One of the staples in my supplement regimen for the last 6 months has been 1500mg of Vitamin C (solgar ester-c). Some days I do 2000mg. Everything I've read says that Vitamin C is super safe in these amounts. Is there anything I should be aware of long-term?
I was on high dose vitamin C as well, but I cannot say it made me feel better. And in fact one of the great shocks for me was when an allopath had me go off all 40 of my supplements, I felt dramatically better.
The biggest problem is there is no *convincing* evidence that supplemental vitamin C either extends life or improves health. You will find studies on both sides of the issue, and it becomes pretty obvious at some point reading these studies that they split hairs either way. You will find very smart people like James Watson (nobel prize for discovering DNA's structure) who refuses to take any Vitamin C at all because he thinks that cancer benefits from Vitamin C more than healthy cells do.
I would feel very good about taking Vitamin C if an osteopath could measure some harmful level of oxidative stress and then prove to me that this goes away when I take Vitamin C. Apparently no osteopath is that invested to spend the time to do that.
Where Vitamin C gets much more interesting is in treatment during some active disease, like a viral infection. The ability to protect the body from massive amounts of oxidative stress might really improve the outcome. I haven't experimented with that, but there is a world of difference between using Vitamin C as a medicine during illness and using Vitamin C as a prophylactic for every day use to protect against oxidative stress.
Here's the bigger problem that I see: the body needs a certain level of free radicals in order to build its endogenous defense systems. When you use too many antioxidants, you mask this system. You are protected from the initial injury of reactive oxygen species, but you never then develop stronger defenses. If you are engaged in appropriate low-intensity exercise, you need hormesis and these interactions to get stronger. Vitamin C could result in people feeling better but then failing to get stronger as a result of exercise.
I'm getting cynical enough about supplements that I only want to take things that have remarkable proven benefits, or for which there is some real experimental evidence that my metabolism would benefit (and then some follow up that proves I did benefit). Taking Vitamin C just as an insurance policy, when the evidence is so weak, doesn't look like a smart bet to me.
Just a P.S. if you do take it: it has an extremely short half life. So if you want to take 2 grams, you are wasting the dose to take it all at once. You would want to spread it out over every three hours. But then of course you increase the risk that your are interfering with the body's ability to respond to free radicals by getting stronger in response to exercise.