Royal jelly is a viscous substance secreted by worker bees and constitutes the essential food for queen bees and their larvae. It is consumed as a health food around the world. In laboratory studies, it demonstrated vasodilatory, hypotensive, antihypercholesterolemic, anti-inflammatory, and estrogenic effects ^{(1) (3) (9)}, although its affinity for estrogen receptors is weaker compared with diethylstilbestrol ⁽³⁾. Royal jelly appeared to increase cytotoxic activity of temozolomide ⁽²⁸⁾, but has also shown both inhibitory ⁽⁷⁾ and proliferative ⁽³⁾ effects. Animal studies suggest royal jelly may be effective against colitis ^(10) (22) and improve testosterone levels ⁽¹⁹⁾.

Evidence on royal jelly in humans is limited. Small clinical studies suggest that it may lower total serum lipid and cholesterol levels in those with moderately elevated levels ⁽⁵⁾, and improve erythropoiesis and glucose tolerance in healthy subjects ⁽²⁰⁾. Other small studies suggest that royal jelly may improve type 2 diabetes ^(23) (24) or cardiometabolic markers ⁽³³⁾, but a meta-analysis determined that supplementation does not improve glucose levels ⁽³⁴⁾, and quality of evidence has been cited as low ⁽³⁵⁾.

A combination supplement that contained royal jelly appeared to benefit patients with mild cognitive impairment ⁽²⁷⁾. Other studies suggest that royal jelly supplementation may improve premenstrual ⁽²⁶⁾ and menopausal symptoms ⁽⁶⁾.

Only a few studies have been conducted in cancer patients. Royal jelly swished, then swallowed, along with standard mouthwash therapy improved symptoms of oral mucositis and healing time in patients receiving radiotherapy and chemotherapy ⁽²⁹⁾. Another small study suggests benefit with topical royal jelly ointment in head and neck cancer patients ⁽³⁰⁾.

Because royal jelly has estrogenic effects ⁽³⁾, women with estrogen receptor-positive breast cancer should avoid this product. Prostate cancer patients should also use caution as royal jelly increased testosterone levels in animal studies ⁽¹⁹⁾.