hat tip to Dr. Ben Goldacres for pointing this out.
I am posting the Good News Bible version, because the King James Version is harder to understand, especially for people whose first language is not English. But you can look it up on any version of the Bible, through Google. How come we did not know this:
The first recorded clinical trial: Daniel 1.12

12 “Test us for ten days,” he said. “Give us vegetables to eat and water to drink. 13 Then compare us with the young men who are eating the food of the royal court, and base your decision on how we look.” 14 He agreed to let them try it for ten days. 15 When the time was up, they looked healthier and stronger than all those who had been eating the royal food. 16 So from then on the guard let them continue to eat vegetables instead of what the king provided. 17 God gave the four young men knowledge and skill in literature and philosophy. In addition, he gave Daniel skill in interpreting visions and dreams. 18 At the end of the three years set by the king, Ashpenaz took all the young men to Nebuchadnezzar. 19 The king talked with them all, and Daniel, Hananiah, Mishael, and Azariah impressed him more than any of the others. So they became members of the king's court. 20 No matter what question the king asked, or what problem he raised, these four knew ten times more than any fortune teller or magician in his whole kingdom.