The White Law / VIS Ethos could be VERY long so I want to identify my underlying reasoning and make it as universal as possible.
With this thread I'm going to deal with a very large section of it.
When it comes to any substance you take into the body; air, food, water, medicine, drugs, poisons, and anything else:
1. You should avoid dependence on the substance. Most of us have to eat, breath, and drink still; we certainly don't want to add even more things we need to that list to function. If you can achieve Inedia, you should do so. It is proper to free ourselves from the bondage of substance.
2. Any substance which does any harm to you should be avoided. Unless you are like that one man who could consume massive quantities of alcohol that would kill any normal man and yet you don't end up drunk at all, you shouldn't be drinking alcohol. If you can demonstrate immunity then you can feel free to swallow burning hot coals, poisons, drugs, pesticides, etc.; in this case it will just be a demonstration of your advanced spiritual cultivation.
3. All substances should not be used as crutches. You have to stand on your own two legs from time to time less they wither; you can get weaker if you do certain things all the time like maintain constantly sterile environment for example. You ought to accept suffering from time to time. such as when deciding not to take pain killers.
4. Whenever possible and forced by necessity, consume only that which does the least harm and has the most positive effect (e.g. select healthiest foods available to you for consumption).
I think that sums it up but maybe I'll have to go more into detail? Don't use a substance as a crutch, don't develop a dependency upon it and if you are already dependent strive to be free yourself from it, don't take things into your body which do you harm, when forced by necessity to consume things only take in that which has the most positive effect with the least harm.
Besides the prohibitions above, you should always use magick whenever you have the opportunity to make your water and food better for you, as described in Initiation Into Hermetics.