Royal jelly is a honey bee secretion that is used in the nutrition of the larvae.
It is secreted from the hypopharyngeal glands in the heads of young workers and used (among other substances) to feed all of the larvae in the colony, including those destined to become workers.
If a queen is needed, a larva is chosen and will receive only royal jelly — and in large quantities — as its food source for the first four days of its growth, and this rapid, early feeding triggers the development of queen morphology, including the fully developed ovaries needed to lay eggs.
Some commercial royal jelly suppliers disseminate misinformation such as "Only queen larvae and adult queens are fed royal jelly".
All larvae in a colony are fed royal jelly, and adult bees do not consume it at all.
People collect and sell royal jelly as a dietary supplement, claiming various health benefits because of components like B-complex vitamins such as pantothenic acid (vitamin B5) and vitamin B6 (pyridoxine).
The overall composition of royal jelly is 67% water, 12.5% crude protein (including small amounts of many different amino acids), and 11% simple sugars, also including a relatively high amount (5%) of fatty acids.
It also contains many trace minerals, some enzymes, antibacterial and antibiotic components, and trace amounts of vitamin C. Contrary to claims by many of those promoting its use, vitamins A, D, and E are completely absent from royal jelly.