry mouth sensation.
Although VAS scale at the evaluation period of 4 weeks and 12 weeks insisted that the administration of royal jelly tablet significantly improved dry mouth sensation, VAS scales over time were unstable. The instability of the VAS scale over time may be due to oral symptoms caused by depression and anxiety, outside of dry mouth sensation.
Recently, burning mouth syndrome, which is defined as a burning sensation or as pain in the oral mucosa, has been reported [8–11]. This syndrome has an etiologically complex relationship with pathophysiological factors - especially depression and anxiety [8, 10]. Dry mouth sensation with normal salivary function has been considered as one of the symptoms of burning mouth syndrome [9–12].
The participants of this study could potentially have burning mouth syndrome. Other uncomfortable oral sensations from burning mouth intricately effect on the VAS scale analysis and the VAS scale cannot accurately detect subjective dry mouth sensation. However, this study only targeted those who suffered from dry mouth with normal salivary function. Whether or not the participants had potential burning mouth syndrome was not a screening item for study inclusion and was unknown.
For dry mouth sensation with normal salivary function, standard treatment and medication are not established [8]. Royal jelly contains a unique component, 10-hydroxy-trans-2-decenoic acid (10H2DA), an unsaturated fatty acid [13]. 10H2DA represents one of the main bioactive components of royal jelly and constitutes the vast majority of the royal jelly lipid content (0.75 to 3.39%), and is one of the main bioactive components [14, 15].
Ito et al. reported in animal models that 10H2DA was effective in improving the stress-induced symptoms of depression and anxiety [13].
In general, double-blind, randomized, placebo controlled clinical trials could provide more scientific evidence [10]. In the clinical trials for burning mouth syndrome there were few reports of long-term follow-up data beyond 2 months [10]. Our study provides important information for further detailed studies of dry mouth sensation with normal saliva function.
Our study revealed that the royal jelly could consumption (800 mg dairy) for 12 weeks is effective for alleviating psychological stress (anxiety and depression) and social activity disorder in patients who suffered from subjective dry mouth sensation with normal saliva function. Further developmental studies are needed in the future.
Our study targeted a limited number of participants and those who suffered from only dry mouth sensation flow, and didn’t include patients with burning mouth syndrome. The treatment of burning mouth syndrome is considered a difficult task for oral health care professionals [12]. Further developmental studies assessing the effects of royal jelly on burning mouth syndrome, induced by depression and anxiety, are expected in the future.