It is certainly based on notions of moderation and balance that would not be out of place in your average Sunday colour supplement. Health essentials include air, food and drink, movement and rest, sleep, and the moderation of extreme emotions.If you read Guardian link, you'll find out more. Oh, crayfish are supposed to be an aphrodisiac. A BBC Worldservice item on the Tacuinum Sanitatis revealed that much of the information in it was lifted from 11th century Arab manuscripts, based on ancient Mesopotamian tablets from 100AD. No link, you'll have to take my word for it.
I love medieval manuscripts; they always have beautiful illustrations. To view a Tacuinum Sanitatis go here. Clicking on the illustrations is very useful, too.