Ibn Sina in his Canon said,
“Therefore we may say that the art of maintaining the health is not the art of averting death, or of averting extraneous injuries from the body; or of securing the utmost longevity possible to the human being.
It is concerned with two other things:
The prevention of putrefactive breakdown; and
the safeguarding of innate moisture from too rapid dissipation, and maintaining it at such a degree of strength that the original type of constitution peculiar to the person shall not change even up to the last moment of life.
This is secured by a suitable regimen, namely
one which will ensure the replacement of the innate heat and moisture which are dispersed from the body as exactly as possible; and
a regimen which will prevent any agents which would lead to a rapid dessication from gaining the upper hand—excluding agents which produce a normal desiccation;
one which safeguards the body from the development of putrefactive processes within it and from the influence of alien heat (whether extraneous or intrinsic).
For all bodies have not the same degree of innate moisture and innate heat. There is a great diversity in regard to them.