I have read quite a bit about vitamin C over the years, and have my own experiences and conclusions to share here. Now, I am not giving “medical advice,” as I do not want to be accused by some bureaucrat of “giving medical advice without being licensed,” etc. But I do have a right to share some information I have learned.
Yes, vitamin C is good for you and necessary, but excessive amounts and in the long term can be harmful. Some people such as myself have some issues in the digestive area and can’t eat some of the foods, such as certain fruits and vegetables, which is where vitamin C is mostly naturally found. So I take some vitamins and other nutritional supplements to make up for what might be missing. I know, some of the supplements might be unreliable, and you really have to do your research when looking for the right ones to take.
Over the past several years I had increased my vitamin C supplementation because I thought it was a good idea. I take it with breakfast, lunch and dinner, because vitamin C absorbs and is excreted from your system very quickly. However, a few months ago I added an extra 1000 mg, and within the next few months I had experienced some muscle aches and some joint pain. I believe that the symptoms coincided with the increase in vitamin C because i had not made any other changes in those months. The symptoms could have been caused by something else, however.
So in doing some more recent research, i have discovered that excessive amounts of vitamin C and/or having high amounts of it in the long term could cause some issues. Some adverse reactions could include osteoarthritis and excessive iron absorption, among other issues. Now, I don’t know if that’s what I had been experiencing, but I did reduce the vitamin C gradually, from a peak of 6000 mg (not all at once, but total per day) down to 3500 mg. And I intend to further reduce it.
One study that Wikipedia points to, however, finds that the higher the amounts of vitamin C the lower the absorption rate. Now, if that’s true, then I wonder how those who take too much vitamin C (which allegedly isn’t absorbing as well as the lower amounts, according to the study) could be developing symptoms that are supposedly being caused by too much vitamin C?
Besides vitamin C, one important aspect of immune system support is probiotic bacteria. That is why probiotic supplements such as acidophilus are very helpful not only in maintaining good digestive system support but immune system support as well.
UPDATE, August, 2019: I had eventually decreased the vitamin C to 1500 mg per day, via 500 mg tablets 3 times per day.