Interesting stuff. The bowel tolerance thing does make me suspicious as to how people are interpreting this. Let's face it, Its hardly a pleasant process we're talking her is it? Here's some of my thoughs and opinions on the subject from 4 years of mega dosing....
After discovering that taking more than my usual 1gram a day would benefit me in many ways, I gradually increased the amounts week by week, month by month. I take now around 15-25k a day depending on how much exercise and how much stress I'm under. I also supplement on the other main anti-oxidants.
MY USUAL ROUTINE
I always start the day with around 8000mg with a glass of water to kick start my digestion of a morning. After a high fibre Bran breakfast with 2 eggs 15 mins after, I will have been "on" twice within 1 hour of so just before I go to work. My lower intestine will be completely clear of digested food, and my energy levels are high afterwards. I rarely get constipated. If I do, its because my hydration levels were not high enough, especially after an hour in the gym. Lack of a high bran breakfast for even 2 days can sometimes make me "itch" as well. Sorry for sharing that info you...
FOOD AND WATER
Its worth bearing in mind that a yeast/flora problem in the intestines could make you senstive to C ? Just a theory. Also, you may me allergic to milk or gluten? I'd recommend getting an allergy test. Also, if you've been on any anti-biotics or prescribed meds, this could cause problems. Also, people think they're eating well but the diet leaves alot to desired. I've found that most people don't understand what a balanced diet is!
Years of Junk food with lots of refined carbs including white bread can ruin your digestive health. I'd even go so far as to recommend colonic irrigation and total de-tox food plan for a week. Doing this can really improve your digestive ability to absorb way more C than 3-4000mgs. You my have IBS ( irritable bowel syndrome) and not even know it. WATER TIP : Drink 2 litres of mineral water every day. I've seen programmes where C.I. was performed and within a week they'd lost nearly a stone (7 kilos). The amount of food trapped inside millions of people is unbelievable.
LETHARGY AND C ?
Sometimes I do feel queezy when I take 8-10grams at once, but its because my body now loves Vitamin C and I'm sure it kick-starts peristalsis in the morning. The food starts to move very quickly, and I can be on the toilet within minutes. I generally have no problem unless I feel I'm under attack from a virus and I'll beef up my amounts until the symptoms go away.
In a word ; Bowel tolerance. I get out AA powder as this has a turbo affect on the immune system in the "I think I may have caught Flu" scenario.
I've followed the foundation's cold flu cure and it works every time. You MUST get it started within 6 hours I'd say else you lower the chance of nipping it in the bud so to speak. Any sort of Nausea you get from taking more than 2-3000mgs can simply be the affect of the C pushing food through the small and large intestine at a faster rate than you're used to.
Note that unless you've a life long habit of eating a decent amount of fibre so that you go on the toilet twice a day already, going on the toilet 3-4 times a day could be interpreted as a problem. Trust me it isn't.
ARE YOU SURE ITS "UPSET STOMACH"?
It's worth bearing in mind that an "upset stomach" or when I hear people speaking Diarrhoea/and stomach cramps, people simply might be interpreting looser stools and not be used to the ease of which Vitamin C helps move the stools through the Colon. Simply put, the higher the fibre in your diet, the faster the food moves through the lower intestine. People may have increased their fibre intake AND vitamin C. The effect of which is a turbo boost to the entire system and lots of wind with associated cramps may follow. The embaressment caused by wind or the pain of lodged food being forced off ( with the associated toxins) can scare the Vit C convert to conclude "this C is a bad idea". Nausea can happen due to toxin release. Thankfully the Vitamin C cn neutralise that effect.
If fibre is chronically low, many people can have 2-6 kg of undigested rotting food in the small and large intestine! So its easy to conclude that when the Vit C comes along and starts forcibly di-toxifiying your entire system, your digestive system is shocked into doing something it's not used to. Result? Loose/very stools and/or explosive diarrhoea. Be aware that loose stools are not a bad thin. IT shows that the digested food if running through Large Intestine (Colon) at a rapid rate. THIS IS WHAT SHOULD BE HAPPENING.
Taking more Vit C doesn't mean that you're going to get explosive diarrhoea! My girlfriend is a Staff Nurse, and hears it all. She knows of people who don't go on the toilet for a week! If not more! Reason? Their diets are very very poor. They are generally overweight too due to malnutrition and low fibre. Many people struggle to go once a day? How many people (especially men) spend 30 minutes in the toilet reading a newspaper?. If you're eating "CLEAN AND HEALTHY" and taking 2-4000mgs+ of C , you really should be on and off the toilet within 2 minutes and feel much much better afterwards. Upset stomach can simply mean that "I'm farting alot". People can associate this with indigestion and potential run-to-the-toilet explosive diarrhoea. If people are gradually increasing their C through the day, any sort of noise, grumbling with occasional trapped wind, can be easily misinterpreted. The result? "Oh I'd better not take as much".
SORRY TO GO ON
My message is find out and test why the C levels are so low to cause explosive diarrheoa (if indeed this is happening at a low 2-4000mgs). Plus increase the fibre by raw fruit and vegetables, nuts, seeds and wholegrains through the day. The previous amounts may not be as bad as you think. Increase your daily amount say to 1000mg every 4 hours with food to attain a "Dynamic Flow" of C throughout the day. When you're used to that, take maybe 1-2000mg every 4 hours. You may be suprised at how much the body can absorb. Oh, consider that you may suffering from a pre-existing condition I mentioned before. There may be other conditions as well which could be making the Bowel Tolerance so low.