Relevent to this topic I give an extract from my site
under the head ”secret of good health and fitness”
Among the Imams, Imam-e-Sadiq (alaih) had special interest in medicine and his prescriptions for good health and cure for many diseases could still be found. One great contribution in this respect is his advice against drinking water during, immediately, before and after meals. This has now been proved very true by modern scientists as it leads to washing away a large portion of the nutrients that one gets from the meals.
Maulae Kainat Hazrat Ali alaihissalaam has given a unique regime to combat most ailments. By adapting a very simple method with no medicine or exercise, this method prescribes drinking about a litre of water first thing in the morning, without mouth washing and abstaining to have anything for the next one hour or so. This is combined with not drinking water immediately before or after meals mentioned earlier. No doubt, recent researches by a Japanese doctor, after extensive trials have suggested exactly a similar treatment claiming a sure cure even for such incurable ailments as Cancer besides many other diseases which could be cured within a few days to a few months. Peoples suffering from any incurable disease may try this recipe with faith and belief, Inshaa Allah, God willing and with the blessings from the Aimmah Masoomeen Alaihissalaam , soon , divine cure will be granted.