3100 B.C.
According to the Greek historian Herodotus of Halicarnassus (485 BC – c420 B.C.), during the construction of the pyramids the workers were fed on large quantities of onions, garlic and radishes.
There is an inscription in Egyptian characters on the pyramid which records the quantity of radishes, onions, and garlic consumed by the labourers who constructed it; and I perfectly well remember that the interpreter who read the writing to me said that the money expended in this way was 1600 talents of silver. If this then is a true record, what a vast sum must have been spent on the iron tools used in the work, and on the feeding and clothing of the labourers. History, Book II (Euterpe)
Herodotus (1992), The Histories. Translated by Rawlinson, G. Everyman's Library.
Harper suggests that in ancient Egypt the onion was recommended as a cure for a condition similar to scurvy. It may be safe to assume that the provision of garlic, onions and radishes was an attempt to keep a large workforce, living and working in close proximity, healthy enough to complete the job at hand.
It wasn't until the 20th century that an antibiotic preparation (Raphanin) was extracted from radish, and Allicin and Allistatin from garlic and onion.
Harper, A.E. (2000) Recommended Dietary Allowances and Dietary Guidance. Cambridge World History of Food. Cambridge University Press.
Ivanovics, G. & Horvath, S. (1947) Raphanin, an antibacterial principle of the radish (Raphanus sativus). Nature 160.