A number of studies evaluated royal jelly for relief of menopausal symptoms in the 1970s. However, recent clinical trials are lacking. Binding to estrogenic receptors (weak in comparison with diethstilbesterol and phytoestrogens), stimulation of mRNA expression in estrogen-responsive genes, and enhanced MCF-7 cell proliferation (which could be blocked by tamoxifen) have all been demonstrated in vitro.
Animal experiments in rats and ewes have also been conducted. Mild hypertrophy of the uterine luminal epithelium was achieved in rats supplemented with royal jelly, while effects in ewes were varied. The effect of royal jelly supplementation on the onset of estrus has shown mixed results in ewes, with one trial showing no effect, while another exhibiting a shorter time to estrus compared with control and no difference compared with gonadotropin. In both experiments, positive effects on pregnancy and lambing rates were demonstrated.
In tissue culture models and ovariectomized rats, a positive effect on osteoporosis was demonstrated. Increased calcium content and recovered bone mass were suggested to be the results of enhanced intestinal calcium absorption, rather than antagonism of the parathyroid hormone.