That one was super strict, no coffee, no tea, nothing.
EDIT - Also, this is _not_ how I would go about this now 5+ years later with more experience under my belt.
Electrolyte supplementation on an extended fast is important, and I drank way _way_ too much water in the early weeks of that fast, which is also dangerous.
If you have some fat (75% of westerners are heavily overweight or obese) you can easily fast on water only for weeks, of course you're not going to be able to exercise heavily every day or run a marathon. But if you're an overweight office worker with no other health issues you'll be just fine.
For anything over a week you probably should get medical assistance to keep an eye on vitamins and electrolytes, but you're not going to drop dead/unconscious/destroy your DNA
What's dangerous is starvation, aka fasting until your body starts giving up, but for the average westerner that's going to take a long time.
Glutathione possibly needs to be included as this will get low and Choline or Carnitine to remove the brain fog that occurred.
Averaged 18kg weight loss over the 18days, never felt so good in my life, like being a teenage male ramped up on Testosterone again, amazingly easy to fall asleep, excellent quality of sleep, vivid dreams which are recalled in the morning, not nightmares or anything like that. Foods which I dont like because of historical reasons smelt appealing and I wanted to eat them, no cravings for anything.
The only water I could really wanted, was the Scottish Highlands water, just didnt like Evian, S. Pellegrino, and the supermarket brands, and I wonder if highly filtered water ie dead water with no contaminants so its almost pure H2O would have been what I wanted, but they dont sell that in supermarkets AFAIK.
Ramadan is one of the fasts where you dont consume fluids during the day, and not consuming fluids will ramp up parts of your immune system which is why its important to drink fluid in order to not get angry. This could be in part because histamine is used by immune cells to move through tissues, but a personality side effect of high amounts is increased aggression. Anyone who supplements with histidine a precursor for histamine may also notice increased aggression. ie explosive rage, so be careful.
I watched my dad do 30-60 days every few years growing up. He always said how clear it made him mentally and the benefits to his health also was visible (until today he mountain-bikes across South East Asia during winter and he is in his late 70ies).
Longest I did was 40 days. Started out with 10 days a few years earlier which broke my misconceptions about if I would be able to do it. Especially the 40 days has been a healing journey for me both physically and mentally. It also gave me massive confidence about my body and taught me more about my limits than what decades of running did. I wouldn't do this long again because I lack the reserves today. But 10-20 days every few years is no issue.
Estimating by weight loss my metabolism was still burning well over 2500kcal daily at the end of the fast.
