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Received Jan 24, 2018; Accepted Mar 27, 2018
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Menopause is a normal part of women’s life, typically between ages 45 and 55 years, when the ovaries naturally stop producing eggs and their menstrual periods end. The decreased production of estrogen level affects autonomic nervous system, which can directly trigger menopause symptoms such as hot flashes, insomnia, mood changes, fatigability, neck stiffness, backache, and low back pain and headache. Particularly, neck stiffness, headache, and low back pain are the main menopausal symptoms in Japanese women [1]. Hormone replacement therapy (HRT) has been widely accepted to relieve menopausal symptoms [2, 3], while it is associated with an increased risk of breast cancer [3, 4]. Therefore, an effective and safe alternative health product for women is needed to improve menopausal symptoms. Various safe alternative health products such as isoflavones, St John’s wort, and Royal Jelly (RJ) can provide relief of menopausal symptoms [5–7].
Among them, RJ has been long used as a nutritional supplement and its safety has been demonstrated by several clinical studies [8–10], so RJ supplementation could be a good option for those having concerns about HRT. Traditionally, RJ has been used to improve menopausal symptoms [11], and case reports have revealed that the menopausal symptoms such as hot flashes, anxiety, irritation, fatigability, neck stiffness, low back pain, and headache were improved with RJ supplementation in menopausal women [7]. However, the placebo-controlled studies of RJ on menopausal symptoms have not been reported. RJ contains a considerable amount of proteins, free amino acids, lipids, vitamins, minerals, and unique fatty acids such as (E)-10-hydroxy-2-decenoic acid (10HDA) and 10-hydroxydecanoic acid (10HDAA) [12]. It is reported that RJ and 10HDA have estrogenic effect and agonist activity for estrogen receptor (ER) β [13, 14]; hence one of the mechanisms for improvement of physical and psychiatric symptoms in menopause is considered to be the estrogenic effect.
Here, a randomized double-blind placebo-controlled study was conducted in order to determine the effect of RJ on menopausal symptoms, specifically in postmenopausal women.
2. Material and Methods
2.1. Participants
The study was carried...